Dispersive Delay Lines Based on the Use Of Narrow Open Metal Reflectors and Fan-Shaped Transducers
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An in-line dispersive delay line (DDL) demands low and controllable reflectivity of the reflectors, especially if the surface acoustic wave (SAW) propagates all the way along the reflecting structure. The metal reflectors are usually too strong and introduce too much attenuation in such a device. The proposed solution of this problem is to spatially separate the acoustic channels for different frequencies with the help of Fan-shaped Transducers (FIDT) and to use narrow open metal reflectors to reduce reflectivity. Special arrangement of FIDT is performed to use 180-deg. reflection of the SAW. Narrow open metal strips with a metallisation ratio of the order of 20% are used as reflectors with small and controllable reflectivity. Reflectivity of such strips is estimated both theoretically and experimentally. Experimental performance of the proposed DDL is presented.
Abstract
An in-line dispersive delay line (DDL) demands low and controllable reflectivity of the reflectors, especially if the surface acoustic wave (SAW) propagates all the way along the reflecting structure. The metal reflectors are usually too strong and introduce too much attenuation in such a device. The proposed solution of this problem is to spatially separate the acoustic channels for different frequencies with the help of Fan-shaped Transducers (FIDT) and to use narrow open metal reflectors to reduce reflectivity. Special arrangement of FIDT is performed to use 180-deg. reflection of the SAW. Narrow open metal strips with a metallisation ratio of the order of 20% are used as reflectors with small and controllable reflectivity. Reflectivity of such strips is estimated both theoretically and experimentally. Experimental performance of the proposed DDL is presented.
참고문헌 (3)
- R.E. Chapman, "In-line reflective array devices", Proc. IEEE Ultrason. Symp., pp.728~733 (1978)
- R. C. Woods, "Dispersive delay lines using 180Δ reflecting metal dot arrays", Proc. IEEE Ultrason. Symp., 88(91), pp.88~91 (1982)
- D. Chen, "Analysis of metal-strip SAW gratings and transducers", IEEE Trans. Sonics Ultrason., SU-32, pp.395~408 (1985)