Amplifier Test Signal Modulation for Current Collapse Measurement
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Solution Overview
Problem
Existing high-frequency measurement methods, such as those using semiconductor inspection apparatuses, face challenges in accurately assessing the high-frequency performance of amplifiers due to current collapse in compound semiconductor transistors, which affects distortion compensation and power gain variation over time.
Innovation Solution
A high-frequency measurement method and apparatus that generates a test signal with alternating power levels to simulate real-world operating conditions, allowing for the measurement of transient responses and gain variations in amplifiers or semiconductor devices, thereby accurately evaluating current collapse and its impact on amplifier characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a direct-current signal is supplied to a field-effect transistor for evaluation, then the device can be tested with simple measurement setup, but it is difficult to accurately grasp variation in high-frequency performance when a high-frequency signal is input to an amplifier
Solution Approach 1:
The invention changes the signal parameter from direct-current to alternating-current with specific characteristics (sine wave modulation at frequency fm, with carrier frequency fc and modulation frequency fm satisfying fc >> fm). This parameter change enables the measurement to reflect actual high-frequency operating conditions while maintaining measurement feasibility.
2Speed
If digital predistortion operates at high speed to monitor broadband signals, then the bandwidth coverage is improved, but the amplifier characteristics vary every moment due to current collapse recovery time, degrading the distortion compensation function
Solution Approach 1:
The invention applies periodic action by using an alternating-current test signal with sine wave modulation that periodically varies the power level. This periodic variation at frequency fm allows measurement of time-dependent characteristics including current collapse recovery, enabling evaluation of how amplifier characteristics vary over time during digital predistortion operation.
3Use of energy by moving object
If an amplifier is operated at highest power level to reduce power consumption, then power efficiency is improved, but current collapse occurs causing power gain and nonlinearity to vary over time
Solution Approach 1:
The invention performs preliminary action by measuring and evaluating current collapse characteristics before actual high-power operation. The alternating-current test signal with controlled power levels allows assessment of time-dependent variations in power gain and nonlinearity, enabling optimization of digital predistortion parameters in advance to compensate for expected variations during highest-power operation.
Data Source
AI summary
A high-frequency 5 measurement method includes generating a test signal (TS), which is a sine-wave signal having a predetermined frequency, in which a period (τ) during which the power level is at a first power level and a period (T-τ) during which the power level is at a second power level lower than the first power level 10 are periodically repeated, inputting the test signal (TS) to a device under test (10) as an input signal, and measuring the difference between an output signal (OUT) of the device under test (10) and an ideal value of the output signal (OUT).