U.S. patent application number 16/725059 was filed with the patent office on 2020-04-30 for complementary metal oxide semiconductor differential antenna transmit-receive switches with power combining circuitry for orthog.
The applicant listed for this patent is Skyworks Solutions, Inc.. Invention is credited to Oleksandr Gorbachov, Lisette L. Zhang.
Application Number | 20200136670 16/725059 |
Document ID | / |
Family ID | 55167547 |
Filed Date | 2020-04-30 |
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United States Patent
Application |
20200136670 |
Kind Code |
A1 |
Zhang; Lisette L. ; et
al. |
April 30, 2020 |
Complementary Metal Oxide Semiconductor Differential Antenna
Transmit-Receive Switches with Power Combining Circuitry for
Orthogonal Frequency-Division Multiplexing Systems
Abstract
A radio frequency (RF) transmit-receive switch has an antenna
port, first and second transmit differential ports and first and
second receive differential ports. Transmit transistor switches are
connected to the transmit differential ports. Primary and secondary
windings of a transmit coupled inductor transformer are connected
to the transmit transistor switches. Receive transistor switches
are connected to the receive differential ports. Primary and
secondary windings of a receive coupled inductor transformer are
connected to the receive transistor switches. A first balun
inductive winding is connected to the antenna port, and a second
balun inductive winding is connected to the transistor
switches.
Inventors: |
Zhang; Lisette L.; (Irvine,
CA) ; Gorbachov; Oleksandr; (Irvine, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Skyworks Solutions, Inc. |
Wobum |
MA |
US |
|
|
Family ID: |
55167547 |
Appl. No.: |
16/725059 |
Filed: |
December 23, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16053075 |
Aug 2, 2018 |
10536187 |
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16725059 |
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15266258 |
Sep 15, 2016 |
10044400 |
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16053075 |
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14810943 |
Jul 28, 2015 |
9450639 |
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15266258 |
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62029882 |
Jul 28, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B 1/006 20130101;
H04B 1/48 20130101 |
International
Class: |
H04B 1/48 20060101
H04B001/48; H04B 1/00 20060101 H04B001/00 |
Claims
1-24. (canceled)
25. A radio frequency transmit-receive switch comprising: a
differential transmit circuit including a first amplifier stage and
a second amplifier stage each connected to a transmit transformer;
a differential receive circuit including a first receive switch and
a second receive switch each connected to a receive transformer;
and a balun connected to the transmit transformer of the
differential transmit circuit and the receive transformer of the
differential receive circuit, and defining an antenna port.
26. The radio frequency transmit-receive switch of claim 25 wherein
the transmit transformer includes a primary winding with first and
second terminals, and a secondary winding with first and second
terminals.
27. The radio frequency transmit-receive switch of claim 26 wherein
the first amplifier stage includes a first transmit transistor with
a gate connected to a first transmit differential port, a source
connected to ground, and a drain connected to the first terminal of
the primary winding.
28. The radio frequency transmit-receive switch of claim 26 wherein
the second amplifier stage includes a second transmit transistor
with a gate connected to a second transmit differential port, a
source connected to ground, and a drain connected to the first
terminal of the secondary winding, wherein the second terminal of
the primary winding is connected to the second terminal of the
secondary winding.
29. The radio frequency transmit-receive switch of claim 25 wherein
the receive transformer includes a primary winding with a first
pair of terminals, and a secondary winding with a second pair of
terminals.
30. The radio frequency transmit-receive switch of claim 29 wherein
the first receive switch includes a first receive transistor
connected across the first pair of terminals of primary
winding.
31. The radio frequency transmit-receive switch of claim 29 wherein
the second receive switch includes a second receive transistor
connected across the second pair of terminals of the primary
winding.
32. The radio frequency transmit-receive switch of claim 25 wherein
the balun is defined by a first winding and a second winding.
33. The radio frequency transmit-receive switch of claim 32 wherein
the transmit transformer and the receive transformer are connected
to the second winding of the balun.
34. The radio frequency transmit-receive switch of claim 32 wherein
the first winding of the balun is connected to the antenna
port.
35. The radio frequency transmit-receive switch of claim 25 further
comprising a control module connected to the first receive switch
and the second receive switch for selective activation and
deactivation thereof.
36. The radio frequency transmit-receive switch of claim 25 further
comprising a power supply transformer with a first winding and a
second winding, the first winding having a first terminal connected
to a power supply voltage and a second terminal connected to the
first amplifier stage, the second winding having a first terminal
connected to the power supply voltage and a second terminal
connected to the second amplifier stage.
37. The radio frequency transmit-receive switch of claim 36,
wherein the first amplifier stage includes a first transmit
transistor with a gate connected to a first transmit differential
port, a source connected to ground, and a drain connected to the
transmit transformer, wherein the second terminal of the first
winding of the power supply transformer is connected to the drain
of the first transmit transistor.
38. The radio frequency transmit-receive switch of claim 37,
wherein the second amplifier stage includes a second transmit
transistor with a gate connected to a second transmit differential
port, a source connected to ground, and a drain connected to the
transmit transformer, wherein the second terminal of the second
winding of the power supply transformer is connected to the drain
of the second transmit transistor.
39. The radio frequency transmit-receive switch of claim 25,
wherein the radio frequency transmit-receive switch can be set to a
transmit mode and a receive mode.
40. The radio frequency transmit-receive switch of claim 39,
wherein, in the receive mode, the first amplifier stage and the
second amplifier stage are deactivated.
41. The radio frequency transmit-receive switch of claim 39,
wherein, in the transmit mode, the first receive switch and the
second receive switch are deactivated.
42. A radio frequency switch circuit comprising: a transmit circuit
with a first power amplifier stage for a first differential input,
a second power amplifier stage for a second differential input, and
a transmit transformer with a first winding connected to the first
power amplifier stage and a second winding connected to the second
power amplifier stage; a receive circuit with a first output switch
for a first differential output, a second output switch for a
second differential output, and a receive transformer with a first
winding connected to the first output switch and a second winding
connected to the second output switch; and a balun connected to the
transmit circuit and the receive circuit.
43. The radio frequency front end circuit of claim 42 wherein the
balun is defined by a first winding connected to an antenna port,
and a second winding connected to the transmit circuit and the
receive circuit.
44. The radio frequency front end circuit of claim 43 wherein the
second winding of the balun is defined by a first end and a second
end, the transmit circuit being connected to the first end of the
second winding of the balun and the receive circuit being connected
to the second end of the second winding of the balun.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application relates to and claims the benefit of U.S.
Provisional Application No. 62/029,882, filed Jul. 28, 2014 and
entitled "CMOS DIFFERENTIAL ANTENNA TRANSMIT-RECEIVE SWITCHES WITH
POWER COMBINING CIRCUITRY FOR OFDM SYSTEM," the entirety of the
disclosure of which is wholly incorporated by reference herein.
STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT
[0002] Not Applicable
BACKGROUND
1. Technical Field
[0003] The present disclosure relates generally to radio frequency
(RF) communications switch devices, and in particular,
complementary metal oxide semiconductor (CMOS) differential antenna
transmit-receive switches with power combining circuitry for
orthogonal frequency-division multiplexing (OFDM) systems.
2. Related Art
[0004] Generally, wireless communications involve a radio frequency
(RF) carrier signal that is variously modulated to represent data,
and the modulation, transmission, receipt, and demodulation of the
signal conform to a set of standards for coordination of the same.
Many different mobile communication technologies or air interfaces
exist, including GSM (Global System for Mobile Communications),
EDGE (Enhanced Data rates for GSM Evolution), and UMTS (Universal
Mobile Telecommunications System) W-CDMA (Wideband Code Division
Multiple Access). More recently, 4G (fourth generation)
technologies such as LTE (Long Term Evolution), which is based on
the earlier GSM and UMTS standards, are being deployed. Besides
these mobile communications modalities, there are local area data
networking modalities such as Wireless LAN (WLAN)/WiFi, WiMax, and
so forth.
[0005] A fundamental component of any wireless communications
system is the transceiver, that is, the combined transmitter and
receiver circuitry. The transceiver encodes the data to a baseband
signal and modulates it with an RF carrier signal. Upon receipt,
the transceiver down-converts the RF signal, demodulates the
baseband signal, and decodes the data represented by the baseband
signal. An antenna connected to the transmitter converts the
electrical signals to electromagnetic waves, and an antenna
connected to the receiver converts the electromagnetic waves back
to electrical signals.
[0006] Depending on the particulars of the communications modality,
single or multiple antennas may be utilized. The output of the
transmitter is connected to a power amplifier, which amplifies the
RF signals prior to transmission via the antenna. The receiver is
connected to the output of a low noise amplifier, the input of
which is connected to the antenna and receives inbound RF signals.
A transmit/receive switch selectively interconnects the antenna to
the output of the power amplifier during transmission, and to the
input of the low noise amplifier during reception. Thus, the power
amplifier, the low noise amplifier, and the antenna switch serves
as key building blocks in RF transceiver circuitry. These
components may be referred to as a front end circuit.
[0007] Conventionally, in order to lower manufacturing costs and
allow full integration of a complete RF System-on-Chip (SoC), a
complementary metal oxide semiconductor (CMOS) technology is
utilized for the power amplifier and the antenna switch circuitry.
SoC devices with integrated front end circuits intended for mobile
communications applications require both a high sensitivity
receiver, a power amplifier with a low error vector magnitude (EVM)
floor, and a local oscillator, all on a single semiconductor die.
Local oscillator pulling and substrate noise coupling render
differential amplifiers a robust choice, and small form factor
integrated circuits suitable for mobile applications are possible
with differential circuits that incorporate coupled inductors.
[0008] Existing transmit/receive or antenna switches are
implemented in CMOS technology with series-shunt NMOS (n-type metal
oxide semiconductor) transistors in the transmit and receive paths
to the antenna. The series switch either passes or blocks the
respective signal path. The shunt switch grounds the undesired
signal and isolates the downstream component, but there is an
associated increase in insertion loss. Another approach involves
utilizing a resonant inductor with the switch in the off state to
achieve a higher impedance as seen by the antenna.
[0009] However, there are several inherent limitations associated
with CMOS switch devices. One of the most significant is low
breakdown voltage, which is exacerbated by the trend towards SoC
devices utilizing standard nanometer processes, together with
increases in output power. Additionally, balun and transformers
with ultra-high coupling factors have been difficult to produce
using standard CMOS processes. It may be possible to utilize dual
or multi-integrated circuit device MIMO (multiple input, multiple
output) front end circuit, but such an implementation results in
greatly increased costs.
[0010] Accordingly, there is a need in the art for a differential
front end architecture that can reduce voltage stress across a CMOS
switch. There is a need for such voltage stress to be reduced by
half for the same transmitted power at the antenna.
BRIEF SUMMARY
[0011] This disclosure is directed to architectures and circuitry
of a low insertion loss single pole, double throw (SP2T) and single
pole, triple throw (SP3T) switches that are fabricated with pure
CMOS processes. With an out-of-phase, 2.times. or 4.times. power
combining techniques, the same power level in an otherwise
significantly more expensive MIMO front end circuits is possible.
Additionally, these circuits are also understood to transform the
impedance to match with a 50 Ohm antenna, as well as incorporate
electrostatic discharge (ESD) protection circuitry in and around
the fully differential transmitter/receiver switches.
Transformer-based power combining may be utilized to achieve high
linear power while avoiding CMOS device breakdown.
[0012] The various embodiments of a radio frequency (RF)
transmit-receive switch may have an antenna port, first and second
transmit differential ports and first and second receive
differential ports. The transmit-receive switch may include a first
transmit transistor switch that is connected to the first transmit
differential port, and a second transmit transistor switch that is
connected to the second transmit differential port. There may also
be a transmit coupled inductor transformer that has a pair of
primary terminals connected across the first transmit transistor
switch and a pair of secondary terminals connected across the
second transmit transistor switch.
[0013] In another embodiment, the transmit-receive switch may
incorporate a first power amplifier output stage that is connected
to the first transmit differential port, as well as a second power
amplifier output stage that is connected to the second transmit
differential port. There may be a transmit coupled inductor
transformer with a pair of primary terminals connected across the
first power amplifier output stage and a pair of secondary
terminals connected across the second power amplifier output
stage.
[0014] The transmit-receive switch may also incorporate a first
receive transistor switch that is connected to the first receive
differential port, and a second receive transistor switch that is
connected to the second receive differential port. There may be a
receive coupled inductor transformer that includes a pair of
primary terminals connected across the first receive transistor
switch and a pair of secondary terminals connected across the
second receive transistor switch.
[0015] The transmit-receive switch may also include a balun with a
first balun inductive winding and a second balun inductive winding.
The first balun inductive winding may be connected to the antenna
port. The second balun inductive winding may be defined by a first
end connected to the first transmit transistor switch or the first
power amplifier output stage, and the first receive transistor
switch. The second balun inductive winding may further be defined
by a second end that is connected to the second transmit transistor
switch or the second power amplifier output stage and the second
receive transistor switch.
[0016] The present disclosure will be best understood by reference
to the following detailed description when read in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] These and other features and advantages of the various
embodiments disclosed herein will be better understood with respect
to the following description and drawings:
[0018] FIG. 1 is a circuit block diagram showing an exemplary
System on Chip (SoC) 802.11ac wireless local area networking (WLAN)
transceiver front end circuit with differential power amplifiers,
low noise amplifiers, and antenna switches;
[0019] FIG. 2 is a schematic diagram of a radio frequency (RF)
transmit-receive switch in accordance with a first embodiment of
the present disclosure;
[0020] FIG. 3 is a circuit block diagram of a power supply tracking
and sensing circuit that may control a transmit-receive switch in
accordance with various embodiments of the present disclosure;
[0021] FIG. 4 is a schematic diagram of a second embodiment of the
RF transmit-receive switch;
[0022] FIG. 5 is a schematic diagram of a third embodiment of the
RF transmit-receive switch;
[0023] FIG. 6 is a schematic diagram of a fourth embodiment of the
RF transmit-receive switch including a WiFi transmit differential
port, a WiFi receive differential port, and a Bluetooth combined
transmit and receive differential port;
[0024] FIGS. 7A and 7B are plots showing the linearity of the first
embodiment of the RF transmit-receive switch (AM-AM in [dB] and
AM-PM in [degree]);
[0025] FIGS. 8A and 8B are plots showing a simulated insertion loss
and rejection characteristics of the first embodiment of the RF
transmit-receive switch in a transmit mode;
[0026] FIGS. 9A and 9B are Smith charts showing the return loss of
the first embodiment of the RF transmit-receive switch in the
transmit mode;
[0027] FIGS. 10A and 10B are plots showing a simulated insertion
loss and rejection characteristics of the first embodiment of the
RF transmit-receive switch in a receive mode;
[0028] FIGS. 11A and 11B are Smith charts showing the return loss
of the first embodiment of the RF transmit-receive switch in the
receive mode;
[0029] FIGS. 12A and 12B are plots showing simulated insertion loss
and rejection characteristics of the first embodiment of the RF
transmit-receive switch with both transmit and receive transistor
switches being deactivated
[0030] FIGS. 13A and 13B are Smith charts showing the return loss
of the first embodiment of the RF transmit-receive switch with both
transmit and receive transistor switches being deactivated;
[0031] FIG. 14 is a Smith chart showing the impedance
transformation in the third embodiment of the RF transmit-receive
switch;
[0032] FIG. 15 is a plot showing simulated insertion loss
characteristics of the third embodiment of the RF transmit-receive
switch;
[0033] FIG. 16 is a Smith chart showing the impedances of the
transmit and receive ports of the third embodiment of the RF
transmit-receive switch during the transmit mode; and
[0034] FIG. 17 is a plot showing simulated rejection
characteristics of the third embodiment of the RF transmit-receive
switch in the transmit mode;
[0035] Common reference numerals are used throughout the drawings
and the detailed description to indicate the same elements.
DETAILED DESCRIPTION
[0036] The detailed description set forth below in connection with
the appended drawings is intended as a description of the presently
preferred embodiments of differential antenna transmit-receive
switches with power combining circuitry for orthogonal frequency
division multiplexing (OFDM) systems. It is not intended to
represent the only form in which the present invention may be
developed or utilized, and the same or equivalent functions may be
accomplished by different embodiments that are also intended to be
encompassed within the scope of the invention. It is further
understood that the use of relational terms such as first and
second and the like are used solely to distinguish one from another
entity without necessarily requiring or implying any actual such
relationship or order between such entities.
[0037] FIG. 1 shows an exemplary radio frequency (RF) front end
circuit 10, in which various embodiments of the transmit-receive
switches of the present disclosure may be utilized. The front end
circuit 10 may be configured for an IEEE 802.11ac wireless data
networking system. Some embodiments of the disclosed switch are
configured specifically for operation in the 2.4 GHz ISM
(Industrial Scientific Medical) frequency band, while others are
configured for operation in the 5 GHz ISM frequency band. Those
having ordinary skill in the art will recognize that the presently
disclosed embodiments may be adapted for operation with other RF
communications systems such as WCDMA, LTE, GSM, and so forth that
may utilize different operating frequencies.
[0038] The front end circuit 10 is generally defined by a transmit
chain 12 and a receive chain 14. An antenna 16 is connected to the
front end circuit 10, and more particularly, selectively connected
to the transmit chain 12 and the receive chain 14 thereof with an
RF transmit-receive switch 18. According to the illustrated
embodiment, the connected transceiver is fully differential, while
the antenna 16 is single-ended. As such, the entire signal path,
including the components comprising such signal path, are
understood to be differential and therefore comprised of two signal
transmission lines.
[0039] In accordance with one embodiment, the front end circuit 10
has one transmit chain 12 and one receive chain 14, so the RF
transmit-receive switch 18 is a single pole, double throw type. The
RF transmit-receive switch 18 is defined by a single-ended port 17
tied to the antenna 16, a first differential port pair 19a tied to
the transmit chain 12, and a second differential port pair 19b tied
to the receive chain 14. During a receive mode, the antenna 16 is
connected to the receive chain 14, that is, within the RF
transmit-receive switch 18, the single-ended port 17 is
electrically connected to the second differential port pair 19b.
Along these lines, during a transmit mode, the antenna 16 is
connected to the transmit chain 12, that is, the single-ended port
17 is electrically connected to the first differential port pair
19a.
[0040] When a signal is being received, the receive chain 14 is
activated. In further detail, the receive chain 14 includes a low
noise amplifier 20, as well as a bypass mode switch 21.
Additionally, the low noise amplifier 20 is connected to an input
matching network 22 that impedance matches the low noise amplifier
20 to the antenna 16, as well as an output matching network 24,
which impedance matches the low noise amplifier 20 to the input of
a transceiver circuit. Relative to the front end circuit 10, an
output port 26 of the receive chain 14 is denoted as RXo, that is,
the receive output.
[0041] A transmission signal generated by the transceiver circuit
and fed to the transmit chain 12, is received at a transmit input
port 28 thereof, which is denoted as TXi. The transmit chain 12 is
comprised of multiple amplification stages, including a first
amplifier 30, a driver amplifier 32, and a power amplifier 34, all
of which may also be collectively referred to as a power amplifier.
Any number of stages may be utilized according to the specific
output power and overall gain needs of the application. The first
amplifier 30 includes an input matching network 36 that impedance
matches the first amplifier 30 to the output of the transceiver
circuit. The inputs to the driver amplifier 32 and to the power
amplifier 34 include respective intermediate stage matching
circuits 38a, 38b, respectively, and the output of the power
amplifier 34 has an output matching network 40 that impedance
matches the power amplifier to the antenna 16.
[0042] The output power of RF emissions is closely regulated during
operation so that permitted maximums are not exceeded. Thus, the
front end circuit 10 includes a power detector 42 for this purpose.
The output from the power amplifier 34 is passed to the power
detector 42 via a directional coupler 44, as well as to the RF
transmit-receive switch 18 that passes the signal to the antenna
16.
[0043] The directional coupler 44 may be a lossless type such as
the one disclosed in co-pending U.S. patent application Ser. No.
14/805,383 that is commonly assigned to the assignee of the present
application and entitled ZERO INSERTION LOSS DIRECTIONAL COUPLER
FOR WIRELESS TRANSCEIVERS WITH INTEGRATED POWER AMPLIFIERS, the
entirety of the disclosure of which is wholly incorporated by
reference herein. As will be recognized by those having ordinary
skill in the art, the directional coupler 44 may be located in
close physical proximity to the signal path of the power amplifier
34 output. The directional coupler 44 has an isolation port that
can be connected to a complex impedance in order to compensate for
the non-ideal reflection coefficient (S22) and non-ideal coupler
directivity to improve output power over varying antenna voltage
standing wave ratios (VSWR). A detector port of the directional
coupler 44 is, in turn, connected to the power detector 42, which
correctly indicates the forward power to the antenna 16 regardless
of the variations in load impedance.
[0044] Again, although the receive chain 14 is shown with a single
stage amplifier and the transmit chain 12 is shown with three
amplifier stages, these are by way of example only and not of
limitation. Any number of amplification stages may be utilized for
the various transmit and receive chains of either of the operating
frequencies.
[0045] In addition to the foregoing components, the front end
circuit 10 may also include a mode control logic module 46, a
bandgap current reference generator 48, a low drop-out voltage
regulator (LDO) 50, and a buck-boost DC to DC converter 52, as
needed. These components are understood to control the operation of
the RF transmit-receive switch 18 by generating proper logic
control voltage levels, as well as protect the logic transistor
from high over-voltage damage. Additional details of these
components will be described more fully below, in the context of
the various embodiments of the RF transmit-receive switch 18 of the
present disclosure.
[0046] The schematic diagram of FIG. 2 is of a first embodiment of
the RF transmit-receive switch 18a, which can be generally
characterized as a single pole, double throw switch that
selectively connects the antenna 16 to the aforementioned transmit
chain 12 and the receive chain 14 shown in the block diagram of
FIG. 1. As will be described in further detail below, the RF
transmit-receive switch 18 combines pass, rejection, and impedance
transformation functions into a single component, and is understood
to be characterized by high linearity and high power handling
capability. The exemplary first embodiment of the RF
transmit-receive switch 18a is configured for use in connection
with an 802.11ac WiFi transceiver, and specifically, with the 5 GHz
operating frequency.
[0047] The first embodiment of the RF transmit-receive switch 18a
includes an antenna port 54, as well as a pair of transmit
differential ports 56a, 56b, and a pair of receive differential
ports 58a, 58b. The first transmit differential port 56a is
understood to be connected to the (+) differential signal
transmission line from the power amplifier 34, while the second
transmit differential port 56b is understood to be connected to the
(-) differential signal transmission line from the power amplifier
34. The transmit (+) differential signal is designated as TX+, and
the transmit (-) differential signal is designated as TX-.
[0048] Along these lines, the first receive differential port 58a
is understood to be connected to the (+) differential signal
transmission line to the low noise amplifier 20, and the second
receive differential port 58b is connected to the (-) differential
signal transmission line to the low noise amplifier 20. The receive
(+) differential signal is designated as RX+, and the receive (-)
differential signal is designated as RX-.
[0049] The single-ended antenna port 54 of the RF transmit-receive
switch 18 is connected to an antenna pad 60 disposed on the
semiconductor substrate. The antenna 16, which is understood to be
external to the RF transmit-receive switch 18, is connected to the
antenna pad 60.
[0050] The first embodiment of the RF transmit-receive switch 18a
includes a first transmit transistor switch 62 that is connected to
the first transmit differential port 56a. More particularly, the
first transmit transistor switch 62 includes a transistor 64 with a
gate 64g, a source 64s, and a drain 64d. The drain 64d of the
transistor 64 is connected to the first transmit differential port
56a. Additionally, the gate 64g is connected to the power supply
voltage Vdd, and the source 64s and the drain 64d are connected to
the output of the mode control logic module 46 described above with
reference to FIG. 1, specifically a transmit mode activation output
ETX 66 thereof. One of the inputs to the mode control logic module
46 is from a power supply tracking and sensing circuit 68.
[0051] With additional reference to the schematic diagram of FIG.
3, one implementation of the power supply tracking and sensing
circuit 68 incorporates a comparator 72 that compares a fraction of
a battery supply voltage (Vbatt) 74 with a bandgap voltage as
generated by the bandgap current reference generator 48. When the
battery voltage Vbatt 74 is higher than the single transistor
breakdown voltage, a signal HV 76 is set to "high" and the output
voltage Vout 78 becomes a fraction of Vbatt 74, with the transistor
Q1 70 being in the on state. If the switching transistor breakdown
voltage is higher than the predefined battery supply voltage Vbatt
74, the signal HV 76 is set to "low" and the output voltage Vout 78
is equal to the battery supply voltage Vbatt 74 with the transistor
Q1 70 being in the off state. This voltage is used for all logic
control voltage supplies Vdd.
[0052] The first embodiment of the RF transmit-receive switch 18a
also includes a second transmit transistor switch 80 connected to
the second transmit differential port 56b. The second transmit
transistor switch 80 includes a transistor 82 also with a gate 82g,
a drain 82d, and a source 82s, and the drain 82d is connected to
the second transmit differential port 56b. The gate 82g is
connected to the power supply voltage Vdd, while the source 64s and
the drain 64d are connected to the transmit mode activation output
ETX 66 of the mode control logic module 46.
[0053] The first embodiment of the RF transmit-receive switch 18a
incorporates a transmit coupled inductor transformer 84 which is
generally comprised of a primary winding 86 and a secondary winding
88 that are electromagnetically coupled to each other. Both the
primary winding 86 and the secondary winding 88 are comprised of a
plurality of turns, and are electromagnetically cross-coupled.
According to one embodiment, the number of turns in the primary
winding 86 and the secondary winding 88 are equal.
[0054] The transmit coupled inductor transformer 84, as well as the
other coupled inductor transformers utilized in the various
embodiments of the RF transmit-receive switch 18, may be configured
as disclosed in co-pending and co-owned U.S. patent application
Ser. No. 14/805,368, entitled ULTRA-HIGH COUPLING FACTOR MONOLITHIC
TRANSFORMERS FOR INTEGRATED DIFFERENTIAL RADIO FREQUENCY AMPLIFIERS
IN SYSTEM-ON-CHIP DEVICES, the entirety of the disclosure of which
is hereby wholly incorporated by reference. As discussed therein,
the winding structures make ultra high coupling factors approaching
0.988 are possible on 10 Ohmcm substrates with a bulk CMOS 40 nm
process. The coupled inductor transformer is contemplated to have a
compact, small form factor, as well as low insertion loss and
robust electrostatic discharge (ESD) protection.
[0055] In further detail, the primary winding 86 has one end that
corresponds to a first primary terminal 86a and another end that
corresponds to a second primary terminal 86b. The primary winding
86 is connected across the source 64s and the drain 64d of the
transistor 64, and specifically to the second primary terminal 86b
and the first primary terminal 86a, respectively. The secondary
winding 88 likewise has one end that corresponds to a first
secondary terminal 88a and another end that corresponds to a second
secondary terminal 88b. The secondary winding 88 is connected
across the source 82s and the drain 82d of the transistor 82, that
is, the first secondary terminal 88a of the secondary winding 88 is
connected to the drain 82d of the transistor 82, and the second
secondary terminal 88b of the secondary winding 88 is connected to
the source 82s of the transistor 82.
[0056] Connected to the aforementioned receive differential ports
58 are a pair of receive transistor switches that connect the
antenna port 54 to the differential signal outputs to the low noise
amplifier. More particularly, there is a first receive transistor
switch 90 that is connected to the first receive differential port
58a, and a second receive transistor switch 92 that is connected to
the second receive differential port 58b.
[0057] The first receive transistor switch 90 has a first
transistor 94 that is cascaded with a second transistor 96. In this
regard, the source 94s of the first transistor 94 is connected to
the drain 96d of the second transistor 96. Furthermore, the drain
94d of the first transistor 94 is connected to the first receive
differential port 58a. Connected across the source and drain of
both of the first and second transistors 94, 96 is a receive mode
activation output ERX 95 thereof. The gates 94g, 96g are both
connected to the power supply voltage Vdd.
[0058] The second receive transistor switch 92 has the same
configuration as the first receive transistor switch 90, though as
mentioned above, it is connected to the second receive differential
port 58b. Accordingly, there is a first transistor 98 with a gate
98g, a source 98s, and a drain 98d, as well as a second transistor
100 with a gate 100g, a source 100s, and a drain 100d. Again, the
second transistor 100 is cascaded with the first transistor 98,
where the source 98s of the first transistor 98 is connected to the
drain 100d of the second transistor 100. Furthermore, the gate 98g
of the first transistor 98 and the gate 100g of the second
transistor 100 are both connected to the power supply voltage Vdd,
while the source 98s and the drain 98d of the first transistor 98,
and the source 100s and the drain 100d of the second transistor 100
are each connected to the receive mode activation output ERX
95.
[0059] There is a receive coupled inductor transformer 102 that is
generally comprised of a primary winding 104 and a secondary
winding 106 that are electromagnetically cross-coupled to each
other. The primary winding 86 and the secondary winding 88 are
comprised of a plurality of turns, and in one embodiment, the
number of turns is equal. The primary winding 104 has one end that
corresponds to a first primary terminal 104a and another end that
corresponds to a second primary terminal 104b. The primary winding
104 is connected across the drain 94d of the first transistor 94
and the source 96s of the second transistor 96, and specifically to
the second primary terminal 104b and the first primary terminal
104a, respectively. The secondary winding 106 has one end that
corresponds to a first secondary terminal 106a and another end that
corresponds to a second secondary terminal 106b. The secondary
winding 106 is connected across the drain 98d of the first
transistor 98 and the source 100s of the second transistor 100. In
particular, the first secondary terminal 106a of the secondary
winding 106 is connected to the drain 98d of the first transistor
98, and the second secondary terminal 106b of the secondary winding
106 is connected to the source 100s of the second transistor
100.
[0060] According to various embodiments of the present disclosure,
a balun 108 couples the transistor switches to the antenna port 54.
The configuration of the balun 108 is also set forth in the
aforementioned U.S. patent application Ser. No. 14/805,368, and
comprised of a primary winding 110 and a secondary winding 112.
Although the number of turns of the primary winding 110 and the
secondary winding 112 are understood to be equal, impedance
transformation may be possible with different primary to secondary
winding ratios. The balun 108 is also understood to convert the
differential signal to a single-ended output, and combine the
output power of differential signals into a single 50 Ohm antenna.
Whether an impedance transformation is necessary may depend on the
output power and the number of other RF transmit-receive switches
18 utilized for delivering the specified power.
[0061] The primary winding 110 of the balun 108 is connected across
the first and second transistor switches of the transmit and
receive chain, that is, a first terminal 110a of the primary
winding 110 is connected to the first transmit transistor switch
62, specifically the source 64s of the transistor 64, and the first
receive transistor switch 90, specifically the source 96s of the
second transistor 96. Moreover, a second terminal 110b of the
primary winding 110 is connected to the second transmit transistor
switch 80, specifically the source 82s of the transistor 82, and
the second receive transistor switch 92, specifically the source
100s of the second transistor 100. The first terminal 112a of the
secondary winding 112 is connected to the antenna port 54, while
the second terminal 112b of the secondary winding 112 is connected
to ground.
[0062] The balun 108 is understood to be fabricated with an
ultra-thick metal, top metal, and redistribution layer (RDL) in a
conventional bulk-CMOS semiconductor process. This is envisioned to
maximize the Q-factor of the transformer, along with minimal
insertion loss. These factors are understood to be important for
high power added efficiency, handle high linear output power from
the power amplifiers 34, and minimal noise figures with respect to
the low noise amplifier 20. Along these lines, the various
components of the RF transmit-receive switch 18, along with the
rest of the components of the System-on-Chip (SoC), may be
fabricated with conventional bulk CMOS processes. However, it is
understood that any other suitable semiconductor process may be
substituted without departing from the disclosure. These include
CMOS silicon-on-insulator (SOI), silicon-germanium heterojunction
bipolar transistor (SiGe HBT), gallium-arsenide (GaAs) and so
forth.
[0063] The first embodiment of the RF transmit-receive switch 18a
may be operated in different ways, that is, the various transistor
switches may be selectively activated to implement transmit and
receive functions, though some involve trade-offs between power
amplifier linear power output versus low noise amplifier noise
figure. In accordance with one embodiment, during a receive mode,
the first receive transistor switch 90 and the second receive
transistor switch 92 may be activated. In this embodiment, during a
transmit mode, the first receive transistor switch 90 and the
second receive transistor switch 92 are deactivated. A parallel
resonance may be created by the inductance associated with the
receive coupled inductor transformer 102, and the capacitance of
the switches as shown. The capacitors shown in FIG. 2 may serve DC
decoupling purposes, as well as for the fine tuning of the
performance of the transmit-receive switch 18.
[0064] FIG. 4 depicts a second embodiment of the RF
transmit-receive switch 18b with an alternative configuration that
is likewise intended for a WiFi/802.11ac front end circuit Like the
first embodiment 18a, however, there is the antenna port 54, the
transmit differential ports 56, and the receive differential ports
56. Furthermore, the second embodiment of the RF transmit-receive
switch 18b also shares the same first transmit transistor switch 62
and the second transmit transistor switch 80, which are
electromagnetically coupled with the transmit coupled inductor
transformer 84. Additionally, the first transmit transistor switch
62 and the second transmit transistor switch 80 are controlled with
the transmit mode activation output ETX 66.
[0065] The second embodiment of the RF transmit-receive switch 18b,
however, incorporates a slightly different receive transistor
switches. More particularly, there is a first receive transistor
switch 114 that utilizes a single transistor 116, and a second
receive transistor switch 118 with a single transistor 120. Thus,
the receive transistor switches do not employ a cascaded transistor
configuration. The transistor 116 includes a gate 116g that is
connected to the power supply voltage Vdd, and both the source 116s
and the drain 116d are connected to the receive mode activation
output ERX 95 of the mode control logic module 46. Similarly, the
transistor 120 includes a gate 120g connected to the power supply
voltage Vdd, and both the source 120s and the drain 120d are
connected to the receive mode activation output ERX 95.
[0066] The transistors 116, 120 are electromagnetically coupled
with the receive coupled inductor transformer 102. The second
primary terminal 104b of the primary winding 104 is connected to
the drain 116d of the transistor 116, and the first primary
terminal 104a of the primary winding 104 is connected to the source
116s of the transistor 116. Furthermore, the first secondary
terminal 106a of the secondary winding 106 is connected to the
drain 120d of the transistor 120, and the second secondary terminal
106b of the secondary winding 106 is connected to the source 120s
of the transistor 120.
[0067] Again, the balun 108 couples the transistor switches to the
antenna port 54. The primary winding 110 of the balun 108 is
connected across the first and second transistor switches of the
transmit and receive chain. The first terminal 110a of the primary
winding 110 is connected to the first transmit transistor switch 62
and the first receive transistor switch 114, specifically the
source 116s of the transistor 116. Moreover, a second terminal 110b
of the primary winding 110 is connected to the second transmit
transistor switch 80 and the second receive transistor switch 118,
specifically the source 120s of the transistor 120. The first
terminal 112a of the secondary winding 112 is connected to the
antenna port 54, while the second terminal 112b of the secondary
winding 112 is connected to ground.
[0068] With the second embodiment of the RF transmit-receive switch
18b, in the receive mode, the first transmit transistor switch 62
and the second transmit transistor switch 80 are deactivated, as
well as the first receive transistor switch 114 and the second
receive transistor switch 118 are activated. In this configuration,
a low system noise figure is contemplated. Furthermore, in the
transmit mode, the first transmit transistor switch 62 and the
second transmit transistor switch 80 are activated, and the first
receive transistor switch 114 and the second receive transistor
switch 118 are deactivated. The deactivated first receive
transistor switch 114 and the deactivated receive transistor switch
118, together with the inductance of the receive coupled inductor
transformer 102 is understood to define a parallel resonance at the
operating frequency in the transmit mode thus decoupling the
transmit chain from being loaded by the receive chain. At the same
time, the inductors of the primary winding 110 and the secondary
winding 106 of the receive coupled inductor transformer balun 108
serve low noise amplifier input matching purposes in the receive
the mode while transmit switches 62 and 80 are deactivated with a
parallel resonance defined by coupled inductors 84 and these
switches. The (-) transmit differential signal and the (+) transmit
differential signal, which are out-of-phase relative to each other,
and combined by the balun 108, with the total output power being
doubled in the transmit mode.
[0069] FIG. 5 is a schematic diagram of a third embodiment of the
RF transmit-receive switch 18c, which includes the antenna port 54,
the first transmit differential port 56a, the second transmit
differential port 56b, the first receive differential port 58a, and
the second receive differential port 58b. This architecture is
likewise contemplated for WiFi 802.11/a/b/n/ac front end circuit,
and is contemplated to maximum transmit linear power. The receive
chain components of the third embodiment of the RF transmit-receive
switch 18c are the same as the first embodiment of the RF
transmit-receive switch 18a. That is, the same first receive
transistor switch 90 and the second receive transistor switch 92
are electromagnetically coupled with the receive coupled inductor
transformer 102. Accordingly, the details pertaining to these
components will not be repeated.
[0070] The third embodiment of the RF transmit-receive switch 18c
does not utilize switches in transmit chain. Instead, there are
output stages of a differential power amplifier. There is a first
power amplifier output stage 122 including a transistor 124 with a
gate 124g, a source 124s, and a drain 124d. The gate 124g of the
transistor 124 is connected to the first transmit differential port
56a, and the source 124s is connected to ground. This configuration
is replicated for a second power amplifier output stage 126, which
likewise includes a transistor 128 with a source 128s connected to
ground, a gate 128g connected to the second transmit differential
port 56b, and a drain 128d. The power supply voltage Vdd is
connected to a transformer 130, specifically to a first winding
130a that is connected to the drain 124d of the transistor 124, and
a second winding 130b that is connected to the drain 128d of the
transistor 128.
[0071] An alternative configuration of a transmit coupled inductor
transformer 132 is utilized in the third embodiment of the RF
transmit-receive switch 18c. The transmit coupled inductor
transformer 132 has a primary winding 134 with a first end
corresponding to a first terminal 134a and a second end
corresponding to a second terminal 134b. The first terminal 134a of
the primary winding 134 is connected to the first power amplifier
output stage 122, and specifically the drain 124d of the transistor
124. The transmit coupled inductor transformer 132 also has a
secondary winding 136 with a first end corresponding to a first
terminal 136a that is connected to the second power amplifier
output stage 126, and specifically the drain 128d of the transistor
128. The second terminal 134b of the primary winding 134 is
connected to the second terminal 136b of the secondary winding
136.
[0072] The balun 108 couples the power amplifier output stages 122
and 126, and the receive chain transistor switches 90 and 92 to the
antenna port 54. The primary winding 110 of the balun 108 is
connected across the first and second transistor switches of the
transmit and receive chain. The first terminal 110a of the primary
winding 110 is connected to the first power amplifier output stage
122 and the first receive transistor switch 90. The second terminal
110b of the primary winding 110 is connected to the second power
amplifier output stage 126 and the second receive transistor switch
92, specifically the source 128s of the transistor 128. The first
terminal 112a of the secondary winding 112 is connected to the
antenna port 54, while the second terminal 112b of the secondary
winding 112 is connected to ground. In the transmit mode, the power
amplifier output stages 122 and 126 are activated, and the coupled
inductors 130 and 132 serve as a load.
[0073] The third embodiment of the RF transmit-receive switch 18c
can also be set to a transmit mode and a receive mode. In the
receive mode, the first power amplifier output stage 122 and the
second power amplifier output stage 126 are deactivated. The
capacitance thereof, together with the inductance from the transmit
coupled inductor transformers 130 and 132 are understood to define
a parallel resonant circuit, thereby not loading the low noise
amplifier input chain. In the transmit mode, the first receive
transistor switch 90 and the second receive transistor switch 92
are deactivated, and the capacitances thereof, with the inductance
from the receive coupled inductor transformer 102 is understood to
define a parallel resonant circuit that prevents loading of the
transmit output chain.
[0074] With reference to FIG. 6, a fourth embodiment of the RF
transmit-receive switch 18d is a single pole, triple throw (SP3T)
type switch that selectively interconnects three differential ports
to one single-ended antenna port 54. This embodiment is
contemplated for a WiFi 802.11b/g/n and Bluetooth.TM. combined
transceiver system. Accordingly, the fourth embodiment of the RF
transmit-receive switch 18d has the transmit differential ports 56
and the receive differential ports 58 that are to be connected to
the WiFi power amplifier outputs and the low noise amplifier
inputs, respectively. There is also understood to be a first
combined transmit-receive differential port 138a and a second
combined transmit-receive differential port 138b for the
Bluetooth.TM. input/output signal lines.
[0075] The WiFi transmit chain and receive chain components of the
fourth embodiment of the RF transmit-receive switch 18d are the
same as the first embodiment of the RF transmit-receive switch 18a.
The same first transmit transistor switch 62 and second transmit
transistor switch 80 are electromagnetically coupled with the
transmit coupled inductor transformer 84. Additionally, the same
first receive transistor switch 90 and second receive transistor
switch 92 are electromagnetically coupled with the receive coupled
inductor transformer 102.
[0076] The combined transmit-receive differential ports 138 are
connected to a pair of combined transmit-receive switches that
connect the antenna port 54 to the Bluetooth.TM. differential
signal inputs and outputs. There is a first combined
transmit-receive transistor switch 140 that is connected to the
first combined transmit-receive differential port 138a, and a
second combined transmit-receive transistor switch 142 that is
connected to the second combined transmit-receive differential port
138b.
[0077] The first combined transmit-receive transistor switch 140
has a first transistor 144 that is cascaded with a second
transistor 146. The source 144s of the first transistor 144 is
connected to the drain 146d of the second transistor 146.
Furthermore, the drain 144d of the first transistor 144 is
connected to the first combined transmit-receive differential port
138a. Connected across the source and drain of both of the first
and second transistors 144, 146 is a combined
transmit-receive/Bluetooth.TM. mode activation output EBT 145. The
gates 144g, 146g are both connected to the power supply voltage
Vdd.
[0078] The second combined transmit-receive transistor switch 142
has the same configuration as the first combined transmit-receive
transistor switch 140, though as mentioned above, it is connected
to the second combined transmit-receive differential port 138b.
There is a first transistor 148 with a gate 148g, a source 148s,
and a drain 148d, as well as a second transistor 150 with a gate
150g, a source 150s, and a drain 150d. The second transistor 150 is
cascaded with the first transistor 148, where the source 148s of
the first transistor 148 is connected to the drain 150d of the
second transistor 150. Furthermore, the gate 148g of the first
transistor 148 and the gate 150g of the second transistor 150 are
both connected to the power supply voltage Vdd, while the source
148s and the drain 148d of the first transistor 148, and the source
150s and the drain 150d of the second transistor 150 are each
connected to the combined transmit-receive/Bluetooth.TM. mode
activation output EBT 145.
[0079] There is a combined transmit-receive coupled inductor
transformer 152 with a primary winding 154 and a secondary winding
156 that are electromagnetically cross-coupled to each other. The
primary winding 154 and the secondary winding 156 are comprised of
a plurality of turns, and the number of turns may be equal. The
primary winding 154 has one end that corresponds to a first primary
terminal 154a and another end that corresponds to a second primary
terminal 154b. The primary winding 154 is connected across the
drain 144d of the first transistor 144 and the source 146s of the
second transistor 146, and specifically to the second primary
terminal 154b and the first primary terminal 154a, respectively.
The secondary winding 156 has one end that corresponds to a first
secondary terminal 156a and another end that corresponds to a
second secondary terminal 156b. The secondary winding 156 is
connected across the drain 148d of the first transistor 148 and the
source 150s of the second transistor 150. In particular, the first
secondary terminal 156a of the secondary winding 156 is connected
to the drain 148d of the first transistor 148, and the second
secondary terminal 156b of the secondary winding 156 is connected
to the source 150s of the second transistor 150. Of the transmit
coupled inductor transformer 84, the receive coupled inductor
transformer 102, and the combined transmit-receive coupled inductor
transformer 152, the transmit coupled inductor transformer 84 is
understood to have the highest inductance value.
[0080] As with the other embodiments of the RF transmit-receive
switch 18, the balun 108 couples the transistor switches to the
antenna port 54. The primary winding 110 of the balun 108 is
connected across the first and second transistor switches of the
transmit chain, receive chain, and combined
transmit-receive/Bluetooth.TM. chain. The first terminal 110a of
the primary winding 110 is connected to the first transmit
transistor switch 62, the first receive transistor switch 90, and
the first combined transmit-receive transistor switch 140,
specifically, the source 146s of the second transistor 146 thereof.
The second terminal 110b of the primary winding 110 is connected to
the second transmit transistor switch 126, the second receive
transistor switch 92, and the second combined transmit-receive
transistor switch 142, specifically the source 150s of the second
transistor 150. The first terminal 112a of the secondary winding
112 is connected to the antenna port 54, while the second terminal
112b of the secondary winding 112 is connected to ground.
[0081] A WiFi transmit, WiFi receive, and Bluetooth.TM. modes are
contemplated in the fourth embodiment of the RF transmit-receive
switch 18d. In the receive mode, with the first transmit transistor
switch 62, the second transmit transistor switch 80, the first
receive transistor switch 90, the second receive transistor switch
92, the first combined transmit-receive transistor switch 140, and
the second combined transmit-receive transistor switch 142 being
deactivated, an extremely low noise figure can be achieved.
Furthermore, in a combined transmit-receive or Bluetooth.TM. mode,
all of the switches can be deactivated, with the components being
optimized for a very low insertion loss. As with the first
embodiment of the RF transmit-receive switch 18a, the inductors
associated with the receive coupled inductor transformer 102 is
understood to have low noise input impedance matching
functions.
[0082] In the WiFi receive mode, the deactivated transmit
transistor switches 62, 80 and the combined transmit-receive
transistor switches 140, 142 are understood to define a parallel
resonance with corresponding inductors of the transmit coupled
inductor transformer 84 and the combined transmit-receive coupled
inductor transformer 152, respectively. The capacitance associated
with these transistor switches 62, 80, 140, and 142 are also part
of the defined parallel resonance.
[0083] In either the WiFi transmit mode or the Bluetooth.TM. mode,
the respective transistor switches 62, 80 or 140, 142 are activated
to provide a low loss path to the antenna 16.
[0084] FIGS. 7A and 7A are graphs showing the linearity of a
simulation of the first embodiment of the RF transmit-receive
switch 18a in the transmit mode with the first and second transmit
transistor switches 62, 80 being activated at an operating
frequency of 5.9 GHz. Additionally, the power handling capability
of the RF transmit-receive switch 18a is illustrated. The graph of
FIG. 7A is of amplitude-amplitude component (AM-AM), and P(0.3 dB)
power is 20 dBM with a phase shift of 10 degrees. The graph of FIG.
7B shows the amplitude-phase component, and is approximately 5
degrees at 23.4 dBm.
[0085] Referring now FIGS. 8A, 8B, 9A, and 9B, simulated signal
insertion loss, rejection and return loss performance of the first
embodiment of the RF transmit-receive switch 18a in a transmit mode
are plotted. FIG. 8A plots the forward transmission
coefficient/attenuation of the transmit signal on the transmit
differential port 56 to the antenna port 54 (S21) during the
transmit mode over a frequency range. As referenced in this
context, the transmit mode is understood to refer to the first and
second transmit transistor switches 62, 80 being activated and the
first and second receive transistor switches 90, 92 being
deactivated. At 5.1 GHz, the attenuation is 0.582 dB (marker m3),
at 5.5 GHz, the attenuation is 0.556 dB (marker m1) and at 5.9 GHz,
the attenuation is 0.576 dB (marker m2). FIG. 8B plots the
rejection of a receive signal, that is, the signal on the receive
differential port 58, in the transmit mode over a frequency range.
At 5.1 GHz, the attenuation is 22.5 dB (marker m12), at 5.5 GHz,
the attenuation is 39.626 dB (marker m10), and at 5.9 GHz, the
attenuation is 25.387 dB (marker m11). The Smith charts of FIGS. 9A
and 9B show the return loss in the transmit mode for the first
embodiment of the RF transmit-receive switch 18a at three different
ports.
[0086] FIGS. 10A, 10B, 11A, and 11B show the simulated signal
insertion loss, rejection and return loss performance of the first
embodiment of the RF transmit-receive switch 18a in a receive mode.
Specifically, FIG. 10A shows the forward transmission
coefficient/attenuation of a signal on the transmit differential
port 56 to the antenna port 54 (S21) during the receive mode over a
frequency range. As referenced in this context, the receive mode is
understood to refer to the first and second receive transistor
switches 90, 92 being deactivated. At 5.1 GHz, the attenuation is
24.004 dB (marker m8), at 5.5 GHz, the attenuation is 39.048 dB
(marker m5) and at 5.9 GHz, the attenuation is 23.371 dB (marker
m6). FIG. 10B plots the attenuation of a receive signal, that is,
the signal on the receive differential port 58, in the receive mode
over a frequency range. At 5.1 GHz, the attenuation is 0.755 dB
(marker m3), at 5.5 GHz, the attenuation is 0.751 dB (marker m1),
and at 5.9 GHz, the attenuation is 0.804 dB (marker 2). The Smith
charts of FIGS. 11A and 11B show the return loss in the receive
mode for the first embodiment of the RF transmit-receive switch 18a
at three different ports.
[0087] FIGS. 12A, 12B, 13A, and 13B show the simulated signal
insertion loss, rejection and return loss performance of the first
embodiment of the RF transmit-receive switch 18a with the first and
second transmit transistor switches 62, 80 and the first and second
receive transistor switches 90, 92 being deactivated. FIG. 12A
shows the forward transmission coefficient/attenuation of a signal
on the transmit differential port 56 to the antenna port 54 (S21)
over a frequency range. At 5.1 GHz, the attenuation is 17.973 dB
(marker m3), at 5.5 GHz, the attenuation is 41.999 dB (marker m1)
and at 5.9 GHz, the attenuation is 18.653 dB (marker m2). FIG. 12B
plots the attenuation of a receive signal, that is, the signal on
the receive differential port 58 over a frequency range. At 5.1
GHz, the attenuation is 15.983 dB (marker m12), at 5.5 GHz, the
attenuation is 22.720 dB (marker m10), and at 5.9 GHz, the
attenuation is 35.386 dB (marker m11). Thus, the transmit side
rejection is approximately 18 dB to 40 dB, while the receive side
rejection is approximately 16 dB to 35 dB. The Smith charts of
FIGS. 13A and 13B show the return loss for the first embodiment of
the RF transmit-receive switch 18a at three different ports.
[0088] Referring to FIG. 14, the Smith chart shows an impedance
transformation from 50 Ohm to 180 Ohm and vice versa in the third
embodiment of the RF transmit-receive switch 18c. The graph of FIG.
15 plots the insertion loss of the third embodiment of the RF
transmit-receive switch 18c, Specifically, at 5.1 GHz, the
attenuation is 0.491 dB (marker m8), at 5.5 GHz, the attenuation is
0.496 dB (marker m5) and at 5.9 GHz, the attenuation is 0.499 dB
(marker m6).
[0089] The Smith chart of FIG. 16 shows the impedances of the
transmit and receive ports of the third embodiment of the RF
transmit-receive switch during the transmit mode. Furthermore, FIG.
17 shows that the rejection of the receive signal, e.g., the signal
on the receive differential port 58 in the transmit mode, is
greater than 17 dB across the 5.1 GHz to 5.9 GHz band.
[0090] The particulars shown herein are by way of example and for
purposes of illustrative discussion of the embodiments of the
present disclosure only and are presented in the cause of providing
what is believed to be the most useful and readily understood
description of the principles and conceptual aspects of the present
disclosure. In this regard, no attempt is made to show details of
these embodiments with more particularity than is necessary for the
fundamental understanding of the present disclosure, the
description taken with the drawings making apparent to those
skilled in the art how the several forms of the present disclosure
may be embodied in practice.
* * * * *