Error correction method of UWB complex format vector modulation based on dual-stage predistortion

Abstract

The present invention proposes a method for correcting errors of UWB complex format vector modulation based on two-stage pre-distortion. shift compensator, transmission channel and vector modulator; the I-level pre-distortion error compensator reversely cancels the amplitude-phase-frequency-response fluctuation characteristics of the wideband vector modulation error in the form of shaping filter pre-distortion; the II-level pre-distortion error compensator will Modulation errors with broadband characteristics that have been equalized by I-level pre-distortion in the entire working band, that is, I / Q gain imbalance and gain imbalance positive angle errors are corrected; the origin offset compensator corrects modulation errors with narrow-band characteristics by means of analog devices That is, carrier leakage. The invention corrects the wideband characteristic vector modulation error by means of digital predistortion, and effectively corrects the wideband complex format vector modulation error.

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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