Using of self-resonance approach for high selectivity low loss SAW filters

Abstract

This paper presents low loss high selectivity SFIU filters realized on the base of self-resonance approach without using matching LC-netuwks. This approach is based on the input ID1 static capacitance conpensation by the radiation suxeptance with chocr sing a definite nunber of finger pairs.The self-resonant SAU f ilters are developed on the base of a ring configuration with reflecting multistrip couplers (Fmsc) and unidirectional lDTs with u-shaped PEES. These filters are realized on 1 d Y -X . M'Y-X, ~~O Y -X .~P Y -X L~N J O~. The optimization o f filter topologies wa5 achieved using computer programs on the base of the equivalent circuit d e l . fit 45 ntr the ring filters on 49OY-X. M 0 Y -X , 128OY-X LihbaO, have shown insertion 105s below 2 dl3,Z-a fractional bandwidth. the stopband attenuation over 50 d6. SAU filters using unidirectional IDTs with U-shaped rtSCs are realized on 128'Y-X,&Y-X,4l0Y-X LiW0,and 150, 3 0 . 7 0 . 1 0 4 Miz center frequencies. These iilters have shown insertion loss oi 2.6-3.0 d6. 5 1 0 % fractinal bandwidth and a b o w 58 dB stooband attenuation.