Frequency Responses of SAW Ladder Filters with Apodized Interdigital Transducers and Width-Controlled Reflectors

Abstract

Frequency responses of surface acoustic unidirection IDT to decrease the insertion loss [8], using wave (SAW) ladder filters with apodized interdigital high frequency shunt element to improve rejection band transducers (IDTs) and width-controlled reflection [9], and utilizing the longitudianl leaky SAW to obtain gratings are investigated in this study. A novel low insertion loss and wide passband [10]. It is known transmission matrix method is employed to simulate the that the use of window functions to design apodized scattering parameters as well as the characteristic IDTs can adjust specifications of SAW bandpass filters impedance of one-port resonators, while the frequency [11] and the stopband suppression can be implemented responses of the multi-section ladder filters cascaded by employing width-controlled reflection gratings [12, from one-port resonators are constructed via the image 13]. To meet high performance requirment for ladder parameter method. Different window functions such as filters and duplxers in 3G systems, the adoption of Kaiser and Chebyshev functions are adopted to adjust the different window functins to design apodized IDTs of overlap width distributions of the IDTs and electrode one-port resonators with width-controlled reflection width variations of the gratings. Effects on the resonance gratings to broaden bandwidth and suppress spurious frequencies and spurious modes of one-port resonators responses is investigated in this study. The transmission are illustrated. Different stepwise weighting schemes are matrix method is applied to calculate the frequency applied to recalculate the width distributions of IDTs and responses of one-port rsonators. By using the image gratings for the realization of the modulated one-port parameter method, the ladder filters with different static resonators. Simulation results show that the bandwidth of capacitance ratios can be matched to both source and the ladder filter can be effectively increased using the load impedances and the correpsonding frequency apodized IDTs. By adjusting the overlap width ratios of responses will be also reported. the one-port resonators in the parallel and series arms, the sideband suppression level of the ladder filter is THEORETICAL MODELING enhanced. The results obtained in this study can be employed to design RF filters with broad bandwidth andThe scchematic of a one-port resonator with apodized good sideband suppression.IDT and width-controlled reflecting grating is shown in Fig. 1 and the corresponding block diagram for applying INTRODUCTION the transmission matrix method is plotted in Fig. 2.