2-D model of the indirectly-heated type microwave power sensor based on GaAs MMIC process

In this paper, a novel two-dimensional (2-D) model is established to describe the temperature distribution of the indirectly-heated type microwave power sensor. Fourier series is applied to obtain the solution of the heat transfer equation based on the boundary conditions. Finite-element method (FEM) analysis is performed to verify the 2-D model and the simulation shows that the 2-D model is more accurate than the existing 1-D model. The power sensor is fabricated by GaAs MMIC process and MEMS technology. Au is chosen for the transmission line and the measuring pad, TaN is fabricated to form the two loaded resistors. Power measurement is accomplished from 0- 100mW under 0.1GHz, 0.5GHz, 1GHz, 5GHz and 10GHz, and the sensitivities are 0.26mV/mW, 0.25mV/mW, 0.23mV/mW, 0.19mV/mW and 0.16mV/mW, respectively. The measured results demonstrate that the 2-D model agrees with the measurement well at low frequency. However, errors increase at high frequency because of electromagnetic coupling loss of the transmission line and the parasitic loss of the load resistors.