Switchable low-loss SAW filter banks with MEMS switches

This paper presents the new switchable low-loss SAW filter banks with MEMS switches having the practically limitless linearity and extra-low power consumption. The SAW filter banks with 8 channels are realized in the 2 circuits. The first circuit contains the channels with a single low-loss SAW filter. The second circuit consists of the channels containing the modules with 2 low-loss SAW filters connected across a high linear and low-noise amplifier. The 4-pole three-transducer resonator SAW filters on 42° YX LiTaO₃ with a 1-dB fractional bandwidth of 2.2% are used in these circuits. Bandpass switching is performed by switching the channel SAW filter by means of the miniature integrated MEMS switches. An optimization of the switchable SAW filter banks parameters is provided with a computer simulation using an equivalent circuit model. The switchable SAW filter bank in the first circuit covers 400-478 MHz range with an amplitude ripple of 1 dB, insertion loss of 3.2 dB, stopband attenuation of about 50 dB, power consumption of 6 mW, third-order intermodulation (IM) distortion level of under -115 dBm in the output of each channel. The 11 dB gain with an amplitude ripple of 1 dB, stopband attenuation about 90 dB, third-order IM distortion level -42 dBm and power consumption 40 mW were obtained in the second circuit with amplifiers in the each channel and same frequency range. IM distortion and power consumption were defined by the amplifier type only and independent of the MEMS switches. The switchable SAW filter banks are built in the form of modules with sizes of 40×40×9 mm.