Modulator with improved linearity in quantized feedback loop

Abstract

Described herein is a modulator with improved linearity in a quantized feedback loop, and specifically a method and an apparatus for reducing ISI in a single-bit [sigma][delta] modulator without reducing the dynamic range of the modulator. In one embodiment, the signal fed back to the input of the modulator is not the single-bit outputs of a quantizer as in the prior art, but rather patterns of such outputs. The patterns are selected so that each pattern has the same number of transition edges and there is thus no mismatch of transition times. In one embodiment, the patterns are created by digital logic. In another embodiment, an analog signal is added to the error signal in the feedback loop which causes the quantizer to generate the patterns. When the amplitude of the input signal exceeds a certain level, the modulator reverts to the typical operation of a prior art modulator, thus preserving the full dynamic range of the modulator.

Description

[0001] This application claims priority to Provisional Application No. 62 / 693,984, filed July 4, 2018, which is hereby incorporated by reference in its entirety. technical field [0002] The present invention relates generally to sigma-delta modulators, and more particularly to sigma-delta modulators with improved linearity. Background technique [0003] Analog-to-digital conversion can be performed using quantized feedback in the control loop. An analog-to-digital converter (ADC) with such characteristics is often referred to as a sigma-delta (∑△) converter or a ∑△ modulator, the term modulator referring to the output digital data having some symbol pattern or modulation. The term ΣΔ modulator and the term noise shaping control loop are often used interchangeably in the art, although the latter is more descriptive. Circuit designers often like to use such ∑△ modulators because in many cases such ∑△ modulators are easier to design and less expensive to manufacture than oth...

AI Technical Summary

Problems solved by technology

However, this solution involves additional components and is therefore expensive in building the ΣΔ modulator

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