Interference cancellation system employing an I/Q quadrature rotator

• US 5,584,065 A
• Filed: 10/13/1994
• Issued: 12/10/1996
• Est. Priority Date: 10/13/1994
• Status: Expired due to Term

• Current Assignee: Exelis Incorporated (L3Harris Technologies, Inc.)
• Original Assignee: American Nucleonics Corp. (Eaton Corporation PLC.)
• Inventors: Monzello, Roy C.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): TO, DORIS HA
• Application Number:
  US08/322,686
• Time in Patent Office: 789 Days
• Field of Search: 455/278.1, 455/296, 455/295, 455/304, 455/305, 455/306, 455/214, 455/289, 455/272, 455/273, 455/84, 455/24, 455/63, 375/346
• US Class Current: 455/296
• CPC Class Codes: H01Q 3/2611 Means for null steering; Adaptive interference nulling
• CPC Class Codes: H04B 1/126 having multiple inputs, e.g. auxiliary antenna for receiving interfering signal aerials in general H01Q

Abstract

An interference cancellation system for cancelling interfering signals which is adapted to be connected to a radio receiver system having a receiver antenna, a receiver and a receiver transmission line interconnecting the receiver antenna and the receiver includes an auxiliary antenna, a first directional coupler connected to the auxiliary antenna, a second directional coupler or error coupler connected to the receiver transmission line, a synchronous detector connected to the first and second directional couplers, a vector rotator connected to the outputs of the synchronous detector, a signal controller connected to the vector rotator and a third directional coupler or summer coupler connected to the receiver transmission line and to the signal controller. The vector rotator enables the internal time match of the cancellation system to be optimized by quadrature positioning by varying resistor values in the vector rotator circuit. After the match is optimized, the phase position between the reference signal path and error signal path can be set independently of the time match.

Claims

1. An interference cancellation system for reducing an interfering signal in a received signal on a transmission line to provide a desired signal to a receiver coupled to the transmission line, the interference cancellation system comprising:

a reference input port for receiving a reference signal substantially corresponding to the interfering signal;

a reference coupler having at least an input port and an output port, the input port of the reference coupler being operatively coupled to the reference input port, at least a portion of the reference signal being provided to the input port of the reference coupler, the reference coupler output port generating thereon a reference signal substantially corresponding to at least a portion of the reference signal;

an error coupler having at least an input port and an output port, the input port of the error coupler being operatively coupled to the transmission line for receiving a sample of the received signal, the received signal substantially corresponding to a combination of the desired signal and the interfering signal, the error coupler output port generating thereon an error signal substantially corresponding to the received signal;

a synchronous detector, the synchronous detector having first and second output ports and first and second input ports, the first and second input ports respectively electrically coupled to the reference coupler and the error coupler and being responsive to the reference signal and error signal, the synchronous detector determining a phase relationship between the reference signal and the error signal, the synchronous detector generating first and second output signals respectively provided on the synchronous detector first and second output ports;

a vector rotator having at least a first and second output port and a first and second input port, the first and second input ports being electrically coupled to the first and second output ports of the synchronous detector respectively, for receiving the first and second synchronous detector output signals, the vector rotator providing quadrature alignment of the first and second synchronous detector output signals and generating an output rotated vector signal therefrom;

a signal controller having at least a first input electrically coupled to the reference input port and a second input electrically coupled to the outputs of the vector rotator and being responsive to the rotated vector signal, the signal controller having an output and providing thereon a cancellation signal in response to the rotated vector signal; and

a summing coupler having at least an input port and an output port, the summing coupler output port providing the cancellation signal to the transmission line.

2. An interference cancellation system as defined by claim 1, wherein the synchronous detector output signals are a signal vector comprising quadrature components and wherein the vector rotator aligns the quadrature components independent of frequency variations.

3. An interference cancellation system as defined by claim 2, wherein the vector rotator comprises an analog circuit to rotate the signal vector quadrature components.

4. An interference cancellation system as defined by claim 3, wherein the vector rotator aligns the quadrature components by resistor value adjustment in the analog circuit of the vector rotator.

5. An interference cancellation system as defined by claim 4, wherein the signal vector is rotated a predetermined number of degrees by a specific resistor value.

6. An interference cancellation system as defined by claim 1, wherein said signal controller further includes an integrator for integrating the first and second synchronous detector output signals rotated by the vector rotator.

7. An interference cancellation system for cancelling an interfering signal received by a radio receiver system, the radio receiver system having a radio receiver, a receiving antenna, and a receiver transmission line coupling the receiving antenna to the receiver, the interference cancellation system comprising:

an auxiliary antenna for receiving a sample of an interfering signal;

a reference coupler coupled to the auxiliary antenna, the reference coupler generating a reference signal thereon substantially corresponding to the sample of interfering signal received by the auxiliary antenna;

a sampler coupler coupled to the receive transmission line, the sampler coupler sampling an interfering signal and desired signal received by the radio receiver system and generating an error signal in response thereto;

a synchronous detector, the synchronous detector being responsive to the reference signal and the error signal and generating a control signal in response thereto;

a vector rotator, the vector rotator being responsive to the synchronous detector control signal, the vector rotator providing quadrature alignment for the control signal and generating a rotated vector signal in response thereto;

a signal controller, the signal controller being responsive to the reference and the rotated vector signals and generating a cancellation signal in response thereto; and

a summer coupler, a summer coupler coupled to the receive transmission line, the summer coupler injecting the cancellation signal into the receive transmission line to substantially cancel an interfering signal present in the radio receiver system.

8. An interference cancellation system as defined by claim 7, wherein the signal controller further includes an integrator for providing an integrated rotated vector signal.

9. An interference cancellation system as defined by claim 7, wherein the synchronous detector output signal is a signal vector comprising quadrature components and wherein the vector rotator aligns the quadrature components independent of frequency variations.

10. An interference cancellation system as defined by claim 9, wherein the vector rotator comprises an analog circuit to rotate the signal vector quadrature components.

11. An interference cancellation system as defined by claim 10, wherein the vector rotator aligns the quadrature components by resistor value adjustment in the analog circuit of the vector rotator.

12. A method for substantially cancelling an interfering signal component from a received signal, the method comprising:

sampling an interfering signal which results in the interfering signal component of the received signal, and providing a reference signal corresponding thereto;

sampling the received signal, the received signal including the interfering signal component, and providing an error signal corresponding to the interfering signal component;

comparing and correlating the reference signal with the error signal and generating a first and second control signals in response thereto;

adjusting the time match of the first and second control signals;

adjusting the phase position and amplitude of the first and second control signals independently of the time match;

generating a cancellation signal corresponding to the time match and phase and amplitude adjusted reference signal, the cancellation signal being 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 so as to effectively cancel the interfering signal component of the received signal.