Fast-settling DC offset removal circuits with continuous cutoff frequency switching

Abstract

A fast-setting DC offset removal circuit with continuous cutoff frequency switching is disclosed. In the preferred embodiment, the circuit is implemented using a pair of RC filters for receiving a differential signal pair and a continuous, variable resistance control circuit. The control circuit can be current-controlled or voltage controlled to provide fast settling of the received signal and the removal of the DC offset components. Additionally, by using a current-controlled control circuit, the cutoff frequency of the RC filter can be ramped from high to low in a continuous manner, thereby minimizing the generation of DC offsets.

Description

technical field [0001] The present invention relates generally to signal conditioning circuits, and more particularly to circuits for fast-settling signal conditioning and DC offset cancellation. Background technique [0002] When processing a received signal, it is often desirable for the received signal to stabilize quickly in order to process the signal. However, as the signal propagates through the stream or is processed in the circuit, undesired direct current (DC) offset components may be introduced into the received signal from multiple sources. These distorted signals would be difficult to decode, thus causing further complications and undesired offsets to downstream circuitry. Therefore, eliminating this undesirable DC offset component and quickly stabilizing the received signal has become an important subject for many applications. [0003] For example, since the zero-intermediate frequency (Zero-IF) structure has lower requirements on channel selection filters a...

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Problems solved by technology

This method cannot be reliably stabilized because the discontinuous switching action itself will gene

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