Switched-capacitor band-pass feed-forward sigma-delta modulator

Abstract

The invention discloses a band-pass feed-forward sigma-delta modulator. The modulator comprises three cascaded switched-capacitor resonator modules, an adder module, a quantizer module and a feedback digital to analog conversion (DAC) module. In the sigma-delta modulator, a feed-forward structure is adopted instead of a common feedback structure, and input ends of resonators only include quantization noise components rather than input signal components, so that input levels of the resonators are lowered, and the loop stability of the whole sigma-delta modulator is enhanced. Thus, the band-pass feed-forward sigma-delta modulator disclosed by the invention is suitable for an analog to digital converter with a high-order single-loop structure, and the requirements of a modulator circuit for analog sub-circuits such as operational amplifiers are lowered. As indicated by a simulation result, the band-pass feed-forward sigma-delta modulator disclosed by the invention reach a dynamic signal-to-distortion ratio range from 96.8dB to 106dB under the conditions of a power supply voltage being 3.3V, a clock frequency being 800KHz, a central frequency being 200KHz and a signal bandwidth being 5KHz, and meets the application requirements of micro mechanical sensor systems such as high-accuracy gyroscopes and acceleration sensors.

Description

technical field [0001] The invention belongs to the technical field of integrated circuits, and in particular relates to a switched capacitor type bandpass feedforward structure sigma-delta modulator. Background technique [0002] Digital circuits have the advantages of fast speed, low power consumption, and high reliability. With the rapid development of digital electronic technology and digital signal processing technology, more and more electronic devices, even micromechanical sensor systems, need to process digital signals. . During the working process of electronic equipment, the signals to be processed are often continuously changing analog variables, such as temperature, pressure, acceleration, etc., which are all analog quantities. The analog quantities of these non-digital signals must first be converted into voltage signals or current signals by sensors. , and then converted into a digital quantity with a certain precision through an analog-to-digital converter be...

AI Technical Summary

Problems solved by technology

The sigma-delta modulator with a single-ring structure has the advantage of being insensitive to non-ideal characteristics of the circuit, but high-order single-ring structure modulators have system stability problems

For sigma-delta modulators, the higher the order, the better the filtering effect on quantization noise, but according to theoretical analysis, it is impossible to mathematically deduce a single-ring 1-bit quantized sigma-delta modulator higher than the second order stability condition

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