Bi-triaxial Photoconductive Switch Module for RF Waveform Generation
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Solution Overview
Problem
Existing photoconductive switch systems suffer from capacitive parasitics, leading to degraded waveforms, decreased output RF amplitude, asymmetric waveforms, and require external DC blocking capacitors, making them space inefficient and prone to poor pulse fidelity.
Innovation Solution
The development of bi-triaxial photoconductive switch modules that eliminate the need for external DC blocking capacitors by using a compact design with two triaxial photoconductive switches in a push-pull configuration, incorporating cast-in-place capacitors and optical delay elements to produce bipolar RF waveforms suitable for RF output antennas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external DC blocking capacitors are used in photoconductive switch modules, then the module can block DC components, but the module size increases and parasitic inductance increases
Solution Approach 1:
The patent combines the DC blocking capacitor function with the energy storage capacitor by positioning the photoconductive switch between the center electrode and outer conductor, where the capacitor is formed between the center electrode and inner conductor. This integration eliminates the need for separate external DC blocking capacitors, reducing module size and parasitic inductance while maintaining DC blocking capability.
Solution Approach 2:
The patent implements a nested coaxial structure where the photoconductive switch is positioned within the capacitor structure. The center electrode, inner conductor, outer conductor, and dielectric material are arranged in concentric layers, with the photoconductive switch nested between the center electrode and outer conductor. This nested configuration achieves compact DC blocking functionality without increasing overall module volume.
2Reliability
If external DC blocking capacitors are used in photoconductive switch modules, then the module can block DC components, but parasitic inductance increases
Solution Approach 1:
The patent combines the DC blocking capacitor function with the energy storage capacitor by positioning the photoconductive switch between the center electrode and outer conductor, where the capacitor is formed between the center electrode and inner conductor. This integration eliminates the need for separate external DC blocking capacitors, reducing module size and parasitic inductance while maintaining DC blocking capability.
3Device complexity
If conventional photoconductive switch configuration is used, then the structure is simple, but waveform fidelity is poor and pulse symmetry is degraded
Solution Approach 1:
The patent employs asymmetric positioning of two photoconductive switches at different angular positions (e.g., 0 degrees and 90 degrees) around the center electrode. This asymmetric configuration, combined with optical delay elements, enables precise control over pulse timing and polarity, achieving symmetric bipolar waveforms with high fidelity while maintaining relatively simple overall structure.
Solution Approach 2:
The patent incorporates optical delay elements in the light paths to the photoconductive switches to pre-synchronize the timing of pulse generation. By introducing controlled time delays in the optical paths, the system achieves precise temporal coordination between switches, ensuring accurate bipolar waveform generation and improved pulse symmetry before the actual switching occurs.
4Volume of stationary object
If compact photoconductive switch module is designed, then the volume is reduced, but parasitic capacitive and inductive effects increase
Solution Approach 1:
The patent implements a nested coaxial structure where the photoconductive switch is positioned within the capacitor structure. The center electrode, inner conductor, outer conductor, and dielectric material are arranged in concentric layers, with the photoconductive switch nested between the center electrode and outer conductor. This nested configuration achieves compact DC blocking functionality without increasing overall module volume.
Solution Approach 2:
The patent transitions from planar or linear capacitor geometries to a three-dimensional coaxial configuration. The capacitor is formed between concentric cylindrical surfaces (center electrode and outer conductor), utilizing the radial dimension for electric field confinement. This dimensional approach reduces parasitic effects by concentrating fields within the dielectric volume while maintaining compact external dimensions.
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 bi-triaxial photoconductive switch modules achieve improved waveform fidelity, reduced parasitic effects, and increased energy storage efficiency, enabling compact and efficient RF power delivery to antenna arrays with enhanced pulse amplitude and symmetry.
Implementation Method 1
A photoconductive switch is an electrical switch that is controlled by an optical input (e.g., light) to cause photo-induced conductivity of the switch material. For example, light applied to the switch material can increase its electrical conductance as a consequence of irradiation with light.
Data Source
AI summary
Methods, systems, and devices describe bi-triaxial photoconductive switch modules that that eliminate the need for external DC blocking capacitors, while providing a highly compact structure that can produce bipolar output waveforms conducive to feeding to radio-frequency (RF) devices, such as antennas. Some implementations of the disclosed bi-triaxial photoconductive switch modules utilize unified cast-in-place capacitors that can be designed with an appropriate geometry, volume and orientation to provide desired energy storage capacity while eliminating or reducing parasitics.