Patent ID: 8023921
Filing Date: 2011-09-20
Classification: H04B

Abstract:
1. 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.