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 (VO
₂
) 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 VO
₂
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 VO
₂
switches, three for each channel, is designed and fabricated. VO
₂
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 VO
₂
switches on the linear and power-handling performance of SAW resonators. VO
₂
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 VO
₂
switches results in improved performance of the filter along with significant size reduction.