Very large bandwidth IF SAW filters using leaky waves on LiNbO3 and LiTaO3

It was previously reported that a leaky wave propagating on 41°Y-X LiNbO₃ and 36°Y-X LiTaO₃ substrates, has a relatively low temperature coefficient of frequency (TCF) and a large electromechanical coupling factor (K²). In this study, we investigated the performance of wide band IF SAW filters using a FAN - shaped structure and leaky wave mode. The optimization of Hanma Hunsinger cells on 41°Y-X LiNbO₃ and 36°Y-X LiTaO₃ substrates enables to have a good reflection coefficient (r) and a large electromechanical coupling factor (K²) for a Leaky wave. The experimental results show the IF SAW filter on 36°Y-X LiTaO₃ gives a good steepness of 1.5% with a reasonable relative bandwidth (9%). Concerning the filter on 41°Y-X LiNbO₃, it presents a large relative bandwidth (55%), low losses (-13dB) and a good Return Loss (-9 dB). These results are very promising compared to those of conventional wide band IF filters using Rayleigh waves.