Abstract: The advantages of withdrawal weighted IDT are: （1）The desired results can be predicted theoretically with better accuracy, because the end and diffraction effects in apodized transducers can be avoided. （2）Input and output transducers can be weighted simutaneously. （3）Apodization loss eliminated. However, this weighting method can be used only in design of narrow-band devices.
In this paper, the mathematical expressions of withdrawal weighting are derived. The modification for neighbour effect and phase error are not necessary, so that the technique of IDT fabrication is simplified by using the new method and it is easy to obtain the desired results in practice.
In this paper, the conditions which must be satisfied in withdrawal weighting are also presented. A computer program has been edited, with aid of this program the optimum withdrawal weighting scheme can be chosen from many schemes, so that the bandwidth of IDT obtained by using this procedure is broader than using former design methods. The thdrawal weighted SAW filters with 3dB bandwidth of 2-8% （Hamming weighting or sine-function under Kaiser window weighting） has been achieved experimentally. The agreement of theory with experiment is good.