Reconditioning equalizer filter for non-constant envelop signals
AssigneeAltera Corporation
InventorKiomars Anvari
Life of this patent
Estimating the term…
Abstract
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.
Claims5
A reconditioning equalizer filter for use with non-constant envelope signals to enhance the performance of a transmitter, the reconditioning equalizer filter comprising:
- a delay-and-gain-adjustment block that operates on a main input baseband signal to produce a primary delay-and-gain-adjusted main baseband signal;
- a peak reduction filter that operates on the main input baseband signal to produce a peak-reduced main baseband signal;
- a feedforward loop that injects an in-band-and-out-of-band-adjusted baseband signal into the main baseband signal, wherein the feedforward loop comprises:
- a delay adjustment block that delays the main baseband signal,
- a first gain adjustment block that gain-adjusts the delayed main baseband signal to produce a second delay-and-gain-adjusted main baseband signal,
- a first digital signal processing block that subtracts the second delay-and-gain-adjusted main baseband signal from the peak-reduced main baseband signal,
- a second digital signal processing block that correlates 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 the delay adjustment in the delay adjustment block and the amount of gain adjustment in the gain adjustment block,
- a low pass filter that filters 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,
- a second gain-adjustment block that adjusts 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
- a digital signal processing summing block that adds 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;
- a third gain adjustment block that adjusts the gain of the modified main baseband signal to produce an output of the reconditioning equalizer filter;
- and
- a controller that uses the main baseband signal, the output of the low pass filter, the output of the reconditioning equalizer filter, and external input to provide control signals to the peak reduction filter, the correlation block, the delay-and-gain-adjustment block, and the second gain-adjustment block.
Dependencies are inferred from the claim text.