RF Receiver DC Offset Estimation During Low-AM Signal Periods

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Solution Overview

Problem

In wireless communications systems, direct current (DC) offsets in RF transmitters and receivers can interfere with signal processing, especially when interruptions are not possible, such as during continuous transmission in 3G or 4G systems, making it difficult to measure and compensate for DC offsets accurately.

Innovation Solution

Estimating the DC offset of RF receivers and power detection circuits when the instantaneous amplitude of continuous-transmission AM RF signals is below specific thresholds, allowing for corrections to improve performance over temperature and supply voltage variations, and using these estimates to regulate output power.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If the RF transmit signal is continuously transmitted without interruption, then the communication system maintains continuous transmission capability, but DC offset measurements cannot be performed accurately

Engineering Contradiction:

Improvecontinuous transmission capabilityVSAvoidDC offset measurement accuracy

Core Design Contradiction:

Duration of action of stationary objectVSMeasurement precision

Solution Approach 1:

The system performs DC offset estimation during periods when the instantaneous amplitude of the continuous transmission signal is below a threshold, effectively using low-amplitude periods as preliminary measurement opportunities without interrupting the continuous transmission

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system changes the operating condition parameter by monitoring signal amplitude and performing DC offset estimation only when the instantaneous amplitude is below a threshold, allowing measurements during low-power states of continuous transmission

Inventive Principle:

Principle #35Parameter changes

2Reliability

If DC offset correction is performed continuously, then receiver performance is maintained, but measurement errors increase due to signal interference

Engineering Contradiction:

Improvereceiver performanceVSAvoidDC offset estimation accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The system dynamically adjusts the DC offset estimation process by continuously monitoring signal amplitude and enabling estimation only when amplitude is below the threshold, making the measurement process adaptive to real-time signal conditions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system uses feedback from the instantaneous amplitude monitoring to control when DC offset estimation is performed, creating a closed-loop system that prevents measurements during high-interference periods

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS8189707B1DC offset correction of a radio frequency receiver used with a continuous transmission radio frequency signal

Publication Date: 2012.05.29 QORVO US INC

AI summary

The present invention relates to estimating a direct current (DC) offset of a radio frequency (RF) receiver when an estimated amplitude of a continuous-transmission amplitude-modulated (AM) RF signal is below a first threshold and when the RF receiver is not receiving an RF input signal. The estimated DC offset of the RF receiver may be used to improve RF receiver performance, particularly over temperature and supply voltage variations. Estimating the DC offset of the RF receiver when the estimated instantaneous amplitude of the continuous-transmission AM RF signal is below the first threshold may minimize errors in the estimated DC offset.