US20080233869A1

US20080233869A1 - Method and system for a single-chip fm tuning system for transmit and receive antennas

Info

Publication number: US20080233869A1
Application number: US11/781,787
Authority: US
Inventors: Thomas Baker; Bojko Marholev
Original assignee: Individual
Current assignee: Broadcom Corp
Priority date: 2007-03-19
Filing date: 2007-07-23
Publication date: 2008-09-25
Also published as: US20080232448A1; US20080233883A1; US20080232447A1; US8391810B2; US20080233897A1; US7586378B2; US8208886B2; US7974590B2; US8027641B2; US20080233911A1; US20120021706A1; US20080233890A1; US20080233881A1; US7792502B2; US20080231375A1; US20080233954A1; US20080233907A1; US20110183628A1; US8270907B2; US8467745B2

Abstract

Aspects of a method and system for a single-chip FM tuning system for transmit and receive antennas may include in a frequency-modulation (FM) radio system comprising an integrated FM radio transmitter and FM radio receiver: receiving via a receive antenna for the FM radio system a radio-frequency (RF) signal transmitted from a transmit antenna of the radio transmitter. A frequency response of said receive antenna and/or a frequency response of said transmit antenna may be adjusted based on said received RF signal. The frequency response of the receive antenna and/or the transmit antenna may be adjusted dynamically, autonomously, sequentially and/or simultaneously. The receive antenna and/or the transmit antenna may be adjusted via a programmable filter, which may comprise inductive and capacitive components. The programmable filter may comprise a programmable array of inductors and/or a programmable array of capacitors.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE

This application makes reference to, claims priority to, and claims the benefit of U.S. Provisional Application Ser. No. 60/895,665, filed on Mar. 19, 2007.
The above referenced application is hereby incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

Certain embodiments of the invention relate to signal processing for communication systems. More specifically, certain embodiments of the invention relate to a method and system for a single-chip FM tuning system for transmit and receive antennas.

BACKGROUND OF THE INVENTION

Communication receiver systems that rely on receiving radio frequency signals are dependent on certain characteristics of the antenna used, in order to ensure correct operation. One such parameter, for example, may be the antenna impedance. If the impedance between the receiver and the antenna is not matched, the feed line may generate reflections at such unmatched impedance interfaces, reflecting the received signal back towards the source. This may generate so-called standing waves and reduces the effective power transfer from the antenna to the receiving device.
Another factor that may impact the operation of a receiver may be variations due to manufacturing. In particular for small antennas and/or antennas that may be operated in physically constrained spaces, small changes in the operating environment may impact the antenna characteristics. For example, small antennas on Printed Circuit Boards (PCBs) may exhibit relatively large sample variation. In addition, due to the close proximity of a PCB antenna with other circuitry, there may be some electromagnetic coupling that may affect the antenna performance. Furthermore, antennas from different manufacturers may also differ in their characteristics.
Antennas generally respond differently at different frequencies. For example, the antenna gain may be frequency dependent. Also, changes in the operating environment, for example temperature, may affect the circuit-antenna matching.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.

BRIEF SUMMARY OF THE INVENTION

A method and/or system for a single-chip FM tuning system for transmit and receive antennas, substantially as shown in and/or described in connection with at least one of the figures, as set forth more completely in the claims.
These and other advantages, aspects and novel features of the present invention, as well as details of an illustrated embodiment thereof, will be more fully understood from the following description and drawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an exemplary FM transmitter and receiver system, in accordance with an embodiment of the invention.

FIG. 2 is a block diagram illustrating an exemplary FM antenna tuning system, in accordance with an embodiment of the invention.

FIG. 3A is a diagram illustrating an exemplary RX antenna tuning system, in accordance with an embodiment of the invention.

FIG. 3B is a diagram illustrating an exemplary TX antenna tuning system, in accordance with an embodiment of the invention.

FIG. 3C is a circuit diagram illustrating an exemplary programmable capacitance, in accordance with an embodiment of the invention.

FIG. 4 is a flow chart illustrating an exemplary sequential RX/TX antenna tuning protocol, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Certain embodiments of the invention may be found in a method and system for a single-chip FM tuning system for transmit and receive antennas. Aspects of the method and system for a single-chip FM tuning system for transmit and receive antennas may comprise, in a frequency-modulation (FM) radio system comprising an integrated FM radio transmitter and FM radio receiver, receiving via a receive antenna for the FM radio system a radio-frequency (RF) signal transmitted from a transmit antenna of the radio transmitter. A frequency response of said receive antenna and/or a frequency response of said transmit antenna may be adjusted based on said received RF signal.
The frequency response of the receive antenna and/or the transmit antenna may be adjusted dynamically, autonomously, sequentially and/or simultaneously. The receive antenna and/or the transmit antenna may be adjusted via a programmable filter, which may comprise inductive and capacitive components. The programmable filter may comprise a programmable array of inductors and/or a programmable array of capacitors. The adjustments of the receive antenna and the transmit antenna may be controlled via a single integrated circuit.
FIG. 1 is a block diagram illustrating an exemplary FM transmitter and receiver system, in accordance with an embodiment of the invention. Referring to FIG. 1, there is shown an FM transceiver system 100 comprising a receiver (RX) antenna 102, a transmitter (TX) antenna 104, an FM receiver 150, an FM transmitter 180 and a device controller 106.
The FM transceiver system 100 may comprise suitable logic, circuitry and/or code that may be enabled to transmit and receive FM signals simultaneously on different frequencies and/or in an alternating or simultaneous fashion on the same frequency. The FM transmitter 180 may comprise suitable logic, circuitry and/or code to enable generation of a transmit signal that may be communicated to the antenna 104. The FM receiver 150 may comprise suitable logic, circuitry and/or logic that may enable reception and/or processing of FM signals, fed to it from the antenna 102. The transmit signal path from the FM transmitter 180 and the receive signal path to the FM receiver 150 may be coupled to the device control 106 that may comprise suitable logic, circuitry and/or code that may be enabled to control and/or process the signals to the FM transmitter 180 and from the FM receiver 150. The control block 106 may control, for example, a gain and/or a demodulation frequency in the FM receiver 150 and, for example, a transmit power and frequency of the FM transmitter 180. In one embodiment of the invention, the device control block 106 may be enabled to perform, for example, base band signal processing. The device control block 106 may be enabled to control other functions.
In various other embodiments of the invention, the FM transceiver system 100 may comprise a stand-alone system or may form part of a device, for example, a personal audio player or a cellular mobile phone. In various embodiments of the invention, the FM transmitter 180 and the FM receiver 150 and/or the FM transceiver system 100 may comprise one or more local oscillator generator comprising suitable logic, circuitry and/or code that may be enabled to generate an oscillating signal for use in at least modulation and demodulation in the FM transmitter 180 and the FM receiver 150, respectively. In some instances, one or more local oscillator generators may be common to both the FM transmitter 180 and the FM receiver 150.
FIG. 2 is a block diagram illustrating an exemplary FM antenna tuning system, in accordance with an embodiment of the invention. Referring to FIG. 2, there is shown a FM radio system 200 comprising antennas 202 and 204, antenna tuning blocks 206 and 208, and a transceiver 210. The transceiver 210 may comprise an FM receiver 212, a Receive-Signal-Strength Indicator (RSSI) block 214, a transmitter 216 and a processor 218.
A signal received at antenna 202 may be communicatively coupled to the antenna tuning block 206. The antenna tuning block 206 may comprise suitable logic, circuitry and/or code that may be enabled to match the antenna 202 to the transceiver 210. The antenna tuning block 206 may comprise, for example, a programmable filter. For small antennas, for example in portable devices, it may be difficult to match the antennas 202 and 204 to the transceiver 210. The antennas 202 and 204 may be subject to considerable sample variation. Differences between antennas may be due to differences between manufacturers and/or tolerances in the manufacturing process. Particularly very small antennas, for example on printed circuit boards, may exhibit large variations between different samples. Furthermore, antenna installation and/or arrangement on a printed circuit board may affect the antenna characteristics, as may environmental factors. For at least the reasons given above, it may be desirable to tune the antennas 202 and 204. The antenna tuning block 206 may be coupled to the receiver 212. The receiver 212 may comprise suitable logic, circuitry and/or code that may be enabled to process received radio-frequency signal. Such processing may comprise demodulation to intermediate frequency, demodulation to baseband, amplification and/or various filtering, for example.
The antenna tuning block 206 may be coupled to the receiver 212. The RSSI block 214 may comprise suitable logic, circuitry and/or code that may be enabled to measure approximately, for example, the power of the received radio-frequency signal. The RSSI block 214 may measure the signal power at radio frequency, intermediate frequency and/or baseband. In another embodiment of the invention, the RSSI block 214 may be communicatively coupled directly to the antenna tuning block 206. The outputs of the receiver 212 and/or the RSSI block 214 may be coupled to the processor 218. The processor 218 may comprise suitable logic, circuitry and/or logic that may be enabled to process baseband signals received from receiver 212 and may control the functionality of the transceiver 210 and the functional blocks comprised therein. The processor 218 may control the antenna tuning blocks 206 and 208 for tuning of the receive antenna 202 and the transmit antenna 204, respectively. The functionality of the processor 218 may not be limited to the functionality described above.
The processor 218 may be communicatively coupled to the transmitter 216. The transmitter 216 may comprise suitable logic, circuitry and/or code that may be enabled to generate radio-frequency signals suited for transmission via the antenna 204. The antenna tuning block 208 may adjust matching between the transmitter 216 and the antenna 204. The antenna tuning block 208 may be, for example, a programmable filter. For example, the antenna tuning block 208 may be set to improve the transmit power transfer from the transmitter 216 to the antenna 204.
Since the radio system 200 may comprise an FM receiver and an FM transmitter, the radio system 200 may be enabled to configure and/or calibrate the antenna tuning blocks 206 and 208 in accordance with an embodiment of the invention. For example, by transmitting an approximately constant transmission power from the transmitter 216, while maintaining the settings of the antenna tuning block 208, a radio frequency (RF) signal may be transmitted from antenna 204. The transmitted signal may, for example, be a pilot tone. The FM receiver 212 may be tuned to the same frequency that may be used for transmission at the FM transmitter 216. Hence, the RF signal transmitted through antenna 204 may be received at antenna 202 and receiver 212. The received signal may be fed to the RSSI block 214 via the antenna tuning block 206. Since the RSSI block 214 may measure the signal power at its input and feed the measured power output to the processor 218, the processor 218 may utilize the RSSI block 214 output to tune the antenna tuning block 206.
In one embodiment of the invention, the processor may tune the antenna tuning block 206 until a high signal power may be reported by the RSSI block 214. High signal power measured at the RSSI block 214 may indicate a good match between the antenna 202 and the transceiver 210 since the received power at the antenna 202 may transfer well to the transceiver 210. In one exemplary embodiment of the invention, the processor 218 may record the measured signal power at the output of the RSSI block 214 over a range of settings of the antenna tuning block 206. The processor 218 may perform this tuning operation over a range of transmission frequencies that may be set at the transmitter 216. The processor 218 may record desirable settings for the antenna tuning block 206 based on measurements for each of a range of transmission channels set at the transmitter 216. In this regard, the processor 218 may generate a look-up table that may comprise the desirable settings for the antenna tuning block 206 for a range of reception frequencies.
Similarly, the processor 218 may maintain the settings of the antenna tuning block 206 approximately constant and output a constant transmission power from the transmitter 216. In these instances, the processor 218 may adjust the setting of the antenna tuning block 208 until a high received signal power may be reported by the RSSI block 214. A high power reported at the RSSI block 214 may indicate a high receive power at the antenna 202, which may be due to a high portion of the approximately constant transmission power at the transmitter 216 being radiated from the antenna 204. In other words, high receive power may indicate a good match between the transmit antenna 204 and the transmitter 216.
FIG. 3A is a diagram illustrating an exemplary RX antenna tuning system, in accordance with an embodiment of the invention. Referring to FIG. 3A, there is shown an antenna equivalent circuit 302, antenna tuning blocks 306 and 308, a transceiver 310 and antenna 304. The antenna equivalent circuit 302 may be a Thevenin equivalent circuit of an antenna and may be used to approximately model the behavior of a receive antenna substantially similar to antenna 202. The antenna equivalent circuit 302 may comprise a voltage source 364 and an antenna impedance 354. The antenna impedance may comprise a resistor 366, an inductor L 368 and a capacitor C 370. The antenna tuning block 306 may comprise a variable inductor dL 372 and a variable capacitor dC 374. The transceiver 310 comprising the receiver 312, the RSSI block 314 and the transmitter 316 may be substantially similar to the transceiver 210 comprising the receiver 212, the RSSI block 214 and the transmitter 216, respectively. The antenna 304 and the antenna tuning block 308 may be substantially similar to the antenna 204 and the antenna tuning block 208.
The antenna equivalent circuit 302 may comprise the voltage source 364, which may represent the received signal at antenna 202, and the antenna impedance 354. The frequency characteristics of the antenna equivalent circuit 302 may be determined primarily by the capacitance C 370 and the inductor L 368. The resonant frequency of the antenna may be defined approximately by (antenna under purely resistive load) the following relationship:
$f 0 \approx \frac{1}{2 π \sqrt{LC}}$
The antenna tuning block 306 may adjust the frequency response and the resonant frequency of the antenna by adjusting the total inductance and capacitance through inductor dL 372 and capacitor dC 374. The resonant frequency may be approximately given by the following relationship:
$f 0 \approx \frac{1}{2 π \sqrt{L_{cor} C_{cor}}}$ $Lcor \approx L + d L$ $C_{cor} \approx {(\frac{1}{C} + \frac{1}{dC})}^{- 1}$
The capacitor dC 374 and the inductor dL 372 may be programmable and may be controlled by a control block substantially similar to the processor 318.
By transmitting an RF signal from antenna 304, a signal may be received at the receive antenna that may be modeled by the antenna equivalent circuit 302. The voltage source 364 may model a received signal strength proportional to the radiate power from antenna 304. By tuning the antenna tuning block 306, for example by varying the inductor dL 372 and/or the capacitor dC 374, the matching of the antenna and the transceiver may be achieved, substantially as described for FIG. 2.
FIG. 3B is a diagram illustrating an exemplary TX antenna tuning system, in accordance with an embodiment of the invention. Referring to FIG. 3B, there is shown an antenna equivalent circuit 304 a, antenna tuning blocks 306 a and 308 a, a transceiver 310 a and antenna 302 a. The antenna equivalent circuit 304 a may be a Thevenin equivalent circuit of an antenna and may be used to approximately model the behavior of a transmit antenna substantially similar to antenna 204. The antenna equivalent circuit 304 a may comprise a voltage source 364 a and an antenna impedance 354 a. The antenna impedance may comprise a resistor 366 a, an inductor L 368 a and a capacitor C 370 a. The antenna tuning block 308 a may comprise a variable inductor dL 372 a and a variable capacitor dC 374 a. The transceiver 310 a comprising the receiver 312 a, the RSSI block 314 a and the transmitter 316 a may be substantially similar to the transceiver 210 comprising the receiver 212, the RSSI block 214 and the transmitter 216, respectively. The antenna 302 a and the antenna tuning block 306 a may be substantially similar to the antenna 202 and the antenna tuning block 206.
The antenna equivalent circuit 304 a and the antenna tuning block 308 a may operate substantially similarly to the antenna equivalent circuit 302 and the antenna tuning block 306.
By transmitting an RF signal from an antenna modeled by the antenna equivalent circuit 304 a, a signal may be received at the receive antenna 302 a. The voltage source 364 a may model a transmitted signal strength proportional to the radiated power from antenna 304 a. By tuning the antenna tuning block 308 a, for example, by varying the inductor dL 372 a and/or the capacitor dC 374 a, the matching of the antenna 204 and the transceiver 210 may be achieved, substantially as described for FIG. 2.
FIG. 3C is a circuit diagram illustrating an exemplary programmable capacitance, in accordance with an embodiment of the invention. Referring to FIG. 3C, there is shown a programmable capacitance 325 comprising switches 330 a-g, 334 a-e, 336 a-g, 340 a-e, 342 a-e, 344 a-g and 348 a-e, and capacitors 332 a-f, 338 a-f, 346 a-f.
In one embodiment of the invention, a programmable capacitor may be implemented in a switchable array (also referred to as a matrix), as illustrated in FIG. 3B. The array may be of size M×N capacitors, where M and N may be positive integers. Depending on how the switches 330 a-g, 334 a-e, 336 a-g, 340 a-e, 342 a-e, 344 a-g and 348 a-e may be set, a large number of values for the programmable capacitance 325 may be set by switching capacitances in series and in parallel, as desired.
A programmable inductance may be implemented in an array fashion in a substantially similar manner to the programmable capacitance illustrated in FIG. 3C.
FIG. 4 is a flow chart illustrating an exemplary sequential RX/TX antenna tuning protocol, in accordance with an embodiment of the invention. The antenna tuning protocol may be initialized in step 402. In step 404, the received signal strength may be measured, for example at the RSSI block 314. In these instances, the transmission power from the transmitter 316, for example, that may be radiated from antenna 304, may be held approximately constant to allow tuning of the receive antenna tuning circuit, for example 306, in step 406. Tuning of the receive antenna tuning block may be performed over a number of channels, as described in FIG. 2. Upon completion of the measuring cycle in step 406, the transmit antenna, for example, 304 may be tuned. In these instances, the settings of the receive antenna tuning block, for example 306 a, may be maintained approximately constant for each channel that may be tuned, as described for FIG. 2, in order to permit sensing of the varying transmit power in function of the transmit antenna tuning block, for example, 308 a. In step 410, the transmit antenna tuning block, for example 308 a, may be adjusted to obtain desirable matching between the transmit antenna 304 and the transceiver 310, substantially as described in FIG. 2. In another embodiment of the invention, the adjustment of the antenna tuning blocks, for example antenna tuning block 206 and/or antenna tuning block 208, may be performed simultaneously or autonomously.
In accordance with an embodiment of the invention, a method and system for a single-chip FM tuning system for transmit and receive antennas may comprise in a frequency-modulation (FM) radio system 200 comprising an integrated FM radio transmitter, for example transmitter 216, and an FM radio receiver, for example receiver 212: receiving via a receive antenna 202 for the FM radio system 200 a radio-frequency (RF) signal transmitted from a transmit antenna 204 of the radio transmitter, as illustrated in FIG. 2. A frequency response of said receive antenna 202 and/or a frequency response of said transmit antenna 204 may be adjusted based on said received RF signal, for example via antenna tuning blocks 206 and 208.
The frequency response of the receive antenna 202 and/or the transmit antenna 204 may be adjusted dynamically, autonomously, sequentially and/or simultaneously. The receive antenna 202 and/or the transmit antenna 204 may be adjusted via a programmable filter, for example as illustrated in FIG. 3A and FIG. 3B, which may comprise inductive and capacitive components, like antenna tuning blocks 306 and 308 a. The programmable filter, for example antenna tuning blocks 306 and 308 a, may comprise a programmable array of inductors and/or a programmable array of capacitors, as described in FIG. 3C. The adjustments of the receive antenna 202 and the transmit antenna 204 may be controlled via a single integrated circuit, for example processor 218.
Another embodiment of the invention may provide a machine-readable storage, having stored thereon, a computer program having at least one code section executable by a machine, thereby causing the machine to perform the steps as described above for a single-chip FM tuning system for transmit and receive antennas.
Accordingly, the present invention may be realized in hardware, software, or a combination of hardware and software. The present invention may be realized in a centralized fashion in at least one computer system, or in a distributed fashion where different elements are spread across several interconnected computer systems. Any kind of computer system or other apparatus adapted for carrying out the methods described herein is suited. A typical combination of hardware and software may be a general-purpose computer system with a computer program that, when being loaded and executed, controls the computer system such that it carries out the methods described herein.
The present invention may also be embedded in a computer program product, which comprises all the features enabling the implementation of the methods described herein, and which when loaded in a computer system is able to carry out these methods. Computer program in the present context means any expression, in any language, code or notation, of a set of instructions intended to cause a system having an information processing capability to perform a particular function either directly or after either or both of the following: a) conversion to another language, code or notation; b) reproduction in a different material form.
While the present invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the present invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present invention without departing from its scope. Therefore, it is intended that the present invention not be limited to the particular embodiment disclosed, but that the present invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A method for processing communication signals, the method comprising:

in a frequency-modulation (FM) radio system comprising an integrated FM radio transmitter and FM radio receiver:

receiving via a receive antenna for said FM radio system a radio-frequency (RF) signal transmitted from a transmit antenna of said radio transmitter;

adjusting a frequency response of said receive antenna and/or a frequency response of said transmit antenna based on said received RF signal.

2. The method according to claim 1, comprising dynamically adjusting said frequency response of said receive antenna and/or said frequency response of said transmit antenna.

3. The method according to claim 1, comprising autonomously adjusting said frequency response of said receive antenna and/or said frequency response of said transmit antenna.

4. The method according to claim 1, comprising sequentially adjusting said frequency response of said receive antenna and/or said frequency response of said transmit antenna.

5. The method according to claim 1, comprising simultaneously adjusting said frequency response of said receive antenna and/or said frequency response of said transmit antenna.

6. The method according to claim 1, comprising adjusting said receive antenna and/or said transmit antenna via a programmable filter.

7. The method according to claim 6, wherein said programmable filter comprises inductive and capacitive components.

8. The method according to claim 7, wherein said programmable filter comprises a programmable array of capacitors.

9. The method according to claim 7, wherein said programmable filter comprises a programmable array of inductors.

10. The method according to claim 1, comprising controlling said adjusting of said receive antenna and said transmit antenna via a single integrated circuit.

11. A system for processing communication signals, the system comprising:

one or more circuits in a frequency-modulation (FM) radio system comprising an integrated FM radio transmitter and FM radio receiver, said one or more circuits enable:

reception via a receive antenna for said FM radio system of a radio-frequency (RF) signal transmitted from a transmit antenna of said radio transmitter;

adjustment of a frequency response of said receive antenna and/or a frequency response of said transmit antenna based on said received RF signal.

12. The system according to claim 11, wherein said one or more circuits dynamically adjust said frequency response of said receive antenna and/or said frequency response of said transmit antenna.

13. The system according to claim 11, wherein said one or more circuits autonomously adjust said frequency response of said receive antenna and/or said frequency response of said transmit antenna.

14. The system according to claim 11, wherein said one or more circuits sequentially adjust said frequency response of said receive antenna and/or said frequency response of said transmit antenna.

15. The system according to claim 11, wherein said one or more circuits simultaneously adjust said frequency response of said receive antenna and/or said frequency response of said transmit antenna.

16. The system according to claim 11, wherein said one or more circuits adjust said receive antenna and/or said transmit antenna via a programmable filter.

17. The system according to claim 16, wherein said programmable filter comprises inductive and capacitive components.

18. The system according to claim 17, wherein said programmable filter comprises a programmable array of capacitors.

19. The system according to claim 17, wherein said programmable filter comprises a programmable array of inductors.

20. The system according to claim 11, wherein said one or more circuits control said adjusting of said receive antenna tuning system and said transmit antenna tuning system via a single integrated circuit.