Design of SAW expander and compressor on LiTaO3 for a TCDMA spread spectrum system

We report on the design and performance of surface-acoustic wave (SAW) minimum shift keying (MSK) tapped delay lines using pseudonoise code sequences with a length of 128 chips, As a substrate, X112 degrees rotY-LiTaO3 has been used due to the system requirements of a given CDMA/TDM4 (TCDMA) radio communication system, System LF frequency, bandwidth of the major lobe, and integration time of the SAW devices were, respectively, 360 MHz, 63.5 MHz, and 3 mu s, We used SAW tapped delay lines employing nonweighted as well as cosine-weighted input interdigital transducers incorporating split-fingers, We designed both expander as well as compressor filters attaining very similar experimental results, We found insertion loss values down to 16 dB and amplitude ripples of less than 2 dB, The close-in selectivity was 28 dB.