Ultra-wide-band complex-format vector modulation error correction method based on two-stage predistortion

Abstract

The invention provides an ultra-wide-band complex-format vector modulation error correction method based on two-stage predistortion. A loop comprises a standard signal generation module, a first-stage predistortion error compensator, a second-stage predistortion error compensator, an origin offset compensator, a transmission channel and a vector modulator; the first-stage predistortion error compensator offsets an amplitude-phase frequency response fluctuating feature of a broadband vector modulator error reversely in a molded filter predistortion manner; the second-stage predistortion error compensator corrects a modulation error, with the broadband feature, after first-stage predistorion balancing in the whole work waveband, namely, the positive-angle error with I / Q gain imbalance and gain imbalance; and the origin offset compensator corrects a modulation error with a narrowband feature, namely carrier wave leakage, via an analog device. According to the invention, the vector modulation error with the broadband feature is corrected in a digital predistortion manner, and the broadband complex-format vector modulation error is corrected effectively.

Description

technical field [0001] The invention relates to the technical field of testing, in particular to an ultra-wideband complex format vector modulation error correction method based on dual-stage predistortion. Background technique [0002] The signals generated by the vector modulation function of the vector signal generator are mainly divided into two types, multi-tone modulation signals and complex modulation signals (such as QPSK, FSK, QAM, etc.). The I / Q vector modulator is a key component to realize vector modulation, and its performance has been significantly improved after years of development. Nevertheless, the modulation error of current mainstream I / Q vector modulators is still obvious and cannot be ignored. Especially under the condition of large modulation bandwidth, the magnitude and phase frequency response characteristics of vector modulation errors fluctuate significantly, and multiple modulation errors overlap and couple at each frequency point, which makes hi...

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Problems solved by technology

[0013] (1) Since the above method is completely based on analog devices, only the error of the carrier frequency point is corrected, and then the compensation data of this frequency point is used for the whole working band, without considering the influence of the amplitude and phase frequency response of the error, so only the single frequency The correction of point or narrowband modulation error is effective, and the correction of wideband modulation error cannot be made effectively;

[0014] (2) Due to the limitation of the bandwidth characteristics of the analog device itself, the expansion of the working bandwidth of the whole machine will be limited, and serious distortion will be caused to signals with large modulation bandwidth;

[0015] (3) The above method requires a series of complex analog circuits, including: calibration source, attenuator, bias voltage generation circuit and phase shifter, etc., due to individual differences in the performance of the analog device itself, the calibration accuracy is limited;

[0016] (4) The compensation parameter list established through the calibration process is obtained under the separate excitation of the calibration source. The actual baseband signal in the normal working state is quite different from the calibration state, and only approximate calibration can be achieved.

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