RF Filter Sharing Across Overlapping Downlink Bands

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Solution Overview

Problem

Conventional radio frequency circuits for multi-band communication require an increased number of filters, leading to larger front-end circuits.

Innovation Solution

A radio frequency circuit design that incorporates filters with asymmetrical frequency responses, allowing sharing of filters across overlapping frequency bands by optimizing attenuation steepness on both sides of the passband, thereby reducing the total number of filters needed.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple filters are incorporated for multi-band functionality, then frequency band coverage is improved, but device complexity and circuit size increase

Engineering Contradiction:

Improvefrequency band coverageVSAvoidnumber of filters

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies universality by designing a single filter that can handle multiple frequency bands (Band 71 and Band 105) simultaneously. The filter is configured with a passband that covers both downlink bands, allowing one filter to perform the function of what would traditionally require multiple filters, thereby reducing device complexity while maintaining multi-band adaptability

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the filtering functions for Band 71 and Band 105 into a single filter component. By combining the passbands of both frequency bands into one filter structure, the invention reduces the total number of filters needed in the radio frequency circuit, directly addressing the contradiction between multi-band coverage and device complexity

Inventive Principle:

Principle #5Merging (Combining)

2Object-affected harmful factors

If filters with higher attenuation steepness are used, then interference between overlapping bands is reduced, but manufacturing precision requirements increase

Engineering Contradiction:

Improveinterference between bandsVSAvoidattenuation steepness control

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The patent applies local quality by implementing asymmetric attenuation characteristics within the filter. Specifically, the filter is designed with higher attenuation steepness on the lower frequency side of the passband compared to the higher frequency side. This localized optimization of attenuation properties effectively suppresses interference in critical regions while maintaining overall filter performance and reducing manufacturing precision requirements across the entire filter structure

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS20250373270A1Radio frequency circuit and communication device

Publication Date: 2025.12.04 MURATA MFG CO LTD

AI summary

A radio frequency circuit includes a first filter having a first passband including downlink bands of first and second bands. The downlink band of the second band at least partially overlaps the downlink band of the first band. The low-frequency edge of the downlink band of the second band is lower than the low-frequency edge of the downlink band of the first band. The low-frequency edge of a first guard band defined on the lower frequency side of the downlink band of the first band, for the downlink band of the first band, coincides with the low-frequency edge of a second guard band defined on the lower frequency side of the downlink band of the second band, for the downlink band of the second band. The first filter has a higher attenuation steepness on the lower frequency side of the first passband than on the higher frequency side.