RF Front-End Phase Adjustment for Duplexer-LNA Isolation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Radio frequency front-end circuits experience degradation in receiving sensitivity due to impedance mismatch between transmission and reception filters, which affects signal isolation and noise input.

Innovation Solution

Incorporating a phase adjustment circuit between the reception filter and low noise amplifier, utilizing a Smith chart to adjust phases and create impedance mismatch at specific frequencies, ensuring noise prevention and reduced transfer loss at fundamental frequencies.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a duplexer circuit with transmission filter and reception filter is used to isolate transmission and reception paths, then isolation between transmission and reception is improved, but receiving sensitivity degrades due to impedance mismatch and noise input

Engineering Contradiction:

Improveisolation between transmission and receptionVSAvoidreceiving sensitivity

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

A phase adjustment circuit is introduced as an intermediary component between the reception filter and the low noise amplifier. This circuit adjusts the phase of the reception signal to prevent impedance mismatch at the LNA input, thereby maintaining receiving sensitivity while preserving the isolation function of the duplexer circuit

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The phase adjustment circuit dynamically adjusts the phase parameter of the reception signal based on the impedance characteristics of the LNA. By changing the phase parameter, the circuit optimizes the impedance match at the LNA input, preventing noise input and maintaining high receiving sensitivity

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If impedance matching is optimized at fundamental frequency for signal transmission, then transfer loss is reduced, but noise at harmonic frequencies is amplified

Engineering Contradiction:

Improvetransfer loss at fundamental frequencyVSAvoidnoise amplification at harmonic frequencies

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The phase adjustment circuit applies different phase corrections for different frequency components. It optimizes impedance matching specifically at the fundamental frequency to minimize transfer loss, while simultaneously creating impedance mismatch at harmonic frequencies to prevent noise amplification

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The phase adjustment circuit dynamically adjusts its characteristics based on the frequency content of the signal. It provides adaptive phase correction that varies with frequency, allowing optimal performance at the fundamental frequency while suppressing noise at harmonic frequencies

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS9960898B2Radio frequency front-end circuit

Publication Date: 2018.05.01 MURATA MFG CO LTD

AI summary

A radio frequency front-end circuit includes a duplexer, a phase adjustment circuit, and a low noise amplifier. The phase adjustment circuit is connected between an Rx filter of the duplexer and the low noise amplifier. The phase adjustment circuit executes phase adjustment such that a quadrant in which an impedance ZLNA(fn) at a particular frequency different from a fundamental frequency of a reception signal when looking at the low noise amplifier side from the Rx filter is present and a quadrant in which an impedance ZRX(fn) at the particular frequency when looking at the Rx filter side from the low noise amplifier is present are not in a conjugate relation in terms of phase.