Non-Uniform Waveguide Cavities for RF Filter Harmonic Suppression

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Solution Overview

Problem

Microwave and radio-frequency (RF) filters face challenges in effectively suppressing harmonics in the frequency response, leading to undesirable high-frequency components in the output signal, with existing solutions either inadequately suppressing harmonics or increasing the size of the filter through additional resonators or slow wave structures.

Innovation Solution

A radio frequency device with a non-uniform width cover, where the cover over the low-pass filter is narrower than over the band-pass filter, creating a narrower channel cavity that shifts the dominant resonance mode and harmonics to higher frequencies, thereby increasing harmonic attenuation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If additional resonators or slow wave structures are used to suppress harmonics, then harmonic suppression is improved, but the filter size increases

Engineering Contradiction:

Improveharmonic suppressionVSAvoidfilter size

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The patent applies local quality by creating a non-uniform cover structure where different sections have different widths. The first cover section has a first width over the band-pass filter, while the second cover section has a second width over the low-pass filter, with the second width being less than the first width. This localized variation in cover width creates different cavity characteristics in different regions, enabling effective harmonic suppression without requiring additional resonators or slow wave structures that would increase overall filter size.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent utilizes parameter changes by varying the physical dimensions of the cover structure. Specifically, the cover width is changed from a first width over the band-pass filter to a second width over the low-pass filter. This dimensional parameter change modifies the resonant characteristics of the cavities, shifting harmonics to higher frequencies and improving suppression while maintaining a compact filter size.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If a uniform width cover is used, then manufacturing is simplified, but harmonic attenuation is insufficient

Engineering Contradiction:

Improvecover manufacturingVSAvoidharmonic attenuation

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent implements local quality by dividing the cover into distinct sections with different widths. The first cover section spanning the band-pass filter has a greater width than the second cover section spanning the low-pass filter. This localized differentiation provides the necessary harmonic attenuation performance while maintaining a relatively simple overall structure that can be manufactured using standard techniques.

Inventive Principle:

Principle #3Local quality

3Reliability

If the cover width over the low-pass filter is reduced, then harmonic suppression is improved, but the structural design becomes more complex

Engineering Contradiction:

Improveharmonic suppressionVSAvoidcover structure design

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies segmentation by dividing the cover into two distinct sections: a first cover section over the band-pass filter and a second cover section over the low-pass filter. The transition between these sections creates a stepped configuration where the second section has a reduced width. This segmentation approach achieves effective harmonic suppression through the width reduction while maintaining a structured, modular design that manages complexity through clear functional division.

Inventive Principle:

Principle #1Segmentation

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 non-uniform width cover design significantly enhances the suppression of harmonics, improving the attenuation from 20 dB to 40 dB or more, reducing the filter size while maintaining effective signal processing.

Implementation Method 1

the first portion and the first surface define a first waveguide cavity having the first width, and a second portion with a second width, less than the first width, covering the second RF component, where the second portion and the first surface define a second waveguide cavity having the second width

Methodology Applied

Scientific EffectWaveguide cavity resonance: Resonance

Implementation Method 2

creating a narrower channel cavity that shifts the dominant resonance mode and harmonics to higher frequencies

Methodology Applied

Scientific EffectWaveguide propagation: Waveguide

Data Source

PatentUS11811122B2Radio frequency device with non-uniform width cavities

Publication Date: 2023.11.07 KNOWLES CAZENOVIA INC

AI summary

A microwave or radio frequency (RF) device includes a substrate and a cover. The substrate has a first surface and an opposing second surface, the first surface including a first RF component and a second RF component electrically coupled to the first RF component in series. The cover is disposed over the first surface of the substrate, where the cover includes a first portion with a first width covering the first RF component, where the first portion and the first surface define a first waveguide cavity having the first width, and a second portion with a second width, less than the first width, covering the second RF component, where the second portion and the first surface define a second waveguide cavity having the second width.