Design and Measurement of Near-Zero Thermopile RF Power Sensors for GaAs MMIC Applications

This article proposes the design and fabrication of near-zero radio frequency (RF) power sensors for GaAs monolithic microwave integrated circuit (MMIC) applications, with the principle of RF power-heat-electricity conversion. These power sensors are designed to be broadband (0.1–30 GHz), modest sensitivity (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 53.71~\mu $ </tex-math></inline-formula> V/mW), and low-cost manufacturing (no substrate membrane structure required). The detailed design of the near-zero RF power sensors is investigated, and the effects of the number of thermocouples and the overlap size between the resistors and the thermopile on RF and sensing performances are revealed in this article. Moreover, the fabrication is completely compatible with the GaAs MMIC technology. In addition, the measured reflection losses of the power sensors are lower than −16.3 dB up to 30 GHz. The measured sensitivities for the sensors B1, B2, C1, and C2 are 55.30, 91.00, 29.70, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$60.29~\mu $ </tex-math></inline-formula> V/mW at 10 GHz, and 32.02, 53.71, 18.01, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$36.63~\mu $ </tex-math></inline-formula> V/mW at 30 GHz, respectively. And the good linearity of the output responses is obtained. Experiments show that the increase of the thermocouples’ number and the overlap distance contributes to improving the sensitivities of the RF power sensors.