Research on Thermocouple Distribution for Microwave Power Sensors Based on GaAs MMIC Process

This letter proposes the research on the thermocouple distribution for indirect-heating thermoelectric microwave power sensors, in order to achieve good sensitivity and signal-to-noise ratio (SNR). These power sensors are designed to operate at 0.01-30 GHz, and the heat distribution of the sensors is simulated to optimize thermocouple distribution numbers. Three microwave power sensors with 2, 6, and 14 pairs of thermocouple distribution are fabricated based on GaAs monolithic microwave integrated circuits process. Measured reflection losses of the three power sensors are lower than -21.5 dB up to 30 GHz. These sensors result in good linearity between measured thermovoltages and the microwave power. At 30 GHz, the obtained average sensitivity is 36.4, 107.1, and 240.4 μV/mW and the corresponding SNR is 1.6 × 10⁶, 2.8 × 10⁶ and 4.2 × 10⁶/W for the 2, 6, and 14 pairs of thermocouple distribution, respectively. Furthermore, experiments show that the sensitivity of the sensors decreases as the microwave frequency increases, with relative measurement errors of less than ~5%.