Switched Dual-Band SAW Filters Using Hybrid and Monolithically Integrated Vanadium Oxide Switches

This article presents design and implementation of switchable dual-band filters using surface acoustic wave (SAW) resonators and vanadium oxide (VO2) switches imbedded within the filter using both hybrid and monolithic integration. The switched dual-band filter has two channels and four switching states: transmission only of the lower channel, transmission only of the upper channel, transmission of both the channels, and no transmission. The experimental results are presented for the first switchable dual- band filter of order 5 with two discrete VO2 switches strategically integrated within the proposed filter's structure using hybrid integration. The five-pole dual-band filter demonstrates a measured insertion loss of 3.7 and 3.9 dB in the transmission states at 765 and 935 MHz, respectively. To improve the overall performance of the proposed switched dual-band filter, a second seven-pole filter with six VO2 switches, three for each channel, is designed and fabricated. VO2 switches are monolithically integrated with SAW resonators on the same substrate using a four-mask in-house fabrication process. The article also presents experimental results to study the impact of the monolithically integrated VO2 switches on the linear and power-handling performance of SAW resonators. VO2 monolithically integrated switched dual-band filter has two channels at 600 and 725 MHz. It exhibits a measured insertion loss of 3.23 and 3.22 dB for the two channels. Depending on the number of detuned resonators in the OFF state for each channel, an isolation of 20-40 dB is demonstrated. The monolithic integration of VO2 switches results in improved performance of the filter along with significant size reduction.