Quadratic amplitude control circuit for cosite interference cancellation

• US 8,086,206 B1
• Filed: 08/15/2011
• Issued: 12/27/2011
• Est. Priority Date: 12/03/2008
• Status: Expired due to Fees

• Current Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Original Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Inventors: Lackey, Raymond J.
• Primary Examiner(s): Nguyen, Hai L
• Application Number:
  US13/209,614
• Publication Number:
  US 20120003948A1
• Time in Patent Office: 134 Days
• Field of Search: 455/296, 455/303
• US Class Current: 455/303
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver

Abstract

A quadratic amplitude matching system and associated method with an associated tuning control system is provided for continuously and automatically tuning a quadratic amplitude matching filter (QAMF) to a band center of an interfering signal to provide improved rejection of an interfering signal coupled from a transmission antenna into a local receive antenna in the presence of local multi-path, thereby providing improved interference cancellation system performance. The matching control system is provided as an element of an interference cancellation system.

Claims

1. A method for implementing a first-order quadratic correction to the amplitude of an input signal across its band by the use of a quadratic amplitude matching filter (QAMF), the method comprising:

a) dividing an input signal into three parallel signal paths;

b) dynamically adjusting a delay time (T) in a first signal path from among said three parallel signal paths for tuning a first narrowband RF lobed filter with one of its quiescent lobes peaked on an interfering signal to be tracked;

c) forming a second more narrowband RF lobed filter in a second signal path from among said three signal paths dependent upon the delay time (T) wherein one of the quiescent lobes of the second narrowband RF filter is peaked on the interfering signal to be tracked;

d) forming a simple FIR filter in the third branch dependent upon the delay time, (T), having a filter configuration in the form of an upward quadratic shape centered on the interfering signal to be tracked,

e) matching each of the first, second and third signal paths to have a uniform path delay dependent upon the delay time (T);

f) weighting each of the first, second and third signal paths according to an external control function, and

g) combining the first, second and third signal paths into a single output to allow facilitate the implementation of a first-order quadratic amplitude distortion of the input signal via the QAMF to match the delayed coupled signal to that of the propagation path for improved interference cancellation of the inserted signal in an interference cancellation system.

2. The method of claim 1, wherein the first narrowband RF lobed filter is sufficiently broad enough in bandwidth to implement a first path characterized by a near-linear and flat amplitude shape.

3. The method of claim 1, wherein the second more narrowband RF lobed filter is controlled to be more narrow than the first narrowband RF lobed filter to implement said second signal path for downward quadratic amplitude adjustment of the inserted signal.

4. The method of claim 1, wherein the FIR filter upward quadratic area is centered on the interfering signal to be tracked to implement said third signal path for upward quadratic amplitude adjustment of the inserted signal.