High data rate communication devices demand high relative bandwidth and therefore wide band filters are necessary. In infrastructure systems like base stations and microwave radiolinks, such filtering function was carried out by ceramic filter technology. They were preferred for their low in-band ripple and VSWR necessary for low EVM and amplifier linearity. We have developed a design technique allowing SAW devices to advantageously replace ceramic filters in many systems.One important parameter that determines the performance of a piezoelectric device is the electromechanical coupling coefficient. RF filters designed on widely used 42°Y-X LiTaO 3 are not meeting the stringent specification requested by infrastructure systems. To increase the width of the bandwidth and reduce the in-band ripple, a material with high electromechanical coupling coefficient is needed. This paper describes the search for the optimal working point using a full FEM/BEM approach and proposes a new design technique on 41°Y-X LiNbO 3 . This technique is applied to high reliability RF filters. On 41°Y-X LiNbO 3 , bandwidths larger than 8% at 3dB attenuation are achieved leading to very low amplitude ripple. A GSM Rx filter for base station at 1747.5MHz is demonstrated. Filter bandwidth is 140MHz leading to ripple in the frequency band 1710MHz to 1785MHz being lower than 0.2dB nominal and 1dB over temperature and total 6 sigma manufacturing. Insertion loss is 2.5dB while image rejection is better than 45dB. Size is 3x3mm 2 in a high reliability ceramic cavity package.The close correspondence between simulation and measurement demonstrates the ability of our methodology to design SAW devices rapidly and accurately on virtually any material. The filters designed by this technique on 41°Y-X LiNbO 3 are demonstrating a wide band and very low in-band ripple perfectly matching the infrastructure systems requirement.

The aim of this work is to miniaturize SAW filters using massive high aspect ratio metallic electrodes. These structures are capable of slowing down the surface wave and reduce the wave-length by 10 times. It is therefore expected that the size of devices using such high metal thickness is reduced by a significant amount. In this work, the relationship of the SAW propagation properties to substrate orientation and metallization thickness is studied theoretically using FEM-BIM approach and experimentally in order to achieve designs of a filter demonstrating a size miniaturization by a factor of 2 and a very low loss 20% bandwidth filters both at 40MHz range. This technique is very promising to miniaturize SAW filter at both low and radio frequency.