Millimeter-wave systems can be used in many security and sensing applications including weather monitoring, vehicle crash avoidance, and aircraft landing guidance. These systems could significantly benefit from advanced tunable filters, especially for multi-channel communication systems. State-of-art tunable filters use solid-state varactors, but this design approach incurs high insertion loss, unacceptable signal-to-noise ratio, and rendered linearity. Tunable filters can also be designed using RF MEMS technology, however most of the existing designs of this type are discrete, lack the required resolution to continuously cover the desired operating band, and also suffer from high insertion loss.
To address this problem, researchers at UC Berkeley have developed, demonstrated and characterized a new approach to designing W-band tunable filters. Prototypes of this Berkeley filter exhibited a 4.05 GHz bandwidth centered at 94.79 GHz with a minimum insertion loss of 2.37 dB, a return loss better than 15 dB, and a center frequency shift of 2.59 GHz. This novel type of tunable filter can also function in a dual role as a phase shifter. Prototypes achieved a phase shift of 110 degrees at 95 GHz.
W-band tunable filter and phase shifters for low-cost, multi-channel millimeter-wave systems
|United States Of America||Issued Patent||7,728,701||06/01/2010||2006-088|