LOW INSERTION LOSS SURFACE-ACOUSTIC-WAVE MATCHED-FILTER WITH LOW SIDELOBE SEQUENCE AND ITS APPLICATION FOR SPREAD-SPECTRUM COMMUNICATION

For direct sequence (DS) spread spectrum communication systems with di fferential phase-shift keying (DPSK) modulation, we have calculated lo w autocorrelation sidelobe pseudo noise (PS) sequences. We constructed a matched filter comprising localized layered structure on a quartz c rystal to obtain low matching loss, As a result of the sequences and t he construction, 14 dB (6 dB improvement on that of the conventional s equences) peak vs sidelobe of correlated output signal and 9 dB lower loss than that of a conventional filter was achieved. We have applied these matched filters to SS rf-modem units for weak-power digital comm unications, In these modem units high data rate (1 Mbps), long communi cation distance (about 20 m) and low current (210 mA when received) pe rformances are obtained.