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US 2010/0136941 A1Published application
Quadratic amplitude control circuit for cosite interference cancellation
AssigneeBAE Systems Information and Electronic Systems Integration Inc.
InventorRaymond J. Lackey
Life of this patent
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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.
Claims28
A method for continuously and automatically tuning a quadratic amplitude matching filter (QAMF) to an inserted signal to allow tracking of the inserted signal to match a dynamically changing quadratic amplitude distortion of the inserted signal for improved interference cancellation system performance, the method comprising:
- a) forming an imaginary broadband RF lobed filter having a single quiescent null within a frequency band of interest;
- b) dynamically adjusting a delay time (T) for tuning the single quiescent null of the imaginary broadband RF lobed filter to effectively block the inserted signal to be tracked;
- c) forming a first narrowband RF lobed filter with a quiescent lobe peak centered on a quiescent null of the inserted signal to be tracked, wherein an output of the first narrowband RF lobed filter output has a near-linear and flat amplitude shape to match a dynamically changing quadratic amplitude distortion of the inserted signal to be tracked;
- d) forming a second narrowband RF lobed filter with a quiescent lobe peak centered on the quiescent null of the inserted signal to be tracked, wherein an output of the second narrowband RF lobed filter has a downward quadratic amplitude shape to match a dynamically changing quadratic amplitude distortion of the inserted signal to be tracked;
- e) forming an FIR filter with a quiescent lobe peak centered on the quiescent null of the inserted signal to be tracked, wherein an output of the FIR filter has an upward quadratic amplitude shape to match a dynamically changing quadratic amplitude distortion of the inserted signal to be tracked;
- f) adjusting an in-line path delay of the first narrowband RF lobed filter, the second narrowband RF lobed filter and the FIR filter to have the same throughput delay;
- and
- g) adjusting combining weights of the respective filter outputs of the first narrowband RF lobed filter, the second narrowband RF lobed filter and the FIR filter to implement a corrective quadratic amplitude shaping of the inserted signal, thereby matching a dynamically changing quadratic amplitude distortion of the inserted signal to be tracked.
5 more elements
An interference cancellation system, comprising:
- (A) an adaptively tuned quadratic control (ATQC) module (200) for providing a tuning procedure directed to a quadratic amplitude matching filter (QAMF) (100) control function to the band of interference and for externally controlling the QAMF control function subsequent to said tuning, said adaptively tuned quadratic control (ATQC) module (200) comprising:
- a) an inline variable lobe filter structure (VLFS) (201) for providing controlled variable time delay for generating a broadband RF tuning filter formed by a delay T and a first narrowband inline control filter for providing a near-flat quadratic control filter lobe formed by a first delay (T) and a second delay (2nT) yielding a total time delay of (2n+1)T centered in the null of the broadband RF tuning filter and weighted by an external amplitude control signal;
- b) a second narrowband inline control filter as a slaved lobe filter structure-down (104) for providing a down quadratic amplitude control filter lobe formed by a delay of (2m+1)T centered in the null of the RF tuning filter and weighted by an external amplitude control signal;
- c) a third narrowband inline control filter as a slaved lobe filter structure-up (105) for providing a up quadratic amplitude control filter lobe formed by a simple FIR filter with inter-tap spacing delay of (2o+1)T centered in the null of the tuning filter and weighted by an external amplitude control signal;
- d) an offline time delay tuning control (TDTC) element (202) for receiving signal samples output from the inline variable lobe filter structure (VLFS) 201 to control a first variable time delay element (T) 205 of the inline variable lobe filter structure (VLFS) 201 to provide said controlled variable time delay to form said broadband RF tuning filter and a second variable time delay element (2nT) (208) of the inline variable lobe filter structure (VLFS) 201 to provide said controlled variable time delay to generate said slope control filter lobe.
- (B) an adaptive control loop (6) for adjusting a complex weighting of the delayed coupled signal (57) to maximally cancel a propagated reference signal.
3 more elements
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.
4 more elements
Dependencies are inferred from the claim text.