Integrated DSP Feedback Loop for Receiver DC Offset Cancellation

Solution Overview

Problem

Direct conversion receivers face a direct current (DC) offset issue due to local oscillator energy leakage, which saturates baseband amplifiers and degrades signal reception, and traditional analog circuitry solutions require large external capacitors increasing board space and cost while introducing noise.

Innovation Solution

A digital signal processing-based feedback circuit using a digital signal processor, analog-to-digital converter, and digital-to-analog converter with integrated MOS capacitors eliminates the need for external capacitors, implementing a DC offset cancellation loop on a single chip.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional analog circuitry is used for DC offset compensation, then DC offset cancellation is achieved, but large external capacitors are required increasing board space and cost

Engineering Contradiction:

ImproveDC offset cancellationVSAvoidboard space

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent replaces the traditional analog circuitry with a digital signal processing-based feedback circuit. The DC offset detection and compensation functions are implemented using a digital signal processor that receives the analog signal, converts it to digital domain, processes it to detect DC offset, generates compensation signal, and feeds it back to cancel the DC offset. This substitution of analog mechanical/electrical components with digital processing eliminates the need for large external capacitors and reduces board space requirements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operating domain from analog to digital for the DC offset compensation process. By converting the analog signal to digital domain using an analog-to-digital converter, processing the signal digitally to detect DC offset components, and then converting the compensation signal back to analog domain using a digital-to-analog converter, the system achieves DC offset cancellation without requiring large analog capacitors. This parameter change from analog to digital domain enables integration on a single chip and eliminates external component requirements.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If traditional analog circuitry is used for DC offset compensation, then DC offset cancellation is achieved, but external capacitors increase system cost

Engineering Contradiction:

ImproveDC offset cancellationVSAvoidsystem cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces the traditional analog circuitry with a digital signal processing-based feedback circuit. The DC offset detection and compensation functions are implemented using a digital signal processor that receives the analog signal, converts it to digital domain, processes it to detect DC offset, generates compensation signal, and feeds it back to cancel the DC offset. This substitution of analog mechanical/electrical components with digital processing eliminates the need for large external capacitors and reduces board space requirements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent merges multiple functions (DC offset detection, signal processing, compensation signal generation) into a single integrated digital signal processing circuit that can be implemented on one chip. The feedback circuit integrates the analog-to-digital converter, digital signal processor, and digital-to-analog converter into a unified system, eliminating the need for separate external capacitor components and reducing overall system complexity and cost.

Inventive Principle:

Principle #5Merging (Combining)

3Measurement precision

If external capacitors are used for DC offset compensation, then DC offset detection is enabled, but noise is picked up by the capacitors

Engineering Contradiction:

ImproveDC offset detectionVSAvoidnoise

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the traditional analog circuitry with a digital signal processing-based feedback circuit. The DC offset detection and compensation functions are implemented using a digital signal processor that receives the analog signal, converts it to digital domain, processes it to detect DC offset, generates compensation signal, and feeds it back to cancel the DC offset. This substitution of analog mechanical/electrical components with digital processing eliminates the need for large external capacitors and reduces board space requirements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS7864088B2Integrated DSP for a DC offset cancellation loop

Publication Date: 2011.01.04 MONTAGE TECH HLDG CO LTD

AI summary

Processes and apparatuses for direct current (DC) offset cancellation using digital signal processing. Some embodiments of the invention are summarized in this section. In one embodiment, a circuit includes: an analog receiver; and a feedback circuit comprising a digital signal processor coupled with the analog receiver to generate a feedback signal to the analog receiver.