An Adaptive Direct Quadrature Frequency Conversion Modulation Error Correction Method

Abstract

The invention discloses a self-adaptive direct quadrature variable-frequency modulation error correction method. The method creates a new quadrature modulation error model, and puts forward a self-adaptive QMC (Quadrature Modulation Compensation) algorithm for direct quadrature variable-frequency modulation error correction on the basis of the model. Through antenna coupling and down-conversion mixing, by obtaining a feedback signal after intermediate-frequency high-speed sampling, a quadrature modulation error inverse distortion coefficient is estimated after the feedback signal and a transmission signal are aligned, and self-adaptive correction is implemented in a numeric field programmable logic device FPGA (field programmable gate array). The self-adaptive direct quadrature variable-frequency modulation error correction method can efficiently and accurately inhibit local oscillator leakage caused by direct-current bias and image interference caused by I / Q amplitude and phase imbalance, and has important significance for self-adaptive direct quadrature variable-frequency modulation error correction.

Description

technical field [0001] The invention relates to an adaptive direct quadrature frequency conversion modulation error correction method, which belongs to the technical field of digital signal processing. Background technique [0002] In a digital communication transmission system, it is necessary to up-convert the baseband signal to a radio frequency, which is beneficial to the efficient transmission of the signal and improves the utilization of spectrum resources. Real signal double or triple frequency conversion converts the digital low-IF signal into an analog low-IF signal, and then performs one or two frequency conversion to the specified frequency point after band-pass filtering. The performance consistency of the multiple frequency conversion system is high, and the local oscillator leakage and image spectrum can be eliminated by filtering. The disadvantage is that it has high requirements for circuit and system design, and the phase noise is poor. In recent years, a n...

AI Technical Summary

Problems solved by technology

However, the direct quadrature frequency conversion technology has high requirements on the amplitude-phase balance of the baseband signal and the local oscillator signal. The unbalanced amplitude and phase will reduce the image frequency interference suppression ability of the frequency converter, and the adjacent channel power rejection ratio of the transmitter will decrease.

At the same time, due to the inevitable existence of crosstalk, radiation, DC offset modulation and other problems in the circuit, local oscillator leakage is caused, and because the useful signal and the leaked local oscillator signal are very close in frequency spectrum, it is impossible to use a filter to filter remove

On the one hand, the leakage signal of the local oscillator will reduce the efficiency of the transmitter, and on the other hand, it will cause the DC operating point of the receiver to shift, which will easily cause nonlinear distortion and even saturation blocking.

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