Dispersive filter having nonperiodical IDT with apodization

This paper is devoted mainly to the analysis of a dispersive filter having an unapodized periodical IDT and a nonperiodical IDT with apodization. The problem to be discussed is the reduction of the Fresnel ripples in the spectrum of nonperiodical structure. The dispersive transducer is apodized by a function such as the reverse form of the amplitude response of a signal with linear frequency modulation. The results of calculations as well as the outcome of experimental investigations for the chosen B=20 MHz, T=10 μs, f₀=70 MHz values are presented in this paper