PD for higher order sigma-delta modulators λ Design Method of Phase Compensator

Abstract

The present application discloses a design method of PD Lambada phase compensator For high order Sigma-Delta modulators. A transfer function of a fractional proportional differential phase compensatorPD Lambada is H(z)=kp+kd(w(z-1))Lambada, where kp is a proportional coefficient, kd is a differential coefficient, and (w(z-1))Lambada is a half order differential operator. A fractional differentialoperator is discretized though using tustin joint continued fraction expansion approximation method. The method has advantages: a defect existed in the conventional integer order phase compensator that phase compensation depth and noise shaping strength are contradictory to each other is solved; in the same time the method has an integral effect through adopting the fractional differential operator, can not only compensate phase lag of the high order Sigma-Delta modulator, but also further improve modulator noise shaping capability.

Description

technical field [0001] This application relates to the field of analog-digital mixed signal processing, especially a PD for high-order Sigma-Delta modulators λ Design method of phase compensator. Background technique [0002] As the functions of digital circuits become more and more powerful, the requirements for the performance of analog-to-digital converters are also getting higher and higher. The conversion accuracy of traditional analog-to-digital converters is generally not high, which cannot meet the high-precision requirements of the system. Sigma-Delta ADC is a kind of oversampling analog-to-digital converter, which belongs to a kind of high-precision analog-to-digital converter, and has low requirements on the performance of the front-end anti-aliasing filter. Therefore, Sigma-Delta modulators are widely used in robot control, speech recognition, communication systems and other fields. Through reading a lot of literature, it is found that Sigma-Delta modulation te...

AI Technical Summary

Problems solved by technology

The second-order system is full-time stable, the system structure is simple, and the circuit is easy to implement. The system only includes circuits such as sensing structures and quantizers, and does not include electrical integrators. However, due to the low order of the system, the Sigma-Delta modulator is limited. Noise shaping capability, there is a large quantization error during analog-to-digital conversion

However, a problem that cannot be ignored is that although the phase lead compensator can compensate for the phase lag, the phase lead compensator will inevitably weaken the system input signal gain, which will cause the noise shaping ability of the Sigma-Delta modulator to decline

Therefore, the present invention proposes an improvement scheme for the problem of reducing the input signal gain in the phase lead compensator

Images