A bandwidth-tunable RF MEMS filter using a series-coupled array of dielectrically transduced square-extensional mode resonators has been developed. Under the proposed digital tuning scheme, the new filter provides channel-agility and bandwidth granularity for analog spectral processors and RF spectrum analyzers and should substantially decrease the number of filters in next generation receivers.
Cornell's new tunable filter uses a novel DC-biasing strategy in a mechanically-coupled resonator array. This method does not require any frequency off-set between constituent resonators. As a result, lithography challenges are minimized, spatial distortion is greatly reduced and spurs in filter transmission are attenuated.
The bandwidth-tunable RF MEMS filter is constructed of a series-coupled array of dielectrically transduced square-extensional mode resonators, and uses a digital tuning scheme that provides channel-agility and bandwidth granularity for analog spectral processors and RF spectrum analyzers. The resonators and filters are fabricated on the 3 µm thick device layer of a heavily doped SOI wafer with a 100 nm thick silicon nitride film sandwiched between the polysilicon electrodes and the silicon device layer. A 511 MHz overtone square-extensional mode resonator has been demonstrated with a quality factor (Q) of 1,800 in air and motional impedance (RX) of 1.1 kO and an array of four such resonators is coupled mechanically to form a channel-select filter with 1.4 MHz bandwidth at 509 MHz center frequency. By switching the DC-biasing scheme, the filter is split into narrower high and low sub-bands, each 700 kHz wide.
The figure above shows four series mechanically-coupled checkeredelectrode resonators. Each resonator has individually addressable RF+DC lines.Potential Applications
¡Obtén la mejor experiencia en la web!
Descarga gratis el nuevo Internet Explorer 8