A SAW filter fabrication of the series connected SPUDT type filter with bidirectional transducer filter

.We have studied to obtain the properly conditions about impedance matching of the SAW filter for the SPUDT type and the bidirectional transducer type later. And we have studied to obtain the SAW filter for the Slanted Finger Interdigital Transducer(SFIT), was formed on the Langasite substrate and was evaporated by Aluminum-Copper alloy and then we performed computer-simulated by simulator In case the SPUDT, we have employed that the number of pairs of the input and output IDT are 50 pairs and the thickness and the width of reflector are $5000{\AA}$ and $3.6{\mu}m$, respectively. And the of the bidirectional transducer, the width of IDT' fingers and the space between IDT' finger and reflector is $1.8{\mu}m$, respectively. Also, we have performed to series connected the SPUDT type with the bidirectional transducer type filter. The frequency response of the fabricated SAW filter has the property that the center frequency is about 190MHz and bahdwidth at the 3dB is probably 5.3MHz after when we have matched impedance. Also, we could obtain that ripple characteristics is less than 0.3dB and insert loss is probably -20dB after when we have matched impedance.

SPUDT와 양방향 변환기를 직렬 연결한 SAW 필터

표면 탄성파 필터 적절한 임피던스 정합 조건도 얻고자 단상 단방향성 및 양방향성 변환기형 필터를 제작하였다. 그리고 경사진 빗살무의 변환기 형태인 표면 탄성파 필터 제작하기 위하여 Langasite 기판위에 빗살무의 전극들을 형성시켜 모의실험을 수행하였으며, 전극재료로는 Al-Cu를 사용하였다. Langasite 기판위에 형성시킨 단상 단방향성 필터의 전극 수는 50쌍, 두께는 $5000{\AA}$으로 하였으며, 반사기 폭은 $3.6{\mu}m$이고 전극 폭과 전극과 반사기 사이의 간격은 각각 $1.2{\mu}m$로 하였다. 양방향성 필터에서는 전극 폭과 간격은 각각 $1.8{\mu}m$로 하였다. 제작한 필터의 임피던스 정합 후 주파수 특성에서 중심 주파수는 190MHz, 대역폭은 5.3MHz정도로 측정되었으며, 리플 특성은 0.3dB 이하이고, -20dB 정도의 삽입 손실이 측정되었다.