Front-End Module Differential Filtering for Receiver Sensitivity

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Solution Overview

Problem

Performance degradation in wireless front-end modules due to self-generated carrier signals, spurious emissions, and noise from external sources, which leads to increased complexity, DC power consumption, and reduced receiver sensitivity, is a significant challenge in modern communications.

Innovation Solution

The implementation of a front-end module that uses differential signal lines shorted at specific frequencies and fed into differential filters with common mode rejection behavior to cancel frequency-specific interference, reducing noise and interference through bandpass filters like BAW or FBAR devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If higher isolation between transmit and receive paths is designed through brute force filtering, then receiver sensitivity is improved, but device complexity and insertion loss increase

Engineering Contradiction:

Improvereceiver sensitivityVSAvoidfilter design complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent converts the harmful transmit signal into a beneficial cancellation source by capturing it through the coupling mechanism and using it to actively cancel receive path interference, transforming the problem of transmit leakage into a solution for improving receiver sensitivity

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent introduces a coupling mechanism as an intermediary element that selectively transfers specific frequency components from the transmit path to the cancellation path, enabling precise interference cancellation without requiring excessive isolation in the main signal path

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If higher isolation between transmit and receive paths is designed through brute force filtering, then receiver sensitivity is improved, but insertion loss increases

Engineering Contradiction:

Improvereceiver sensitivityVSAvoidinsertion loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent converts the harmful transmit signal into a beneficial cancellation source, reducing the need for excessive filtering that would otherwise cause high insertion loss in the receive path

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the frequency characteristics of the coupling mechanism to selectively pass only the interfering frequency components while blocking the desired signal bandwidth, enabling cancellation without sacrificing receive signal strength

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If stringent out-of-band isolation requirements are imposed on filters, then interference rejection is improved, but device complexity increases

Engineering Contradiction:

Improveinterference rejectionVSAvoidfilter specifications

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The coupling mechanism acts as a frequency-selective intermediary that performs preliminary filtering of interference components before they reach the main receive path, relaxing the isolation requirements on the primary filters

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces complex mechanical filtering structures with an electrical coupling mechanism that achieves interference rejection through circuit-level frequency selection and active cancellation

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 approach effectively reduces in-band interference, relaxes filtering requirements, and improves overall performance by leveraging common mode rejection, thereby decreasing insertion loss and complexity while maintaining effective noise cancellation.

Implementation Method 1

a first bandpass filter connected between the first and second differential signal lines and configured to provide a first frequency-specific short between the first and second differential signal lines

Methodology Applied

Scientific EffectResonance: Resonance

Implementation Method 2

feeding those differential signal lines into a differential filter with common mode rejection behavior

Methodology Applied

Scientific EffectCommon mode rejection:

Data Source

PatentUS11336325B2Methods and apparatus for enhanced transceiver performance using differential filtering

Publication Date: 2022.05.17 SKYWORKS SOLUTIONS INC

AI summary

Noise-cancellation techniques based on differential filtering, and front-end modules and wireless devices incorporating same. An example of a front-end module includes a transmit contact, a receive contact, and an antenna contact, a duplexer including a transmit filter connected in a transmit path between the transmit and antenna contacts, and a receive filter connected in a receive path between the antenna and receive contacts, the transmit filter having an input and the receive filter having an output, differential signal lines connected to one of the input of the transmit filter or the output of the receive filter, and configured to provide a differential transmit signal to the input of the transmit filter or provide a differential receive signal from the output of the receive filter, and a bandpass filter connected between the differential signal lines and configured to provide a frequency-specific short between the differential signal lines.