Transistor Test Fixture Integrated Couplers Signal Distortion
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Solution Overview
Problem
Existing RF transistor test fixtures face challenges in accurately measuring high-power transistors due to signal distortion caused by parasitic components and low-pass behavior of passive networks, which attenuate higher harmonic components, leading to incomplete reconstitution of the original signal waveform.
Innovation Solution
The integration of signal couplers, such as micro-strip or coaxial wire bridge couplers, close to the device under test (DUT) within the test fixtures, which utilize electromagnetic coupling to extract signal components with minimal insertion loss and parasitic effects, allowing for more accurate detection of harmonic components and reconstruction of the original signal waveform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If signal couplers are placed farther from the DUT for easier measurement access, then measurement accessibility is improved, but signal distortion increases due to parasitic components and low-pass behavior of passive networks
Solution Approach 1:
The patent introduces de-embedding networks as intermediary components that mathematically compensate for the effects of passive networks between the measurement plane and DUT. These networks act as mediators that reverse the low-pass filtering and parasitic effects, allowing accurate signal reconstitution even when measurement equipment is positioned away from the DUT.
Solution Approach 2:
The patent replaces physical proximity requirements with mathematical signal processing. Instead of requiring measurement equipment to be physically close to the DUT, the system uses de-embedding algorithms and Fourier transformations to digitally reconstruct the original signal waveform, substituting mechanical positioning constraints with computational compensation.
2Device complexity
If passive networks are used for signal transmission, then signal routing is simplified, but higher harmonic components are attenuated due to low-pass behavior
Solution Approach 1:
The patent implements a feedback mechanism where the measured signal is processed through de-embedding networks that calculate and apply compensation for the passive network's frequency response. The system measures the actual attenuation and distortion introduced by passive networks, then uses this information to reverse the effects and recover the original harmonic content.
Solution Approach 2:
The patent changes the parameter representation of the signal from time domain to frequency domain using Fourier transformations. This allows the system to identify and compensate for frequency-dependent attenuation in passive networks, recovering harmonic components that would be lost in the time domain representation.
3Ease of manufacture
If measurement is performed at a distance from the DUT, then measurement setup is simplified, but reconstitution of original signal form becomes less accurate
Solution Approach 1:
The patent performs preliminary characterization of the passive networks connecting the measurement plane to the DUT. By measuring and storing the transfer functions and parasitic parameters of these networks in advance, the system can apply pre-calculated compensation factors during actual measurements, simplifying the measurement setup while maintaining accuracy.
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 approach enables more accurate characterization of RF transistors by reducing signal distortion and enhancing the detection of higher harmonic components, improving the accuracy of signal reconstitution and measurement, especially at high frequencies.
Implementation Method 1
The integration of signal couplers, such as micro-strip or coaxial wire bridge couplers, close to the device under test (DUT) within the test fixtures, which utilize electromagnetic coupling to extract signal components with minimal insertion loss and parasitic effects
Data Source
AI summary
Microwave transistor test fixtures, both micro-strip and coaxial, include integrated wideband directional signal sensors/couplers and allow the detection of the main signal and its harmonic components, injected into and delivered by a transistor in high power operation mode, by using a phase-calibrated network or signal analyzer and allows this way the reproduction of real time signal waveforms. The fixtures are best calibrated using equivalent TRL calibrated fixtures allowing overcoming the incompatibility of the internal ports connecting to the transistor terminals with coaxial cables attached to VNA.