Design and performance of SAW low insertion loss filters (Ⅰ) single phase unidirectional transducer

The principle and the design method of EWC/SPUDT is presented.The relationship that directivity of sAW excited unidirectionally on Ewc/SPUDT depends on the phase of the reffective coefficient of the reflective strip is discussed.The measured frequency response of the IF filters for wireless communications and the filters for antenna duplexer of Chinese CT1 fabricated on ST-X Quartz,y112° LiTaO₃ and Y128° LiNbO₃ substrates are presented.Their insertion loss are 4.6 dB,3.5 dB and 3 dB with bandwidth 0.6%,0.75% and 1.4% respectively and out-of-band rejections more than 50 dB.