| 摘要 |
1351286 Surface wave filters MULLARD Ltd 18 May 1971 15482/71 Heading H3U In an I.F. acoustic surface wave filter for a colour T.V. receiver, comprising launching transducers 2, or 12, luminance receiving transducers 4, or 14, and chrominance receiving transducers 3, or 13 mounted on a piezoelectric wafer 1, or 11, the required luminance delay is provided by having the effective spacing of transducers 2, 4; 12, 14 greater than that for transducers 2, 3; 12, 13. The transducers are dimensioned so that the bandpass for the luminance signal is greater than that for the chrominance signal. The transducers 13, 14 may be spaced from each other. The filter may be associated with integrated circuit detectors and amplifiers. The layers 7, 8; 17, 18 are wax damping material. The transducers are formed of gold by a photo-lithographic process. The wafer may be lithium niobate, ammonium dihydrogen phosphate, cadmium sulphide, or a poled ferro-electric ceramic such as sodium potassium niobate, barium titanate or lead zirconium titanate. |
