Interference cancellation system and radio system for multiple radios on a small platform

• US 5,574,978 A
• Filed: 05/12/1994
• Issued: 11/12/1996
• Est. Priority Date: 05/12/1994
• Status: Expired due to Term

• Current Assignee: Exelis Incorporated (L3Harris Technologies, Inc.)
• Original Assignee: American Nucleonics Corp. (Eaton Corporation PLC.)
• Inventors: Fitzgerald, Barry F., Bahu, Mark B., Talwar, Ashok K.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): ARTHUR JEANGLAUDE, GERTRUDE
• Application Number:
  US08/242,160
• Time in Patent Office: 915 Days
• Field of Search: 455/63, 455/19, 455/24, 455/84, 455/296, 455/278.1, 455/136, 455/82, 455/83, 455/78, 455/50.1, 455/67.3, 455/303
• US Class Current: 455/63.1
• CPC Class Codes: H04B 1/123 using adaptive balancing or compensation means adaptive filter circuits and algorithms H03H
• CPC Class Codes: H04B 1/126 having multiple inputs, e.g. auxiliary antenna for receiving interfering signal aerials in general H01Q
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver

Abstract

A radio system and interference cancellation system for use with the radio system include a receiving radio and a transmitting radio which are coupled to a common antenna. A reference coupler provides a reference signal in response to the signal transmitted by the transmitting radio and provides the reference signal to a vector modulator and a synchronous detector. A receiver coupler is responsive to the transmitted signal which is reflected by the antenna and to the signal which is desired to be received and provides a received signal containing an interfering signal component and a desired signal component. An error coupler samples the received signal which includes any residual interfering signal component after cancellation, and provides an error signal to the synchronous detector. The synchronous detector compares the reference signal with the error signal and provides a detector output to the vector modulator. The vector modulator adjusts the phase and amplitude of the reference signal and generates a cancellation signal from the reference signal, which cancellation signal is summed with the received signal to cancel the interfering signal component, leaving the desired signal.

Claims

1. An interference cancellation system for use with at least one receiving radio receiving a desired signal and at least one transmitting radio generating a transmitted signal which interferes with the desired signal, the at least one receiving radio and the at least one transmitting radio being situated in close proximity to each other and having a common antenna for receiving and transmitting signals, the common antenna reflecting a portion of the transmitted signal to generate a reflected transmitted signal, the interference cancellation system comprising:

a reference coupler, the reference coupler being responsive to the transmitted signal and providing a reference signal in response thereto;

a receiver coupler, the receiver coupler being responsive to the reflected transmitted signal and to the desired signal and providing a received signal in response thereto, the received signal including an interfering signal component corresponding to the reflected transmitted signal and a desired signal component corresponding to the desired signal;

an error coupler, the error coupler being responsive to the received signal and providing an error signal in response thereto;

a synchronous detector, the synchronous detector being responsive to the error signal and to a first portion of the reference signal and generating at least one detector output signal in response thereto;

a vector modulator, the vector modulator being responsive to the at least one detector output signal and to a second portion of the reference signal and generating a cancellation signal in response thereto, the cancellation signal being adjusted by the vector modulator to be substantially equal in amplitude and opposite in phase to the interfering signal component of the received signal; and

a summing coupler, the summing coupler being responsive to the received signal and to the cancellation signal and being provided for summing the cancellation signal and the received signal to thereby cancel the interfering signal component from the received signal.

2. An interference cancellation system as defined by claim 1, which further comprises at least one of an integrator and an amplifier, the at least one of an integrator and an amplifier being responsive to the at least one detector output signal and generating a control signal in response thereto, the vector modulator being responsive to the control signal for generating the cancellation signal.

3. An interference cancellation system as defined by claim 1, wherein the reference coupler, vector modulator and summing coupler define a reference signal path, the reference signal path having a reference signal loss associated therewith;

wherein the common antenna has a reflected signal loss associated therewith;

wherein the receiver coupler and summing coupler define a received signal path, the received signal path having a received signal path loss associated therewith; and

wherein the reference signal path loss is one of less than and equal to the sum of the reflected signal loss and the received signal path loss.

4. An interference cancellation system as defined by claim 1, wherein the interference cancellation system defines a reference signal path from the reference coupler to the summing coupler, the reference signal path having a reference signal path loss associated therewith;

wherein the interference cancellation system defines a reflected signal path which the transmitted signal and the reflected transmitted signal take when the transmitted signal is reflected by the common antenna to generate the reflected transmitted signal, the reflected signal path having a loss associated therewith;

wherein the interference cancellation system defines a received signal path from the receiver coupler to the summing coupler, the received signal path having a received signal path loss associated therewith; and

wherein the reference signal path loss is at most equal to the sum of the reflected signal path loss and the received signal path loss.

5. An interference cancellation system as defined by claim 1, which further comprises a low noise amplifier, the low noise amplifier being operatively coupled between the error coupler and the at least one receiving radio.

6. An interference cancellation system as defined by claim 1, which further comprises an N-way power splitter, the N-way power splitter having an input and N outputs, where N is an integer greater than 1, the input of the N-way power splitter being operatively coupled to the error coupler, one of the N outputs being operatively coupled to the at least one receiving radio, and at least another of the N outputs being operatively coupled to at least another receiving radio.

7. An interference cancellation system as defined by claim 1, wherein the interference cancellation system further comprises an N-way power splitter, the N-way power splitter being responsive to the received signal and providing N output signals in response thereto, where N is an integer greater than 1;

wherein the at least one receiving radio is responsive to one of the N output signals; and

wherein at least another receiving radio is responsive to at least another of the N output signals.

8. An interference cancellation system for use with at least one receiving radio receiving a desired signal and a first transmitting radio generating a first transmitted signal which interferes with the desired signal and at least a second transmitting radio generating at least a second transmitted signal which interferes with the desired signal, the at least one receiving radio and the first and at least second transmitting radios being situated in close proximity to one another and having a common antenna for receiving and transmitting signals, the common antenna reflecting a portion of the first transmitted signal to generate a first reflected signal and reflecting a portion of the at least second transmitted signal to generate at least a second reflected signal, the interference cancellation system comprising:

an N-way power splitter, where N is an integer greater than one, the N-way power splitter being responsive to the first reflected transmitted signal and to the at least second reflected transmitted signal and to the desired signal and providing a received signal in response thereto, the received signal including an interfering signal component corresponding to the first reflected transmitted signal and to the at least second reflected transmitted signal and a desired signal component corresponding to the desired signal;

a first reference coupler, the first reference coupler being responsive to the first transmitted signal and providing a first reference signal in response thereto;

at least a second reference coupler, the at least second reference coupler being responsive to the at least second transmitted signal and providing at least a second reference signal in response thereto;

means responsive to the received signal and providing a first error signal and at least a second error signal in response thereto;

a first synchronous detector, the first synchronous detector being responsive to the first error signal and a first portion of the first reference signal and generating at least one first detector output signal in response thereto;

at least a second synchronous detector, the at least second synchronous detector being responsive to the at least second error signal and to a first portion of the at least second reference signal and generating at least one second detector output signal in response thereto;

a first vector modulator, the first vector modulator being responsive to the at least one first detector output signal and to a second portion of the first reference signal and generating a first cancellation signal in response thereto;

at least a second vector modulator, the at least second vector modulator being responsive to the at least one second detector output signal and to a second portion of the at least second reference signal and generating at least a second cancellation signal in response thereto; and

means responsive to the received signal and to the first cancellation signal and to the at least second cancellation signal and being provided for summing the first and at least second cancellation signals and the received signal to thereby cancel the interfering signal component from the received signal.

9. A radio system having interference suppression capabilities, which comprises:

at least one receiving radio receiving a desired signal;

at least one transmitting radio generating a transmitted signal which interferes with the desired signal, the at least one receiving radio and the at least one transmitting radio being situated in close proximity to each other;

a common antenna, the common antenna being operatively coupled to the at least one receiving radio and the at least one transmitting radio and being provided for receiving and transmitting signals, the common antenna reflecting a portion of the transmitted signal to generate a reflected transmitted signal;

a reference coupler, the reference coupler being responsive to the transmitted signal and providing a reference signal in response thereto;

a receiver coupler, the receiver coupler being responsive to the reflected transmitted signal and to the desired signal and providing a received signal in response thereto, the received signal including an interfering signal component corresponding to the reflected transmitted signal and a desired signal component corresponding to the desired signal;

an error coupler, the error coupler being responsive to the received signal and providing an error signal in response thereto;

a synchronous detector, the synchronous detector being responsive to the error signal and to a first portion of the reference signal and generating at least one detector output signal in response thereto;

a vector modulator, the vector modulator being responsive to the at least one detector output signal and to a second portion of the reference signal and generating a cancellation signal in response thereto, the cancellation signal being adjusted by the vector modulator to be substantially equal in amplitude and opposite in phase to the interfering signal component of the received signal; and

a summing coupler, the summing coupler being responsive to the received signal and to the cancellation signal and being provided for summing the cancellation signal and the received signal to thereby cancel the interfering signal component from the received signal.

10. In combination:

a radio system, the radio system including;

at least one receiving radio receiving a desired signal;

at least one transmitting radio generating a transmitted signal which interferes with the desired signal, the at least one receiving radio and the at least one transmitting radio being situated in close proximity to each other; and

a common antenna operatively coupled to the at least one receiving radio and the at least one transmitting radio and being provided for receiving and transmitting signals, the common antenna reflecting a portion of the transmitted signal to generate a reflected transmitted signal; and

an interference cancellation system coupled to the radio system, the interference cancellation system including;

a reference coupler, the reference coupler being responsive to the transmitted signal and providing a reference signal in response thereto;

a receiver coupler, the receiver coupler being responsive to the reflected transmitted signal and to the desired signal and providing a received signal in response thereto, the received signal including an interfering signal component corresponding to the reflected transmitted signal and a desired signal component corresponding to the desired signal;

an error coupler, the error coupler being responsive to the received signal and providing an error signal in response thereto;

a synchronous detector, the synchronous detector being responsive to the error signal and to a first portion of the reference signal and generating at least one detector output signal in response thereto;

a vector modulator, the vector modulator being responsive to the at least one detector output signal and to a second portion of the reference signal and generating a cancellation signal in response thereto, the cancellation signal being adjusted by the vector modulator to be substantially equal in amplitude and opposite in phase to the interfering signal component of the received signal; and

a summing coupler, the summing coupler being responsive to the received signal and to the cancellation signal and being provided for summing the cancellation signal and the received signal to thereby cancel the interfering signal component from the received signal.

11. A method of receiving and transmitting signals in a radio system, the radio system having at least one receiving radio receiving a desired signal and at least one transmitting radio generating a transmitted signal which interferes with the desired signal, the at least one receiving radio and the at least one transmitting radio having a common antenna for receiving and transmitting signals, which comprises the steps of:

reflecting from the common antenna a portion of the transmitted signal to generate a reflected transmitted signal;

sampling the transmitted signal and providing a reference signal in response thereto;

sampling the reflected transmitted signal and the desired signal and providing a received signal in response thereto, the received signal including an interfering signal component corresponding to the reflected transmitted signal and a desired signal component corresponding to the desired signal;

sampling the received signal and providing an error signal in response thereto;

comparing the error signal and a first portion of the reference signal and generating at least a first signal in response thereto;

generating a cancellation signal in response to the at least first signal and to a second portion of the reference signal, and adjusting the cancellation signal so that the cancellation signal is substantially equal in amplitude and opposite in phase to the interfering signal component of the received signal; and

summing the cancellation signal and the received signal to thereby cancel the interfering signal component from the received signal.