Quadrature Demodulator Phase Error Detection

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Solution Overview

Problem

Quadrature demodulators in RF communication circuits face challenges in detecting and correcting phase shift errors between in-phase and quadrature RF signals, leading to inaccurate signal output.

Innovation Solution

An apparatus and method involving RF and LO signal choppers, a phase shifter, mixer, filters, and a digital signal processor to generate a baseband signal, extract phase and offset errors, and implement cancellation loops to adjust the demodulator, ensuring a 90-degree phase difference and removing errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If phase shift is used to extract quadrature components, then signal demodulation is enabled, but phase shift errors cause output errors

Engineering Contradiction:

Improvesignal demodulation capabilityVSAvoidoutput signal accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent implements feedback mechanisms through offset cancellation loops and phase error cancellation loops that continuously monitor and correct errors in the quadrature demodulator, using the extracted error signals to adjust and compensate for phase and offset deviations in real-time

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces mechanical or fixed phase shift arrangements with electronically controllable phase shifters that can be dynamically adjusted through digital control, allowing precise compensation of phase errors without mechanical adjustments

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If multiple filters and processing stages are added to extract and correct errors, then measurement precision improves, but device complexity increases

Engineering Contradiction:

Improvephase error detection accuracyVSAvoidcircuit structure complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent segments the error detection and correction process into distinct functional blocks including separate filter stages (low-pass, band-pass), independent offset cancellation loops, and phase error cancellation loops, allowing each component to be optimized independently while maintaining overall system precision

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent designs the quadrature demodulator with multi-functional components that serve both signal processing and error detection functions, such as the mixer that performs both demodulation and error signal generation, reducing the need for separate dedicated error detection hardware

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS11855815B1Real time phase error detection in quadrature demodulators

Publication Date: 2023.12.26 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

An apparatus for detecting a Q-demodulator's real-time phase and offset error includes an RF signal path configured to receive an RF signal from an RF component, a first chopper to chop the RF signal at a first frequency to generate a chopped RF signal, an LO signal path configured to receive an LO signal, a second chopper to chop the LO signal at a second frequency to generate a chopped LO signal, a summing mechanism to combine the chopped LO signal to the chopped RF signal into a combination signal. The apparatus further includes a Q-demodulator comprising a phase shifter configured to shift a phase of the combination signal and a phase of the LO signal, and a mixer configured to multiply the shifted combination signal by the shifted LO signal to generate a baseband signal, and at least two filters configured to extract different signals contained in the baseband signal for analysis.