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In this letter, development of a low-loss radio frequency (RF) microelectromechanical (MEMS) 4-bit X-band monolithic phase shifter is presented. These microstrip circuits are fabricated on 0.021-in-thick high-resistivity silicon and are based on a reflection topology using 3-dB Lange couplers. The average insertion loss of the circuit is 1.4 dB with the return loss >11 dB at 8 GHz. To the best of our knowledge, this is a lowest reported loss for X-band phase shifter and promises to greatly reduce the cost of designing and building phase arrays.

As the need for low-loss phase shifters increases, so does the interest in radio frequency (RF) MEMS as a solution to provide them. In this paper, progress in building low loss Ka-band phase shifters using RF MEMS capacitive switches is demonstrated. Using a switched transmission line 4-bit resonant phase shifter, an average insertion loss of 2.25 dB was obtained with better than 15-dB return loss. A similar 3-bit phase shifter produced an average insertion loss of 1.7 dB with better than 13-dB return loss. Both devices had a phase error of less than 13 in the fundamental states. To our knowledge, these devices represent the lowest loss Ka-band phase shifters reported to date.

This paper overviews the application of RF MEMS switches in tunable filters as well as circuit developments for bandpass filters covering 110 MHz to 2.8 GHz. RF MEMS have several desirable features, including small size, low power requirements, and low loss. The basic operation of Raytheon's RF MEMS capacitive membrane switch is described. An overview of the technique used to integrate the switch into a variable capacitor structure with sixteen capacitance states is provided. Variable capacitor structures are used to construct multipole lumped bandpass filter designs, each with sixteen states. Finally, measured data from two representative five-and six-pole bandpass filters are presented. Characterization data demonstrates that the insertion loss for the five-pole filter using on-chip inductors was between 6.6 and 7.3 dB, and between 3.7 and 4.2 dB for the six-pole filter using off-chip inductors.