TABLE OF CONTENTS Low-loss phase shifters are of critical importance for modern-phased array tracking radar and covert communications systems comprising of thousands such devices. Recently developed MEMS capacitive switches have demonstrated low IL, reduced parasitics, excellent linearity, and improved performance over conventional RF switches. Deployment of such switching devices in multi-bit phase shifters can significantly reduce the IL, weight, size, and power consumption [7]. Note 1-bit distributed MEMS phase shifter design can be extended to cascade several such devices to develop a multi-bit phase shifter with much lower IL.
A 3-bit distributed MEMS phase shifter consists of three 1-bit phase shifters designated for 180 , 90 , and 45 phase shift, respectively. It is important to mention that each one-bit phase shifter comprises of a CPW transmission-line loaded periodically using several shunt MEMS capacitors. The estimated length of the phase shifter circuit is 11 mm and the device can be fabricated on a glass substrate with dielectric constant of 5.7 to keep the fabrication cost to minimum. The phase shift of the synthetic CPW transmission line can be varied by switching the MEMS-based capacitors in up and down positions under appropriate bias conditions. The dc control bias for each 1-bit phase shifter is applied between the RF signal line and the ground pad of the CPW transmission line. This dc bias generates strong electric field beneath the MEMS switch membrane, which...
