Radio frequency power sensor based on MEMS technology

We present the first measurement results of a power sensor for radio frequency (rf) signals (50 kHz - 40 GHz) with almost no dissipation during the measurement. This sensor is, therefore, a ´through´ power sensor, that means that the rf signal is available during the measurement of its power. The power detection has been realized by measuring capacitively the movement of a grounded aluminum membrane, which is suspended above the transmission line carrying the rf signal. The power sensor is thus a capacitive MEMS technology based sensor. The fabrication is done by aluminum surface micromachining on an AF45 glass wafer. We measured the capacitance as a function of the applied rf power and found a linear relationship as predicted from theory.