Reconditioning equalizer filter for non-constant envelope signals

摘要

A technique for a reconditioning equalizer filter for non-constant envelope signals is described. The input to a transmitter chain is modified by a reconditioning equalizer filter, prior to being applied to the transmitter. The reconditioning equalizer filter modifies and smoothens the amplitude of the signal. The modified and smoothened signal has its peaks reduced which results in lower Crest Factor. The input to the reconditioning equalizer filter could be a baseband, intermediate frequency (IF) or radio frequency (RF) signal. When the signal is an IF or RF signal, it needs to be down-converted to baseband before being applied to the reconditioning equalizer filter. The reconditioning equalizer filter could be performed in a digital or analog domain.

主权项

1. A reconditioning equalizer method for use with non-constant envelope signals to enhance the performance of a transmitter, the reconditioning equalizer method comprising:
delay-and-gain adjusting a main input baseband signal to produce a primary delay-and-gain-adjusted main baseband signal; peak-reduction filtering the main input baseband signal to produce a peak-reduced main baseband signal; injecting an in-band-and-out-of-band-adjusted baseband signal into the main baseband signal in a feedforward loop, wherein the injecting comprises: delaying the main baseband signal, gain-adjusting the delayed main baseband signal to produce a second delay-and-gain-adjusted main baseband signal, subtracting the second delay-and-gain-adjusted main baseband signal from the peak-reduced main baseband signal, correlating the main baseband signal and the result of the subtraction of the second delay-and-gain-adjusted main baseband signal from the peak-reduced main baseband signal to calculate the amount of delay adjustment in the delaying and the amount of gain adjustment in the gain-adjusting, low-pass filtering the result of the subtraction of the second delay-and gain-adjusted main baseband signal from the peak-reduced main baseband signal to adjust in-band and out-of-band components in the baseband signal, adjusting the gain of the filtered subtraction of the second delay-and-gain-adjusted main baseband signal from the peak-reduced main baseband signal for injection into the primary delay-and-gain-adjusted main baseband signal, and summing the primary delay-and-gain-adjusted main baseband signal and the low-pass-filtered and gain-adjusted subtraction of the second delay-and-gain-adjusted main baseband signal from the peak-reduced main baseband signal to produce a modified main baseband signal; adjusting the gain of the modified main baseband signal to produce an output; and using the main baseband signal, the output of the low pass filter, the output of the reconditioning equalizer filter, and external input to control the peak-reduction filtering, the correlating, the delay-and-gain adjusting, and the adjusting the gain of the filtered subtraction.