A surface acoustic wave filter for color television IF section is realized to promote a domestic production.
For this purpose, computer aided design programs are implemented. An optimization technique is used in synthesizing a transducer pattern to achieve an asymmetrical amplitude and a nonlinear phase characteristics. A diffraction analysis for parabolic substrates and an equivalent circuit analysis for uniform electrodes are constructed in addition to a simple analysis based on an impulse response.
Then, the USA NTSC type filter is actually designed considering several second order effects, fabricated on a 128℃ rotated Y-cut X-propagation lithium niobate wafer by an etching technique, packaged in a TO-8 case, and finally measured by a network analyzer.
TV IF 용 SAW filter 를 최근 개발된 설계방법을 사용하여 128˚ $LiNbO_3$ wafer 에 실현하였다.
Design 은 computer aided program 을 이용하였는데 최적화 방법을 사용하여 비대칭 진폭특성과 비선형 위상특성을 쉽게 얻을 수 있었다. Fabrication 은 resolution 이 좋은 mask를 사용하였고 optimum substrate를 이용함으로써 bulkwave를 많이 줄 일 수 있었다. 그러나 diffraction 이 생겨 filter 의 특성이 다소 저하 되었고 설계시와 다른 substrate 를 사용하였기 때문에 중심 주파수가 조금 높아졌다.
