IQ Load-Pull Measurement for Impedance Mismatch Testing
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Solution Overview
Problem
Existing measurement systems face challenges in accurately testing devices under test due to impedance mismatches, leading to signal reflections that impair performance measurements, and lack the capability to simulate a variety of load conditions.
Innovation Solution
A measurement system utilizing a directional coupler and IQ analysis/synthesis circuit to generate and analyze forward and backward-travelling signals, allowing for precise control of impedance presented to the device under test, enabling testing under various load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If impedance matching is used to eliminate reflections, then measurement accuracy is improved, but the ability to test under non-matched conditions is lost
Solution Approach 1:
An IQ synthesizer circuit is introduced as an intermediary component that generates a backward-travelling signal to actively cancel reflections in the measurement system. This mediator enables the system to maintain impedance matching conditions artificially, allowing accurate measurements while preserving the ability to simulate various load conditions including non-matched conditions through software control of the synthesizer.
Solution Approach 2:
The system dynamically changes the parameters of the backward-travelling signal generated by the IQ synthesizer to adapt to different testing requirements. By adjusting the amplitude and phase of the synthesized signal, the system can simulate various load conditions and impedance scenarios while maintaining measurement accuracy through active reflection cancellation.
2Measurement precision
If linear correction techniques are used to account for reflections, then measurement accuracy is improved, but the system cannot actively control impedance conditions
Solution Approach 1:
The system employs a feedback mechanism where the IQ analysis circuit continuously monitors the forward and backward-travelling signals, and this information is fed back to the IQ synthesizer to dynamically adjust the synthesized backward signal. This closed-loop feedback enables both accurate reflection cancellation and active control of impedance conditions, overcoming the limitations of passive linear correction techniques.
Solution Approach 2:
The measurement system performs self-correction by automatically generating the appropriate backward-travelling signal through the IQ synthesizer based on its own measured reflections. The system serves itself by actively managing its own impedance conditions without requiring external correction devices or complex calibration procedures.
3Difficulty of detecting and measuring
If directional couplers are used to separate forward and backward signals, then signal analysis capability is improved, but transient oscillations occur during impedance changes
Solution Approach 1:
The IQ synthesizer performs preliminary action by pre-generating the backward-travelling signal before the full measurement cycle begins. This advance preparation allows the system to establish stable signal conditions and reduce transient oscillations that would otherwise occur when impedance conditions change during measurement.
Data Source
AI summary
A measurement system includes a common port, the common port being connectable to a signal output of the device under test. The measurement system further includes a signal line being connected to the common port, wherein the signal line includes a first directional coupler portion and a second directional coupler portion. The measurement system further includes a signal processing circuit, wherein the signal processing circuit includes an IQ analysis circuit and an IQ synthesizer circuit. The IQ analysis circuit is connected with the common port via the first directional coupler portion so as to receive a forward-travelling signal from the common port. Further, a testing method of testing a device under test is described.