Ultra high frequency (UHF) phononic crystal devices operating in mobile communication bands

Recently phononic crystal slabs operating in the very high frequency (VHF) range have been reported and have gained interest for RF signal processing. This paper reports phononic crystal slabs and devices operating in the commonly used GSM-850 and GSM-900 cellular phone bands, representing nearly an order of magnitude increase in operating frequency compared to the state-of-the-art. Phononic crystals centered at 943 MHz are formed by arranging 1.4 ¿m diameter W rods in a square lattice with a pitch of 2.5 ¿m inside a 1.85 ¿m thick suspended SiO₂ membrane. The resulting phononic crystal has a bandgap width of 416 MHz or 44% and a maximum bandgap depth of 35 dB. Waveguide devices formed by placing defects in the phononic lattice have also been realized with propagation frequencies of 780 and 1060 MHz.