Multi-Path RF Low-Pass Filter for Lower Receive Loss

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Solution Overview

Problem

Existing radio-frequency modules suffer from high loss in low-pass filters for radio-frequency signals that do not require harmonic wave attenuation.

Innovation Solution

The radio-frequency module includes a low-pass filter with multiple paths, one path having a smaller reactance for transmit signals to attenuate harmonic waves while reducing loss for receive signals by bypassing capacitors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If all radio-frequency signals go through the same path in a low-pass filter, then harmonic wave components are attenuated, but the loss in the low-pass filter becomes large for signals that do not require attenuation

Engineering Contradiction:

Improveharmonic wave componentsVSAvoidloss in low-pass filter

Core Design Contradiction:

Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The low-pass filter is divided into multiple paths (first path and second path) with different reactance characteristics. The first path has larger reactance for attenuating harmonic waves, while the second path has smaller reactance for low-loss signal transmission. This segmentation allows different signal types to be routed through appropriate paths, resolving the contradiction between attenuation and loss reduction.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different paths within the low-pass filter are assigned different local qualities (reactance values). The first path is designed with larger reactance specifically for harmonic wave attenuation, while the second path is designed with smaller reactance specifically for minimizing loss in signals that do not require attenuation. This local quality differentiation enables the filter to optimize performance for different signal conditions simultaneously.

Inventive Principle:

Principle #3Local quality

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This configuration effectively attenuates harmonic wave components in transmit signals while minimizing loss in receive signals, enhancing signal quality and efficiency.

Implementation Method 1

The second path has a smaller reactance than the first path

Methodology Applied

Scientific EffectReactance:

Implementation Method 2

The low-pass filter has multiple paths. Each of the paths forms a part of at least one of the transmit path or the receive path

Methodology Applied

Scientific EffectLow-pass filter: Filter (electronic)

Data Source

PatentUS12431933B2Radio-frequency module and communication device

Publication Date: 2025.09.30 MURATA MFG CO LTD

AI summary

Loss in a low-pass filter is reduced. A radio-frequency module includes an antenna terminal, a power amplifier, a low-noise amplifier, and a low-pass filter. The low-pass filter is disposed on a transmit path between the antenna terminal and the power amplifier and on a receive path between the antenna terminal and the low-noise amplifier. The low-pass filter has multiple paths. Each of the paths forms a part of either one or both of the transmit path and the receive path. The paths include a first path and a second path. The second path has a smaller reactance than the first path.