Frequency and Bandwidth Agile Millimeter-Wave Filter Using Ferroelectric Capacitors and MEMS Cantilevers

This paper demonstrates for the first time a tunable bandpass filter with simultaneous frequency and bandwidth control using a combination of ferroelectric barium–strontium–titanate capacitors and cantilever microelectromechanical systems (MEMS) switches. The center frequency of the filter is tuned in a continuous fashion from 30 to 35 GHz with insertion loss ranging from 10 to 2.7 dB. The fractional bandwidth of the filter can also be independently controlled by a tuning scheme that uses MEMS switches to vary the inter-resonator coupling. The two-pole filter prototypes resulted in fractional bandwidths of 9.6% (wideband configuration) and 4.8% (narrowband configuration) for a tuning ratio of approximately 2 : 1. The third-order filters resulted in bandwidths of 7.8% (wideband configuration) and 3.1% (narrowband configuration) for a passband tunable ratio of approximately 2.5 : 1.