DEMODULATION CAPABILITY

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of U.S. Provisional Application 61/789,829, filed March 15, 2013, entitled "Frequency Selective Logarithmic Amplifier with Intrinsic Frequency Demodulation Capability," the contents of which are hereby incorporated by reference in their entirety,

TECHNICAL FIELD

[0ΘΘ2] The subject matter disclosed herein relates to a regenerative selective logarithmic detector amplifier (LDA) with integrated FM demodulation capabilities. It can receive a wired or wireless FM modulated signal and amplify or demodulate it with high sensitivity, high skirt ratio and minimized noise when compared to the prior art. When tssed in conjunction with other circuits such as a phase lock loop (PLL) or mixer, it cars improve interference rejection and frequency selectivity and be Socked on a precise channel in frequency and phase. The LDA produces intermittent oscillations that are self-quenched when reaching a given threshold. It also embeds the circuitry to perform direct FM discrimination. This plus the fact that the instantaneous regeneration gain is low-medium permit io detect signals of small amplitudes buried in the noise. The LDA converts an analog or digital FM, AM, or FM & AM modulated signal and produces a train of almost constant amplitude and quasi-digital pulses in an intermediate frequency over a wide dynamic range. A digital frequency to voltage converter (VFC) may be used to convert the pulse frequency in a digital voltage word with simple processing. Alternatively a simple analog VFC or peak detector can be used to demodulate the input signal to baseband with audio or video bandwidth, innovation factors include direct FM demodulation, high sensitivity and signal regeneration from noise level, high skirt ratio and quasi digital output data without the need of AFC.

BACKGROUND

[0003] Regenerative selective logarithmic detector amplifiers (LDAs) disclosed herein have similarities to super-regenerative receivers (SRO) In term of circuit topology. However, the LDA is a phase sensitive regeneration detector, while the SRO is an amplitude sensitivity regeneration device. In particular, the LDA has a self-quenching mechanism wish low gain that amplifies the signal from the noise floor over a number of cycles. In contrast, the SRO has

. j - external quenching and high gain thai makes its electrical behaviors and performances quite different. There are also some similarities between the LDA, and DC or baseband log amps: both provide logarithmic amplification over a wide dynamic range. Furthermore, the LDA can have an intrinsic capability to demodulate analog or digital FM or AM & FM simultaneously.

Examples of LDAs can be foursd in U.S. Patent No. 7, 1 1 ,235. issued to DockOn AG, the contents of which are hereby incorporated by reference in their entirety.

[ΘΘΘ ] The SRO typically suffers from poor selectivity and higher output noise when used for narrow band signals, SROs also may drift in temperature when the oscillator is LC based. The. SRO receiver was quickly replaced by the super-heterodyne receiver for mainstream radio, because the latter has superior selectivity and sensitivity. However, the SRO is simple and low power, and has been nsed over many decades for remote control systems, short distance telemetry, and wireless security. Selectivity arid drift limitations were addressed al the end of the 1980s by the use of SAW devices. In the first decade of the 21 st century, articles show a renewed interest in SROs for use in low power receivers up to the GHz, range, and for moderate to high data rate applications.

[0005] Baseband log amps are based on multiple Gilbert cells, and typically provide a good linearity over a mid to large dynamic range at low to high frequencies. Simpler logarithmic amplifiers (e.g. DC log amps) are based on transistor logarithmic current versus voltage transfer characteristic, and address applications ranging from DC to low frequency,

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Throughout the drawings, reference numbers may be re-used to indicate correspondence between referenced elements. The drawings are provided to illustrate examples described herein and are not intended to limit the scope of the disclosure.

[0007] Figure 1 depicts example input and output signals from an LDA.

[0008] Figure 2 depicts a combination of the input and output signals from Figure 1 ,

[0009] Figure 3 depicts an inpot with sigual and noise, a regenerated signal, and output frequency pulses at low level.

fOOIO] Figure 4 depicts an input with signal and noise, regenerated signal, arid output frequency pulses at higher input level.

[001 Ij Figure 5 depicts time variant oscillations and quenching cycle of an LDA witA FM demodulation capability.

[0012] Figure 6 depicts a quadripole with a parallel resonant circuit and a series resonant circuit. [0013] Figure 7 depicts a bode plot showing the approximate response of th quadripole.

[0014] Figures 8A, 8B. SC. arid 8D depict various embodiments of a block Diagram of LDA with integral FM demodulation circuit. Figure 8E shows where a narrow hand CNB) FM demodulation can be done versus the center of the LDA frequency Bell-shape response. Fig. 8F shows the demodulation of a relatively wideband (WB) FM signal.

[0015] Figure 9 depicts an embodiment of a schematic of an LDA with FM

demodulation.

[0016] Figure 10 depicts an example of a conversion of a pseudo-digital frequency input to a digital output, pulse stream.

[0017] Figure i i depicts conversion of digital pulse stream to digital equivalent voltage sample.

[0018] Figure 12 depicts an example of an analog frequency to voltage converter.

[0019] Figure 13 depicts one embodiment of an analog detector.

[0020] Figure 14 depicts another implementation of an LDA,

[0021] Figure 15 depicts examples of matching network designed with microsrrip lines.

[0022] Figure 16 depicts examples of matching network designed with right-left handed transmission lines (CRLH-TLs).

[0023] Figure 17 depicts an example of a solution for matching at two frequencies using the matching network designed with right-left handed transmission lines (CRLH-TLs) shown in Figure 16.

[0024] Figure 18 depicts one potential implementation of CRLH-TLs.

[0025] Figure 1 depicts an example of an LDA as a high sensitivity FM radio receiver and demodulator.

[0026] Figure 20 depicts an example of a varicap circuit implementation for differential- or single-ended tuning voltage with a fixed reference voltage and potentiometer.

[0027] Figure 21 depicts an embodiment of LDA-puSsed oscillator locked in frequency in a phase lock loop (PLL) to a precise reference frequency tuned to the desired FM radio channel where the antenna is integral of the resonant circuit of the LDA and radiowaves are coupled directly to the inductive part of the resonant circuit.

[0028] Figure 22 depicts an embodiment of an LDA based FM radio receiver (FM- LDA) wsth digital channel tuning with a CPL antenna connected to the input RF„1N. [0029] Figure 23 depicts a high-sensitivity, low-noise amplifier replacement based on FM-LDA and PLL for FSK or FH-SS modulations with an antenna connected to the RF„IN input,

[0030] Figure 24A depicts an embodiment of a high-sensitivity, low-noise amplifier based on FM-LDA for FS . or FH-SS modulations with super-heterodyne topology.

[0031] Figure 24B depicts an embodiment of a L A replacement for a FSK Receiver based on FM LDA and super heterodyne reception.

[0032] Figure 25 depicts an e am le of a FM-LDA LNA replacement.

[0033] Figure 26 depicts another embodiment of an LNA replacement for an FSK receiver based or¾ LDA in FM mode and PLL.

[9034] Figure 27 depicts an embodiment of a FM-LDA based FSK repeater. The implementation of such wireless repeater is similar to the LNA replacement.

DETAILED DESCRIPTION

[0035] The LDA technology described herein brings significant enhancements to the state of the art SROs and log amps. For examples, LDAs can have intrinsic ability to demodulate frequency with high skirt ratio, very high sensitivity and noise suppression, very high dynamic range, superio discrimination, and flexible placement in a receiver chain without drawback. Table I compares various LDA, SRO. and amp technologies with their respective pros and cons.

Table 1 - CompansoK of LDA, S^O, n smp tec nologies:

[0036] The following other methods may be envisioned to process a weak signal buried into the noise; averaging, selective amplification, filtering, synchronized detection, spread spectrum and nonlinear RAMAN optic amplifier:

[0037] ^■■ -· Averaging; Noise is reduced over n periods; however the signal is NOT amplified. Also the averaging needs an accurate trigger for reference, and this trigger that may be noisy arid problematic at low signal levels.

[0038] -" Selective amplification arsd/or filtering: Amplification and or filtering are frequency dependent and stationary, so they do not provide any improvement over time in the frequency pass band, nor reduce the noise in thai pass band. This is problematic if the bandwidth is large. Also, selective amplifiers have a limited noise rejection,

[0039] - Synchronized detection: uses a phase lock loop (PLL) to lock it to the input signal, which selectivity m lies a narrow band unless more complicated methods are used, and may also be problematic at very low signal levels.

[0040] - Direct Sequence Spread Spectrum (DS-SS): Bits are spread over a wide frequency spectrum during the transmitting modulation process, eventually communicated over a lossy medium. The receiver dispreads energy and makes the demodulated signal appear much above the noise floor (e.g. GPS with a typical spreading factor of one thousand). By this means, very high attenuation can be overcome. Of course at the end this method can use a DS-SS transmitter that is not practical for many applications.

[0841] - RAMAN distributed optic amplifier: With such devices, the SNR can be improved and transport of data on fiber optic on hundreds or thousands of kilometers possible with minimum regeneration,

[0042] The LDA technology described herein concerns a regenerative logarithmic detector amplifier (LDA) with integrated FM demodulation (FM-LDA) that can receive wired or wireless FM, AM, or FM & AM signals with increased sensitivity, interference rejection, and bandwidth relative to circuits in current use. The LDA cars also amplify signals while minimizing noise.

[G043] The FM~LDA achieves these goals with integral hardware that improves the signal-to-naise ratio SNR of an AM or FM input signal by restarting its cycle automatically, and without external means, whenever the in ut signal reaches a specific amplitude over time (threshold). The LDA circuit thereby convert amplitude or frequency modulated input to an output stream of low intermediate frequency ("IF') frequency pulses, in which the instantaneous frequency modulates with the input wave (i.e. A /FM transposed to an IF band). This output stream is provided as a quasi-digital frequency-pulsed modulated signal. When AM modulated the conversion is made through an intrinsic logarithmic scale and then output.

[0044] The same frequency-pulsed modulated output can also be converted to baseband or demodulated (GHz to Fjrtax) to a voltage varying with time via the adjunction of an analog frequency to amplitude converter, a peak detector or a digital counter, logic inverter, and digital sealing circuit.

[0045] The innovative FM-LDA circuit, can perform several functions, some simultaneously: Logarithmic amplification, signal regeneration, frequency conversion, noise filtering, interference rejection, and analog/digital amplitude/frequency demodulation. More:

[0Θ46] - in AM mode, the output frequency is proportional to the logarithm of the input voltage,

[0047] - By amplifying the signal while reducing noise over n cycles, as part of the non-conventional process of frequency transformation, the LDA acts as a regenerative receiver and amplifier,

[Θ048] - An intrinsic log function converts linear input to logarithmic output, making the detection possible at very low input levels which allows for roughly 100 dB of usable dynamic range.

[0049] - The LDA can transcode an FM input to a different frequency

[0050] - The LDA can use adjustable frequencies to handle various channels and circuit boards,

[0051] - The LDA receiver circuit provides very high sensitivity

[00S2] - The LDA is cost-effective, scalable, and capable of being integrated directly into IC chips [ΘΘ53] ~ The LDA can accommodate analog, digital, AM, and FM demodulation. Other type of demodulation such P are feasible with the adjunction of additional circuitry - making it useful in a w de range of practical applications.

[0054] Applications ate numerous. LDA technology can be integrated into nearly every electronic system that would benefit from higher sensitivity, higher dynamic range, lower power consumption, better interference rejection, increased bandwidth, better signal to noise ratio SNJ¾ , longer range, and/or cleaner amplification.

[00551 Figure I depicts example input and output signals from an LDA. An LDA can give a low-level input signal 101 within its frequency capture bandwidth, masked by white Gaussian input noise 102. The LDA can regenerate an amplified input signal 103 over a number of periods, until reaching a threshold level. When the input threshold level is reached, the LDA can generate an output pulse, and restart its cycle.

[ΘΘ56] Because Gaussian noise is random and uneorrelated with the input signal, and as the regenerated amplified input signal 103 increases, the noise can be averaged out and kepi to the same value therefore not amplified over a number of periods, as shown by reduces noise 104.

[0057] Figure 2 depicts a combination of the input and output signals from Figure I . When combining input signals 201 over a number of periods, the resulting curve 202 represents a regenerated and amplified signal with reduced jitter over time.

[0058] This effect is similar to a LASER in which photons are amplified in a cavity at a specific wavelength. At a resonance frequency, a standing wave builds up energy constructively over time. At the end of the buildup period, a discharge of higher energy is produced, and the process restarts.

[0059] Another example to explain the regeneration process (hat takes place from the noise floor and the slow buildup of coherent energy (and reduction of amplitude jitter) is the following. There is a large noisy room with two similar mechanical forks of high quality factor and identical frequency resonance, each one at the other side of the room, The first fork

(excitation source) is beating at a low and constant level. The second fork can barely "hear" the first one due to the high level of noise. After some time, the second fork will amplify and resonate at t e tone frequency of the first one with high amplitude level irrespective of the noise level in the room due to its high quality factor, due to the weak coupling between booh forks and finally due to its slow synchronous buildup of mechanical energy. An important factor is the slow response in order to build up the signal but average out the random noise. [0060] Figure 3 depicts an input with signal and noise 301 , a regenerated signal 302, and output frequency pulses 303 at low level. Figure 4 depicts an input with signal and noise 401 , regenerated signal 402, and ontput frequency pulses 403 at higher input level. Figures 3 and 4 show a longer time scale of the input, and the effect on output frequency: The input signal (including noise) is shown in at the top, the regenerated signal is shown in the middle, and the output repetition rate is shown at the bottom. When the input signal is at a low level , as shown in Figure 3, the IDA takes time to regenerate the signal and reach a constant threshold value. In the time window of Figure 3, five regeneration cycles are created. Figure 4 shows a higher input signal and a corresponding faster regeneration time to reach the threshold, As a result, the LDA produces more regeneration cycles in the same time window. In addition, the output pulses are almost constant in amplitude for any low-to-high input signals, which is remarkable given the large dynamic range involved.

[0061 ] As far as the AM mode, the output frequency of the LDA is proportional to the logarithm of the input voltage:

F _Q(jT f ₀ + K ₂ x (£ _/ jy _dS ) in Hz

where:

Fo is a minimum fix frequency,

K and .2 are constant values,

^V ^ _ms {t) is the RMS value of the input signal V _tfl (t),

L _!Nd() the input level L _iN in dBm,

F ₀ ; _jT (t) is the output frequency.

[0062] If desired, the output frequency can be converted into voltage modulation in analog or digital form. In this case, the output voltage after low pass filtering becomes

where:

V _0U7 fiMsiO ' ^{s €} out ut voltage, and

3 and K4 constant values.

[0063] An LDA with FM demodulation circuit can possess many intrinsic properties of value to a wide range of commercial technologies. The following paragraphs include a non- exclusive list of the types of value thai may be possible from an LDA with FM demodulation circuit.

[0064] The conversion of voltage modulated input signals to frequency modulation in the IF range, and the use of logarithmic decompression, are particularly effective at reducing noise arsd expanding the dynamic range of weak signals relative to noise. These attributes make the LDA ideally suited to many applications, such as;

[0©65] - splatter-prone radar; micro-signal medical devices like ultrasound, MRIs, and CAT scans; fish finders and sonar in general; and collision avoidance

66] - signal analyzers, power meters, and RF transmitter amplifiers

[0067] - wireless networks such as Ws-Fs

[O MsS] - simple, low power consumption freqwency-to-digital converters based on LDAs, as a replacement for high resolution, fast, but expensive AD converters

[006 ] - pipeline metering and communication in the oil, water, and gas industries [0070] ~ replace expensive ADC converters with several possible configurations of LDAs, PLLs

[0071] The ability of LDAs to filter random noise from weaker signals gives them the means to extract, for example, a few dBs of signal from the noise floor for smart phone devices or cellular base station receivers. To further reduce the output power of cell phones (improved RF budget link), and thereby extend their battery life and range by a factor n, LDA technology cars be integrated into mobile phones. Further, cellular base stations could use LDAs to recover weaker signals. LDAs can also reduce the power consumption of microprocessors, such as CMOS processors, by integrating the LDAs directly into processing chips.

[©©72] Since the LDA regenerates the input signal and actively reduce noise, the LDA can significantly increase the SNR ratio even if placed after the first or second block in an amplification chain. For instance, a very good sensitivity for FM radio demodulation at 88- 108 MHz has been measured when combining an LDA with a low-noise amplifier.

[0073] LDAs can demodulate directly analog/digital AM, FM and other modulations such as FH-SS, and n-ary analog and digital FM and AM modulations with addition of more circuitry such as PLL(s), mixer(s), syrjthesizer(s), etc,

[0074] LDAs can regenerate many types of Sow level RF signals if tuned near or at the RF modulating frequency. [0075] Simplification of wireless digital receiver by replacing several functions of a standard digital receiver (RF to low intermediate frequency or to baseband with direct digital conversion).

[0076] In baseband microvolt sensors (e.g. audio bandwidth 20Hz - 20KHz), The LDA can be used as a very low noise and high discrimination conversion gain amplifier with digital output,

[0077] In one embodiment, the LDA can be regarded as a LC circuit with a variable conductance, the latter varying cyclically from positive to negative. Figure 5 depicts time variant oscillations and quenching cycle of an LDA with FM demodulation capability. More specifically, Figure 5 depicts a cycle 501 from the start of the cycle 502 so the end of the cycle 503. The oscillation builds up 504 until it reaches a threshold level 505 where the oscillation is shunt 506 progressively to zero.

[0078] Figure 6 depicts a quadripole 600 with a parallel resonant circuit 601 and a series resonant circuit 602. The LDA with FM demodulation capability is based on the use of a quadripole made of a parallel and series resonator circuits 601 and 602 as shown in Figure 6. It is designed to be a bandpass fdter with a null phase in the passband. An example of parallel resonant circuit is a L an C connected in parallel, a line of transmission having open(s) or short(s) stub(s) adequately placed, a crystal resonator, a SAW circuit, a BAW, or a combination of these, etc. An example of series resonant circuit is a L an C mounted in series, a line of transmission having open(s) or short(s) stub(s) adequately placed, a crystal resonator, a SAW circuit, BAW, or a combination of these, etc.

[0079] The transfer function in amplitude and phase of the quadripole of Figure 6 is shown in figure 7. Horizontal scale is frequency in Hz and vertical scales are respectively gain in dB and phase in degree.

[0080] Figure 7 depicts a bode plot showing the approximate response of the quadripole. The useful operating range for FM/AM demodulation in shown in the ellipse with dashed lines. The plots it? Figure 7 show the amplitude versus the frequency (top) and response phase vs. frequency (bottom), Depending on the design of the quadripole and interaction with the rest of the LDA, the gain can be designed to be flat or rounded versus pointy with the two spikes as shown in the diagram.

[0081] Figure 8A depicts a block Diagram of LDA with integral FM demodulation circuit. The behavior principle is the following: An amplifier A8 I is made to oscillate with the capacitor€81 in loopback. A typical amplifier may be a NPN, PNP transistor, a FET transistor. A MOS transistor, a dual gate FET transistor, etc. Also, th configuration of the active circuit cars be Darlington, common-base, common collector, common emitter, Cascode, differential pair, etc. Other types of amplifier, such as single or multiple stages amplifiers, logic amplifier may be used. An amplifier can be made by any number of processes, such as Silicon, Bi-CMOS, GaAs, or any other process.

[0082] The simplest implementation is to have a 180-degree shift from the input 801 to the output of the amplifier A I and the oscillation to be maintained with CSI as a weak or strong coupling. In other word, the value of C81 reduces the amplifier gain to a low value as desired. The quadripole is added to the output of A8 I and due to its high lower attenuation in the passband makes the amplifier resonate at or around the center frequency. The optimal F demodulation mode happens when the circuit is adjusted to the center of the null phase range arsd operates there as shown in Figure 7. Moreover the maximum frequency deviation that can be demodtdated without distortion is equal or larger than the null phase bandwidth, so the bandpass filter quadripole can be designed to accommodate the target deviation, whether narrow or wide.

[0SB3] Another important piece of the LDA behavior is the R€ circuit RS I and C83 acting as a sampling circuit. When connected to the amplifier, it charges cyclically and as its potential grows, the voltage across RS I grows that increase the output current of the amplifier. At the same time, the input bias current of the amplifier reduces and at a given threshold switches off the amplifier and therefore the oscillations. At this point, the charge accumulated into C83 discharges in R83 and as a consequence the voltage on RS I and C83 decreases to zero. The cycle restarts and ince the potential on R81 and C83 is low the amplifier bias current tends to increase and after a little period of time the oscillation build up again,

[0084] After low pass filtering, the signal on R8 ! and C83 is the output repetition frequency and its shape may resemble the envelope of the cyclic oscillation frequency shown in Figure 5.

[008S] The diode D81 couples the amplifier to the RC circuit 81 and C83 and acts as a low pas filter with good RF behavior. It has a low impedance when in conduction (positive half cycle of the input voltage) and high impedance when in non-conduction (negative half cycle of the input voltage) acting as a rectifier and low pass filter when loaded with a RC circuit.

[0086] The input is weakly coupled to the top of diode D l . The input matching is important and a good matching can improve the performance by a significant factor. An optional capacitor may be connected between the cathode of D8 1 and the bias of the amplifier to increase die coupling and facilitate the repetitive cycling.

. I ] - [0087] In another implementation, the diode D81 cars be replaced with ars inductor of relatively high value e.g. ten times the value of the inductanee(s) of the resonator and in a range of i OOnH to i mH, If the LDA oscillation operating frequency is too high, the parasitic may impact adversely the low pass effect and a more ideal component such as a diode may be «sed. In a further additional implementation. D81 can be replaced by an active component such as a transistor that is properly biased.

[0088] There are several types of FM discriminator or demodulators: Foster-Seeley, Travis, quadrature detector. PLL amongst other. Th Foster-See!ey discriminator uses a special center-tapped transformer that is tuned for the frequency of use and two diodes in a full wave rectification. When there is no deviation, both halves of the transformer are equal. When a FM signal is applied, the balance is destroyed and a signal appears at the output that is proportional to the frequency deviation.

[0089] The Travis discriminator is similar to Forster-Seeley whereas the secondary of the transformer has a center tap and two opposite branches, each branch connected to a tuning circuit and a slope detector. First inning circuit resonates slighdy higher than the carrier, while the second one slightly lower. The output is the difference between the voltages of slope detector 1 and 2. When a FM modulation is applied and deviates toward a frequency higher than the carrier, the voltage of detector 1 goes positive while the one of detector 2 negative. The output voltage and difference between both is positive, When a FM modulation deviates toward Sower than carrier frequency, the opposite happens and die output voltage becomes negative. The addition of the two resonance curves of opposite signs, gives a nice "S" curve characteristic output, for which the large middle section is linear.

[0096] In die quadrature detector, the input is split in 2 and one of the paths is delayed by 90 degrees and applied to a resonant LC circuit. The 2 signals finally feed a phase comparator and the result that is low pass filtered is the demodulated FM output,

[0691] The PLL is one FM discriminator and was adopted with the easy access of integrated circuits. The phases of the incoming FM signal versus the one of a voltage-controlled oscillator (VCO) are compared. The result is low pass filters and controls the VCO. As the frequency of the input changes, a correction voltage appears at the phase detector that wants to compensate the phase difference by increasing or decreasing die phase and frequency of the VCO. If the loop bandwidth of the PLL is designed appropriately, the correction voltage to the VCO is also the demodulated output voltage. [ΘΘ92] In contrast, the LDA technologies disclosed herein bring some, important novelties. An S-curve characteristic output is provided as other discriminators and the LDA simulates the performance of a Travis discriminator simply by having a low gain amplifier that is only oscillating if the phase of input and output are 180 degree from each of other. However in the LDA technologies disclosed herein the S-curve exceeds the quadripole passband bandwidth. In consequence the FM-LDA does not need an automatic frequency control APC as conventional FM discriminators and it does not need to sit exactly in the center of the S curve. In our implementation there is an auto-centering effect,

[0093] When the phase is distorted into the S-curve, the LDA oscillator tries to stay at the center of it. If the deviation goes high in frequency, the repetition rate decreases, if the deviation goes below or lower in frequency, the repetition goes faster. It is similar to having a power meter which can have three readings: close to center channel, center channel or above channel. If the S-curve is very wide, it can demodulate very wide FM. On the other side, if the S-curve is narrow, it can demodulate narrow FM.

[0094] The output repetition frequency contains the phase and frequency information and is modulated at a low intermediate frequency by the FM input signal. Standard FM discriminators employ a constant amplitude. In the LDA technologies disclosed herein, this is provided intrinsically by the LDA that has a large amplitude input dynamic range and that provides an almost constant repetition rate amplitude regardless of the input amplitude large or very small. The baseband signal is recovered by an analog or digital frequency to voltage converter (FVC).

[0095] Since being regenerated by the FM-LDA. the advantages here include one or more of the following: very high sensitivity over a high dynamic range, constant repetition output amplitude, high skirt ratio (high selectivity), and simultaneous FM & AM demodulation that add a few more dB of amplitude to the baseband demodulation amplitude.

[0096] Figures SB and 8C depict other embodiments of an LDA with integral FM demodulation circuit and an alternate output. The embodiments in Figures 8B and 8C include a low pass filter 802 configured to filter signals passing to an alternate output. In Figure 8B, the low pas filter 802 filters signals exiting the parallel resonant circuit to the alternate output. In Figure 8C, the low pas filter 802 filters signals that enter the. parallel and series resonant circuits. Other variations of these embodiments are possible.

[0097] In another implementation of FM-LDA, the series resonant circuit may be removed and the LDA may still demodulate analog or digital FM based on the slope detection method. Narrow band or relatively wide band FM may be demodulated. Digital FM includes modulation such as n-ary FS , MSK and Gaussian filtered or not Gaussian filtered. An example of analog FM is audio FM modulation from 20~20KHz. An example of digital FM modulation is 4-GFSK. Fig 8D shows the block diagram of the LDA. This is similar to Fig, 8A, 8B, 8C, 9, and 14 where the series resonant circuit has been removed. All the other descriptions, functions and methods described in this patent continue to apply for this implementation for instance ihe analog or digital F V converter.

[0098J In that slope, detection configuration, the optimal FM demodulation mode happens when the input RF modulated signal frequency is adjusted to the left or right slope of d e frequency Bell shape of the LDA. Fig 8E shows where a narrow band (NB) FM

demodulation can be done versus the center of the LDA frequency Beli-shape response. Since the information is carried by the rate of change, little distortion is expected whether the deviation is up in the slope, centered in the slope or low in the slope. A preferred implementation is to demodulate on the right slope center where the analog (e.g. audio) or data is not inverted.

Oppositely if demodulation is done on the left slope, the analog signal or data will be inverted. It may be un ^» in verted by negating the signal or multiplying it by - I further on in the receiver chain.

[(KI99J Fig. 8F shows the demodulation of a relatively wideband (WB) FM signal. For this to happen, the LDA needs to exhibit a wider bandwidth and may be designed such as the Q factor of the resonant circuit is lowered and other parameters of the LDA updated. This may include the amplifier AC and DC gain, the bias, the feedback capacitor C8 I of figure 8B, amongst other. Irs consequence the response of the LDA provides more available slope bandwidth to demodulate the wide band FM modulates signal at shown on fig. 8F.

[0100] Coming back to Fig. 8D, the discriminated output is shown following the matching network 803. To complete the FM demodulation output needs to be followed by an analog or digital frequency to voltage converter. Three alternate outputs are possible that may have a matching network S04 and a low pass filter 802. These three alternate may provide a higher power level of the demodulated signal and may not require a frequency to voltage converter if the low pass filter cut frequency is lower than the repetition frequency f _rep . In a first alternative 805, the signal is picked up from the input of the amplifier AS J . In a second alternative 806, di signal is picked up from the output of the amplifier AS I , In a third alternative 807, the signal is picked up from a split in the capacitors in the parallel resonant circuit.

[0101] Figure 9 depicts an embodiment of a schematic of an LDA with FM

demodulation. Figure 9 shows an implementation of an LDA with FM demodulation capability. The parallel resonator circuit L I/C93 and series resonators circuit L92/C98 are found on the collector of the amplifier. In one embodiment, the amplifier can be a NPN transistor. The transistor providing a 180 degree phase shift between collector and emitter,€91 the feedback oscillator capacitor, VG91 the input source signal coupled through a capacitor (not shown), the bias VS92, R93, and C96, D92 the diode coupling to the C circuit R94 _f € 1 1 and the output VM91. An optional C97 is shown for improving the quenching process.

[0102] Figure 10 depicts an example of a conversion of a pseudo-digital frequency input 1001 to a digital output pulse stream 1002. As discussed earlier, the repetition frequency rate is quasi-digital and needs little processing to be shaped in to a digital signal. First if the amplitude peak to peak is smaller than around O.SVpp, it can be amplified, If as shown the amplitude is 0.1 Vpp, the gain is about 5 to 20. The amplification can be done in one or several steps. Thereafter the amplified signal is compared with a reference voltage V_tef and create a logic " I" when above V_ref and "0" otherwise. One or more logic gates can be added to provide sharp edges and TTL level to the now digital signal. The digital repetition frequency output signal 1002 can contain the information in phase and instantaneous frequency. As said eariier it can be carried over long distance or in a noisy environment and is noise insensitive since the information is not in amplitude.

[§103] Figure 1 1 depicts conversion of digital pulse stream 1 1 01 to digital equivalent voltage sample 1 105. The digital repetition freqtsency signal 1 101 can be converted into a digital voltage V(k) 1 103 by going through an instantaneous frequency meter 1 102. Alternatively, the digital repetition frequency signal 1 101 can be passed through a period meter followed by a digital inverse function. The digital voltage V(k) 1 105 is obtained after scaling 1 104 as follow:

V(k) = F(k)*Kf + Vo

Where

Fik): klh sample of instantaneous frequency,

K . a constant in Hz

VQ: constant offset voltage thai corresponds to the

voltage(frequency) generated when the LDA input is terminated on 50 ohm. V{0) ~ F(k)*K ! at 50 Ohm

[0104] Figure 12 depicts an example of an analog frequency to voltage converter

(FVC). The FVC can be used in conjunction with the FM-LDA. It connects to the repetition frequency output of the LDA. As its name indicates, it provides an output with mean value being the converted voltage. Further low pass Filtering may be added. This is a simple FVC but it has .some limitations: the slew rate is slower than the previous digital approach for instance and typically needs a few pulses to settle to an accurate mean voltage value,

[01Θ5] Figure 13 depicts one embodiment of an analog detector. Oilier embodiments are possible. The analog detector can be connected to the repetition frequency output (VM I ), figure 9 or as well at die input of the amplifier, base of T 1 of figure 4. Further low pass filtering and amplification may be added.

[Θ106] Figure 14 depicts another implementation of au LDA. In this preferred embodiment of a FM LDA demodulator, the temperature compensated bias 1404 for the amplifier input A 141 may be designed to temperature compensates the amplifier A 141 . For instance if the amplifier is made of a bipolar transistor, its VBE will change with ~2mV7degree. If the DC bias voltage is made to decrease as well by ~2mV degree, the DC voltage on the emitter will remain constant and therefore the DC current through the resistor RI4I as well,

[0107] In another implementation of bias source, a temperature compensated current source may be used. When the amplifier is acting as a current amplifier with a constant low frequency gain, the output current will substantially be equal to the bias current multiplied by the gain. With a temperature, compensated bias current the amplifier output current will also be temperature compensated if we assume thai the low frequency gain remain constant with temperature. For instance if the amplifier is made of a bipolar transistor, and if the DC base current is temperature compensated and constant, the DC collector current will be constant as well. The DC emitter current is the addition of both base and collector currents, that is also constant. A constant current across the. resistor R 141 creates a constant DC voltage irrelevant of me variation of the base-emitter voltage. The input bias current source being high impedance will automatically provide a voltage that will change with the base-emitter voltage VBE of - 2mV/degree and compensate it.

[0108] An LDA with FM demodulation may suffer from some weaknesses such as leak of RF energy from its oscillator throughout the input port. This is an aggravating factor for at least two reasons. First, when the LDA is used as the first stage in a RF receiver, the RF energy is fed backward to the antenna. This causes the antenna to radiate unwanted energy in possibly unintended frequency band{s) and cause EMI noise. Second, the leaking energy can be reflected back to the LDA input with a different phase versus the input signal— a fact that defeats the purpose of regeneration (regeneration is the slow buildup of a resonance phase coherent with the input signal). Therefore it reduces the RF sensitivity. [0109] Also additional use of gain can be obtained when a low noise amplifier LNA precedes the log detector amplifier LDA. Indeed being a regenerative device, the LDA may not fully described by the noise law for linear circuits such as in conventional receiver chain where the first amplifier of the chain is the key element in determining the noise figure of the receiver, as defined per the Frits' formula:

NF = 10 * log(F) in (dB) and F ~ F _A1 + ½^ + «½2^L + ... j _n ) with NF: Total noise figure, ratio in dB

F: total noise figure, ratio in linear

F _Ai : Linear noise figure of the i ^!h amplifier of the amplifying chain GA,: Linear gain of the i* amplifier

In the case of a regenerative log amp, the regenerative part can improve the SNR when placed in first place or at any location in the receive chain. Therefore the regenerative LDA cars make good use of a preceding low noise amplifier even in a noise limited amplifier receiver chain. Such LDA may amplify further a signal buried in the no se because the dynamic range is extended on the low side (noise level) of the signal. In such a noise-limited receiver hut without LDA, the hypothetic addition of a LNA would be of little use since the system would be noise limited.

[0110] For instance adding a 20dB gain LNA in front of a noise limited receiver without LDA would barely increase the sensitivity level by 0 to 2dB. On the other side, by using a log amp with regeneration factor of say 8dB would improve the sensitivity by a factor of 6 to 8dB.

[§111] Therefore the addition of a matching circuits ) 1 01 at the LDA input may improve the coupling with the preceding circuit aud reduce the input reflections. Furthermore the addition of an isolator 1403 at the input 1402 (e.g., an amplifier with high factor of isolation) may further improve regeneration and gain opportunity,

[0112] As stated before, the LDA can be regarded as a LC circuit with variable conductance, the later varying cyclically from positive to negative. Consequently the input impedance may vary with time and moves, for example, on an arc in the low right quadrant of the Smidt chart in relation with the time variant LDA oscillation cycle. Several input matching scenarios are possible:

[0113] - A fix matched conjugate at the mean value.

[0114] - A fix matched conjugate at the impedance value corresponding to the most interesting behavior point that is the signal buildup from the noise. fOllSj - A fix matched conjugate at the maximum oscillation amplitude level (point in time where ihe threshold is reached).

[0116] - A dual impedance matching at a point where a fix matched conjugate is at the mean value or at a point where a fix matched conjugate is at the impedance value corresponding to the most interesting behavior point that is the signal bu ldup from the noise,

[ttl l?] - Variable impedance for instance in sy sehronidty with the LDA behavior cycle

[01 IS] Figure 15 depicts examples of matching network designed with microstrip Ones. For example, the series microstrip will change the real part of the impedance and the shunt stub will adjust the imaginary part. The shunt stub can be opened or shorted. The shunted stub can be placed before or after the series microstrip Sine depending where the normalized load impedance is situated ort the Smith chart. If the normalized load impedance is inside the l +jx circle on the Smith chart then the stub should be placed after and if the. normalized load impedance is ouiside the l +jx dreie on the Smith chart then the shunted stub should be placed before the series microstrip hue.

[8119] It is possible to replace these conventional microstrip lines with composite right-left handed transmission lines (CRLH-TLs) iri order to control different impedances at different frequencies. Figure 16 depicts examples of matching network designed with right-left handed transmission lines (CRLH-TLs).

[0120] Figure 1 ? depicts an example of a solution for matching at two frequencies using the matching network designed with righi-ieft handed transmission lines (CRLH-TLs) shown in Figure 16.

[9121] The CRLH-TL B shown in Figure 17 can be opened ended or short-circuited. In an alternate implementation, the topology of Figure 17 can be slightly modified for similar results. The CLA can be moved to the right of CRA and LLA. In another alternate

implementation, the topology of Figure I ? can be slightly modifsed for similar results. CLB can moved to the right of C B and LLB.

[0122] For example the CRLH-TL A can be designed to have a frequency fj with a phase Φ; and a frequency fa with a phase Φ . A CRLH-TL can be designed by using for example a series inductor LRA, a shunt capacitor CRA, a series capacitor CLA and a shunt inductor LLA. The CRLH-TL B can have, for example, a series inductor LRB, a shunt capacitor CRB, a series capacitor CLB and a shunt inductor LLB, The impedances of the CRLH-TL A and CRLH-TL B can be defined by:

OT23] The series CRLH-TL A can define the real part of the impedance and the shnnt CRLH-TL B can define the imaginary pan. It is also possible to design variable impedances by replacing the fixed components LRA _f CRA, LLA, CLA and L B, C B , LLB, CLB by variable/tunable capacitors and variable/tunable inductors. Tiierefore, the impedances can be changed accordingly to the frequency of operation. For example these variable impedances can be inserted at the input and output of the LDA, between the L A output and the LDA input, A variable matching can be inserted at the output of the repetition frequency. Or in order to have a variable/tunable LDA, it is possible to tune the oscillation frequency to different values by replacing the fixed values of the inductor and the capacitor by variable ones.

[0124] Different implementations are. possible. For example, it is possible to have a fixed CRLH-TL A with a variable CRLH-TL B. In another example, it is possible to have a variable CRLH-TL A with a fixed CRLH-TL B. In yet another example, it is possible to have a variable CRLH-TL A and a variable CRLH-TL B.

[0125] Figure 18 depicts one potential implementation of C LH-TLs. The series branch CRLH-TLA is figure 18 is connected to the LDA and a parallel CRLH-TLB is connected to LN A/input and branch left open at the bottom where the topology of Figure 17 was modified such as CLA is moved to the right of CRA (toward LDA).

[0126] Figure 19 depicts an example of an LDA 1 00 as a high sensitivity FM radio receiver and demodulator. In this embodiment, the FM-LDA can be used as RF front end for a FM radio. The FM radio channel antenna 190 S can feed directly the LDA input 1 02. An optional LNA 1903 and matching circuit 1904 can be used to increase the sensitivity arid reduce the leakirsg though the input port. The demodulated audio output can be obtained by converting the LDA output repetition rate into a voltage with a FVC 1 05 either analog or digitally. The FM channel is selected with the DC voltag V„tune 1906 applied to the varicap.

This configuration gives a wide band FM demodulation output. Other configurations are possible where narrow band FM can be demodulated {e.g., using a PLL implementation, as discussed below).

[0127] Figure 20 depicts an example of a varicap circuit implementation for differential- or single-ended tuning voltage with a fixed reference voltage and potentiometer R l . Figure 20 shows a possible implementation of a differential- or single-ended control of the varicap. A DC voltage V„tune is applied on the varicap Cv through high impedance v20 l and Rv202.

[§12§] I s the model of small variations, arsd assuming that the top node of the parallel resonant circuit is at an AC ground, the total additional capacitance CADD of the varicap branch is Cv series with C20S arsd C202, as follows:

c _ADD _ _ _{1 l} ¹ _i

The total capacitance, Cy, then becomes:

C _T ~ C_ oo €RE$..PA8AL Ί ^~ Cor HER

Irs order to ma imize the effect of Cy in its branch, C201 and C202 should be greater or much greater than Cv.

[©129] The capacitance of CQTHKR nia be the combination of all other contributions of capacitance seen ai the bottom node of parallel resonance circuit. It may include the contribution of an active component's equivalent capacitance {e.g. transistor C,„€E // C _„ CB), the one of the feedback capacitor C81 of Figtsre 8, plus parasitic capacitance due the printed circuit, etc. In another implementation the capacitance of the parallel circuit is removed arsd replaced by the arm of the varicap, In this case, the term CKES PARAL is zero in the formulas above.

[Θ130] In this simpler implementation of a F3VI LDA based receiver, the adjustment of frequency is done manually or mechanically with an adjustable capacitor or inductance. The capacitor of the parallel resonance circuit is replaced by an adjustable capacitor that adjusts the frequency radio channel. Practically, a bunch of fix selectable capacitors may be added to extend and cover the entire frequency bandwidth of 88MH2. to 108MHz (i.e., a range of frequencies),

[0131] In a semi-digital implementation of the previous circuit, the fix capacitance of the parallel resonant circuit may be replaced by two or more fixed capacitors of same or different values and selectable independently, connected in parallel. Since the total capacitance between two nodes is additive when capacitors are added Irs parallel, a preferred implementation of this circuit will be to use a binary sequence so for instance C- _: -C, ..., 0,~2 ^Ν χ€. With a binary sequence, every capacitance value from value C to value 2 ^N - 1 can be produced plus zero.

OT32] Other sequence of capacitors may be chosen for instance to linearize the output frequency versus the input selection since the output frequency is roughly proportional to the inverse square root of the LC product. In another embodiment, the inductance may be varied instead of or in addition to the capacitors with a sequence that can be binary, decimal or otherwise varied.

[0133] In another embodiment, one small-value varicap can be added to a bank or inventory of fixed selectable capacitors. The small-value varicap can be added to increase the adjustment resolution. In yet embodiment, several varicaps can be used in parallel. For example, several capacitors, including at least Ct, <¾, and C3, can be placed in parallel. One capacitor€3 can have capacitance in a range of about 0.5C to about 1.5C; another capacitor€ can have capacitance in a range of about IC to about 3C; and another capacitor C3 can have capacitance in a range of about 2C to about 6C. Additional capacitors can be also be placed in parallel to supplement capacitors Cj, Q, and Cj. In yet another embodiment, a collection of LC circuit can be switched ON and OFF to change the oscillation frequency of ihe LDA.

[0134] Some LDA implementations can have certain drawbacks. For example, some LDA implementations can have poor selectivity and possible drift with temperature. Figure 21 depicts an LDA~pulsed oscillator 2104 locked in frequency and phase in a phase lock loop (PLL) 2102 to a precise reference frequency tuned to the desired FM radio channel. The selection of the channel can be controlled by a digital JC, a processor unit or by the end user with a "digital dialer" such as found in the FM car radios,

[0135] The pnlse oscillations of the LDA 2104 are filtered, amplified and digitized and feeding a frequency divider by W 2103. A phase/frequency comparator compares the signal issued from the N divider and a reference signal. The reference signal can be generated from a local oscillator 2101 such as a digital crystal oscillator divided by a counter M 2106. The phase/frequency comparator 2107 creates a correction voltage proportional to the

phase/frequency difference between both input signals. Several types of comparators can be used with various properties namely gain, output range, output impedance and type of output signal (pulse, variable voltage, etc). A low pass filter follows, that determines the loop response of the PLL. The filtered signal Vc(t) feeds the varicap of the parallel resonant circuit of the LDA 2104 as described previously. Effectively the log amp is used as a controlled VCO. The demodulated FM signal is the control voltage Vc{t). To be effective, the loop bandwidth of the PLL 2102 can be adjusted appropriately, in diis configuration should be lower than the lowest audio frequency of the FM radio channel, say SQHz. The PLL loop bandwidth is affected by the ratio M, the phase comparator gain in rad/s and the VCO gain in MHz V.

[0136] For an adjustment step of 0.1 MHz in the FM radio band of 88.0MHz to

108.0MHz, the comparison frequency may be of 0. 1 MHz maximum or any modulo value below such as SOKHz, 25, 20, lO Hz, etc. in one embodiment, M and N can adjusted for getting this value of 0.1 MHz ai the input of the phase comparator. In this case, the ratio N can be set to i OxF„channel in MHz for instance 880 for 88.0MHz, 88 ! for 88 J MHz, ... , 1079 for (07.9MHz and 1080 for 108.0MHz.

[0137] An optional squelch function 2108 can be added as usually used n FM radio. This can prevent noisy audio content from being passed through when there is no radio channel present. The squelch switch 21 OS may be controlled by the audio demodulated RMS value of the LDA audio output voltage. When the RMS value exceeds a given threshold, it is assumed that the LDA is Socked onto a radio channel of sufficient level.

[0138] Some advantages of this embodiment, as opposed to a standard FM radio receiver, include without limitation:

[0139] - No external antenna since the FM signal is received directly in the high impedance parallel resonant circuit of the LDA. This saves a non-negligible amount of assembly and cost since no external antenna is needed. However the RF sensitivity may be limited to the physical size of the later and miss to be high sensitivity if the circuit is put for instance into a car dash board or any non-free space location where there is excess of radio propagation attenuation.

[0140] - High selectivity due to PLL and FM-LDA high skirt ratio

[0141] - Simple/cheap FM radio front-end circuit

[0142] - Small PCB area (e.g., I square inch)

[0143] - May need as low a one inductance per circuit

[0144] - Digital frequency adjustment as current FM radios

[0145] - Mid to high sensitivity in the order of - 1 lOdBm

[0146] - Car application: Portion of dashboard needs to be non-conductive.

[0147] - Integration possible (component or integrated circuit)

[0148] It should be noted that two demodulated audio outputs are possible. One possible output is a narrow band FM (or phase) with the control voltage of the VCO (i.e., Vc(i}). Another possible output is a wide band FM with the regular LDA pulse frequency output that is converted to voltage with a simple frequency-to-voltage converter.

[0149] Figure 22 depicts an embodiment of an LDA-based FM radio receiver with digital channel tuning with antenna. This embodiment is similar to the previous one depicted in Figure 21 , with at least the following differences. First, the embodiment depicted in Figure 22 can provide very high sensitivity due to its inclusion of an antenna 2210, a LNA 2209 and a regenerative LDA 2204. Second, a suitable antenna is a roughly omnidirectional small (e.g., 2 square inch) antenna 2210 thai can be printed on the same primed circuit board embedding the magnetic H (loop) and electrical field E (monopo!e/dipo!e) reception for best coupling and penetration through partition such as a car dashboard. A very suitable and preferred printed antenna for this use is a CPL antenna that maximize both the H and E field due to its geometry.

[§150] An LDA based FM radio receiver with the features described herein can be built for digital radio, satellite radio, and the like. Similar types of topologies can be used for satellite radios and digital radios.

[0151 j An LDA can be used in a FM receiver, an AM receiver, or a combined FM and AM receiver and demodulator. One advantage for the LDA receiver with FM demodulation is that it can demodulate FM, AM or both simultaneously. This provides a gain of a few dB versus conventional discriminators. Another advantage is the high skirt ration of the LDA that provides superior selectivity, For instance in the case of FM radio, a high skirt ratio can permit better audio quality when listening to a weak signal while a strong one is very close (e.g., it has the ability to discriminate both the strong and the week signal),

[©152] Figure 23 depicts a high-sensitivity, low-noise amplifier replacement based on FM-LDA and PLL for FSK or frequency hopping spread spectrum FH-SS modulations. This embodiment can target intrinsic demodulation of digital FM signals and digital FM FH-35.

[0153] The LDA 2304 in FM mode can demodulate intrinsically the FSK input 23 10 modulation with a high sensitivity. Adding the LDA in a PLL 2302 can increase the selectivity with a higher skirt ratio, increase the interference rejection and permit to select precisely the narrow band or wide channel desired. This is a direct demodulation to BB or low IF and there is no super-heterodyne stage here. The input noise bandwidth may cover the entire frequency band (more than the channel BW) or oppositely only one particular channel. However in both cases the regeneration factor may increase the signal-to-noise ratio.

[Ill 54] The output may be selected from one of the following and depending of the application:

[0155] - FJData„out: That output is the repetition frequency output also called F _„ rep. Each bit of data is provided as an instantaneous frequency (to he exact one over the

instantaneous period of F„rep pulse to pulse). The output is quasi-digital and noise insensible! It can effectively be sent to long cable if needed without noise problem. Also since the data is in the frequency domain, there is no need of costly, power hungry fast ADC. Data cars be extracted with i circuit discussed previously with respect to Figures 10 and 1 1 and data(k) delivered, [0156] - Data„out(t); Da la is already conve ed in baseband frequency (OHz to Fmax). The Data„Gut{t) output voltage can be sitght!y processed with limited signal shaping or de~ emphasizing if previously emphasized.

[0157] - NB FM ata„out.(t}: This is a narrow band (NB) FM voltage output that also happens to be the control voltage for the VCO of the PLL for which the value corresponds to the phase correction or narrow band FM for the PLL to attempt to follow the input signal The bandwidth of the PLL should be set correctly (usually lower than the data rate) for the system to behave correctly.

[0158J In another embodiment, and for further reducing the input noise bandwidth _* a set of selectable parallel and series resonators cars be added to the LDA. When implemented in art integrated circuit., the added complexity may not be a relevant factor anymore,

[§159] In a further embodiment, the circuit can be used for amplification and demodulation of one or more frequency modulated signal(s) issued from one or more sensor(s). Typical applications may cover sensor such as crystal resonator oscillating at a frequency function of the temperature or other physical parameters. The input may be wireless or wired. Some impedance matching or polarization/bias network may he used to interface the one or more sensor(s) and the FM-LDA. Other sensors may include piezoelectric sensors, aceelerometers, even array of sensors. Modulation may include frequency chirping or sweeping. In yet another embodiment, if the selectivity is of paramount importance, a super-heterodyne stage cars he added in the input such as shown in Figures 24A aitd 24B. Figure 24A depicts an embodiment of a high-sensitivity, low-noise amplifier based on FM-LDA for FSK or FH-SS modulations with super-heterodyne topology.

[0.160] Figure 24 A and 24B depicts an embodiment of a L A replacement for a FSK receiver 2401 based on FM LDA and super heterodyne reception. At the circuit level, the advantage of the super heterodyne topology may be to generate a fix input frequency that, permits to apply a high order filter and therefore gaining a high selectivity. Also the following circuits in the receive chain are treating a signal at a fix frequency whatever the channel selected .since the variable channel frequency called F in Fig. 24A, is selected by a variable frequency on LOl such as the mixer output 2402 provides an intermediate frequency IF that is equal to difference of the frequency of RF minus the one of LOl amongst other terras that are generally filtered out. In another words, LOl is selected by the receiver such as to select one channel amongst N channels in RF frequency and down-convert it in frequency to and intermediate fix frequency IF regardless of the channel selected. The LDA being intrinsically a narrow band amplifier and regenerative device, it filters-out the frequency componersts outside of his frequency bandwidth of operation with a high order of filtering. It exhibits the functionality of art active band pass filter with high order of filtering on both the high cutting frequency and low cutting frequency sides. One application of the LDA is providing more range, more signal-to-noise ratio, more dynamic range and more interference rejection as a component or sub-system replacement. If the LDA solution is integrated in an integrated circuit or a small module such as done currently for VCO modules in the industry, it may be a high performance drop-in replacement for a RF low noise amplifier LNA in a number of FM FS /FH-SS receivers. The value would be to increase the performance without completely redesigning the receiver but replacing one component.

[0161] In the embodiment of Fig, 24B _t a standard RF LNA can be replaced by a circuit based on the LDA with FM demodulation, A number of advantages can be derived by making such a replacement, including without limitation:

[0162] - higher sensitivity (recover very weak signals),

[0163] - higher selectivity due to high skirt ratio reject close and far frequency interferences) ,

[0164] ~ higher dynamic range (weak to strong signal),

[0165] - lower noise bandwidth (does not amplify an entire frequency band as a usual

LNA),

[0166] - higher rejection of interferences,

[0167] - higher rejection of saturation due to mid-strong interferences outside of the frequency band of use.

[0 68] This embodiment has also superior performance versus a classic super* heterodyne receiver, mainly the higher sensitivity, the higher dynamic range, the higher rejection of strong interferences, and the higher selectivity due to the high skirt ratio. This embodiment can be used for FM narrow or wideband modulation, digital FS or FM based FH-SS.

[0169] If the RF input signal is on a tlx FM band, local oscillators LO I and L02 can fixed. If the signal is in a channel in a frequency band (i.e., a range of frequencies), local oscillators LOI and L02 can be adjustable. If the input signal is digital FM and frequency- hopping spread spectrum, LO I and L02 can be agile and change their frequency and follow the input RF signal as it hopes from channel to channel. The super-heterodyne structure and high skirt ratio of the LDA provide a high selectivity and high rejection of interferences. Whereas the LNA can cover the entire frequency band of use, the. LDA technologies disclosed herein focus on the selected channel. The performance is therefore superior such as listed above. §i?0] The input signal in figure 24B is down converted using a mixer 2402 to a fix IF frequency at F„ F ~ FJLQi . The unwanted component at FJRF + FJLO l is filtered out by the LDA 2403 that is frequency selective and designed to match the IF frequency with a given bandwidth f_fF +/- BW. The LDA 2403 is regenerating the input signal so provides a high sensitivity even after a mixer 2402. A LNA 2404 can be integral to the LDA 2403 to further improve the sesisitivity and increase the isolation to the input port and avoid RF energy to iick out on the input (mixer 2402 and antenna 2401 ), The output frequency repetition of the LDA 2403 may be at least I to 2 times faster than the highest data input, 2 scenarios may appear; First, the LDA is not synchronized with the symbol rate of the input data and in order to respect the Nyquist criiena, the output frequency F_rep should be at least twice higher than the highest input data rate. 2) Second, the LDA is synchronized with the symbol rate of the input data and in this case the output frequency F„rep may be at least once the highest input data rate because what may really count is the rate of change of F„rep that should be twice or more the one of the input data, Finally it is mixed (up converted) back to RF with another mixer 2406 and L02 at the output RF frequency.

0171J h should be noted that the output signal could contain an image at FJRF - 2xF„rep, In most cases the following receiving stages may reject anyway signal out of the frequency channel therefore this may not cause any troubie. If needed, an image rejection mixer may be used to cancel the image at FJRF - 2xF_rep,

[§1?2] Figure 25 depicts an example of a FM-LOA LNA replacement. An LNA 2501 can have an RF input 2502, a RF output 2503, one or more voltage supply 2507, and ground connections 2504. Additionally, it may have a connection the receiver reference frequency 2505 in order to be phase coherent. Also if there is more than one channel in the selected frequency band, a channel input information 2506 can be provided, it may be a digital word for instance the number 913 for 13MHz. This number can be coded in binary " i 1 10010001 ", hexadecimal "391 " or other,

[( 173] Figure 26 depicts another embodiment of an LNA replacement for an FSK receiver based on LDA in FM mode and FLL. This implementation is similar to embodiment depicted in Figure 24B, but is simpler in some ways. When compared to a RF LNA, the embodiment depicted in Figure 26 can have a higher sensitivity, higher discrimination, and higher interference rejection. There is no heterodyning so the LDA _¾ 2601 may cover the entire frequency band of use, is wide band, and may be set to the correct channel with the use of a PLL 2602 locked to the reference local oscillator 2603. The input noise bandwidth can be larger since it may contain the entire frequency band of use in which the channel is to be selected. As a consequence the receive sensitivity may be reduced; however since it is a regenerative system, it is not obvious to determine what may be the impact if any.

[0174] Figure 27 depicts an embodiment of a FM-LDA based FSK repeater. The. implementation of such wireless repealer is similar to the LNA replacement. However, several differences are possible. One difference may be that the output image may not be or not well rejected since very close in frequency to the output RF of the mi er 2706 so the output mixer 2706 may be replaced by an image rejection mixer, An optional power amplifier 270? and bandpass filter 2708 may be added and finally feeding a re-emitting antenna 2709. Analog repeater requires that the retransmission frequency being at another channel otherwise the system may interfere itself and may oscillate. To retransmit in the same frequency some intelligence and memory may be used and the signal can be retransmitted not at the same time as the receive signal with time division multiple access TDM A or carrier sense multiple access with collision avoidance CSMA/CA protocols,

[01.75] Another benefit of the a FM LDA versus a classic FM detector is that simultaneous demodulation of FM and AM can bring an addition of about 4dB or more of demodulated baseband volume. The LDA. may demodulate the FM modulation and exhibit a repetition rate in a IF frequency that holds the information of amplitude and phase, for which the instantaneous frequency variation of the pulse to pulse correspond to the input signal v(t). The signal can be extracted by feeding a FVC and getting Vj>ui{t) or applying a digital FVC. The repetitive output pulse signal is insensible to noise since the info is FM modulated. This may benefit applications where transmission of a signal over a noisy environment or over a long line is needed.

[0176] Conditional language used herein, such as, among others, ⁴ "can," "could," "might," "may," "e.g.," and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain examples include, while other examples do not include, certain features, elements, and/or steps. Thus, such conditional language is not generally intended to imply that features, elements and/or steps are. in any way required for one or more examples or that one or more examples necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or steps are included or are to be performed in any particular example. The terms

"comprising," "including," "having," and the like are synonymous and are used inclusively, in an open-ended fashion, and do not exclude additional elements, features, acts, operations, and so forth. Also, the term ⁴ⁱ os" is used in sis inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term "or" means one, some, or all of the elements in the list.

[0177] In general, the various features and processes described above may be used independently of one another, or may be combined in different ways. All possible combinations and subcombinations are intended to fall within the scope of this disclosure. In addition, certain method or process blocks may be omitted in some implementations. The methods and processes described herein are also not limited to any particular sequence, and the blocks or states relating thereto can be performed m other sequences that are appropriate. For example, described blocks or states may be performed in an order other than that specifically disclosed, or multiple blocks or states may be combined in a single block or state. The example blocks or states may be performed in serial, in parallel, or in some other manner. Blocks or states may be added to or removed from the disclosed examples. The example systems and components described herein may be configured differently than described. For example, elements may be added to, removed from, or rearranged compared to the disclosed examples.

[0178] While certain example or illustrative examples have been described, these examples have been presented by way of example only, and are not intended to limit the scope of the subject matter disclosed herein. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of certain of the subject matter disclosed herein.