Silicon Photoconductive Switch Frequency Tuning via Laser Position

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Solution Overview

Problem

Silicon photoconductive switches in high power microwave systems are fixed-frequency, and existing tunable dielectric materials require high thermal loads and are high-loss, limiting their utility and safety.

Innovation Solution

A location-tuned RF switch device using a photosensitive material with a variable illumination incidence location and a variable area of inductance, allowing inductance to vary with the illumination location, enabling frequency tuning without excessive thermal loading, using a laser and potentially GaN or silicon materials.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If ferroelectric or other tunable dielectric materials are used to change the electrical properties of a transformer/transmission line, then frequency tuning is achieved, but thermal load becomes very high and dielectric strength is reduced

Engineering Contradiction:

Improvefrequency tuningVSAvoidthermal load

Core Design Contradiction:

Adaptability or versatilityVSTemperature

Solution Approach 1:

The patent replaces the mechanical/electrical tuning method (using ferroelectric materials requiring high current) with an optical control method. A photoconductive switch controlled by a laser pulse changes the electrical properties of the transmission line, enabling frequency tuning without the high thermal load associated with electrostatic tuning methods.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the electrical properties of the transmission line by varying the position of the photoconductive switch along the transmission line. This positional parameter change alters the effective inductance and capacitance, enabling frequency tuning without requiring high current through dielectric materials.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

Engineering Contradiction:

Improvefrequency tuningVSAvoidmicrowave loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent substitutes photoconductive switching for ferroelectric material tuning. The photoconductive switch uses optical control to change electrical properties, avoiding the high loss and reduced dielectric strength inherent in ferroelectric materials when subjected to the high currents required for tuning.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a photoconductive material as an intermediary between the optical control signal and the microwave transmission line. This intermediary enables frequency tuning by changing the electrical properties of the transmission line without requiring high current through lossy dielectric materials.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of energy

If silicon photoconductive switches are used in high power microwave systems, then low loss and high power capability are achieved, but frequency tuning capability is lost

Engineering Contradiction:

Improvemicrowave lossVSAvoidfrequency tuning

Core Design Contradiction:

Loss of energyVSAdaptability or versatility

Solution Approach 1:

The patent makes the silicon photoconductive switch dynamic by positioning it at variable locations along the transmission line. This positional dynamics enables frequency tuning capability while maintaining the low loss and high power characteristics of silicon photoconductive materials.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent makes the silicon photoconductive switch multi-functional by combining its inherent low-loss switching capability with frequency tuning capability through variable positioning. The same component performs both switching and frequency selection functions.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

Enables flexible frequency tuning of RF switches with minimal thermal impact, enhancing the tunability and efficiency of high power microwave systems while maintaining overall efficiency and reducing thermal loading risks.

Implementation Method 1

Silicon photoconductive switches are an inexpensive, low-loss, and high-power option for use in modular, laser-triggered, high power microwave systems

Methodology Applied

Scientific EffectPhotoconductivity: Photoconductivity

Implementation Method 2

a light source having a varied illumination incidence location with respect to the transmission line

Methodology Applied

Scientific EffectLight propagation and reflection: Reflection

Data Source

PatentUS11243418B2RF frequency tuning in silicon photoconductive-switch-based high power microwave systems

Publication Date: 2022.02.08 BAE SYSTEMS INFORMATION ANDELECTRONIC SYSTEMS INTEGRATION INC

AI summary

An RF frequency tuning-in-silicon photoconductive-switch-based high power microwave system including a cradle; a transmission line proximate the cradle; a photosensitive silicon material switch component also proximate the cradle; a laser light source having a varied illumination incidence location on the photosensitive material; and a laser alignment component providing the location of the illumination incidence location on the photosensitive material; whereby the inductance of the switch varies as a function of the incidence location of the illumination on the photosensitive material.