SAW Filter Module Impedance Matching Without Lossy Inductors

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Solution Overview

Problem

Conventional filter modules with capacitive SAW resonators experience degraded insertion loss and noise figure due to the use of inductive elements for impedance matching, which lower the Q factor and affect performance.

Innovation Solution

A filter module with a band-pass filter and a matching resonator that is inductive in the passband, positioned between the input and output contacts, and an extension coil that shifts the resonant frequency, allowing for impedance matching without a conventional matching inductor, thereby maintaining a higher Q factor and reducing insertion loss and noise figure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional matching inductor is connected to a capacitive filter for impedance matching, then the impedance is matched, but the Q factor is lowered and insertion loss increases

Engineering Contradiction:

Improveimpedance matchingVSAvoidinsertion loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent replaces the conventional matching inductor (a passive electrical component) with a SAW resonator that provides inductive reactance through acoustic wave resonance. This substitution eliminates the need for separate inductive components while achieving the same impedance matching function, thereby preserving the Q factor and reducing insertion loss.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operating parameters of the SAW resonator by configuring it to operate in a frequency range where it exhibits inductive reactance (between its resonant frequency and antiresonant frequency). This parameter change allows the resonator to function as an inductive element for impedance matching without requiring a separate matching inductor.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a matching inductor is added to achieve impedance matching, then the impedance is matched, but the noise figure is degraded

Engineering Contradiction:

Improveimpedance matchingVSAvoidnoise figure

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent substitutes the matching inductor with a SAW resonator that provides inductive reactance through acoustic resonance. This substitution eliminates the additional noise figure degradation that would be introduced by a conventional inductor, while still achieving the required impedance matching.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If additional matching components are added to the filter, then impedance matching is achieved, but the device complexity increases

Engineering Contradiction:

Improveimpedance matchingVSAvoidfilter structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent makes the SAW resonator multi-functional by configuring it to simultaneously provide both filtering and impedance matching functions. The resonator operates in a frequency range where it exhibits inductive reactance, allowing it to serve as both the filter element and the matching element, thereby eliminating the need for separate matching components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the filtering function and impedance matching function into a single integrated structure. The SAW resonator is configured to provide both the frequency selectivity of a filter and the inductive reactance needed for impedance matching, combining what would traditionally require separate components into one unified element.

Inventive Principle:

Principle #5Merging (Combining)

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

The proposed solution achieves impedance matching with reduced insertion loss and noise figure by using an inductive matching resonator and extension coil, enhancing the filter's performance without the need for additional matching inductors.

Implementation Method 1

a filter configured with capacitive elements such as SAW resonators

Methodology Applied

Scientific EffectSurface acoustic wave resonance: Surface Acoustic Wave

Implementation Method 2

a matching resonator for impedance matching of the filter, the passband of the filter being included in a band ranging between a resonant frequency and an antiresonant frequency of the impedance matching resonator

Methodology Applied

Scientific EffectAcoustic resonance: Resonance

Implementation Method 3

an extension coil connected in series with the matching resonator

Methodology Applied

Scientific EffectInductive loading: Inductor

Data Source

PatentUS10333484B2Filter modules and filter arrays having inductive impedance

Publication Date: 2019.06.25 SKYWORKS SOLUTIONS INC

AI summary

Aspects and examples reduce the insertion loss and the noise figure of a filter module, which is configured by capacitive elements such as surface acoustic wave resonators and impedance matched. In one example, the filter module includes a filter having a certain passband and a matching resonator for impedance matching of the filter, the passband of the filter being included in a frequency band ranging between a resonant frequency and an antiresonant frequency of the matching resonator, and a center frequency of the passband of the filter being lower than a center frequency of the band ranging between the resonant frequency and the antiresonant frequency of the matching resonator.