Virtual image inhibiting method and circuit

Abstract

The invention discloses a virtual image inhibiting method. Based on N-1-order finite impact response filter, a frequency-irrelevant virtual image correction algorithm and a coordinate rotating digital computing method are adopted, and the computing capacity of a system on chip is combined to inhibit virtual images of input signals. The method is characterized by comprising the following steps of:selecting N frequency points fi in the frequency band of an input signal, and generating a sinusoidal waveform corresponding to each frequency point fi one by one by adopting the coordinate rotating digital computing method; mixing and filtering the series of sinusoidal waveforms obtained with the input signal one by one, traversing the N frequency points fi, obtaining a set of two mixed paths ofamplitude difference and phase difference, and inputting into the system on chip, solving an equation set that the set is associated with the N-1-order finite impact response filter to obtain N coefficient sets, and correcting the output two paths of amplitude difference and phase difference to inhibit virtual images through a method for assigning the N-1-order finite impact response filter.

Description

technical field [0001] The present invention relates to a signal processing method, in particular to a method for suppressing and filtering a virtual image in a complex signal processing mode and its realization circuit. With minimal hardware overhead and without interrupting normal signal processing, the adaptive correction matching changes quadrature circuit. Background technique [0002] In modern communication systems, the receiver is the most critical core. From the perspective of intermediate frequency output, the receiver mainly includes different structures suitable for real signal processing and complex signal processing. From the perspective of real signal processing, the receiver structure is as follows: figure 1 As shown, the local oscillator frequency of the received signal: f LO = f RF + f IF , virtual image frequency: f IMG = f RF +2f IF . This traditional real signal processor cannot distinguish between signals and virtual images (such as figure 2 ...

AI Technical Summary

Problems solved by technology

A frequency-independent virtual image suppression correction algorithm is used to correct the frequency-related two-way mismatch problem. In narrowband communication (such as GSM with a bandwidth of 200kHz), the actual virtual image suppression ratio performance is limited to 60-70dB in a circuit that matches no more than 30dB. In broadband communication (2Mhz WCDMA), the actual virtual image suppression ratio is limited between 50-60dB, while in 6-8M bandwidth TV reception, the correction algorithm can basically only guarantee 45-50dB VIR

Therefore, the frequency-independent virtual image suppression correction algorithm cannot meet the requirements of broadband communication (>70dB)

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