Variable time delay control structure for channel matching
AssigneeBAE Systems Information and Electronic Systems Integration Inc.
InventorRaymond J. Lackey
Life of this patent
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Abstract
A cosite interference cancellation system is provided for improved rejection of a signal coupled from a transmission antenna into a local receive antenna in the presence of local multipath. The cosite interference cancellation system and associated method advantageously provide improved signal rejection by continuously controlling (adjusting) a matching time delay to reduce cosite interference.
Claims19
A method of matching a time delay of a first received signal in a controlled propagation path to a second received signal over an uncontrolled propagation path, the method comprising:
- (a) sampling a first signal of a known source;
- (b) delaying the first sampled signal in a variable delay line under control of a delay control signal;
- (c) sampling the first signal after all delays over the controlled propagation path;
- (d) sampling the second signal received over the uncontrolled propagation path;
- (e) forming a delayed sample of the first received signal;
- (f) forming a delayed sample of the second received signal;
- (g) generating a first autocorrelation value from the sampled first signal and the delayed sample of the second received signal;
- (h) generating a second autocorrelation value from the delayed first signal and the delayed sample of the second received signal;
- (i) computing a difference value between the first autocorrelation value and the second autocorrelation value;
- (j) decreasing a delay control signal to more closely match the time delay between the first received signal and the second received signal in the case where the difference value is negative and its absolute value is greater than a predetermined threshold;
- (k) otherwise increasing the delay control signal to more closely match the time delay between the first received signal and the second received signal in the case where the difference value is positive and its absolute value is greater than the predetermined threshold;
- and
- (l) repeating steps (a)-(k).
An interference cancellation system, comprising:
- (A) a variable delay line (19) for adjusting a signal propagation time of a sampled transmission signal (40), the variable delay line (19) comprising:
- (i) at least one fixed delay element (80, 82) in series with the propagated received signal path;
- (ii) a variable delay element (11) for continuously varying a delay of sampled transmission signal (40) to implement a match between the sampled transmission signal (40) and a propagated received signal (30) yielding a delayed coupled signal (57);
- (B) an adaptive time delay control (ATDC) module (10) for calculating a delay to be added to a first propagation path to achieve a match of the first signal passing through a controlled propagation path with a second signal passing through an uncontrolled propagation path;
- and
- (C) an adaptive control loop (6) for adjusting a complex weighting of the delayed coupled signal (57) to maximally cancel the propagated transmission signal received in antenna signal (30).
The interference cancellation system of claim 18, wherein the at least one other signal is a desired signal anticipated by a protected receiver (25) of the interference cancellation system.
Dependencies are inferred from the claim text.