One-die filter bank for 1.8–2.7 GHz system employing low loss multi-layered surface acoustic wave substrate technology

Abstract This paper describes the realization of an integrated filter bank using a single multi-layered surface acoustic wave (SAW) substrate and a common electrode thickness. Through finite element method simulations, we have confirmed that the loss and the electromechanical coupling coefficient of multi-layered SAW devices are relatively insensitive to the ratio of electrode thickness to electrode pitch compared to those of leaky-SAW devices. Based on this, we designed and fabricated a time division duplex filter bank comprising four filters that cover the 1.8–2.7 GHz range on a single die using a common electrode thickness. The measured performance demonstrates a low insertion loss less than 1 dB and a low temperature coefficient of frequency in the range from −24.5 to +15.5 ppm °C −1 for all bands. These results indicate that multi-layered SAW devices are highly suitable for integrated filter design.