A High-Performance RF MEMS Power Sensor for Near-Zero Detection Applications

This letter proposes a high-performance RF MEMS power sensor for near-zero detection applications based on thermoelectric and capacitive operation principles, with a significant improvement in dynamic range of −17 to 26.5 dBm, capacitance sensitivity of $\ge 0.22$ fF/mW and bandwidth of 4-24 GHz. The thermoelectric element is used to detect lower minimum power through the design of the reduced thermocouples’ number and shortened load resistors-thermopile effective distance. The capacitive element is used to detect higher maximum power through the design of the floated anchor of the cantilever beam. This power sensor is fabricated using the GaAs monolithic microwave integrated circuit (MMIC) and MEMS process. The tested return loss is less than −12.6 dB up to 24 GHz. For the input low-power level of 0.02 to 100 mW (−17 to 20 dBm), the measured sensitivity of the thermoelectric element is close to $50.6~\mu \text{V}$ /mW@4 GHz, $43.2~\mu \text{V}$ /mW@12 GHz and $31.3~\mu \text{V}$ /mW@24 GHz, respectively. For the input high-power level of 100 to 450 mW (20 to 26.5 dBm), the measured sensitivity of the capacitive element is close to 0.23 fF/mW@4 GHz, 0.59 fF/mW@12 GHz and 0.22 fF/mW@24 GHz, respectively. Experimental results show that the thermoelectric element can achieve uniform sensitivity and linearity within its scale range, and the capacitive element can achieve high linearity with better sensitivity.