Signal Injection for Active Device Reflection Coefficient Measurement
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Solution Overview
Problem
Existing methods for measuring characteristic performance parameters of active devices, such as transistors, are limited by their reliance on mathematical calculations that do not physically apply or measure source impedance, and assume perfect unilaterality, which is rarely true, leading to inaccurate results.
Innovation Solution
A method using a signal generator and receivers, such as a Vector Network Analyzer, to measure incident and reflected waves at both input and output ports of a DUT, applying perturbations to determine the source and output reflection coefficients by taking multiple measurements before and after perturbation, allowing for control and measurement of source and output impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If mathematical calculation is used to calculate source impedance without physically applying or measuring it, then the measurement process is simplified, but the accuracy of the measurement result deteriorates
Solution Approach 1:
The patent introduces a perturbation signal as an intermediary to physically probe the source impedance. Instead of relying solely on mathematical calculations, a small test signal is injected into the system to measure the actual impedance characteristics, thereby improving measurement accuracy while maintaining operational simplicity through automated signal injection and measurement.
2Device complexity
If perfect unilaterality (S12 = 0) is assumed in the measurement model, then the measurement process becomes simpler, but the accuracy of the measurement result deteriorates because this assumption is rarely true in practice
Solution Approach 1:
The patent employs feedback by using the perturbation signal response to iteratively refine the measurement of source and output reflection coefficients. The measured data from the perturbation signal is fed back into the calculation process to compensate for bilateral effects (S12 ≠ 0), thereby improving measurement accuracy without requiring complex manual adjustments or assumptions of perfect unilaterality.
3Measurement precision
If multiple measurements are taken before and after applying perturbation signals, then the accuracy of reflection coefficient determination improves, but the measurement time increases
Solution Approach 1:
The patent uses periodic action by applying perturbation signals at specific intervals during the measurement process. Instead of continuous measurement, perturbation signals are injected periodically to capture the necessary data points for calculating reflection coefficients, thereby reducing overall measurement time while maintaining sufficient accuracy through strategically timed measurements.
Data Source
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AI summary
A method for measuring characteristic performance parameters ┌S; ┌OUT of an active device under test (DUT) 10 having an input port and an output port. The method comprises connecting the input port of the DUT 10 to a signal generator 1, and the output port to an output load impedance ZL; 5, subjecting the DUT 10 to a large signal input test signal, and executing a first measurement a1', b1'; a2', b2' of the incident wave a1; a2 and reflected wave b1; b2 at a DUT reference plane. The method further comprises subjecting the DUT 10 to a perturbation signal combined with the large signal input test signal, and executing a second measurement a1", b1"; a2", b2" of the incident wave a1; a2 and reflected wave b1; b2 at the DUT reference plane, and determining the characteristic performance parameter from the first measurement and the second measurement.