Planar Half-Mirror Resonator for Tunable Millimeter Wave Filtering

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Solution Overview

Problem

Current millimeter waveband filters face challenges in achieving high-sensitivity and high-accuracy measurements above 100 GHz due to increased conversion loss and noise, difficulty in separating locally-generated harmonics, and limitations in design flexibility and radiation loss, particularly with existing Fabry-Perot resonators.

Innovation Solution

A millimeter waveband filter design featuring a waveguide transmission line with planar radio-wave half mirrors and varying space and permittivity mechanisms to selectively output frequency components, allowing for tunable resonant frequencies with low radiation loss and high design freedom.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a confocal Fabry-Perot resonator is used to achieve high Q, then the resonator can reflect millimeter waves with spherical mirrors, but the focus becomes out of focus when changing the distance between mirror surfaces, causing Q to drastically decrease

Engineering Contradiction:

ImproveQ valueVSAvoidfrequency tuning capability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent inverts the conventional confocal Fabry-Perot resonator design by using planar mirrors instead of spherical mirrors. This inversion allows the resonator to maintain high Q values while enabling frequency tuning through distance adjustment, as the planar mirror configuration avoids the focus degradation issue inherent in spherical mirror systems.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the geometric parameter of the mirrors from spherical to planar, fundamentally altering the resonator's optical path and focusing characteristics. This parameter change enables the system to achieve both high Q values and frequency tunability, as the planar mirrors maintain consistent focus properties across different mirror spacing configurations.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If planar half mirrors are used in a Fabry-Perot resonator to maintain Q when changing mirror distance, then frequency tuning becomes possible, but the structure becomes an open type resonator causing large loss from spatial radiation

Engineering Contradiction:

Improvefrequency tuning capabilityVSAvoidspatial radiation loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent merges the planar Fabry-Perot resonator structure with a waveguide enclosure, combining the frequency tuning capability of the open resonator with the radiation suppression benefits of the closed waveguide structure. This integration allows the system to maintain high Q values while enabling frequency adjustment.

Inventive Principle:

Principle #5Merging (Combining)

3Stability of the object's composition

If the waveguide diameter is increased to achieve perfect plane waves for planar Fabry-Perot resonator, then wavefront quality improves, but the size of the device increases

Engineering Contradiction:

Improvewavefront qualityVSAvoiddevice size

Core Design Contradiction:

Stability of the object's compositionVSVolume of moving object

Solution Approach 1:

The patent applies preliminary wavefront shaping within the waveguide before the waves reach the resonator mirrors. By pre-conditioning the electromagnetic waves to have planar wavefronts through the waveguide's mode selection, the system achieves the required wave quality without needing to increase the waveguide diameter, thus avoiding device size expansion.

Inventive Principle:

Principle #10Preliminary action

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 filter achieves high selective properties and low loss in the millimeter waveband, enabling precise measurement and frequency tuning with reduced distortion and radiation loss, while maintaining filter characteristics across a wide frequency range.

Implementation Method 1

a waveguide which propagates electromagnetic waves with a predetermined frequency range of a millimeter waveband from one end to the other end in a TE10 mode

Methodology Applied

Scientific EffectElectromagnetic wave propagation: Electromagnetic Induction

Implementation Method 2

a resonator, which is formed between the pair of radio-wave half mirrors, is selectively output from the other end of the transmission line; in order to change an electrical length between the pair of radio-wave half mirrors

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS9184486B2Millimeter waveband filter and method of varying resonant frequency thereof

Publication Date: 2015.11.10 ANRITSU CORP

AI summary

The millimeter waveband filter includes: a transmission line that is formed by a waveguide which propagates electromagnetic waves with a predetermined frequency range of a millimeter waveband from one end to the other end in a TE10 mode; and a pair of radio-wave half mirrors that are disposed opposite each other with a space interposed therebetween so as to block the inside of the transmission line and have planar shapes and a characteristic of transmitting a part of the electromagnetic waves with the predetermined frequency range and reflecting a part thereof. In the electromagnetic waves incident from the one end side of the transmission line, a frequency component centered on a resonant frequency of a resonator, which is formed between the pair of radio-wave half mirrors, is selectively output from the other end of the transmission line.