U.S. patent application number 14/181478 was filed with the patent office on 2015-08-20 for methods for increasing rf throughput via usage of tunable filters.
This patent application is currently assigned to PEREGRINE SEMICONDUCTOR CORPORATION. The applicant listed for this patent is PEREGRINE SEMICONDUCTOR CORPORATION. Invention is credited to Dan William Nobbe.
Application Number | 20150236798 14/181478 |
Document ID | / |
Family ID | 53799075 |
Filed Date | 2015-08-20 |
United States Patent
Application |
20150236798 |
Kind Code |
A1 |
Nobbe; Dan William |
August 20, 2015 |
Methods for Increasing RF Throughput Via Usage of Tunable
Filters
Abstract
Methods and devices are described for increasing RF throughput
in a multiple RF paths RF transmit/receive system with a plurality
RF transmit/receive systems. In one case a tunable notch filter is
used to reduce channel interference between the plurality of RF
transmit/receive systems.
Inventors: |
Nobbe; Dan William; (Crystal
Lake, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PEREGRINE SEMICONDUCTOR CORPORATION |
San Diego |
CA |
US |
|
|
Assignee: |
PEREGRINE SEMICONDUCTOR
CORPORATION
San Diego
CA
|
Family ID: |
53799075 |
Appl. No.: |
14/181478 |
Filed: |
February 14, 2014 |
Current U.S.
Class: |
370/278 |
Current CPC
Class: |
H03F 2200/18 20130101;
H03F 3/04 20130101; H04L 27/20 20130101; H04B 1/18 20130101; H04B
1/525 20130101; H04B 7/015 20130101; H03F 2200/451 20130101; H03F
2200/471 20130101; H03F 3/21 20130101; H03F 2200/555 20130101; H04B
1/44 20130101; H03F 3/195 20130101; H04B 15/005 20130101; H03F
3/213 20130101; H03F 1/30 20130101; H04B 17/12 20150115; H03F 3/193
20130101; H03F 1/301 20130101; H03F 2200/456 20130101 |
International
Class: |
H04B 15/00 20060101
H04B015/00; H04B 7/02 20060101 H04B007/02; H04B 7/015 20060101
H04B007/015 |
Claims
1. A radio frequency (RF) circuital arrangement comprising: a first
transmit/receive system comprising a first transmit path configured
to transmit a first transmit RF signal at a first transmit/receive
port, and a first receive path configured to receive a first
receive RF signal at the first transmit/receive port; a second
transmit/receive system comprising a second transmit path
configured to transmit a second transmit RF signal at a second
transmit/receive port, and a second receive path configured to
receive a second receive RF signal at the second transmit/receive
port, and one or more tunable notch filters configured to reduce a
radio frequency interference of a transmit/receive system of the
first and second transmit/receive systems over the other
transmit/receive system.
2. The RF circuital arrangement of claim 1, wherein a tunable notch
filter of the one or more tunable notch filters is connected
between a transmit/receive port of the first and the second
transmit/receive ports and a duplexer unit in correspondence of the
transmit/receive port.
3. The RF circuital arrangement of claim 1, wherein a tunable notch
filter of the one or more tunable notch filters is connected
between a duplexer unit of a transmit/receive system of the first
and the second transmit/receive systems and an input RF amplifier
of the transmit/receive system.
4. The RF circuital arrangement of claim 1, wherein the tunable
notch filter of the one or more tunable notch filters is connected
between a transmit amplifier of a transmit/receive system of the
first and the second transmit/receive systems and a duplexer unit
in correspondence of the transmit/receive system.
5. The RF circuital arrangement of any one of claims 2-4, wherein
the tunable notch filter is connected in a series and/or a shunt
configuration.
6. The RF circuital arrangement of claim 1, further comprising one
or more RF switches, wherein the one or more RF switches are
configured to enable and/or disable an effect of the one or more
tunable notch filters over a transmit/receive system of the first
and second transmit/receive systems.
7. The RF circuital arrangement of claim 6, wherein a switch of the
one or more RF switches is connected in parallel to a tunable notch
filter of the one or more tunable notch filters.
8. The RF circuital arrangement of claim 7, wherein the switch is
connected between a first and a second input/output terminal of the
tunable notch filter.
9. The RF circuital arrangement of claim 6, wherein a switch of the
one or more switches is connected in series to a tunable notch
filter of the one or more tunable notch filters.
10. The RF circuital arrangement of claim 7 or claim 9, wherein a
switch of the one or more switches comprises stacked
transistors.
11. The RF circuital arrangement of claim 1, wherein a tunable
notch filter of the one or more tunable notch filters is a
band-reject filter configured to reject a frequency band in
correspondence of a first transmit/receive channel and to pass a
frequency band in correspondence of a second transmit/receive
channel adjacent to the first transmit/receive channel.
12. The RF circuital arrangement of claim 11, wherein the frequency
band is in correspondence of one of: a) a frequency of operation of
a transmit RF signal of the first and the second transmit RF
signals, b) a harmonic of a), and c) an intermodulation product of
any combination of a) and b).
13. The RF circuital arrangement of claim 1, wherein a tunable
notch filter of the one or more tunable notch filters comprises one
or more variable reactive elements.
14. The RF circuital arrangement of claim 13, wherein the one or
more variable reactive elements are partitioned in one or more
stages interconnected via series and/or shunt connections.
15. The RF circuital arrangement of claim 13, wherein a reactive
element of the one or more variable reactive elements comprises one
of: a) a digitally tunable capacitor, and b) a digitally tunable
inductor.
16. The RF circuital arrangement of claim 1, wherein during
operation of the circuital arrangement, the first and the second
transmit/receive systems are adapted to simultaneously transmit
and/or receive an RF signal over a channel of a plurality of
channels of a frequency band.
17. The RF circuital arrangement of claim 1, wherein the first
transmit/receive port comprises a first transmit/receive antenna
and the second transmit/receive port comprises a second
transmit/receive antenna.
18. The RF circuital arrangement of claim 1, further comprising one
or more transmit/receive systems similar to the first/second
transmit/receive systems, wherein one or more of the one or more
tunable notch filters are configured to reduce a radio frequency
interference of a transmit/receive system of the RF circuital
arrangement over the other transmit/receive systems of the RF
circuital arrangement.
19. A radio frequency (RF) integrated circuit comprising: an RF
switch comprising a first switch terminal and a second switch
terminal; a RF tunable notch filter comprising a first port and a
second port, wherein in a first configuration of the RF integrated
circuit the first port is connected to the first switch terminal
and the second port is connected to the second switch terminal, and
in a second configuration of the RF integrated circuit the first
port is connected to the second switch terminal; a first
input/output terminal connected to the first switch terminal; a
second input/output terminal connected to the second port; and a
control terminal, wherein during operation, a control signal at the
control terminal of the RF integrated circuit is configured to tune
the RF tunable notch filter and/or control the RF switch to
enable/disable a current flow through the RF tunable notch
filter.
20. The RF integrated circuit of claim 19, wherein the RF tunable
notch filter comprises one or more variable reactive elements.
21. The RF integrated circuit of claim 20, wherein a reactive
element of the one or more variable reactive elements comprises one
of: a) a digitally tunable capacitor, and b) a digitally tunable
inductor.
22. The RF integrated circuit of claim 19 monolithically integrated
on a same integrated circuit.
23. The RF integrated circuit of claim 22 fabricated using a
technology comprising one of: a) Silicon on Sapphire, b) Silicon on
Insulator, c) bulk-Silicon, and d) micro-electro-mechanical
systems.
24. The RF circuital arrangement of claim 19 configured for
operation in one of: a) a differential mode, and b) single-ended
mode.
25. A communication device for transmitting and receiving RF
signals via one or more antennas, the communication device
comprising the RF circuital arrangement of claim 1 or claim 18,
wherein the one or more antennas of the communication device are
coupled to a plurality of transmit/receive ports of a plurality of
transmit/receive systems of the RF circuital arrangement.
26. The communication device of claim 25 further comprising a
transceiver unit, wherein during operation of the communication
device, the transceiver unit is adapted to send/receive a plurality
of transmit/receive RF signals to/from the plurality of
transmit/receive systems of the RF circuital arrangement.
27. The communication device of claim 26, wherein, during operation
of the communication device, the transceiver unit is adapted to
control the one or more tunable notch filters based on a
characteristic of one or more RF signals of the plurality of
transmit/receive RF signals.
28. The communication device of claim 27, wherein the
characteristic comprises a frequency spectra of the one or more RF
signals.
29. The communication device of claim 28, wherein the frequency
spectra comprises at least one of: a) spectra of a frequency of
operation of an RF signal of the one or more RF signals, b) spectra
of a harmonic of a) and c) spectra of an intermodulation product of
the one or more RF signals.
30. A method for reducing radio frequency (RF) interference in an
RF circuital arrangement, the method comprising: providing a
plurality of RP transmit/receive systems coupled to a plurality RF
antennas; connecting in a path of a first RF transmit/receive
system of the plurality of RF transmit/receive systems one or more
RF tunable notch filters; adjusting an RF tunable notch filter of
the one or more RF tunable notch filters based on a characteristic
of a transmit/receive RF signal of an RF transmit/receive system of
the plurality of RF transmit/receive systems other than the first
RF transmit/receive system; and based on the adjusting, reducing an
RF interference of the transmit/receive RF signal over the first RF
transmit/receive system.
31. The method of claim 30, further comprising: monitoring the
characteristic of the transmit/receive RF signal; based on the
monitoring, detecting a change of the characteristic; based on the
detecting, further adjusting the RF tunable notch filter; and based
on the further adjusting, maintaining a reduced RF interference of
the transmit/receive RF signal over the first RF transmit/receive
system.
32. The method of claim 31, further comprising: based on the
maintaining, providing a larger operating frequency spectrum to the
first transmit/receive RF system; based on the providing,
increasing a number of transmit/receive channels available to the
first transmit/receive RF system; and based on the increasing,
increasing data throughput of the RF circuital arrangement.
33. The method of claim 30, wherein the characteristic of the
transmit/receive RF signal comprises a known operating frequency of
the transmit/receive RF signal.
34. The method of claim 33, wherein the known operating
characteristic is in correspondence of a selected transmit/receive
channel.
35. The method of claim 34, wherein selection of the selected
transmit/receive channel is performed by a transceiver unit.
36. A radio frequency (RF) circuital arrangement comprising: a
transmit path configured to transmit, during a transmit mode of
operation of the RF circuital arrangement, a transmit RF signal at
a transmit/receive port of the RF circuital arrangement; a receive
path configured to receive, during a receive mode of operation of
the RF circuital arrangement, a receive RF signal at the
transmit/receive port, and a tunable notch filter configured to
reduce a radio frequency interference of the transmit RF signal
over the receive RF signal, wherein during operation, the RF
circuital arrangement is configured to simultaneously operate in
the transmit and receive modes of operation.
37. The RF circuital arrangement of claim 36, wherein the transmit
path and the receive path are coupled to the transmit/receive port
via a duplexer unit and wherein the tunable notch filter is
connected between the duplexer unit and one of: a) an input RF
amplifier of the receive path, b) a transmit RF amplifier of the
transmit path, and c) the transmit/receive port.
38. The RF circuital arrangement of claim 36 or claim 37, wherein
the tunable notch filter is connected in a series or shunt
configuration.
39. The RF circuital arrangement of claim 38, further comprising an
RF switch coupled to the tunable notch filter, wherein during
operation of the RF circuital arrangement, the RF switch is
configured to enable and/or disable an effect of the tunable notch
filter over the receive RF signal.
40. The RF circuital arrangement of claim 39, wherein the switch
comprises stacked transistors.
41. The RF circuital arrangement of claim 39, wherein the switch is
connected in one of: a) parallel configuration and b) serial
configuration to the tunable notch filter.
42. The RF circuital arrangement of claim 36, wherein the tunable
notch filter is a band-reject filter configured, during operation
of the RF circuital arrangement, to reject a frequency of operation
of the transmit RF signal and to pass a frequency of operation of
the receive RF signal.
43. The RF circuital arrangement of claim 42, wherein: the
frequency of operation of the transmit RF signal is in
correspondence of a transmit channel of a plurality of transmit
channels; the frequency of operation of the receive RF signal is in
correspondence of a receive channel of a plurality of receive
channels; and the RF circuital arrangement is configured to operate
in one or more transmit and receive channels.
44. The RF circuital arrangement of claim 36, wherein the tunable
notch filter comprises one or more variable reactive elements.
45. The RF circuital arrangement of claim 44, wherein a reactive
element of the one or more variable reactive elements comprises one
of: a) a digitally tunable capacitor, and b) a digitally tunable
inductor.
46. The RF circuital arrangement of claim 36, wherein the
transmit/receive port comprises a transmit/receive antenna.
47. A communication device for transmitting and receiving radio
frequency (RF) signals via an antenna, the communication device
comprising the RF circuital arrangement of claim 43, wherein the
antenna of the communication device is coupled to the
transmit/receive port of the RF circuital arrangement.
48. The communication device of claim 47 further comprising a
transceiver unit, wherein during operation of the communication
device, the transceiver unit is configured to send the transmit RF
signal and to receive the receive RF signal respectively to/from
the transmit path and receive path of the RF circuital
arrangement.
49. The communication device of claim 48, wherein, during operation
of the communication device, the transceiver unit is adapted to
control the tunable notch filter based on a transmit channel
frequency and/or a receive channel frequency in correspondence of
the transmit RF signal and the receive RF signal respectively.
50. A method for reducing radio frequency (RF) interference in an
RF circuital arrangement, the method comprising: providing an RF
transmit path to transmit a transmit RF signal over an antenna;
providing an RF receive path to receive a receive RF signal over
the antenna; coupling a tunable notch filter to the RF transmit or
the RF receive path; adjusting the tunable notch filter based on a
frequency of operation of the transmit RF signal; and based on the
adjusting, reducing an RF interference of the transmit RF signal
over the receive RF signal.
51. The method of claim 50, wherein the adjusting further
comprises: further adjusting the tunable notch filter based on a
frequency of operation of the receive RF signal.
52. The method of claim 50, wherein the frequency of operation is
in correspondence of a frequency of a selected transmit channel and
wherein the adjusting is performed under control of a controller
unit aware of the selected transmit channel.
53. The method of claim 52, wherein the controller unit is a
transceiver unit.
54. The method of claim 51, wherein the adjusting is based on an
intermodulation product of the frequency of operation of the
transmit RF signal and the frequency of operation of the receive RF
signal.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is related to U.S. patent
application Ser. No. ______ entitled "Devices and Methods for
Duplexer Loss Reduction" (Attorney Docket No. PER-100-PAP) filed on
even date herewith and incorporated herein by reference in its
entirety. The present application is also related to U.S. patent
application Ser. No. ______ entitled "Integrated Tunable Filter
Architecture" (Attorney Docket No. PER-115-PAP) filed on even date
herewith and incorporated herein by reference in its entirety.
[0002] The present application may be related to U.S. Pat. No.
6,804,502, issued on Oct. 12, 2004 and entitled "Switch Circuit and
Method of Switching Radio Frequency Signals", the disclosure of
which is incorporated herein by reference in its entirety. The
present application may also be related to U.S. Pat. No. 7,910,993,
issued on Mar. 22, 2011 and entitled "Method and Apparatus for use
in improving Linearity of MOSFET's using an Accumulated Charge
Sink", the disclosure of which is incorporated herein by reference
in its entirety. The present application may also be related to
U.S. patent application Ser. No. 13/797,779 entitled "Scalable
Periphery Tunable Matching Power Amplifier", filed on Mar. 3, 2013,
the disclosure of which is incorporated herein by reference in its
entirety. The present application may also be related to
International Application No. PCT/US2009/001358, entitled "Method
and Apparatus for use in digitally tuning a capacitor in an
integrated circuit device", filed on Mar. 2, 2009, the disclosure
of which is incorporated herein by reference in its entirety. The
present application may also be related to U.S. patent application
Ser. No. 13/595,893, entitled "Method and Apparatus for Use in
Tuning Reactance in a Circuit Device", filed on Aug. 27, 2012, the
disclosure of which is incorporated herein by reference in its
entirety. The present application may also be related to U.S.
patent application Ser. No. 14/042,312, filed on Sep. 30, 2013,
entitled "Methods and Devices for Impedance Matching in Power
Amplifier Circuits", the disclosure of which is incorporated herein
by reference in its entirety. The present application may also be
related to U.S. Pat. No. 7,248,120, issued on Jul. 24, 2007,
entitled "Stacked Transistor Method and Apparatus", the disclosure
of which is incorporated herein by reference in its entirety. The
present application may also be related to U.S. patent application
Ser. No. 13/828,121, filed on Mar. 14, 2013, entitled "Autonomous
Power Amplifier Optimization", the disclosure of which is
incorporated herein by reference in its entirety. The present
application may also be related to U.S. patent application Ser. No.
13/967,866 entitled "Tunable Impedance Matching Network", filed on
Aug. 15, 2013, the disclosure of which is incorporated herein by
reference in its entirety. The present application may also be
related to U.S. patent application Ser. No. 13/797,686 entitled
"Variable Impedance Match and Variable Harmonic Terminations for
Different Modes and Frequency Bands", filed on Mar. 12, 2013, the
disclosure of which is incorporated herein by reference in its
entirety. The present application may also be related to U.S.
patent application Ser. No. 14/042,331 entitled "Methods and
Devices for Thermal Control in Power Amplifier Circuits", filed on
Sep. 30, 2013, the disclosure of which is incorporated herein by
reference in its entirety. The present application may also be
related to U.S. patent application Ser. No. 13/829,946 entitled
"Amplifier Dynamic Bias Adjustment for Envelope Tracking, filed on
Mar. 14, 2013, the disclosure of which is incorporated herein by
reference in its entirety. The present application may also be
related to U.S. patent application Ser. No. 13/830,555 entitled
"Control Systems and Methods for Power Amplifiers Operating in
Envelope Tracking Mode", filed on Mar. 14, 2013, the disclosure of
which is incorporated herein in its entirety.
BACKGROUND
[0003] 1. Field
[0004] The present teachings relate to RF (radio frequency)
circuits. More particularly, the present teachings relate to
methods for increasing data throughput in an RF transmit/receive
system.
[0005] 2. Description of Related Art
[0006] Radio frequency (RF) devices, such as cell phone
transmitters, are becoming increasingly complex due to additional
frequency bands, more complex modulation schemes, higher modulation
bandwidths, and the introduction of data throughput improvement
schemes such as simultaneous RF transmission and/or reception
within a same or different, but closely spaced, bands or channels
within a band (e.g. voice, data), and aggregate transmission
wherein information is multiplexed over parallel RF transmissions.
Due to the high integration and closely spaced transmit/receive
paths of a front-end stage used in such RF devices, RF signal
interference from neighboring paths, either receive or transmit,
can influence RF signal of a transmit/receive path (e.g. via
intermodulation) and therefore affect (e.g. reduce) a corresponding
throughput by increasing spectrum usage within a frequency band and
therefore limiting the number of simultaneous RF transmission
and/or reception (e.g. number of usable channels) within a
frequency band.
SUMMARY
[0007] According to a first aspect of the present disclosure, a
radio frequency (RF) circuital arrangement is presented, the
arrangement comprising: a first transmit/receive system comprising
a first transmit path configured to transmit a first transmit RF
signal at a first transmit/receive port, and a first receive path
configured to receive a first receive RF signal at the first
transmit/receive port; a second transmit/receive system comprising
a second transmit path configured to transmit a second transmit RF
signal at a second transmit/receive port, and a second receive path
configured to receive a second receive RF signal at the second
transmit/receive port, and one or more tunable notch filters
configured to reduce a radio frequency interference of a
transmit/receive system of the first and second transmit/receive
systems over the other transmit/receive system.
[0008] According to second aspect of the present disclosure, a
radio frequency (RF) integrated circuit is presented, the
integrated circuit comprising: an RF switch comprising a first
switch terminal and a second switch terminal; a RF tunable notch
filter comprising a first port and a second port, wherein in a
first configuration of the RF integrated circuit the first port is
connected to the first switch terminal and the second port is
connected to the second switch terminal, and in a second
configuration of the RF integrated circuit the first port is
connected to the second switch terminal; a first input/output
terminal connected to the first switch terminal; a second
input/output terminal connected to the second port, and a control
terminal, wherein during operation, a control signal at the control
terminal of the RF integrated circuit is configured to tune the RF
tunable notch filter and/or control the RF switch to enable/disable
a current flow through the RF tunable notch filter.
[0009] According to a third aspect of the present disclosure, a
method for reducing radio frequency (RF) interference in an RF
circuital arrangement is presented, the method comprising:
providing a plurality of RF transmit/receive systems coupled to a
plurality RF antennas; connecting in a path of a first RF
transmit/receive system of the plurality of RF transmit/receive
systems one or more RF tunable notch filters; adjusting an RF
tunable notch filter of the one or more RF tunable notch filters
based on a characteristic of a transmit/receive RF signal of an RF
transmit/receive system of the plurality of RF transmit/receive
systems other than the first RF transmit/receive system, and based
on the adjusting, reducing an RF interference of the
transmit/receive RF signal over the first RF transmit/receive
system.
[0010] According to a fourth aspect of the present disclosure, a
radio frequency (RF) circuital arrangement is presented, the
arrangement comprising: a transmit path configured to transmit,
during a transmit mode of operation of the RF circuital
arrangement, a transmit RF signal at a transmit/receive port of the
RF circuital arrangement; a receive path configured to receive,
during a receive mode of operation of the RF circuital arrangement,
a receive RF signal at the transmit/receive port, and a tunable
notch filter configured to reduce a radio frequency interference of
the transmit RF signal over the receive RF signal, wherein during
operation, the RF circuital arrangement is configured to
simultaneously operate in the transmit and receive modes of
operation.
[0011] According to a fifth aspect of the present disclosure a
method for reducing radio frequency (RF) interference in an RF
circuital arrangement is presented, the method comprising:
providing an RF transmit path to transmit a transmit RF signal over
an antenna; providing an RF receive path to receive a receive RF
signal over the antenna; coupling a tunable notch tilter to the RF
transmit or the RF receive path; adjusting the tunable notch filter
based on a frequency of operation of the transmit RF signal, and
based on the adjusting, reducing an RF interference of the transmit
RF signal over the receive RF signal.
BRIEF DESCRIPTION OF DRAWINGS
[0012] The accompanying drawings, which are incorporated into and
constitute a part of this specification, illustrate one or more
embodiments of the present disclosure and, together with the
description of example embodiments, serve to explain the principles
and implementations of the disclosure.
[0013] FIG. 1 shows an exemplary block diagram of a
transmit/receive system comprising a transmit path and a receive
path used in a multi-band and multi-channel RF front-end stage of
an RF device, as used, for example, in a cellular phone.
[0014] FIG. 2A shows an exemplary graph of frequency spectra of an
RF transmit signal and an RF receive signal of the transmit/receive
system of FIG. 1.
[0015] FIG. 21 and FIG. 2C show exemplary graphs of frequency bands
and associated frequency channels which can be used in the
transmit/receive system of FIG. 1.
[0016] FIG. 2D shows an exemplary embodiment according to the
present disclosure of a transmit/receive system comprising a
tunable notch filter in a receive path.
[0017] FIG. 3 shows an exemplary block diagram of a multiple RF
paths transmit/receive system comprising two parallel
transmit/receive systems which can be used to increase throughput
of an RF front-end stage.
[0018] FIG. 4A shows a frequency plan which can be used by the
multiple RF paths transmit/receive system of FIG. 3.
[0019] FIG. 4B shows a frequency plan comprising intermodulation
products of two RF signals.
[0020] FIG. 4C shows a frequency plan comprising intermodulation
products of two RF transmit signals of the multiple RF paths
transmit/receive system of FIG. 3, wherein an intermodulation
product can occupy one or more receive channels of a receive band
used by the multiple RF paths transmit/receive system.
[0021] FIG. 4D shows the frequency plan of FIG. 4C for a case where
additional to the two RF transmissions, an RF reception is also
taking place. As depicted in FIG. 4D, a spectrum of an
intermodulation product between the two RF transmit signals can
occupy a portion of the spectrum used for an RF receive signal.
[0022] FIGS. 5A-SB show embodiments according to the present
disclosure of the multiple RF paths transmit/receive system of FIG.
3, wherein a tunable notch filter is used to reduce interference of
one transmit/receive system over the other.
[0023] FIG. 6 shows an embodiment according to the present
disclosure of the multiple RF paths transmit/receive system of FIG.
3, wherein series and shunt connected tunable notch filters within
both the transmit/receive systems are used to immune either
transmit/receive system with respect to the other.
[0024] FIG. 7 shows an embodiment according to the present
disclosure wherein switches are used to bypass the series and shunt
connected tunable notch filters used in FIG. 6.
[0025] FIG. 8A shows an embodiment according to the present
disclosure of a monolithically integrated tunable notch filter in
parallel connection with an RF switch.
[0026] FIG. 8B shows an embodiment according to the present
disclosure of a monolithically integrated tunable notch filter in
series connection with an RF switch.
[0027] FIG. 9 shows an exemplary embodiment of a switch with
stacked transistors.
DETAILED DESCRIPTION
[0028] Throughout this description, embodiments and variations are
described for the purpose of illustrating uses and implementations
of the inventive concept. The illustrative description should be
understood as presenting examples of the inventive concept, rather
than as limiting the scope of the concept as disclosed herein.
[0029] As used in the present disclosure, the terms "switch ON" and
"activate" may be used interchangeably and can refer to making a
particular circuit element electronically operational. As used in
the present disclosure, the terms "switch OFF" and "deactivate" may
be used interchangeably and can refer to making a particular
circuit element electronically non-operational. As used in the
present disclosure, the terms "amplifier" and "power amplifier" may
be used interchangeably and can refer to a device that is
configured to amplify a signal input to the device to produce an
output signal of greater magnitude than the magnitude of the input
signal.
[0030] The present disclosure describes electrical circuits in
electronics devices (e.g., cell phones, radios) having a plurality
of devices, such as for example, transistors (e.g., MOSFETs).
Persons skilled in the art will appreciate that such electrical
circuits comprising transistors can be arranged as amplifiers. As
described in a previous disclosure (U.S. patent application Ser.
No. 13/797,779, incorporated herein by reference in its entirety),
a plurality of such amplifiers can be arranged in a so-called
"scalable periphery" (SP) architecture of amplifiers where a total
number (e.g., 64) of amplifier segments are provided. Depending on
the specific requirements of an application, the number of active
devices (e.g., 64, 32, etc.), or a portion of the total number of
amplifiers (e.g. 1/64, 2/64, 40% of 64, etc. . . . ), can be
changed for each application. For example, in some instances, the
electronic device may desire to output a certain amount of power,
which in turn, may require 32 of 64 SP amplifier segments to be
used. In yet another application of the electronic device, a lower
amount of output power may be desired, in which case, for example,
only 16 of 64 SP amplifier segments are used. According to some
embodiments, the number of amplifier segments used can be inferred
by a nominal desired output power as a function of the maximum
output power (e.g. when all the segments are activated). For
example, if 30% of the maximum output power is desired, then a
portion of the total amplifier segments corresponding to 30% of the
total number of segments can be enabled. The scalable periphery
amplifier devices can be connected to corresponding impedance
matching circuits. The number of amplifier segments of the scalable
periphery amplifier device that are turned on or turned off at a
given moment can be according to a modulation applied to an input
RF signal, a desired output power, a desired linearity requirement
of the amplifier or any number of other requirements.
[0031] The term "amplifier" as used in the present disclosure is
intended to refer to amplifiers comprising single or stacked
transistors configured as amplifiers, and can be used
interchangeably with the term "power amplifier (PA)". Such terms
can refer to a device that is configured to amplify a signal input
to the device to produce an output signal of greater magnitude than
the magnitude of the input signal. Stacked transistor amplifiers
are described for example in U.S. Pat. No. 7,248,120, issued on
Jul. 24, 2007, entitled "Stacked Transistor Method and Apparatus",
the disclosure of which is incorporated herein by reference in its
entirety. Such amplifier and power amplifiers can be applicable to
amplifiers and power amplifiers of any stages (e.g., pre-driver,
driver, final), known to those skilled in the art.
[0032] As used in the present disclosure, the term "mode" can refer
to a wireless standard and its attendant modulation and coding
scheme or schemes. As different modes may require different
modulation schemes, these may affect required channel bandwidth as
well as affect the peak-to-average-ratio (PAR), also referred to as
peak-to-average-power-ratio (PAPR), as well as other parameters
known to the skilled person. Examples of wireless standards include
Global System for Mobile Communications (GSM), code division
multiple access (CDMA), Worldwide Interoperability for Microwave
Access (WiMAX), Long Term Evolution (LTE), as well as other
wireless standards identifiable to a person skilled in the art.
Examples of modulation and coding schemes include binary
phase-shift keying (BPSK), quadrature phase-shift keying (QPSK),
quadrature amplitude modulation (QAM), 8-QAM, 64-QAM, as well as
other modulation and coding schemes identifiable to a person
skilled in the art.
[0033] As used in the present disclosure, the term "band" can refer
to a frequency range. More in particular, the term "band" as used
herein refers to a frequency range that can be defined by a
wireless standard such as, but not limited to, wideband code
division multiple access (WCDMA) and long term evolution (LTE).
[0034] As used in the present disclosure, the term "channel" can
refer to a frequency range. More in particular, the term "channel"
as used herein refers to a frequency range within a band. As such,
a band can comprise several channels used to transmit/receive a
same wireless standard.
[0035] FIG. 1 shows a block diagram of a transmit/receive system
(100) comprising a transmit path and a receive path which can be
used in a multi-band and multi-channel RF front-end stage of an RF
device, such as, for example, a cellular phone. The
transmit/receive system (100) of FIG. 1 comprises a transceiver
unit (140) adapted to generate an RF signal to be transmitted via
an antenna (110) of the system. An RF transmit path of the
transmit/receive system (100) can comprise an RF amplifier module
(120) and a duplexer unit (130). The RF amplifier module (120) can
amplify the RF signal provided by the transceiver unit (140) and
further shape the RF signal in a way more suitable for
transmission, such as described in, for example, U.S. patent
application Ser. No. 13/829,946 and U.S. patent application Ser.
No. 13/830,555, both of which are herein incorporated by reference
in their entirety. Furthermore, as known to the person skilled in
the art, the amplifier module (140) can comprise a plurality of
series connected amplifiers, such as a driver and a final, wherein
each of the series connected amplifiers may further comprise
stacked transistors such as described in, for example, U.S. Pat.
No. 7,248,120, incorporated herein by reference in its entirety,
and/or parallel amplifiers such as scalable periphery amplifiers,
as described in, for example, U.S. patent application Ser. No.
13/797,779, incorporated herein by reference in its entirety,
and/or efficiency improvement amplifiers such as envelope tracking
amplifiers, as described in U.S. patent application Ser. No.
13/829,946, incorporated herein by reference in its entirety.
Furthermore, the various series connected amplifiers may further be
coupled via impedance matching and/or harmonic termination
networks, as described in, for example, U.S. patent application
Ser. No. 13/967,866 and U.S. patent application Ser. No.
13/797,686, both incorporated herein by reference in their
entirety. The amplifier module (130) thus feeds an amplified RF
signal of the amplifier module (120) to the duplexer unit (130),
which duplexer unit further filters the RF signal to be transmitted
through a band-pass filter centered at a frequency of operation of
the band within which the RF signal is transmitted. The duplexer
unit (130) can allow simultaneous transmit and receive via a same
transmit/receive port, such as the antenna (110), by filtering the
transmit RF signal such as not to affect (e.g. overload) a receive
RF signal to the receive path and filtering a receive RF signal
according to a receive frequency band and channel. A received RF
signal, subsequent to filtering by the duplexer (130), can be fed
to the transceiver unit (140) via an internal amplifier (e.g. low
noise amplifier) which is tuned for the frequency of the received
RF signal and has an input stage closely matched to the receive
path electrical characteristics (e.g. impedance) at the tuned
frequency. Once the received RF signal is amplified, the
transceiver unit (140) can further down convert the received
amplified signal to an intermediate frequency (IF) signal used for
decoding of the information (e.g. voice, data) in the received RF
signal.
[0036] FIG. 2A shows an exemplary graph of frequency spectra of an
RF transmit signal (210) and an RF receive signal (220) of the
transmit/receive system (100) of FIG. 1. The transmit RF signal has
an RF spectrum (210) centered at a transmit center frequency
f1.sub.T and of peak power P.sub.T at the transmit center
frequency. Similarly, the receive RF signal has an RF spectrum
(220) centered at a receive center frequency fl.sub.R and of peak
power P.sub.R at the receive center frequency. As depicted in the
exemplary graph of FIG. 2A, the transmit RF signal can have an
energy several order of magnitude higher than the energy of the
receive RF signal, such as, for example, P.sub.T/P.sub.R>100.
The separation between the receive and the transmit channels in
correspondence of the receive and transmit signals, as measured for
example by the difference between f1.sub.T and f1.sub.R, and in
combination with the filters of the duplexer unit (130) of FIG. 1,
allow for a detection of the RF receive signal. Therefore, design
of the duplexer (130) can be according to a desired
transmit/receive channel separation, latter channel separation
taking into consideration spread in frequency required for the
specific modulation scheme used in the RF transmit/receive
signal.
[0037] As previously mentioned, a transmit/receive RF signal can be
in correspondence of a frequency band associated to a wireless
standard (e.g. mode), and in turn, the frequency band can comprise
a plurality of channels which can be used to transmit/receive an RF
signal according the defined modulation scheme of the wireless
standard. FIG. 2B shows two adjacent bands (230) and (240), each
band comprising a plurality (e.g. 3) of adjacent channels with
center frequencies (f1.sub.R, f2.sub.R, f3.sub.R) for the channels
of band (230) and center frequencies (f1.sub.T, f2.sub.T, f3.sub.T)
for the channels of band (240). Separation of the various channels
(e.g. distance between two adjacent center frequencies) can be such
as to allow a frequency spread defined by the attending modulation
scheme. The bands (230, 240) shown in FIG. 21 can be used for the
transmit/receive system (100) of FIG. 1, such as for example, band
(230) for receiving and band (240) for transmitting. Accordingly,
the transmit/receive system can use any of the three channels of
band 230) for transmitting and any of the three channels of band
(240) for receiving. The duplexer unit (130) of the
transmit/receive system (100) can be designed such as to have a
center frequency for its receive filter according to the center
frequency of the receive band (230) and a center frequency for its
transmit filter according to the center frequency of the transmit
band (240). As shown in the exemplary graph of FIG. 2B, at a given
time of operation of the transmit receive system (100), a transmit
channel defined by the center frequency f1.sub.T can be used
simultaneously with a receive channel defined by the center
frequency f3.sub.R, and at another time of operation as depicted by
FIG. 2C, a transmit channel defined by the center frequency
f2.sub.T can be used simultaneously with a receive channel defined
by the center frequency f2.sub.R. In some cases the spacing (e.g.
frequency spread) between the transmit and receive channels can be
kept constant, such as, for example, exclusively using the pairs
(f1.sub.T, f1.sub.R), (f2.sub.T, f2.sub.R) or (f3.sub.T, f3.sub.R)
as transmit/receive frequency centers. As depicted by the two FIGS.
2B and 2C, the further apart the two channels used for transmit and
receive, the least the interference between the transmit and
receive signals can be. As the RF transmit signal can have far more
energy than that of an RF receive signal, interference of the
transmit RF signal into the receive path can have a noticeable
effect on reception of the receive RF signal (e.g. overload of the
receive path). Therefore, one can minimize such interference effect
by increasing the receive/transmit channel spacing, or by not using
all possible combinations transmit/receive channels (e.g. constant
spacing as per above), both at the cost of reduced number of
channels for a given frequency band of operation. Alternatively and
according to the various embodiments of the present disclosure,
filtering can be used to further reduce the amount of transmit RF
signal reaching the receiver.
[0038] According to an embodiment of the present disclosure, a
method for reducing such interference effect while maintaining a
higher number of transmit/receive channels is provided. Such method
uses a tunable filter in the receive and/or transmit path to
further immune the two paths with respect to each other. For
example, a tunable band-reject filter tuned at a center frequency
of an RF transmit signal (e.g. f1.sub.T, f2.sub.T, f3.sub.T) can be
placed in the receive path to reject a transmit RF frequency in the
receive path such as depicted in FIG. 2D. Such tunable band-reject
filter (235) of FIG. 2D can be placed after the duplexer unit (130)
(e.g. between duplexer and input amplifier of transceiver 140) and
can be designed to provide band-reject filters centered at any one
of the frequencies (f1.sub.T, f2.sub.T, f3.sub.T) of the channels
used in the transmission of the RF signal. Although not shown in
the exemplary embodiment of FIG. 21), the tunable band reject
filter can comprise one or more stages (e.g.
resistor-inductor-capacitor RLC) interconnected in a series and/or
a shunt configuration and coupled and/or connected to the receive
path in a series and/or shunt configuration (shunt configuration
not shown in FIG. 2D). Some examples of such filters are provided
in the above mentioned U.S. application Ser. No. ______ entitled
"Integrated Tunable Filter Architecture" (Attorney Docket No.
PER-115-PAP) filed on even date herewith and incorporated herein by
reference in its entirety. A controller unit aware of the operation
of the transmit/receive system of FIG. 2D, such as, for example,
the transceiver unit (140), can control the configuration of the
tunable band-reject filter (235) according to the channel (e.g. a
corresponding frequency of operation) being used for transmission
and/or reception at a given time of operation of the system. A
band-reject filter configuration of the tunable band-reject filter
(235) of FIG. 2D can reject a frequency within a transmission
channel while pass frequencies outside the transmission channel.
This tunable notch filter (e.g. band-reject) can be used to reduce
the attenuation requirements of the duplexer. Since the controller
knows the frequency assignments (e.g. channels used) at that
moment, it can place the center of the notch at the appropriate
frequency. The design requirements for such notch filter may be
easier than design requirements of a bandpass filter or the
duplexer filter. Fewer resonators may be required because the
filter doesn't have to cover the entire band (e.g. consisting of
various channels) and the shape of the filter response can be less
important than the shape of a bandpass and/or duplexer filter. The
reduced number of resonators (e.g. filter stages) typically results
in lower insertion loss (e.g. less than 1.5 dB versus larger than
2.0 dB) and smaller physical implementations of such tunable notch
filter.
[0039] The person skilled in the art readily knows that the system
block diagram depicted in FIG. 1 is a simplistic representation of
a single path transmit/receive system used in an RF front-end
stage, as such front-end stage can include a plurality of similar
transmit/receive paths sharing the same antenna (110), and the same
transceiver unit (140). In other exemplary configurations, the
plurality of the transmit/receive paths can use different antennas,
such as to further increase data throughput via simultaneous RF
transmit/receive on a same or different bands and/or channels, as
depicted in FIG. 3. Some examples of such system implementations
using a plurality of transmit/receive paths and antennas are
carrier aggregation, multiple-input multiple-output (MIMO), or
simply multiple radios in one end product such as a mobile cell
phone.
[0040] With further reference to FIG. 3, a block diagram of a
multiple paths (e.g. two paths) transmit/receive system (300) is
shown, wherein each transmit/receive path uses a separate antenna.
Principle of operation of each of the two transmit/receive paths is
the same as described in relation to the block diagram depicted in
the FIG. 1. A first transmit/receive path of the system (300) of
FIG. 2 is defined by the transceiver unit (140), the amplifier
module (120), the duplexer unit (130) and the antenna (110),
whereas a second transmit/receive path of the system (300) is
defined by the transceiver unit (140), the amplifier module (320),
the duplexer unit (330) and the antenna (310). It should be noted
that the antenna (110, 130) can be considered as a common
transmit/receive port for the corresponding transmit/receive path
as other types of ports can be envisioned such as to allow
simultaneous outflow and inflow of signals to the transmit/receive
system 300, such as, for example, a coupler and/or other devices
known to the skilled person. It should further be noted that
although the exemplary multiple RF paths transmit/receive system
(300)) of FIG. 3 uses a single transceiver unit (140) for all
transmit/receive paths, according to some embodiments, different
transceiver units can be used for each of the plurality of
transmit/receive paths or for groups of the plurality of
transmit/receive paths.
[0041] The duplexer units (130) and (330) of FIG. 3 can be designed
for certain transmit/receive frequency bands of operation. As
previously mentioned, transmit/receive system (140, 120, 130, 110)
can transmit at a first transmit band and receive at a first
receive band, whereas transmit/receive system (140, 320, 330, 310)
can transmit at a second transmit band and receive at a second
receive band. In some cases, the first and second transmit/receive
bands can be a same band (e.g. same frequency span) and in other
cases they can be different, as the configuration depicted in FIG.
3 can allow increased in data throughput by using the multiple
(e.g. two) transmit/receive paths for an aggregate transmit/receive
scheme (e.g. of a same mode) or by using the multiple
transmit/receive paths for transmit/receive different modes.
[0042] FIG. 4A shows a frequency plan that can be used by the
multiple RF paths transmit/receive system (300) of FIG. 3 to
increase data throughput. In the frequency plan depicted in FIG.
4A, a first frequency band (410) can range from a frequency f.sub.1
to a frequency f.sub.2, while a second frequency band (420),
adjacent to the frequency band (410), can range from the frequency
f.sub.2 to a frequency f.sub.3. Similarly, at a far end side of the
frequency plan of FIG. 4A, a frequency band (430) can range from a
frequency f.sub.4 to a frequency f.sub.5, while an adjacent
frequency band (440), can range from the frequency f.sub.5 to a
frequency f.sub.6. Within the frequency band (410, 420, 430, 440),
a first channel (410a. 420a. 430a, 440a) may be adjacent to a
second channel (410b, 420b. 430b. 440b), while a third channel
(410f. 4201, 430f, 440f) may be separated from the first and the
second channels.
[0043] In a first mode of operation of the multiple RF paths
transmit/receive system (300) of FIG. 3 and with reference to the
frequency plan of FIG. 4A, a mode being defined by, for example, a
wireless system standard, separate frequency bands can be used by
the multiple transmit/receive paths of the multiple RF paths
transmit/receive system (300) for each signal transmission and
signal reception. For example, any channel (410a, 410b, . . . ,
410f) of frequency band (410) can be used for reception of an RF
signal via the transmit/receive system (140, 120, 130, 110) while
any channel (430a, 430b, . . . , 430f) of frequency band (430) can
be used for reception of an RF signal via the transmit/receive
system (140, 320, 330, 310). Similarly and simultaneous to the
reception, any channel (420a. 420b, . . . , 420f) of frequency band
(420) can be used for transmission of an RF signal via the
transmit/receive system (140, 120, 130, 110) while any channel
(440a, 440b, . . . , 440f) of frequency band (440) can be used for
reception of an RF signal via the transmit/receive system (140,
320, 330, 310). In such mode of operation of the multiple RF paths
transmit/receive system (300) of FIG. 3, transmission over the band
(420) by one of the transmit/receive systems of the multiple RF
paths system (300) can coincide with transmission and/or reception
over the bands (430, 440) by the other transmit/receive system, and
similarly, transmission over the band (440) by one transmit/receive
system of the multiple RF paths system (300) can also coincide with
transmission and/or reception over the bands (410, 420) by the
other transmit/receive system. Therefore, during operation of the
multiple RF paths transmit/receive system (300) of FIG. 3, an
exemplary spectrum occupied by each of the transmit/receive systems
of the multiple RF paths system (300) can be represented by the
graphs depicted in FIGS. 2B and 2C, wherein the frequency bands
(230, 240) can be (410, 420) for the transmit/receive system (140,
120, 130, 110) or (430, 440) for the transmit/receive system (140,
320, 330, 310).
[0044] According to a second mode of operation of the multiple RF
paths transmit/receive system (300)) of FIG. 3 and with reference
to the frequency plan of FIG. 4A, a mode being defined by, for
example, a wireless system standard, a same frequency band can be
used by the multiple transmit/receive paths of the multiple RF
paths transmit/receive system (300) for each signal transmission
and signal reception. For example, any channel (410a, 410b, . . . ,
410f) of frequency hand (410) can be used for reception of an RF
signal via the transmit/receive system (140, 120, 130, 110) while
the same channels (410a, 410b, . . . , 410f) of frequency band
(410) can be used for reception of an RF signal via the
transmit/receive system (140, 320, 330, 310). Similarly and
simultaneous to the reception, any channel (420a, 420b, . . . ,
420f) of frequency band (420) can be used for transmission of an RF
signal via the transmit/receive system (140, 120, 130, 110) while
any channel (420a, 420b, . . . , 420f) of the same frequency band
(420) can be used for reception of an RF signal via the
transmit/receive system (140, 320, 330, 310). In such mode of
operation of the multiple RF paths transmit/receive system (300) of
FIG. 3, transmission by one of the transmit/receipt systems of
system (300) over the band (420) can coincide with transmission
and/or reception over the bands (410, 420) by the other
transmit/receive system, and similarly, transmission over the band
(440) by one transmit/receive system of the multiple RF paths
system (300) can also coincide with transmission and/or reception
over the bands (430, 440) by the other transmit/receive system of
the multiple RF paths system (300). Therefore, during operation of
the multiple RF paths transmit/receive system (300) of FIG. 3, a
spectrum occupied by each of the transmit/receive systems of the
multiple RF paths system (300) can be represented by the graphs
depicted in FIGS. 2B and 2C, wherein the frequency bands (230, 240)
can be either (410, 420) for both transmit/receive systems (140,
120, 130, 110) and (140, 320, 330, 310), or (430, 440) for both the
transmit/receive systems (140, 120, 130, 110) and (140, 320, 330,
310).
[0045] According to an embodiment of the present disclosure, a
tunable notch filter, such as a narrow tunable band-reject filter,
can be placed (e.g. via a series and/or a shunt
connection/coupling, such as depicted in FIG. 6 later described) in
either or both transmit/receive systems (140, 120, 130, 110) and
(140, 320, 330, 310) in order to immune the two systems from
interfering with each other (as depicted for example in FIG. 5A and
FIG. 5B later described). As it is known to the person skilled in
the art, RF signals at different frequencies used within a same
system, such as in the multiple RF paths transceiver/receive system
(300) of FIG. 3 operating in either first or second mode of
operation as described in the prior sections, can influence each
other via, for example, coupling (e.g. via radiation and/or
crosstalk) and/or intermodulation (e.g. intermodulation
distortion).
[0046] As it is well known to the person skilled in the art,
intermodulation between two signals at differing frequencies
(f.sub.1, f.sub.2) can engender sideband signals centered around
each of the frequencies and distant from each frequency by the
difference of the frequencies (f.sub.1, f.sub.2), as depicted in
FIG. 4B. As shown in the FIG. 4B, two signals (e.g. RF signals)
centered at frequencies (f.sub.1, f.sub.2) with frequency spectra
(401) and (402) respectively, can engender intermodulation
components (403, 404) centered at frequencies (2*f.sub.1-f.sub.2)
and (2*f.sub.2-f.sub.1). Let's consider the multiple RF paths
transmit/receive system (300) of FIG. 3 operating in the second
mode as described above, wherein both transceiver/receive systems
transmit and receive using a same band. FIG. 4C depicts the
transmit spectrum (401/402) of the first/second transmit/receive
system operating within a transmit band (420) (e.g. referring to
FIG. 4A) and using a corresponding transmit channel of center
frequency f1.sub.T/f3.sub.T (e.g. channels 420a. 420b of FIG. 4A).
Such operation of the multiple RF paths transmit/receive system
(300) can engender intermodulation components (403/404). In
particular and as depicted by FIG. 4C and with further reference to
FIG. 4A, such intermodulation components can occur within an
adjacent reception band (410) and therefore can affect reception
over one or more reception channels of the reception band (410)
used by the multiple RF paths transmit/receive system (300)) as
depicted by the receive spectrum (408) of the receive band (410) in
FIG. 4D. Presence (or not) of intermodulation and location within a
frequency spectrum can be predicted based on the operation mode of
the multiple RF paths transmit/receive system (300). According to
the various embodiments of the present disclosure, a tunable notch
filter can be used to decrease the signal level at the frequency
f.sub.1 and/or at the frequency f.sub.2, thus reducing the
amplitude of the intermodulation product (e.g. filter 535 of FIG. 6
later described), or the notch can be used to attenuate the
intermodulation product (e.g. filter 545a of FIG. 6 later
described) that is generated (e.g. 2*f.sub.2-f.sub.1). Such
decrease of intermodulation distortion can effectively counter the
limiting effect of the intermodulation on the performance of a
radio system (e.g. system 300 of FIG. 3).
[0047] The teachings according to the present disclosure provide
methods and apparatus to reduce such interference in a multiple RF
paths transmit/receive system, such as the exemplary system
depicted in FIG. 3. It follows, that according to an exemplary
embodiment of the present disclosure, a tunable notch filter, such
as for example a tunable narrow band-reject filter tuned at a
center frequency of an RF transmit signal, can be used in a
transmit/receive system to immune such system from a second
transmit/receive system operating at a different RF transmit
frequency. This is depicted in FIG. 5A, wherein a tunable notch
filter (535) is used in a multiple RF paths transmit/receive system
(500), similar to the system (300) of FIG. 3, such as to immune a
transmit/receive system (140, 320, 330, 310) from the
transmit/receive system (140, 120, 130, 110). In the embodiment
according to the present disclosure as depicted in FIG. 5A, the
tunable notch filter (535) placed (e.g. in series connection)
between the antenna (310) and the duplexer (330) of the
transmit/receive system (140, 320, 330, 310) can be tuned to a
frequency of operation of the transmit/receive system (140, 120,
130, 110), such as for example, an RF transmit frequency. According
to other embodiments of the present disclosure, the tunable notch
filter (535) can be placed at any point of the transmit/receive
path between the transceiver unit (140) and the antenna (310), and
can be connected in either a series or a shunted configuration to
the transmit/receive path, the connection type being dependent on
the design of the tunable notch filter used. According to yet
further embodiments of the present disclosure, one or more tunable
notch filter similar to the tunable notch filter (535) can be
placed at any point of the transmit/receive system (140, 320, 330,
310) between the transceiver unit (140) and the antenna (310).
According to yet another embodiment of the present disclosure, a
filter of the tunable notch filter (535) of FIG. 5A can be a narrow
band-reject filter which rejects a frequency within a first
transmission channel used by the transmit/receive system (140, 120,
130, 110) while passes frequencies outside the first transmission
channel and therefore can allow the transmit/receive system (140,
320, 330, 310) to use a transmission channel or reception channel
adjacent to the first transmission channel, and thereby increase a
total data (RF) throughput of system (500).
[0048] It should be noted that when the exact same bands (e.g.
transmit band) are being used in both transmit/receive systems
(e.g. as per system 500 of FIG. 5A), a duplexer of one
transmit/receive system can protect its receiver from its
transmitter as well as the second transmitter. However, in the case
where the second transmitter operates at other bands (e.g.
different from one used by the first transmitter), the duplexer may
not have sufficient attenuation at those bands and therefore cannot
protect its receiver from the second transmitter. Furthermore
transmitter nonlinearity can generate increased modulated spectral
bandwidth and harmonics not sufficiently attenuated by the
corresponding duplexer filter and which can be detrimental to the
other receiver. It follows that according to the various
embodiments of the present disclosure, the notch filter (e.g. 535)
may be in the portion of the transmit path preceding the duplexer
(e.g. 330) as depicted in FIG. 5B, or in the common
transmit/receive path between the duplexer and antenna as depicted
in FIG. 5A. The person skilled in the art readily knows that such
problems as related to isolation of transmit signals are more
pronounced when the two radio paths (e.g. (140, 120, 130, 110) and
(140, 320, 330, 310) are in one small area such as a mobile phone,
where isolation between the antennas (110, 310) may be quite
limited (e.g. 15 dB of isolation) and therefore a transmitted
signal from one antenna can influence quality of reception over the
other antenna. In the embodiment depicted by FIG. 511, the notch
filter (535) can be tuned at a center frequency corresponding to a
harmonic of the operating frequency of the RF signal amplified by
(320).
[0049] Although the exemplary configuration depicted by FIGS. 5A-5B
show one tunable notch filter in the bottom transmit/receive
system, according to an embodiment of the present disclosure, one
or more tunable notch filters (e.g. 545a, 545b) similar to the
tunable notch filter (535) can be placed (e.g. via a series and/or
a shunt connection) at any point of the transmit/receive system
(140, 120, 130, 110) as depicted, for example, in FIG. 6. In the
exemplary embodiment according to the present disclosure depicted
in FIG. 6, the tunable notch filter (545a) is shunted to the
receive path of the transmit/receive system (140, 120, 130, 110),
whereas the tunable notch filter (545b) is in series connection
between the antenna (110) and the duplexer unit (130). The
exemplary embodiment according to the present disclosure as
depicted in FIG. 6 can immune from interference either
transmit/receive system from the other. Tunable notch filters
(545a, 545b) can be tuned to reduce effect of the frequency
spectrum used in the transmit/receive system (140, 320, 330, 310)
on the frequency spectrum used in the transmit/receive system (140,
120, 130, 110) similar to the way that tunable notch filter (535)
can reduce effect of the frequency spectrum used in the
transmit/receive system (140, 120, 130, 110) on the frequency
spectrum used in the transmit/receive system (140, 320, 330,
310).
[0050] In the embodiment according to the present disclosure as
depicted in FIG. 6, the various tunable notch filters (535, 545a,
545b) can be controlled via a controller unit aware of the
operation of each transmit/receive system (140, 120, 130, 110) and
(140, 320, 330, 310), such as the transceiver unit (140). Depending
on a mode of operation (e.g. modulation, frequency) of each of the
transmit/receive systems, the controller unit can know how to tune
a tunable notch filter in order to immune each of the
transmit/receive systems from interference of the other. In some
cases, it is possible that no tunable notch filter is necessary,
and therefore, according to some embodiments of the present
disclosure, the tunable notch filter can be switched in or out of a
corresponding path, such as depicted in FIG. 7, wherein RF switches
(725a, 725b, 725c) can be used to switch in or out tunable notch
filters (545a, 545b, 535).
[0051] According to a further embodiment of the present disclosure,
the combination of tunable notch filter (e.g. 545a, 545b, 535) and
switch (e.g. (725a-c) can be monolithically integrated within a
same integrated circuit as depicted in FIG. 8A and FIG. 8B. The
integrated circuit of FIG. 8A/SB comprises a control terminal
(CNTRL) which can be used to control the configuration of the
internal switch (725c/725a) and the tuning of the tunable notch
filter (535/545a) via a control signal, generated, for example, by
a transceiver unit or a signal-aware controller module. The person
skilled in the art will know that such control signal can comprise
one or more digital and/or analog signal lines and a corresponding
interface can be implemented in a variety of methods which are
outside the scope of the present disclosure. As noted in the
previous sections of the present disclosure, the integrated circuit
of FIG. 8A can be used in a series connection with a signal path
connected to ports S.sub.1 and S.sub.2 of the integrated circuit,
whereas the integrated circuit of FIG. 8B can be used in a shunt
connection with a signal path connected to port S (or port N) of
the integrated circuit and a common reference potential connected
to the port N (or port S) of the integrated circuit. In both
configurations of the integrated circuit depicted by FIG. 8A and
FIG. 8B, the turning ON/OFF of the switch can cause a current to
flow nor not through the tunable notch filter and therefore affect
or not a characteristic of a signal coupled to the integrated
circuit. Furthermore, such integrated circuit as depicted in FIG.
8A and FIG. 8B can be made to operate in a single-ended or
differential signal mode, as required by a receive/transmit path
wherein such integrated circuit is used. As known by the person
skilled in the art, a receive path of a multiple RF paths
transmit/receive system such as one depicted in the various figures
of the present disclosure can comprise a differential signal path
(e.g. input to a transceiver unit).
[0052] The tunable notch filters described in the various
embodiments according to the present disclosure can be constructed
using one or more variable reactive elements, such as variable
capacitors and variable inductors. Digitally tunable capacitors
(DTC) and/or digitally tunable inductors, as described in, for
example. International Application No. PCT/US2009/001358 and U.S.
patent application Ser. No. 13/595,893, can also be used in
constructing such tunable notch filter. The person skilled in the
art readily knows how to realize such tunable filters and how to
select components with values (e.g. ranges of values) consistent
with a desired tilter bandwidth and attenuation. As known by the
person skilled in the art, such components can be partitioned into
various filter stages via series and/or shunt connections, and in
turn, the various filter stages can be interconnected (e.g.
cascaded) via series and/or shunt connections. Some exemplary
embodiments of tunable notch filters are described in the above
mentioned U.S. application Ser. No. ______ entitled "Integrated
Tunable Filter Architecture" (Attorney Docket No. PER-115-PAP)
filed on even date herewith and incorporated herein by reference in
its entirety.
[0053] Although the various exemplary embodiments of the present
disclosure are based on a multi-path transmit/receive system
showing two separate transmit/receive systems (e.g. (140, 120, 130,
110) and (140, 320, 330, 310)), each with a dedicated
transmit/receive antenna (e.g. (110, 310), such limitation of two
transmit/receive systems is mainly exemplary in nature and not
intended to limit the scope of the invention which can certainly be
extended to more than two such transmit/receive systems, each with
a dedicated transmit/receive antenna. In such configuration, a
controller unit can tune the various tunable notch filters
according to the known signal spectra used in the various
transmit/receive systems. Such spectra can comprise not only known
operating frequencies (e.g. channel frequencies) associated to the
various transmitted and received signals within the various
transmit/receive systems, but also can comprise various harmonics
and intermodulation products thereof which alone or in combination
can affect operation of one or more of the various transmit/receive
systems. Additionally, each transmit/receive system can comprise
more than one transmit/receive path, as a plurality of parallel
transmit/receive paths can be connected to an antenna via a
dedicated antenna switch, as typically done in current RF front-end
stages used in current cellular devices.
[0054] By way of further example and not limitation, any switch or
switching circuitry of the present disclosure, such as switches
(725a-c) of FIG. 7 can be implemented using transistors, stacked
transistors (FETs), diodes, or any other devices or techniques
known to or which can be envisioned by a person skilled in the art.
In particular, such switching circuitry can be constructed using
CMOS technology and various architectures known to the skilled
person, such as, for example, architecture presented in U.S. Pat.
No. 7,910,993, issued on Mar. 22, 2011 and entitled "Method and
Apparatus for use in Improving Linearity of MOSFET's using an
Accumulated Charge Sink", and in U.S. Pat. No. 6,804,502, issued on
Oct. 12, 2004 and entitled "Switch Circuit and Method of Switching
Radio Frequency Signals", both incorporated herein by reference in
their entirety. FIG. 9 shows an exemplary embodiment of a
single-pole single-throw switch with stacked transistors, which the
skilled person can use as an elementary component of the various
switches used in the various embodiments according to the present
disclosure.
[0055] Although FETs (e.g. MOSFETs) can be used to describe
transistor and stacked transistor switches used in the various
embodiments of the present disclosure, a person skilled in the art
would recognize that either P-type or N-type MOSFETs may be used.
The skilled person would also recognize that other types of
transistors such as, for example, bipolar junction transistors
(BJTs) can be used instead or in combination with the N-type or
P-type MOSFETs. Furthermore, a person skilled in the art will also
appreciate the advantage of stacking more than two transistors,
such as three, four, five or more, provide on the voltage handling
performance of the switch. This can for example be achieved when
using non bulk-Silicon technology, such as insulated Silicon on
Sapphire (SOS) technology and silicon on insulated (SOI)
technology. In general, the various switches used in the various
embodiments of the present disclosure, including when
monolithically integrated with a tunable notch filter, such as
depicted in FIG. 8, can be constructed using CMOS, silicon
germanium (SiGe), gallium arsenide (GaAs), gallium nitride (GaN),
bipolar transistors, or any other viable semiconductor technology
and architecture known, including micro-electro-mechanical (MEM)
systems. Additionally, different device sizes and types can be used
within a stacked transistor switch such as to accommodate various
current handling capabilities of the switch.
[0056] The examples set forth above are provided to give those of
ordinary skill in the art a complete disclosure and description of
how to make and use the embodiments of the present disclosure, and
are not intended to limit the scope of what the inventors regard as
their disclosure. Modifications of the above described modes for
carrying out the disclosure may be used by persons of skill in the
art, and are intended to be within the scope of the following
claims. All patents and publications mentioned in the specification
may be indicative of the levels of skill of those skilled in the
art to which the disclosure pertains. All references cited in this
disclosure are incorporated by reference to the same extent as if
each reference had been incorporated by reference in its entirety
individually.
[0057] It is to be understood that the disclosure is not limited to
particular methods or systems, which can, of course, vary. It is
also to be understood that the terminology used herein is for the
purpose of describing particular embodiments only, and is not
intended to be limiting. As used in this specification and the
appended claims, the singular forms "a", "an", and "the" include
plural referents unless the content clearly dictates otherwise. The
term "plurality" includes two or more referents unless the content
clearly dictates otherwise. Unless defined otherwise, all technical
and scientific terms used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which the
disclosure pertains.
[0058] A number of embodiments of the disclosure have been
described. Nevertheless, it will be understood that various
modifications may be made without departing from the spirit and
scope of the present disclosure. Accordingly, other embodiments are
within the scope of the following claims.
* * * * *