Burst-Communication Modem Based on SAW Elastic Convolvers
M. Kowatsch, J. Lafferl, Franz Seifert · 1982
A burst-type spread spectrum communication modem has been developed, with orthogonal code shift keying (CSK) employed for data modulation. A burst consists of a 7-bit preamble followed by a block of 1000 message bits, transmitted at 84 kbit/s. The spread spectrum modulation scheme is biphase phase shift keying (BPSK) combined with noncoherent frequency hopping (FH). Each bit of both the preamble and the message portion of a burst is encoded by a different 255-chip Kasarni sequence with a chip rate of 21.4 MHz. The total transmission bandwidth is 340 MHz. The receiver signal processing is based on two SAW elastic convolvers, which act as programmable matched filters. Performance measurements in a simulated communications channel show good agreement with theory. Measured processing gain is 30 dB, dynamic range is about 55 dB.