GOVERNMENT LICENSE RIGHTS

This invention was made with government support under CNS-1111541 and CNS- 1035303 awarded by the National Science Foundation. The Government has certain rights in the invention.

TECHNICAL FIELD

The present disclosure relates generally to ultra wideband transceivers, and more particularly, to integrated ultra- low-power ultra wideband transceivers.

BACKGROUND

It is a reality that biomedical and "internet-of-things" applications, among others, are driving the volume of wireless sensors, and therefore, ultra wideband transceivers associated therewith, into the cubic-mm regime. At the mm-scale, complete integration of such sensor transceivers is necessary, and their operation within the limits of a micro- battery used to power the components of such sensor transceivers becomes a challenge. With CMOS scaling and ultra-low-power circuits allowing for a reduction in battery volume, the antenna and crystal, which is used to perform clocking functions, of such sensor transceivers quickly become the largest components in a cubic-mm sensor node.

SUMMARY

According to one embodiment, an integrated ultra wideband transceiver comprises a transmitter, a receiver, and a clock generator comprising a relaxation oscillator. The transceiver further comprises a baseband controller electrically connected to, and configured to exert a measure of control over, at least one of the transmitter, receiver, and clock generator; and a micro-battery operative to provide operating power to each of the transmitter, receiver, clock generator, and baseband controller.

In accordance with another embodiment, an integrated ultra wideband transceiver comprises a transmitter, a receiver, and at least one on-chip monopole antenna electrically connected to at least one of the transmitter or receiver for transmitting and/or receiving electrical signals. The transceiver further comprises a clock generator comprising a temperature-compensated relaxation oscillator; a baseband controller electrically connected to, and configured to exert a measure of control over, at least one of the transmitter, receiver, or clock generator; and a micro-battery operative to provide operating power to each of the transmitter, receiver, clock generator, and baseband controller.

In accordance with another embodiment, an RC network comprises first resistor and a series combination of a capacitor and a second resistor, wherein the first resistor is electrically connected in circuit with the series combination of the capacitor and the second resistor.

In accordance with another embodiment, an integrated ultra wideband transceiver comprises a transmitter, a receiver, a first on-chip monopole antenna electrically connected to the transmitter for transmitting electrical signals, and a second on-chip monopole antenna electrically connected to the receiver for receiving electrical signals. The transceiver further comprises a clock generator comprising a temperature- compensated relaxation oscillator, and a baseband controller electrically connected to, and configured to exert a measure of control over, at least one of the transmitter, receiver, or clock generator. The transceiver still further comprises a micro-battery operative to provide operating power to each of the transmitter, receiver, clock generator, and baseband controller; a current limiter electrically connected between the micro-battery and at least one of the transmitter, receiver, clock generator, or baseband controller; and a storage capacitor electrically connected to the current limiter and the at least one of the transmitter, receiver, clock generator, or baseband controller.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred exemplary embodiments will hereinafter be described in conjunction with the appended drawings, wherein like designations denote like elements, and wherein:

Figure 1 is a diagrammatic and schematic view of an illustrative embodiment of an integrated ultra wideband transceiver; Figure 2 is a plan view of an illustrative implementation of the integrated ultra wideband transceiver illustrated in Figure 1 ;

Figures 3a-3d are diagrammatic and schematic views of illustrative embodiments of a receiver and various components thereof of the ultra wideband transceiver illustrated in Figure 1 ;

Figures 4a-4d are diagrammatic and schematic views of illustrative embodiments of a relaxation oscillator and various components thereof of the integrated ultra wideband transceiver illustrated in Figure 1 , and graphical representations of illustrative operational characteristics of the relaxation oscillator; Figures 5a-5d are diagrammatic and schematic views of illustrative embodiments of a transmitter and various components thereof of the integrated ultra wideband transceiver illustrated in Figure 1 , and graphical representations of illustrative operational characteristics of the transmitter;

Figures 6a-6d are graphical representations of measurements/performance results of various components of an illustrative implementation of the transceiver illustrated in Figure 1;

Figure 7 comprises a series of tables containing performance information of various components of an illustrative implementation of the transceiver illustrated in Figure 1; Figures 8a and 8b are diagrammatic and schematic views of another illustrative embodiment of a relaxation oscillator and various components thereof of the integrated ultra wideband transceiver illustrated in Figure 1.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Described below are embodiments of an integrated ultra wideband transceiver. As used herein, the term "integrated" is intended to mean that the components of the transceiver are disposed on a single chip to form a "system-on-a-chip." As will be described in greater detail below, in an embodiment, the transceiver is an impulse-radio ultra wideband (IR-UWB) transceiver having one or more on-chip monopole antennas, while in another embodiment, the transceiver may include the option of wire-bonding to an off-chip antenna. In accordance with an illustrative implementation, the transceiver is a 9.8GHz transceiver that includes, for example, a corresponding 2mm monopole antenna for each of the transmitter and receiver of the device. Further, rather than comprising a crystal for performing a clocking function as is conventional in many known transceiver devices, the transceiver comprises a clock generator in the form of relaxation oscillator, which, in an embodiment, may comprise a temperature-compensated relaxation oscillator. Due to modern mm-scale battery limitations, it may be desirable, in certain embodiments, to limit the peak current draw of the transceiver to <100uA, which is far below typical power consumption of such transceivers. Furthermore, because external capacitors may be too large for mm-scale sensor nodes, duty-cycling only at the packet level may not be an option. Accordingly, in certain embodiments, the transceiver may include current limiting at the battery supply; while an integrated baseband controller or modem of the transceiver may duty-cycle the RF-front-end at the bit-level in order to operate it off integrated storage capacitance. Finally, while many conventional or known transceivers operate at <1V, in an embodiment, in an embodiment, the voltage of a micro-battery may be on the order of 3.2-4. IV, and integrated conversion efficiency may be <80%. Thus, transceiver of the present disclosure is designed to operate various components or blocks thereof over the entire voltage range of the battery of the transceiver. Referring now to the drawings, Figure 1 is a diagrammatic and schematic view of an illustrative embodiment of an integrated ultra wideband transceiver 10 (referred to below simply as "transceiver 10"). In the illustrated embodiment, the transceiver 10 generally comprises a micro-battery 12, a receiver (RX) 14, a clock generator (Clock Gen) 16, a transmitter (TX) 18, and a baseband controller 20. In an embodiment, the transceiver 10 further comprises one or more integrated (i.e., on-chip) antennas 22 (e.g., antennas 22 _ls 22 ₂ ) electrically connected to the transmitter 18 and/or receiver 14. Alternatively, each of the transmitter 18 and receiver 14 may be configured to be electrically connected to one or more off-chip antennas. In addition to the above, the transceiver 10 may further comprise a number of other components such as, for example and without limitation, one or more of a current limiter 24, a storage capacitor 26 (e.g., an on-chip storage capacitor), and/or a sleep controller 28, each of which will be described in greater detail below. In an embodiment, the transceiver 10 further comprise a controller 29, for example, an I ² C controller, that is configured to provide or facilitate bidirectional communication, for example, with other dies stacked in a Osensor node (e.g., between the baseband controllers 20 thereof). As will be appreciated by those having ordinary skill in the art, the controller 29 may comprise any variety of electronic processing device(s), memory device(s), input/output (I/O) device(s), and/or other components (e.g., software, firmware, and middleware) required to carry out the functionality of the controller 29 described herein.

Figure 2 depicts a plan view of the transceiver 10 depicted in Figure 1. As illustrated in Figure 2, in an illustrative embodiment, a die comprising the transceiver 10 (i.e., die 30) occupies an area of approximately 2.73mm ² , dominated by the baseband controller 20 (i.e., modem). In the embodiment illustrated in Figure 2, the entire transceiver 10 is designed to operate from just the seven (7) pads 32 on the edge to enable die stacking; the remaining pads are for debugging and may be left open.

The micro-battery 12 of the transceiver 10 is configured to provide operating power to various components of the transceiver 10. In an embodiment, the micro-battery 12 may have a voltage of 3.2-4. IV and one or more components of the transceiver 10, such as, for example, the receiver 14 and the transmitter, and a combined power amplifier and electronic oscillator 34 of the transmitter 18 (e.g., the combined power amplifier and voltage controlled oscillator - PA/VCO 34), in particular, may each have an operating voltage equal or substantially equal to the voltage of the micro-battery 12. In such an instance, and with reference to Figure 1 , to protect the micro-battery 12 from over-current and/or under-voltage conditions, the current limiter 24 may be electrically connected between the micro-battery 12 and one or more of the components operating at the battery voltage. Further, and as illustrated in Figure 1, the internal storage capacitor 26, which, in the illustrated embodiment, is electrically connected to the output of the current limiter 24 and one or more of the components operating at the battery voltage, may be provided to allow those components to draw higher current during, as will be described below, duty- cycled operation.

While certain components of the transceiver 10 may be operated at a voltage that is equal or substantially equal to the voltage of the micro-battery 12, other components may be operated at different voltage levels. For example, to reduce power consumption, certain components or blocks of the transceiver 10, such as, for example, the baseband controller 20, I ² C controller 29, sleep controller 28, clock generator 16, and a pulse generator 36 of the transmitter 18, may operate at a voltage that is below the voltage of the micro-battery 12. For instance, in the embodiment illustrated in Figure 1 , such components may operate from, for example, a 1.2V V _DD - It will be appreciated that while certain voltage levels or magnitudes have been specifically identified above, in other embodiments, voltage levels other than those expressly provided herein may be used, and such embodiments remain within the spirit and scope of the present disclosure.

In any event, in view of the limited resources of the micro-battery 12, one or more (and in an illustrative embodiment all) of the components or blocks of the transceiver 10 may have a low-power sleep state, and may be toggled back and forth between an active state and the sleep state. For example, certain components or blocks, such as, for example, the receiver 14, portions of the transmitter 18 (e.g., the combined power amplifier/oscillator 34 and the pulse generator 36), and the current limiter 24 may be duty- cycled at the bit-level by the baseband controller 20. Other components, such as, for example, the I ² C controller 29, clock generator 16, and baseband controller 20 itself, may be duty-cycled at the packet-level by the sleep controller 28. In such an embodiment, the sleep controller 28 may remain "on" continuously unless and until an under-voltage condition occurs. Further, the sleep controller 28 may be configured to begin and end the wake -up procedure for each packet using, for example, I ² C communication that is known in the art with modified I/Os to eliminate pull-up resistors. Accordingly, it will be appreciated by those having ordinary skill in the art that the baseband controller 20 and sleep controller 28 may each comprise any variety of electronic processing device(s), memory device(s), input/output (I/O) device(s), and/or other components (e.g., software, firmware, and middleware) required to carry out the respective functionality of the baseband controller 20 and sleep controller 28 described herein above and below. It will be further appreciated that while one particular scheme or arrangement for controlling the sleep state of one or more transceiver components has been provided, the present disclosure is not meant to be so limited. Rather, it is contemplated that other suitable schemes or techniques for controlling the sleep state of the components of the transceiver 10 may be utilized, and such embodiments remain within the spirit and scope of the present disclosure. With continued reference to Figure 1, the receiver 14 is configured to receive signals comprised of one or more pulses, such as, for example, pulses in the 9.8GHz range. In an embodiment, the receiver 14 is electrically connected between and to the baseband controller 20 and an antenna 22. As was at least briefly described above, the baseband controller 20 may be configured to exert a measure of control over some or all of the operations or functions of the receiver 14 (e.g., the baseband controller 20 may be configured to duty-cycle the receiver 14). For example, the baseband controller 20 may be configured to control (e.g., toggle) the operational state (e.g., active and sleep states) of some or all of the components of the receiver 14 to reduce the average power supplied to the receiver 14. One reason this may be necessary is that if the receiver 14 was constantly in the active state, the peak power of the micro-battery 12 may not be suitable to support the power drawn by the receiver 14, and thus, the receiver 14 may stop working. By way of illustration, assume the receiver 14 is receiving data at a bit rate of lOkb/s (i.e., 1 bit every ΙΟΟμβ), and that the peak power of the micro-battery 12 is 10μW. If the receiver 14 is active the entire time, the on-chip storage capacitor 26 may fully deplete, and because the peak power of the micro-battery 12 may not be able to support the active power of the receiver 14 (>300μW), the receiver 14 may stop working. In an embodiment, the average power supplied to the receiver 14 may be reduced by duty-cycling the receiver 14 at a frequency that is faster than the bit rate. For example, if the bit rate is lOkb/s such that one (1) bit of data is received every ΙΟΟμβ, the receiver 14 may be active for only βμβ of the ΙΟΟμβ bit time, and off or in a sleep state for the remaining 94μβ every bit cycle. In such an embodiment, the receiver 14 may be configured to align those βμβ of active-time around the time the bit arrives so no data is lost. Between βμβ intervals, only a portion of the receiver 14 is powered down or put into the sleep state. All of the biasing circuitry remains active with low power, and only the higher power RF circuits are powered down. It will be appreciated that the example above and the various values corresponding thereto has been provided as one non-limiting example, and that embodiments wherein the receiver receives data at a different bit rate and/or the micro-battery has a different peak power, remain within the spirit and scope of the present disclosure. As illustrated in Figure 1, the antenna 22 to which the receiver 14 is connected may be a dedicated antenna (i.e., antenna 22 ₂ ) or, alternatively, an antenna that is common to both the receiver 14 and transmitter 18. In an embodiment, the antenna 22 may comprise an integrated or on-chip antenna (i.e., the antenna is disposed on the same chip as the receiver 14 and other components of the transceiver 10); while in another embodiment, the antenna 22 may comprise an off-chip antenna to which the receiver 14 is configured to be electrically connected via, for example, one or more electrical conductors. For purposes of illustration, the description below will be with respect to the antenna comprising the on-chip antenna 22 ₂ depicted in Figure 1, though the present disclosure is not intended to be so limited. In the illustrated embodiment, the antenna 22 ₂ may comprise a dedicated monopole antenna, for example, a 2mm monopole antenna. It will be appreciated, however, that present disclosure is not intended to be limited to any particular type or size of antenna and it will be appreciated that any; rather, suitable antennas of a different size(s) and or type(s) may also be utilized.

As shown in Figures 3a-3d, which depict illustrative embodiments of the receiver 14 and various components thereof, and which are collectively referred to herein as Figure 3, the receiver 14 may have a non-coherent, energy-detection architecture. In such an embodiment, the architecture may comprise four (4) RF gain stages 38 (i.e., 38i-38 ₄ ) that amplify pulses received by the receiver 14 before down-converting them with a squaring mixer 40 located downstream from the gain stages 38. More particularly, the signal, or the pulses thereof, may be self-mixed using a common emitter amplifier with a resistive load as the squaring mixer. Once the pulses are down-converted by the mixer 40, the signal passes through a downstream baseband gain stage 42 before the signal path is split into two paths. Along one of the two paths, the pulses are passed directly to a downstream comparator 44. Along the other path, the signal is filtered by, for example, a low-pass filter (LPF) 46 to provide an auto-zeroed, DC-compensated reference level that is then passed to the comparator 44 for use in performing one or more comparisons. As illustrated in Figure 3 a, a reset signal (RST1) enables fast settling of the low-pass filter 46 for fast receiver turn-on. Finally, the comparator 44— which may comprise a continuous- time latching comparator with controllable hysteresis — is configured to digitize the incoming pulses. In an illustrative embodiment, bipolar junction transistors 48 may be used for higher RF gain efficiency (g _m /Ic), while the RF gain stages may be stacked in order to reuse current and better utilize the supply voltage. Additionally, in an illustrative embodiment, the RF center frequency may be tunable via four (4) binary-weighted control bits. It will be appreciated that while the receiver 14 has only been described with respect to the particular architecture described above and illustrated in Figure 3, it is contemplated that other suitable receiver architectures may be utilized. Accordingly, the present disclosure is not intended to be limited solely the receiver architecture described herein or any other particular architecture; rather embodiments of the transceiver 10 wherein the receiver 14 has an architecture other than that described herein remain within the spirit and scope of the present disclosure.

As briefly described above, in an exemplary embodiment, the transceiver 10 of the present disclosure comprises the clock generator 16 to perform a clocking function for the transceiver 10 and allow for the synchronization of the operation of various components of the transceiver 10. As illustrated in Figure 1, the clock generator 16 is electrically connected to the baseband controller 20, and the baseband controller 20 is configured to exert a measure of control over the operation of the clock generator 16.1 I ⁿ order to reduce both power consumption and area of the transceiver 10, as compared to conventional transceivers that typically utilize crystals to perform a clocking function, in an exemplary embodiment, the transceiver 10 of the present disclosure includes a relaxation oscillator rather than a crystal.

In an embodiment, the relaxation oscillator comprises a temperature-compensated relaxation oscillator. More particularly, and with reference to Figures 4a and Figures 8a and 8b, the transceiver 10 may comprise a relaxation oscillator 48 with a modified RC network 50 and a single-ended hysteretic comparator 52 (e.g., inverting comparator) for on-chip clocking. The oscillator 48 may further include an output buffer electrically connected to and downstream of the comparator 52 that is operative to drive the clock output. In the illustrated embodiments, the RC network 50 is electrically connected in circuit (e.g., serially) with, and is disposed upstream of, the comparator 52. In an illustrative embodiment, the RC network 50 comprises a resistor Rl electrically connected in circuit (e.g., series) with the series combination of a resistor R2 and a capacitor C. More particularly, the first resistor Rl may be electrically connected in series with the capacitor C, which, in turn may be electrically connected in series with the second resistor R2. The second resistor R2 may be electrically connected between the capacitor C and ground. In the embodiment illustrated in FIG. 4a, the resistor Rl may also be connected in circuit with another capacitor (e.g., a variable capacitor) VC, the circuit combination of the resistor Rl and capacitor VC being connected in circuit with the combination of the resistor R2 and capacitor C, as shown.

The comparator 52 has switching thresholds of V _H and V _L , which define the charging and discharging levels of the RC network 50. When the output of the comparator 52 is logic high, the capacitor C of the RC network 50 is being charged until the voltage becomes larger than V _H - Then the output of the comparator 52 flips to the logic low state and discharges the capacitor C until the voltage reaches V _L . Oscillation is achieved through back and forth charging and discharging processes, and the frequency is determined by the resistance and capacitance of the RC network 50. Accordingly, it will be appreciated that the particular values of the components of the RC network 50 may be chosen to take into account factors such as the frequency of oscillation (i.e., target reference frequency) and temperature stability. For purposes of illustration, in a non- limiting example the resistor Rl is a P+ polysilicon 24ΚΩ resistor, the resistor R2 is an N+ doped diffusion resistor of 28ΚΩ, and the capacitor C is a MIM capacitor; and the temperature coefficients for these components may be as follows: resistor Rl - 77ppm/°C; resistor R2 - 1810 ppm/°C; and 15ppm/°C.

The arrangement of the RC network 50 illustrated in Figure 4a serves to add an additional zero in the transfer function from the resistor R2 of the RC network 50 over conventional relaxation oscillators, thereby providing an additional degree-of-freedom for temperature compensation. More particularly, with the addition of the resistor R2, the transfer function is (s) =— — _s ] _10wn Figure 4b, as temperature increases, l ÷ s{R ₁ + R _J )C

the initial step at time t=0 from the zero increases, but the time constant of the exponential decay also increases, offsetting the step and resulting in a constant time, T, to trigger the switching threshold, V _H - The same trend applies as temperature decreases in that the initial step decreases while the time constant also decreases so that the overall period remains unchanged. Unlike conventional approaches that decrease temperature dependency with a combination of resistors with positive and negative temperature coefficients, the RC network 50 provides more degrees of freedom on resistor selections (i.e., the temperature coefficients of the resistors do not need to be opposite -polarity). In an embodiment, Rl may be chosen to have a smaller temperature coefficient and R2 to have a larger temperature coefficient. By tuning the combination of Rl, R2, C, V _H , V _L , the period of the RC network 50 may remain fairly constant over a wide temperature range.

As shown in Figures 4c and 8b, the comparator 52 may comprise stacked inverters with hysteresis levels set by two resistors, R3 and R4 (i.e., the resistors R3, R4 set the hysteresis levels of the comparator 52 to be a certain, known, and temperature independent fraction of the power supply voltage. This works in conjunction with the RC network 50 to provide the target frequency and temperature independence of the oscillator 48). Stacking field effect transistors (i.e., transistors 56) in the manner illustrated serves to reduce leakage power while the oscillator 48 is asleep, and a capacitor bank (e.g., a 5-bit capacitor bank such as that shown in Figure 8b) may be included with the oscillator 48 for one-time process calibration of frequency. In an embodiment, the comparator 52 comprises three (3) stacked inverters along with the resistors R3, R4. The first two stacked inverters with resistors R3, R4 serve as a high gain amplifier with resistive feedback, providing a sharp transition for the step response and the proper value of V _H and V _L . With particular reference to the embodiment illustrated in Figure 8b, assume for purposes of example only that the output of the hysteresis comparator is at ground and the input of the last inverter is V _DD - In such an instance, the voltage V _T between R3 and R4 can be described in terms of comparator input Vi _n as Vt = Vin + (——— )(Y _DD — V n).

R ₃ + R ₄

When V _T is equal to V _DD /2, which is the switching threshold of the stacked inverters, VL can be solved as Vin = V _L = ^^^ ³ W _DD . Similarly, when the comparator output is

V _DD , V _t then becomes Vt = (——— )Vin . Finally, V _H can be solved by applying

R _^ + R 4,

R + R

V _t =Vo _D 2 such that Vin = V _H = ( W _DI In an embodiment, the value of the resistor R3 is twice the value of the resistor R4, so that V _H is around 3/4V _DD and V _L is around 1/4V _DD regardless of the supply voltage. Such an arrangement provides the oscillator 48 immunity to V _DD variation. The last inverter flips the polarity for charging and discharging the RC network 50 to create the oscillation.

As shown in Figure 4d, in one implementation provided for illustrative purposes only, the oscillator 48 has a measured variation of 1% over a range of 0°C to 50°C that allows the transmitter 18 and receiver 14 of the transceiver 10 to be heavily duty-cycled between pulses by, for example, the baseband controller 20, in order to give the on-chip storage capacitor 26 time to fully recharge and also sufficient accuracy to maintain network synchronization.

It will be appreciated that while a particular embodiment of the relaxation oscillator 48, RC network 50, and comparator 52 is described in detail above, the present disclosure is not meant to be limited to such an embodiment. Rather, it is contemplated that other arrangements or constructions of the oscillator 48, RC network 50, and/or comparator 52 that are suitable for the purposes of this disclosure may be utilized, and such other arrangements/constructions remain within the spirit and scope of the present disclosure.

Turning back to the illustrative embodiment of the transceiver 10 illustrated in Figure 1, as briefly described above, the transmitter 18 of the transceiver 10 may comprise a combined power amplifier/voltage controlled oscillator 34 and a pulse generator 36. As with the receiver 14 described above, the transmitter 18 is electrically connected between and to the baseband controller 20 and an antenna 22, and the baseband controller 20 may be configured to exert a measure of control over some or all of the operations or functions of the transmitter 18. For example, the baseband controller 20 may exert a measure of control over the pulse generator 36 of the transmitter 18 to control the content and/or format of electronic signals generated by the pulse generator 36, as well as controlling when the pulse generator 36 generates those electronic signals, to cite a few possibilities. As illustrated in Figure 1 , the antenna 22 to which the transmitter 18 is connected may be a dedicated antenna (i.e., the antenna 22i) or, alternatively, an antenna that is common to both the transmitter 18 and the receiver 14. In an embodiment, the antenna 22 may comprise an integrated or on-chip antenna (i.e., the antenna is disposed on the same chip as the transmitter 18 and other components of the transceiver 10); while in another embodiment, the antenna 22 may comprise an off-chip antenna to which the transmitter 18 may be electrically connected via, for example, one or more electrical conductors. For purposes of illustration, the description below will be with respect to the antenna comprising the on-chip antenna 221 depicted in Figure 1, though the present disclosure is not intended to be so limited. In the illustrated embodiment, the antenna 221 may comprise a dedicated monopole antenna, for example, a 2mm monopole antenna. It will be appreciated, however, that the present disclosure is not intended to be limited to any particular type or size of antenna, and that suitable antennas of different size(s) and/or type(s) may also be utilized.

Figures 5a-5d depict illustrative examples of the composition and operational characteristics of illustrative embodiments of the transmitter 18 and various components thereof, and are referred to herein collectively as Figure 5. In an embodiment, pulses transmitted by the transmitter 18 are generated by the combined power amplifier/voltage controlled oscillator 34 shown in Figure 1 and in the illustration of the portion of the transmitter in Figure 5. In an embodiment such as that illustrated in Figure 5, an LC cross- coupled topology is utilized for fast turn-on time, and a transformer-coupled scheme (the transformer being identified as reference numeral 54 in Figures 5a and 5b) boosts the signal swing delivered to the antenna 221. The area of the internal matching network between the voltage controlled oscillator and the power amplifier is reduced by direct transformer coupling.

In an embodiment, the transmitter 18 is enabled by the baseband controller 20 through the digital pulse generator 36 of the transmitter 18. In an illustrative embodiment, the pulse generator 36 has a 4-bit tuning range of 1.2ns to 6.0ns, and when enabled, the transmitter 18 is operable to deliver a 700m V _pp pulse to a 50Ω load, for example. Further, the center frequency of the transmitted signal may be tuned using, for example, a capacitor bank (e.g., a 7-bit capacitor bank). In the embodiment illustrated in Figure 5, the cross- coupled capacitors control the oscillating signal magnitude on the base terminals and are designed so that voltage swing never exceeds the breakdown voltage of the bipolar junction transistors 58 _ls 58 ₂ of the transmitter 18. In an illustrative embodiment, while the transmitter 18 is generating a pulse, the internal power supply voltage on the storage capacitor 26 may drop rapidly (e.g., approximately 200mV in a few ns, in an embodiment) due to protection provided by the current limiter 24. Between pulses, the storage capacitor 26 recharges. The tail device is large such that it enters the saturation region fast once the transmitter enable signal (TX EN in Figure 5) is high. In an illustrated embodiment, a 60mA current is drawn from the voltage controlled oscillator when it begins oscillating; however, due to the high on-to-off current ratio of the bipolar junction transistors 58 (>10 ⁸ ), the sleep power of the transmitter 18 is 170pW. Transmitter 18 has been described with respect to the architecture disclosed above and illustrated in Figures 1 and 5, it is contemplated that other suitable transmitter architectures may be utilized. Accordingly, the present disclosure is not intended to be limited solely the illustrative transmitter architecture described herein or any other particular architecture; rather embodiments of the transceiver 10 wherein the transmitter 18 has an architecture other than that described herein remain within the spirit and scope of the present disclosure.

With reference to Figures 6a-6d and 7, and for purpose of illustration only, a description of the performance of one particular, non-limiting implementation of the transceiver 10 will now be provided. In this particular implementation, the transceiver 10 was fabricated in 0.18μιη BiCMOS with MIM capacitors, and the load to which the transmitter 18 delivers a pulse is a 50Ω load. The power spectrum density of the transmitter 18 is shown in Figure 6a. In this implementation, the transmitter 18 has a tuning range of 9-12GHz, and when tuned to 9.8GHz, the transmitter 18 has a peak output power of 0.9dBm and satisfies the FCC mask. At a 30kb/s data rate, the average power of the transmitter 18 is only 22^W at 3.6V. As shown in Figure 6b, the magnitude response of the receiver 14 is tuned to 9.8GHz. At a 10 ^"3 bit error rate, the receiver 14 has a sensitivity of about -67dBm (as shown in Figure 6c) and a 30kb/s data rate while consuming an average of 37μW from a 3.6V supply with 6% duty-cycling. The baseband controller 20 (i.e., modem) uses pulse position modulation ("PPM") and includes early/late tracking of pulses for each PPM window to maintain synchronization. At a 3MHz oscillation frequency of the relaxation oscillator 48, the entire baseband system consumes 269μW, of which the clock consumes 12^W. As provided in Figure 6d, the current limiter 24 has a 6-38 uA tuning range, which is sufficient for sustained operation of the transmitter 18 and the receiver 14. The current limiter 24 consumes only 223nW, yielding a 94% efficiency. Each block of the transceiver 10 consumes <lnW while asleep by carefully including thick-oxide headers on all blocks, making this system ideal for heavily duty-cycled cubic-mm sensor nodes. A complete performance summary of illustrative transceiver implementation described over is provided in Figure 7. The above-described performance relates to one particular implementation of the transceiver 10 delivering a pulse(s) to a particular load, and the present disclosure is not intended to be limited to such an implementation. Rather, it is contemplated that the transceiver 10 may be implemented in a number of suitable ways other than that corresponding to the performance characteristics described above, and each such implementation remains within the spirit and scope of the present disclosure.

It is to be understood that the foregoing description is of one or more embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to the disclosed embodiment(s) and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art.

As used in this specification and claims, the terms "e.g.," "for example," "for instance," "such as," and "like," and the verbs "comprising," "having," "including," and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that the listing is not to be considered as excluding other, additional components or items. Further, the term "electrically connected" and the variations thereof is intended to encompass both wireless electrical connections and electrical connections made via one or more wires, cables, or conductors (wired connections). Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.