MSK SAW tapped delay lines on LiTaO3 with moderate processing gain for CDMA indoor and mobile radio applications

We report on the design and performance of two SAM MSK Tapped Delay Lines (TDLs) using PN code sequences of length 128 chips, As a substrate, LiTaO₃ has been used due to the system requirements of a given CDMA/TDMA system. Center frequency, bandwidth of the major lobe, and integration time were 266.66 MHz, 65.7 MHz, and 3 μs, respectively. TDL 1 employed two non-weighted transducers, whereas TDL 2 incorporated one cosine-apodized transducer. Split-fingers with a metalization height of 150 nm (aluminum) were used. The experimental data of both design approaches were very similar with an unmatched insertion loss of 37 dB which is improved by more than 18 dB by proper matching. Amplitude ripple was less than 1 and 2 db, respectively, and the close-in selectivity was 23 dB