# Patent

## Title
Method and system for FM transmit and FM receive using a transformer as a duplexer

## Abstract

Aspects of a method and system for FM transmit and FM receive using a transformer as a duplexer may include communicating radio frequency signals via an antenna coupled to primary windings of a radio frequency transformer, wherein secondary windings of the radio frequency transformer may be utilized for receiving and/or transmitting the communicated radio frequency signals. The receiving and transmitting may be operated in time division duplex mode or simultaneously. A number of windings between a pair of connector terminals of the secondary windings used for transmitting of the radio frequency signals may be less than or equal to a number of windings of the primary windings. A number of windings between a pair of connector terminals of the secondary windings used for receiving of the radio frequency signals may be greater than or equal to a number of windings of the primary windings.

## Background
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. 60/895,698, filed on Mar. 19, 2007.
This application also makes reference to:
U.S. application Ser. No. 11/750,103 filed on even date herewith; and
U.S. application Ser. No. 11/750,091 filed on even date herewith.
Each of the above referenced applications 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 equalizing antenna circuit matching variations.
BACKGROUND OF THE INVENTION
Many communication systems require appropriate coupling of the antenna to the receiver and transmitter hardware. One reason, may be a need to match impedances between the transmitter and/or the receiver and the antenna. Impedance matching may attempt to equalize the output impedance at the antenna to the input impedance of the system that may be connected to the antenna. By matching the impedance, the power transfer from and to the antenna may be maximized and reflections due to impedance mismatch may be reduced. In some instances, matching impedances may be undesirable though. For example, an antenna coupled to a high impedance load may provide better voltage transfer while the high impedance may lower the loading of the antenna. In some cases, this may be referred to as impedance bridging. In most cases, however, suitable impedance matching may be desirable and may require some type of a matching network between antenna and the receiver and/or transmitter.
In many modern radio frequency communication systems, mobile communication terminals are increasingly miniaturized and it may become increasingly important to provide matching circuitry with a reduced number of limited-size components. For implementations of matching circuits on circuit boards, it may be particularly desirable to reduce the number of required system components.
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 FM transmit and FM receive using a transformer as a duplexer, 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 RF receiver system, in accordance with an embodiment of the invention.
FIG. 2A is a circuit diagram illustrating an exemplary duplex transformer, in accordance with an embodiment of the invention.
FIG. 2B is a circuit diagram illustrating an exemplary duplex transformer with a differential antenna, in accordance with an embodiment of the invention.
FIG. 3 is a flow chart illustrating simultaneous receiver and transmitter operation, 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 FM transmit and FM receive using a transformer as a duplexer. Aspects of the method and system for FM transmit and FM receive using a transformer as a duplexer may comprise communicating radio frequency signals via an antenna coupled to primary windings of a radio frequency transformer, wherein secondary windings of the radio frequency transformer may be utilized for receiving and/or transmitting the communicated radio frequency signals. The receiving and transmitting may be operated in time division duplex mode or simultaneously. A number of windings between a pair of connector terminals of the secondary windings used for transmitting of the radio frequency signals may be less than or equal to a number of windings of the primary windings. A number of windings between a pair of connector terminals of the secondary windings used for receiving of the radio frequency signals may be greater than or equal to a number of windings of the primary windings. The antenna may be a single-ended antenna, coupled to a first terminal of the primary windings, and a second terminal of the primary windings may be coupled to ground. In another embodiment of the invention, the antenna may be a differential antenna and a first antenna terminal may be coupled to a first terminal of the primary winding and a second antenna terminal may be coupled to a second terminal of the primary winding. The communicated radio frequency signals may be frequency modulated, Bluetooth signals and/or Wireless LAN signals.
FIG. 1 is a block diagram illustrating an exemplary RF receiver system, in accordance with an embodiment of the invention. Referring to FIG. 1, there is shown an RF receiver system 100 comprising an antenna 102, an RF transformer 104 and an RF transceiver 106.
A radio frequency (RF) transformer may comprise suitable logic, circuitry and/or code to enable suitable coupling of the antenna 102 to the RF transceiver 106. The RF transformer 104 may, for example, match the impedance of the antenna to the RF transceiver 106. The RF transceiver 106 may comprise suitable logic, circuitry and/or code to enable processing and generating of RF receive signals and/or RF transmit signals, respectively.
FIG. 2A is a circuit diagram illustrating an exemplary duplex transformer, in accordance with an embodiment of the invention. Referring to FIG. 2A, there is shown an antenna 202, an RF transformer 204, a power amplifier 206, a low-noise amplifier 208, a transmitter chain 210 and a receiver chain 212. The RF transformer 204 may comprise a primary winding 214 and a secondary winding 216.
In accordance with various embodiments of the invention, an RF transformer 204 may be used as a transmit transformer and/or a receive transformer, coupling antenna 202 to the power amplifier 206 to enable transmission, and to the low-noise amplifier 208 to enable reception, respectively. When a signal is received at antenna 202, it may be fed to the primary winding 214 of the RF transformer 204. The primary winding 214 may comprise L1 windings. The primary winding 214 may transfer electrical energy received via the antenna 202 to the secondary winding 216 by magnetic coupling. The low-noise amplifier 208 may be coupled to the secondary winding 216 and may comprise suitable logic, circuitry and/or code to enable amplification of a signal received at the secondary winding 216. The secondary winding 216 may comprise, for example, L2-2 windings. Typically, since the received signal at the antenna 202 may be a low-energy signal, the secondary winding 216 may comprise L2-2>L1 windings. A larger number of windings for the secondary winding 216 may increase the impedance and may lead to a higher voltage gain. In other words, the antenna 202 may be less strongly loaded and the signal received by the low-noise amplifier 208 may be stronger than it would be if the number of windings L2-2 were equal to, or smaller, than L1. The amplified signal at the output of the low-noise amplifier 208 may be fed to the receiver chain 212, which may comprise suitable logic, circuitry and/or code to enable processing of the received radio frequency signal.
For transmission, the transmitter chain 210 may comprise suitable logic, circuitry and/or code to enable generation of RF transmit signals. The generated RF transmit signals from the transmitter chain 210 may be coupled to the input of the power amplifier 206. For an RF transmit signal, it may be desirable to transmit at higher power levels than the power levels of a receive signal. Hence, the RF transmit signal may be amplified in the power amplifier 206, which may comprise suitable logic, circuitry and/or code to enable power amplification of the signal at its input. The output of the power amplifier 206 may be coupled to the secondary winding 216. The secondary winding 216 may comprise multiple access points, or terminals, to the coil that may lead to a different number of effective windings if different terminals of the winding may be used. In an exemplary embodiment of the invention, the secondary winding 216 may comprise 200 windings (for example, L2-2). There may be a terminal 50 turns in from each end of the coil, so that the usage of the two inner terminals may be similar to that of a coil of 100 turns (for example, L2-1).
For transmission purposes, the number of effective windings L2-1 of the secondary winding 216 may generally be desired lower than L2-2 because a lower impedance for transmission may be desirable. In one embodiment of the invention, an impedance of approximately 50 Ohm or less for transmission may be desirable. The secondary winding 216 may transfer electrical energy received via power amplifier 206 to the primary winding 214 by magnetic coupling, from where the signal may be fed to the antenna 202.
In some instances, reception and transmission may occur in a time division duplex (TDD) mode. In this case, only transmission or reception may occur at any given instance in time. In another embodiment of the invention, transmission and reception may take place simultaneously. It may generally be desirable that the transmit frequency be different from the receive frequency in case of simultaneous operation, to reduce interference problems, for example.
Although not depicted, in another embodiment of the invention, a bias terminal of the secondary winding 216 may be communicatively coupled to an electrical signal, for example a voltage VDD. The bias terminal may be located, for example, approximately in the center of the secondary winding 216. In this instance, the secondary winding 216 may act like a load for the PA 206 and the electrical signal applied at the terminal, for example VDD, may provide biasing of the secondary winding 216 and the PA 206. In various embodiments of the invention with an electrical signal communicatively coupled to the bias terminal of the secondary winding 216 as described above, it may be desirable to couple the LNA 208 to the secondary winding 216 via a plurality of capacitors that may block DC signal components on the secondary winding 216 due to the electrical signal applied at the bias terminal.
FIG. 2B is a circuit diagram illustrating an exemplary duplex transformer with a differential antenna, in accordance with an embodiment of the invention. Referring to FIG. 2B, there is shown a differential antenna 202a, an RF transformer 202a, a power amplifier 206a, a low-noise amplifier 208a, a transmitter chain 210a and a receiver chain 212a. The RF transformer 204a may comprise a primary winding 214a and a secondary winding 216a. The RF transformer 202a, the power amplifier 206a, the low-noise amplifier 208a, the transmitter chain 210a and the receiver chain 212a may be substantially similar to the RF transformer 204, the power amplifier 206, the low-noise amplifier 208, the transmitter chain 210 and the receiver chain 212, respectively, as illustrated and described in FIG. 2A.
In one embodiment of the invention, a differential antenna 202a with two output terminals may be coupled to the RF transformer 204a. A differential antenna 204a may be, for example, a coil antenna as illustrated in FIG. 2B or a loop antenna. Whereas the transformer in FIG. 2A may also perform a conversion function from an unbalanced signal to a balanced signal and vice versa (balun functionality), a differential antenna with dual antenna ports may already provide a balanced differential receive signal to the RF transformer 204a. 
FIG. 3 is a flow chart illustrating simultaneous receiver and transmitter operation, in accordance with an embodiment of the invention. In one embodiment of the invention, RF signal reception may be simultaneous with RF signal transmission. In another embodiment of the invention, RF signal reception and RF signal transmission may be separated in time, as described above. In the case of RF signal transmission, a baseband signal may be generated in step 304. From the baseband signal generated in step 304, an RF transmit signal may be generated in step 306. The RF transmit signal may be amplified in step 308 before it may be magnetically coupled in step 310. Generally, magnetic coupling of the RF signal in step 310 may occur at a RF transformer. In step 312, the RF transmit signal may be transmitted from an antenna.
In the case of reception, the RF receive signal may be received by an antenna in step 312. The RF receive signal may be magnetically coupled to a receive signal chain in a transformer in step 310. The RF receive signal may be amplified by, for example, a low-noise amplifier in step 316. In step 318, the RF signal may be processed. For example, in step 318, the signal may be demodulated and converted to baseband. In step 304, the baseband receive signal may be appropriately processed further.
In accordance with an embodiment of the invention, a method and system for FM transmit and FM receive using a transformer as a duplexer may comprise communicating radio frequency signals via an antenna 202 coupled to primary windings 214 of a radio frequency transformer 204, wherein secondary windings 216 of the radio frequency transformer 204 may be utilized for receiving and/or transmitting the communicated radio frequency signals. The receiving and transmitting may be operated in time division duplex mode or simultaneously, as described in FIG. 2A and FIG. 3. A number of windings L2-1 between a pair of connector terminals of the secondary windings 216 used for transmitting of the radio frequency signals may be less than or equal to a number of windings of the primary windings, L1. A number of windings L2-2 between a pair of connector terminals of the secondary windings 216 used for receiving of the radio frequency signals may be greater than or equal to a number of windings of the primary windings, L1. The antenna may be a single-ended antenna 202, coupled to a first terminal of the primary windings 214, and a second terminal of the primary windings 214 may be coupled to ground, as illustrate in FIG. 2A. In another embodiment of the invention, the antenna 202a may be a differential antenna and a first antenna terminal may be coupled to a first terminal of the primary winding 214a and a second antenna terminal may be coupled to a second terminal of the primary winding 214, as illustrated in FIG. 2B. The communicated radio frequency signals may be frequency modulated, Bluetooth signals and/or Wireless LAN signals.
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 FM transmit and FM receive using a transformer as a duplexer.
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:
communicating radio frequency signals via an antenna coupled to primary windings of a radio frequency transformer, wherein secondary windings of said radio frequency transformer are utilized for receiving and/or transmitting said communicated radio frequency signals, wherein said receiving and said transmitting operate simultaneously.

2. The method according to claim 1, wherein a number of windings between a pair of connector terminals of said secondary windings used for said transmitting of said radio frequency signals, is less than or equal to a number of windings of said primary windings.

3. The method according to claim 1, wherein a number of windings between a pair of connector terminals of said secondary windings used for said receiving of said radio frequency signals, is greater than or equal to a number of windings of said primary windings.

4. The method according to claim 1, wherein said antenna is a single-ended antenna, coupled to a first terminal of said primary windings, and a second terminal of said primary windings is coupled to ground.

5. The method according to claim 1, wherein said antenna is a differential antenna, and a first differential antenna terminal is coupled to a first terminal of said primary winding and a second differential antenna terminal is coupled to a second terminal of said primary winding.

6. The method according to claim 1, wherein said communicated radio frequency signals are frequency modulated.

7. The method according to claim 1, wherein said communicated radio frequency signals are Bluetooth signals.

8. The method according to claim 1, wherein said communicated radio frequency signals are Wireless LAN signals.

9. A system for processing communication signals, the system comprising one or more circuits, said one or more circuits enable:
communication of radio frequency signals via an antenna coupled to primary windings of a radio frequency transformer, wherein secondary windings of said radio frequency transformer are utilized for receiving and/or transmitting said communicated radio frequency signals, wherein said receiving and said transmitting operate simultaneously.

10. The system according to claim 9, wherein a number of windings between a pair of connector terminals of said secondary windings used for said transmitting of said radio frequency signals, is less than or equal to a number of windings of said primary windings.

11. The system according to claim 9, wherein a number of windings between a pair of connector terminals of said secondary windings used for said receiving of said radio frequency signals, is greater than or equal to a number of windings of said primary windings.

12. The system according to claim 9, wherein said antenna is a single-ended antenna, coupled to a first terminal of said primary windings, and a second terminal of said primary windings is coupled to ground.

13. The system according to claim 9, wherein said antenna is a differential antenna, and a first differential antenna terminal is coupled to a first terminal of said primary winding and a second differential antenna terminal is coupled to a second terminal of said primary winding.

14. The system according to claim 9, wherein said communicated radio frequency signals are frequency modulated.

15. The system according to claim 9, wherein said communicated radio frequency signals are Bluetooth signals.

16. The system according to claim 9, wherein said communicated radio frequency signals are Wireless LAN signals.