PCB MEMS-Based Tunable Coplanar Patch Antenna

In this paper, a tunable coplanar rectangular patch antenna (CPA) designed using a MEMS varactor is reported. The MEMS varactor is monolithically integrated with the antenna on duroid substrate using printed circuit processing techniques. Specifically, the MEMS varactor located at one of the radiating edges capacitively loads the CPA. The resonant frequency of the antenna is tuned electrostatically by applying a DC bias voltage between the MEMS varactor and the actuation pad on the antenna. The movable MEMS varactor membrane deflects downward towards the actuation pad due to electrostatic force of attraction caused by the applied DC bias voltage. The deflection of the varactor membrane decreases the air gap thereby increasing the loading capacitance. The increase in the loading capacitance results in a downward shift in the resonant frequency of the CPA. The CPA is center fed at the second radiating edge using a 50 Omega CPW feed line. The CPA operates in the frequency range from 5.185 to 5.545 GHz corresponding to the down and up states of the varactor. The tunable frequency range is about 360 MHz and the return loss is better than 40 dB in the entire tuning range. In this tuning range, the required DC voltage is in the range of 0-116 V.