Fixed-Geometry Cavity Probe With Reflective Stub Coupling Tuning

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Solution Overview

Problem

Existing microwave cavity resonator probes are sensitive to geometry and manufacturing tolerances, making them difficult to manufacture reliably and adjust for optimal coupling coefficients without altering the radiating element's fixed geometry.

Innovation Solution

A fixed-geometry probe design with a transmission line that forms a reflective stub, allowing external adjustment of the coupling coefficient by trimming the stub's length or varying the terminating impedance, without changing the radiating element's geometry inside the cavity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a continuous-loop probe is used with fixed geometry, then the manufacturing process is simple, but the coupling coefficient is sensitive to manufacturing tolerances and difficult to adjust

Engineering Contradiction:

Improveprobe manufacturing simplicityVSAvoidcoupling coefficient consistency

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent introduces a movable plunger that can be adjusted along the probe shaft to change the effective length of the radiating element. This dynamic adjustment mechanism allows the coupling coefficient to be tuned after manufacturing, resolving the contradiction between simple manufacturing and precise coupling control. The plunger's position can be varied to compensate for manufacturing tolerances and achieve the desired coupling coefficient.

Inventive Principle:

Principle #15Dynamics

2Reliability

If the probe geometry is adjusted to optimize coupling coefficient, then the coupling performance improves, but the manufacturing complexity increases

Engineering Contradiction:

Improvecoupling coefficient optimizationVSAvoidprobe structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent divides the probe into distinct segments: a fixed shaft portion and an adjustable plunger portion. This segmentation allows the basic probe structure to remain simple for manufacturing, while the plunger segment provides the necessary adjustment capability. The segmented design minimizes overall complexity while achieving reliable coupling coefficient optimization.

Inventive Principle:

Principle #1Segmentation

3Reliability

If the radiating element geometry is changed to adjust coupling, then the coupling coefficient improves, but the fixed geometry requirement is violated

Engineering Contradiction:

Improvecoupling coefficient controlVSAvoidradiating element geometry stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent introduces a plunger as an intermediary element between the probe shaft and the cavity resonator. The plunger serves as the adjustable radiating element that can be moved to change coupling without altering the fixed geometry of the main probe structure. This intermediary approach allows coupling adjustment while maintaining the stability and fixed geometry of the primary radiating structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 design simplifies the manufacturing and adjustment of microwave energy exchange, improving the reliability and consistency of coupling coefficients, enhancing the performance of microwave circuits like oscillators and filters.

Implementation Method 1

A second end of the transmission line is terminated outside the cavity resonator with a terminating impedance creating a mismatch with the line's characteristic impedance to create a reflective stub

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

A portion of the transmission line's outer conductor(s) is removed within the cavity resonator to form a fixed-geometry radiating element to exchange microwave energy with the cavity resonator

Methodology Applied

Scientific EffectElectromagnetic coupling: Electromagnetic Induction

Implementation Method 3

A microwave cavity resonator is typically a closed metallic structure (e.g., a metallic cylinder) and resonates with higher amplitude at specific set frequencies, called resonant frequencies

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS11791532B1Microwave cavity resonator and fixed-geometry probe

Publication Date: 2023.10.17 RAYTHEON CO

AI summary

A fixed-geometry probe for exchanging microwave energy with a cavity resonator is easy to manufacture, reliable and readily adjustable external to the cavity to select a coupling coefficient. The probe includes a transmission line that enters, turns and exits the cavity resonator. A first end of the transmission line lies outside the cavity resonator for connection to a microwave circuit to exchange microwave energy. A portion of the transmission line's outer conductor(s) is removed within the cavity resonator to form a fixed-geometry radiating element to exchange microwave energy with the cavity resonator in accordance with the coupling coefficient. The line's outer conductor is connected to the cavity resonator on either side of the radiating element. A second end of the transmission line is terminated outside the cavity resonator with a terminating impedance creating a mismatch with the line's characteristic impedance to create a reflective stub. The coupling coefficient is controlled by the length of the reflective stub and terminating impedance.