Reliable and Compact 3- and 4-Bit Phase Shifters Using MEMS SP4T and SP8T Switches

This paper presents radio frequency (RF) microelectromechanical system-based 3- and 4-bit phase shifters using single-pole-four-throw (SP4T) and single-pole-eight-throw (SP8T) switches. The design is fabricated on 635 μm alumina substrate using a surface micromachining process. SP4T and SP8T switches demonstrate measured return loss of >16 dB, worst case insertion loss of 1.66 dB, and isolation of >13.6 dB up to 40 GHz. Total area of the SP4T and SP8T switches is 0.98 mm
²
and 1.66 mm
²
, respectively. Switches are capable of handling 1 W of incident RF power and can sustain up to 1 billion cycles at 85°C. Finally, 3- and 4-bit phase shifters deliver measured return loss of >12 dB, average insertion loss of <;5.4 dB, and average phase error of 1.65° at 35 GHz. The total area of the phase shifter (4-bit) is 7.5 mm
²
, which is lowest reported till date. Reliability tests of phase shifters demonstrate 1 billion cycles with 0.1 W of power in cold switching. In addition, phase shifters also worked satisfactory up to 400 million cycles with 0.5 W of power at 85 °C in hot switching condition. Devices were enclosed within a low-cost package and characterized them systematically.