Development of compact 180° phase shifters based on MEMS technology

Abstract

The paper introduces a novel approach for the design of Micro Electro Mechanical Systems (MEMS) technology based devices whereby, several actuating structures (bridges) are employed to generate required phase shifting application. At present, the development of 180° phase shifter structures have been reported which emphasizes on the concept of maximum miniaturization. Miniature switched capacitors and popular space-filling curves viz., Peano and Hilbert Curves have been exploited to implement novel phase shifter designs. Phase shifters employing both Peano Curve and Hilbert Curve based structures, resulting in 180° phase shift, have been designed, fabricated and characterized to obtain 180° phase shift at 15GHz design frequency. Measurements are conducted to record Capacitance vs. Voltage response curve, RF performance (Return Loss (S11 in dB) and Insertion Loss (S21 in dB) characteristics), differential phase shift (in degrees) and the mechanical frequency of vibration. Devices are reported to actuate at a voltage as low as 8.5V only, with a capacitance ratio as high as Cr=7 are added advantages exhibited by the device. Space-filling curve based phase shifters suggest improvement in achieving highly compact structures (1mm×1mm and 0.88mm×0.88mm) and acceptable performance throughout the frequency range of interest.