Adaptive cancellation of multi-path interferences

• US 20110319044A1
• Filed: 06/28/2010
• Published: 12/29/2011
• Est. Priority Date: 06/28/2010
• Status: Active Grant

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: ITT Manufacturing Enterprises, Inc. (ITT, Inc.)
• Inventors: Bornazyan, Gevork George
• Granted Patent: US 8,428,542 B2
• Time in Patent Office: Days
• US Class Current: 455/233.1
• CPC Class Codes: H04B 1/1036 with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters H04B1/123 takes precedence; filter circuits H03H
• CPC Class Codes: H04B 1/1081 Reduction of multipath noise by equalising H04B7/005

Abstract

A multi-path signal interference cancellation system cancels multiple time delayed signal components of a multi-path interference signal received by a receive antenna and carried on a receiver transmission line of a radio receiver system. The interference cancellation system includes a plurality of adaptive interference canceller circuits, each of which has a synchronous detector, a signal controller and an integrator as essential parts of closed control loops defined by the canceller circuits. The integrator has gain and bandwidth characteristics associated therewith which are adjustable to adjust the gain and bandwidth of each closed control loop. An intensity profile of the multi-path interference signal is generated and stored in a memory. An intensity profile signal from the memory is provided to the integrator of each adaptive interference canceller circuit to adjust the gain and bandwidth of the integrator and the loop in which it is situated to maximize the error detection residual signal-to-noise ratio of each adaptive interference canceller circuit. Each adaptive interference canceller circuit generates a cancellation signal from which a synthesized cancellation signal is generated and effectively injected onto the receiver transmission line to cancel the multiple time delayed signal components of the multi-path interference signal carried thereon so that the radio receiver of the radio receiver system only receives a desired signal.

Claims

1. A multi-path signal interference cancellation system for connection to a radio receiver system having a receive antenna, a receiver and a receiver transmission line electrically coupling the receive antenna to the receiver, the receive antenna receiving multiple time delayed signal components of an interference signal following multiple paths to the receive antenna, which comprises:

a reference antenna, the reference antenna receiving the interference signal and providing a reference signal corresponding thereto;

a coupler, the coupler being electrically coupled to the receiver transmission line and providing an error sample signal;

a storage circuit for storing an intensity profile of the multi-path interference signal and generating an intensity profile signal in response thereto;

a plurality of adaptive interference canceller circuits, each adaptive interference canceller circuit having a synchronous detector, a signal controller and at least one integrator, the synchronous detector of each adaptive interference canceller circuit receiving at least a portion of the reference signal and at least a portion of the error sample signal and generating at least one detector output signal in response thereto, the at least one integrator of each adaptive interference canceller circuit having gain and bandwidth characteristics associated therewith and being responsive to the at least one detector signal and the intensity profile signal and generating an integrator output signal adjusted in at least one of gain and bandwidth in response to the at least one detector signal and the intensity profile signal, the signal controller of each adaptive interference canceller circuit receiving at least a portion of the reference signal and the integrator output signal and generating in response thereto a cancellation signal;

a subtractor, the subtractor being electrically coupled to the receiver transmission line and effectively injecting the cancellation signal generated by each signal controller of each adaptive interference canceller circuit onto the receiver transmission line, the cancellation signals effectively injected onto the receiver transmission line being substantially equal in amplitude and substantially opposite in phase to the multiple time delayed components of the multi-path interference signal received by the receive antenna so as to minimize or cancel the multiple time delayed components of the multi-path interference signal.

2. A multi-path signal interference cancellation system as defined by claim 1, wherein each adaptive interference canceller circuit of the multi-path signal interference cancellation system includes a time delay circuit, the time delay circuit being responsive to at least a portion of the reference signal and providing a time delayed output signal, the synchronous detector and signal controller of each adaptive interference canceller circuit being at least partially responsive to the time delayed output signal and respectively generating the at least one detector output signal and cancellation signal in at least partial response thereto.

3. A method of cancelling a multi-path interference signal having multiple time delayed signal components which is received by a receive antenna and receiver transmission line connected thereto of a radio receiver system, which comprises the steps of:

generating an intensity profile of the multi-path interference signal;

generating cancellation signals from a plurality of adaptive interference canceller circuits, each adaptive interference canceller circuit having a synchronous detector generating at least one detector output signal, at least one integrator responsive to the at least one detector output signal and generating an integrator output signal, and a signal controller generating a respective one of the cancellation signals in response to the integrator output signal, the at least one integrator having gain and bandwidth characteristics associated therewith;

adjusting at least one of gain and bandwidth of the at least one integrator based on the intensity profile; and

injecting onto the receiver transmission line a synthesized cancellation signal corresponding to the cancellation signals generated by the signal controllers of the adaptive interference canceller circuits, the synthesized cancellation signal injected onto the receiver transmission line being substantially equal in amplitude and substantially opposite in phase to the multiple time delayed components of the multi-path interference signal received by the receive antenna and carried on the receiver transmission line to minimize or cancel the multiple time delayed components of the multi-path interference signal on the receiver transmission line.

4. An integrator for use in each of a plurality of adaptive interference canceller circuits of a multi-path signal interference cancellation system, each adaptive interference canceller circuit having a synchronous detector generating at least one detector output signal and a signal controller generating a cancellation signal, the integrator being at least partially responsive to the at least one detector output signal and generating an integrator output signal in at least partial response thereto, the signal controller being at least partially responsive to the integrator output signal and generating the cancellation signal in at least partial response thereto, which comprises:

a programmable gain circuit and a programmable bandwidth circuit, the programmable gain circuit having an adjustable gain and being responsive to the at least one detector output signal of the synchronous detector and to the intensity profile signal and adjusting the gain thereof in response to the intensity profile signal, the programmable gain circuit generating a programmable gain circuit output signal corresponding to the at least one detector output signal adjusted in amplitude, the programmable bandwidth circuit having an adjustable bandwidth and being responsive to the programmable gain circuit output signal and to the intensity profile signal and adjusting the bandwidth thereof in response to the intensity profile signal, the programmable bandwidth circuit generating the integrator output signal which is provided to the signal controller.

5. An integrator as defined by claim 4, wherein the integrator is an analog integrator;

and wherein the programmable gain circuit includes an operational amplifier configured as an amplifier circuit having a gain which is adjustable based on the intensity profile signal.

6. An integrator as defined by claim 5, wherein the programmable bandwidth circuit includes a first stage integrator circuit, a second stage adjustable gain circuit and a third stage buffer amplifier circuit, the third stage buffer amplifier circuit generating the integrator output signal, the first stage integrator circuit being responsive to the programmable gain circuit output signal generated by the programmable gain circuit and to the integrator output signal, and summing and integrating the programmable gain circuit output signal and the integrator output signal and generating an integrator circuit output signal in response thereto, the second stage adjustable gain circuit having an adjustable gain and being responsive to the integrator circuit output signal and to the intensity profile signal and adjusting the gain thereof in response to the intensity profile signal, the second stage adjustable gain circuit generating a second stage adjustable gain circuit output signal corresponding to the first stage integrator circuit output signal adjusted in amplitude, the third stage buffer amplifier circuit being responsive to the second stage adjustable gain circuit output signal and generating the integrator output signal in response thereto.