Receiver Filter With Cross-Coupled Resistor Arrays For Image Rejection

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Solution Overview

Problem

Conventional receivers for RF signals struggle to effectively eliminate image interference due to phase or gain mismatches in complex band-pass filters, which reduces their ability to suppress image interference.

Innovation Solution

A receiver design incorporating two low-pass filters with cross-coupled resistor arrays and a modulator-demodulator to adjust resistor values based on image rejection ratios, enhancing image rejection capabilities and reducing circuit area.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a complex band-pass filter is configured to filter image signals, then image rejection capability is improved, but phase or gain mismatches between the two paths reduce the suppression ability

Engineering Contradiction:

Improveimage interference suppressionVSAvoidphase and gain match stability

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent replaces the conventional complex band-pass filter with a low-pass filter combined with resistor arrays. This substitution eliminates the need for precise phase and gain matching between multiple paths, as the new architecture uses resistive networks to achieve image rejection without requiring complex signal path synchronization.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the filtering approach from frequency-selective band-pass filtering to resistance-based signal mixing. By adjusting resistor values in the resistor arrays, the system achieves image rejection through parameter optimization rather than relying on stable phase and gain relationships in a complex filter structure.

Inventive Principle:

Principle #35Parameter changes

2Area of stationary object

If conventional band-pass filters are used, then circuit area is reduced, but they are unable to eliminate mirror symmetric interfering signals

Engineering Contradiction:

Improvefilter circuit areaVSAvoidimage signal elimination

Core Design Contradiction:

Area of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The patent segments the filtering function into two parts: a low-pass filter for basic signal filtering and resistor arrays for image rejection. This segmentation allows each component to perform its specialized function efficiently, achieving image signal elimination without requiring a large complex band-pass filter.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The resistor arrays act as intermediaries between the low-pass filter and the output, enabling image rejection functionality to be added without significantly increasing the overall circuit area. The resistor networks provide the necessary signal mixing and rejection capability in a compact form factor.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS20240372520A1Filter, receiver for processing radio frequency signals and calibration method

Publication Date: 2024.11.07 REALTEK SEMICON CORP

AI summary

A filter includes a first low-pass filter and a second low-pass filter. The first low-pass filter is located at a first channel, and includes a first resistor array coupled with a complex-signal input terminal. The second low-pass filter is located at a second channel, and includes a second resistor array coupled with the complex-signal input terminal. The complex-signal input terminal is configured to provide complex signals to the first channel and the second channel. The filter further includes a third resistor array and a fourth resistor array. The third resistor array is cross-coupled between the first low-pass filter and the second low-pass filter. The fourth resistor array is coupled between the complex-signal input terminal and the third resistor array. The first resistor array, the second resistor array and the fourth resistor array include variable resistors.