Low loss SAW matched filters with low sidelobe sequences and spread spectrum applications

A 300 MHz SAW matched filter with reduced mismatch-loss and with a coded transducer by a low autocorrelation sidelobe sequence has been developed for a 1 Mbps SS low power-transmission wireless communication modem. This low autocorrelation sequence of 25 chips was searched to apply a DS spreading DPSK signal. The sequence reduced the output signal sidelobe 6 dB lower than a 31 chip m-sequence, and further obtained a higher processing gain than that of Barker sequences. Furthermore, to reduce the mismatch-loss in temperature stable SAW matched filters, a localized layered structure has been developed. ZnO is deposited only on the normal transducer on a ST-cut quartz substrate, reducing the mismatch-loss by 9 dB. An SS radio modem unit using this SAW matched filter shows a bit error ratio lower than 10/sup -4/ with a low current consumption of 210 mA, considering such a high data rate of 1 Mbps and a low received power of -100 dBm.