TRANSCEIVERS

BACKGROUND

[0001] Within power amplifier low-noise amplifier (PALNA) applications the power handling capability of a transistor switch can be increased by stacking more devices in series in shunt operation or increasing the periphery in series operation. However both of these options either increase the losses or decrease the isolation of the switch network. Additionally, especially at millimeter-wave frequencies, series switch devices add loss to the signal path in on-state and suffer from capacitive feedthrough in the off state thus decreasing isolation. Therefore, shunt switches are typically utilized at millimeter- wave frequencies. However, current millimeter- wave switches suffer from poor linearity. Currently switch networks are limiting the linearity of MMIC PALNA systems.

SUMMARY OF THE INVENTION

[0002] The present invention provides for improved linearity in a compact switch while also providing low-insertion loss, especially useful for PALNA systems. Within at least some solutions according to the present invention the linearity of the switch is improved by at least 6-dB which is a significant achievement when compared to state-of- the-art. The present invention provides for switches which may be especially useful within millimeter-wave integrated (MMIC) power amplifier low-noise amplifier (PALNA) systems.

[0003] In at least some instances the present invention allows for the quarter-wave power distribution network to be replaced by a transformer based SPST or SPMT switch thus allowing for a decreased footprint and inherent ESD protection.

[0004] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims. [0005] According to a first aspect of the present invention, there is provided a Single-Pole Single-Throw (SPST) or Single-Pole Multi-Throw (SPMT) transformer based switch configured to be connected to a power amplifier (PA) and/or Low Noise Amplifier (LNA), said transformer based switch comprising:

an input single pole port, and

a circuit comprising:

a transformer having a primary and secondary winding, wherein one end of the primary winding is connected to the input single pole port and the other end is configured to be connected to a ground potential,

at least one switch connected at one end to an end of the secondary winding of the transformer, the other end of the at least one switch being either:

connected to a negative end of the secondary winding, or configured to be connected to a ground potential,

an output port comprising a first output port connected to one end of the secondary winding of the transformer and a second output port connected to the other end of the secondary winding of the transformer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIGURES 1A and 1B illustrate transformer based switches according to certain embodiments of the present invention.

[0007] FIGURE 2A illustrates a transformer based switch adapted for use with a power amplifier according to an embodiment of the present invention.

[000S] FIGURE 2B illustrates a transformer based switch having both a portion adapted for use with a power amplifier and a portion adapted for use with a low noise amplifier according to certain embodiments of the present invention.

[0009] FIGURE 3 shows a transformer based switch having two circuits, one adapted for use with a power amplifier and one adapted for use with a low noise amplifier according to at least some embodiments of the present invention. [0010] FIGURE 4A illustrates a single-pole dual-throw (SPDT) transformer based switch for PALNA applications in accordance with at least some embodiments of the present invention.

[0011] FIGURE 4B illustrates the same SPDT transformer based switch having additional features according to certain embodiments of the present invention.

[0012] FIGURE 5 illustrates a transformer based Single-Pole 4-Throw (SP4T) switch in accordance with at least some embodiments of the present invention.

[0013] FIGURE 6 illustrates a transformer based Single-Pole 4-Throw (SP4T) switch for PALNA applications in accordance with at least some embodiments of the present invention.

EMBODIMENTS

[0014] Transformer based switches for PALNA applications according to the present invention provide not only lower insertion loss for both the PA and LNA paths and lower power consumption when the PA path is active. Additionally, the transformer based switches provide for a smaller component than traditional quarter wavelength distribution networks. Furthermore, differential operation as allowed by at least some embodiments of the present invention improves the linearity of the switch and any connected power amplifier.

[0015] As discussed above, at least some embodiments of the present invention provide for as much as a 3 dB improvement when compared with power combining techniques previously employed in PALNA applications. Up to a 6 dB improvement is possible within certain embodiments as the transformer provides for a low-impedance load as seen by the PALNA components.

[0016] FIGURES 1A and 1B illustrate Single-Pole Multi-Throw (SPMT) and Single-Pole Single-Throw (SPST) transformer based switches 100 respectively. These switches are configured to be connected to a power amplifier (PA) and/or Low Noise Amplifier (LNA). As shown the transformer based switch 100 comprises an input single pole port 130, and a circuit 102. The circuit 102 having a transformer 110, at least one switch 120, 124, and an output port 131. The transformer 110 of figures 1A and 1B has a primary winding 112 and secondary winding 114 winding, wherein one end of the primary winding 112 is connected to the input single pole port 130 and the other end is configured to be connected to a ground potential. As illustrated, at least one end of the switch 120 is connected to an end of the secondary winding 114 of the transformer 110. However, the switch 120 of the circuit may be configured in one of two ways.

[0017] As illustrated within figure 1B, the other end of the switch 120 may be connected to the other end of the secondary winding 114. Alternatively, as illustrated within figure 1 A, the other end of the switch 120 may be configured to be connected to a ground potential. Within both alternatives the circuit also has an output port 131 comprising a first output port 132 connected to one end of the secondary winding 114 of the transformer 110 and a second output port 133 connected to the other end of the secondary winding 114 of the transformer.

[0018] Within certain embodiments of the transformer based switches according to the present invention the transformer is a linear transformer, preferably a center tap transformer, more preferably a center tap transformer having a center tap configured to be connected to a ground potential, preferably an alternating current (AC) ground potential.

[0019] In embodiments of the present invention adapted to provide a transformer based switch for a power amplifier, the impedance transformation allows for easier switch design as well as selection and optimization of the power amplifier. Power transformation as provided by at least some embodiments of the present invention provides for an impedance at the secondary winding of the transformer half that which is provided at the input port.

[0020] As illustrated within FIGURE 2A, according to at least some embodiments of the present invention the circuit of the transformer based switch 200 may comprise a PA circuit 202. Within certain embodiments this circuit may be used, for example, within a transmitter circuit, such as a transmitter circuit employing a power amplifier. As within the embodiments illustrated within figures 1A and 1B, once again there is a single pole input port 230, a transformer 210 having primary 212 and secondary 214 windings and an output port 231 having a first output port 232 and a second output port 233. However, within the transformer based switch of figure 2A, there at two switches, one acting as a positive port switch 220, and the other as a negative port switch 224. Within at least some embodiments there are additional positive and negative port switches. [0021] Within the embodiment shown in figure 2A there is at least one positive port switch 220 connected at one end to a positive end of the secondary winding 214 of the transformer 210, the other end of the switch being configured to be connected to a ground potential. On the opposite side of the circuit there is at least one negative port switch 224 connected at one end to a negative end of the secondary winding 214 of the transformer 210, the other end of the switch being configured to be connected to a ground potential.

[0022] As shown within figure 2A at least some transformer based switches according to the present invention further comprise a power amplifier 290 connected to the output port.

[0023] FIGURE 2B shows the transformer based switch of figure 2A further comprising an LNA circuit 203 according to an embodiment of the present invention. The LNA circuit comprises a quarter wavelength impedance 240 connected at one end to the input single pole port 230, an LNA output port 235 connected to the other end of the quarter wavelength impedance 240, and at least one LNA circuit switch 220 connected at one end to the LNA output port 235, the other end being configured to be connected to a ground potential.

[0024] As shown within figure 2B at least some transformer based switches according to the present invention further comprise a low noise amplifier 291 connected to the LNA output port.

[0025] A transformer based switch according to the embodiment of figure 2B could find use, for example, in a PALNA transceiver application. Within such an application the PA circuit 202 would act as the transmitter portion and LNA circuit 203 would act as the receiver portion.

[0026] LIGURE 3 illustrates a transformer based switch similar to that of figure 2B, only within the embodiment illustrated within figure 3; the LNA circuit is slightly more robust. Once again there is a single pole input port 330, a transformer 310 having primary 312 and secondary 314 windings and an output port 331 having a first output port 332 and a second output port 333. As within figure 2 A, the PA circuit 302 comprises two switches, one acting as a positive port switch 320, and the other as a negative port switch 324. Within at least some embodiments there are additional positive and negative port switches. A power amplifier 390 is illustrated where it would be connected to the PA circuit. [0027] Within figure 3 the LNA circuit 303 comprises a second transformer 315 having a primary 317 and secondary 319 winding, wherein one end of the primary winding 317 of the second transformer 315 is connected to the input single pole port 330 and the other end is configured to be connected to a ground potential. The LNA circuit now has an LNA output port 335 comprising a first port 336 connected to one end of the secondary winding 319 of the second transformer 315 and a second port 337 connected to the other end of the secondary winding 319 of the second transformer 315. Finally there is an LNA circuit switch 320 connected at one end to first port 336 of the LNA output port 335 the other end being connected to the second port 337 of the LNA output port 335. Once again a low noise amplifier 391 is illustrated where it would be connected to the output port.

[0028] Within at least some transformer based switches according to the present invention the switches can be transistors, for example, bipolar transistors, each transistor having a base connected to a switch port, said switch ports being configured to be connected to a switching potential. At least two embodiments having transistors according to the present invention are illustrated within figures 4 A and 4B.

[0029] FIGURE 4A shows a Single-Pole Multi-Throw (SPMT) transformer based switch 400 for use in Power Amplifier and Low Noise Amplifier (PALNA) applications in accordance with at least some embodiments of the present invention. Such a switch may be employed, for example, in a transceiver. As shown, the transformer based switch 400 comprises: an input single pole port 430, a Power Amplifier (PA) circuit 402 and a Low Noise Amplifier (LNA) circuit 403. The PA circuit 402 comprises a first transformer 410, transistors 420, 424 and ports 432, 434, 437. The first transformer 410 of the PA circuit 402 has a primary 412 and secondary 414 winding and as shown the primary winding 412 is connected at one point to the input single pole port 430 and at another point the primary winding 412 is configured to be connected to a ground potential illustrated within the figures as a ground symbol.

[0030] There are at least two transistors employed within the PA circuit 402 of the transformer based switch 400, at least one positive port transistor 420 and at least one negative port transistor 424. The at least one positive port transistor 420 is arranged such that its emitter is connected to a positive end of the secondary winding 414 of the first transformer 410, its collector is configured to be connected to a ground potential and its base is connected to a first switch port 432, said first switch port 432 being configured to be connected to a switching potential. The at least one negative port transistor 424 is arranged such that its emitter is connected to a negative end of the secondary winding 414 of the first transformer 410, its collector is configured to be connected to a ground potential and its base is connected to a second switch port 434, said second switch port 434 being configured to be connected to a switching potential.

[0031] As also illustrated within Figure 4A, the PA circuit has a first output port 437 comprising a positive port connected to the positive end of the secondary winding 414 of the first transformer 410 and a negative port connected to the negative end of the secondary winding 414 of the first transformer 410. As shown within figure 4 A, at least some embodiments of the present invention comprise a power amplifier connected to the first output port 437 of the transformer based switch 400.

[0032] Illustrated at the bottom of figure 4A is the Low Noise Amplifier (LNA) circuit 403. This LNA circuit 403 comprises a second transformer 415, a transistor 421 and an output port 439. As illustrated the second transformer 415 has a primary 417 and secondary 419 winding. The primary winding 417 of the second transformer 415 is connected at one point to the input single pole port 430 and at another point it is configured to be connected to a ground potential. The transistor 421 of the LNA circuit 403 is configured such that its emitter is connected to a positive end of the secondary winding 419 of the second transformer 415, its collector is connected to a negative end of the secondary winding 419 and its base is connected to a third switch port 435, said third switch port 435 being configured to be connected to a switching potential.

[0033] As discussed herein the negative and positive ends of the transformer windings may have a variety of meanings. As illustrated within the figures these ends may be opposing terminal ends of the windings. These negative and positive ends could also refer to locations along a transformer winding divided by taps, for example the negative end could be at a terminal end of the winding and the positive at a tapped location along the winding. For a further example the negative and positive ends could be at two separate tapped locations along the winding. Similarly primary and secondary windings of transformers may sometimes be an arbitrary label and may refer to an entire winding on one side of a transformer or a portion of a winding on one side of a transformer.

[0034] As further illustrated, the LNA circuit’s 403 output port forms a second output port 439 of the transformer based switch 400. The second output port 439 comprising a positive port connected to the positive end of the secondary winding 419 of the second transformer 415 and a negative port connected to the negative end of the secondary winding 419 of the second transformer 415. As also shown in figure 4 A, at least some embodiments of the present invention comprise a low noise amplifier 491 connected to the second output port 439 of the transformer based switch 400.

[0035] In at least some embodiments of the present invention the first and second switch ports 432, 434 are configured to be connected to the same potential. For example, they may be conductively connected using a trace. In other embodiments the first and second switch port 432, 434 are configured to be connected to different potentials. For example they could be labeled differently and/or conductively isolated on a printed circuit board.

[0036] FIGURE 4B illustrates the same SPDT transformer based switch 400 as discussed above with regards to figure 4A, save for the fact that the switch 400 of figure 4B illustrates additional features according to certain embodiments of the present invention. For example, at least some transformer based switches according to the present invention employ impedances 440, 442 connected between the base of transistors and their respective switch ports, preferably impedances which are selected such that they are quarter wavelength impedances. While not illustrated within Figure 4B, an impedance, such as a quarter wavelength impedance, is also employed between the base of the transistor 421 and switch port 435 of the LNA circuit 403 in at least some embodiments of the present invention.

[0037] Certain embodiments employ capacitors 450, 452, 455 configured to be connected between each of the switch ports and a ground potential. Such capacitors are sometimes referred to as DC blocking capacitors.

[0038] Within at least some embodiments the transformers 410, 415 are linear transformers. Certain embodiments employ center tap transformers and in some embodiments those center tap transformers have a center tap configured to be connected to a ground potential.

[0039] Within at least some embodiments of the present invention the PA and LNA circuits are configured to operate at different frequencies. [0040] Within figures 1 through 4 the outputs are illustrated in a differential fashion, that is, they are designated as positive and negative ports. However, at least some switches according to the present invention may be operated in a non-differential fashion such that each output port is configured to provide an independent output.

[0041] As shown previously, in according with at least some embodiments of the present invention, the PA circuit 402 of the transformer based switch 400 of figures 4A and 4B may also be employed independently. This may be useful in situations where only a transmitter is desired or multiple transmitters are a variety of frequencies are desired.

[0042] FIGURE 5 illustrates a transformer based Single-Pole 4-Throw (SP4T) switch 500 in accordance with at least some embodiments of the present invention. The transformer based switch of figure 5 would find use across a variety of PALNA applications. As illustrated within figure 5 there are two substantially identical circuits 502, 503. Each circuit comprises a transformer 512 and 515 having a primary 512, 517 and secondary 514, 519 winding. The primary windings 512, 517 are connected at one end to the single pole input port 530 and are configured to be connected to a ground potential at the other end. The secondary windings 514, 519 are connected at one end to a first output port 533, 537 and at the other to a second output port 535, 539. Connected to each end of the secondary winding 514, 519 is a switch 520, 521, 524, 525 connected at one end to the secondary winding, the other end being configured to be connected to a ground potential.

[0043] FIGURE 6 illustrates a transformer based Single-Pole 4-Throw (SP4T) switch 600 for PALNA applications in accordance with at least some embodiments of the present invention. As seen in the figure, two transformer-based SPDT switches (602, 604) are employed to form a SP4T switch. Which may be employed, for example, in a transceiver, such as a transceiver configured to operate on four different frequencies, for instance a cellular phone transceiver.

[0044] Once again the transformer based switch 600 comprises a single pole input port 630 connected to windings 612, 617 two transformers 610, 615. Opposite the connection to the input port 630 these windings 612, 617 are grounded. Starting at the secondary windings 614, 619 of each transformer 610, 615 are mirrored SPDT switches 602, 604. [0045] The transformer based switches 602, 604 each comprise a transformer 610, 615, an output port 633, 635 and 637, 639, switch ports 632, 634, 636, 638 and transistors 620 - 627. Within each of the SPDT switches 602, 604 at least one of the transistors acts as a positive port transistor 620, 621 having: an emitter connected to a positive end of the respective secondary winding 614, 619 of the transformer, a collector configured to be connected to a ground potential and a base connected to a respective first and third switch port 632, 636, said first switch ports 632, 636 being configured to be connected to a switching potential. Additionally each SPDT switch 602, 604 has at least one negative port transistor 624, 625 having: an emitter connected to a negative end of the respective secondary winding 614, 619 of the transformer, a collector configured to be connected to a ground potential and a base connected to a second and fourth switch port 634, 638 respectively, said second and fourth switch ports 634, 638 being configured to be connected to a switching potential.

[0046] As further illustrated, each SPDT switch 602, 604 has an output port comprising a positive port 633, 637 connected to the positive end of the respective secondary winding 614, 619 and a negative port 635, 639 connected to the negative end of the respective secondary winding 614, 619.

[0047] As shown in figure 6, certain embodiments according to the present invention employ resistors 641, 643, 645, 647 at the base of the transistors in place of quarter-wave short circuited stubs.

[0048] Certain SP4T transformer based switches according to the present invention employ a pair of parallel transistors per side of the secondary winding. These pairs are illustrated in figure 6 as 620 and 622, 624 and 626, 621 and 623, and 625 and 627.

[0049] Figures 4A, 4B and 6 show embodiments of the present invention wherein the switches are implemented as bipolar junction transistors (BJT); however a variety of different switch implementations may be employed depending on the application. For example, switches in at least some embodiments are implemented using transistors, diodes or MEMS (Micro Electro Mechanical Systems). Embodiments employing transistor switches may employ BJTs or field-effect transistors (FET), including metal-oxide- semiconductor field-effect transistors (MOSFET), metal-semiconductor field-effect transistors (MESFET) and high-electron-mobility transistors (HEMT). At least some embodiments of the present invention, especially those employing the asymmetrical LNA and PA circuits of figure 4A, may employ MESFETs or HEMTs.

[0050] To ease in illustration, the embodiments of figures 4B and 6 show only a pair of parallel transistors. However, depending on the type of switch employed and the design frequency of the circuit three, four or another plurality of switches may be employed in the switch implementation.

[0051] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0052] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases“in one embodiment” or“in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment.

[0053] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0054] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0055] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[0056] The verbs“to comprise” and“to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", i.e. a singular form, throughout this document does not exclude a plurality.

ACRONYMS LIST

AC Alternating Current

BJT Bipolar Junction Transistor

FET Field-Effect Transistor

HEMT High-E lectron-Mobility T ransistor

LNA Low Noise Amplifier

MEMS Micro Electro Mechanical Systems

MESFET Metal-Semiconductor Field-Effect Transistor

MOSFET Metal-Oxide-Semiconductor Field-Effect Transistor

PA Power Amplifier

SPDT Single-Pole Dual-Throw

SPMT Single-Pole Multi-Throw

SPST Single-Pole Single-Throw

SP4T Single-Pole Four-Throw

REFERENCE SIGNS LIST transformer based switch

circuit

transformer

primary winding of the transformer secondary winding of the transformer

, 124 switch

single pole input port

output port

first output port

second output port transformer based switch

Power Amplifier (PA) circuit

Low Noise Amplifier (LNA) circuit transformer

primary winding of the transformer secondary winding of the transformer positive port switch

LNA circuit switch

negative port switch

single pole input port

output port

first output port

second output port

LNA output port

power amplifier

low noise amplifier transformer based switch

Power Amplifier (PA) circuit

Low Noise Amplifier (LNA) circuit transformer

primary winding of the transformer secondary winding of the transformer positive port switch

LNA circuit switch

negative port switch

single pole input port

output port

first output port

second output port

LNA output port

first port

second port

power amplifier

low noise amplifier transformer based switch

Power Amplifier (PA) circuit

Low Noise Amplifier (LNA) circuit transformer

primary winding of the transformer secondary winding of the transformer second transformer

primary winding of the second transformer secondary winding of the second transformer, 422 positive port transistor

, 423 LNA circuit transistor

, 426 negative port transistor

single pole input port

first switch port

second switch port

third switch port

first output port

second output port

, 442 impedance

, 452 capacitor capacitor

power amplifier

low noise amplifier transformer based switch

, 503 circuits

, 515 transformer

, 517 primary winding of the transformer, 519 secondary winding of the transformer, 521 switch

, 525 switch

single pole input port

, 537 first output port

, 539 second output port transformer based switch

, 404 transformer based SPDT switch, 415 transformer

, 417 primary winding

, 419 secondary winding

, 422 positive port transistor

, 423 positive port transistor

, 426 negative port transistor

, 427 negative port transistor

single pole input port

first switch port

second switch port

third switch port

fourth switch port

, 637 positive output port

, 639 negative output port

, 643 resistance

, 647 resistance