MULTIPLE CHIRP SPREAD SPECTRUM SYS- TEM AND OVERLAY SERVICE
Junglrwan Kim, Timothy Pratt, TRI T. HA · 1988
An asynchronous spread spectrum system called Coded Multiple Chirp is proposed and the possible spread spcctrum overlay over an analog FM-TV is investigated by computer simulation. In the proposed system, multiple single-sloped up and down clurps are encoded by a PN code and decodcd by dechirpers (pulse comprcssion filters) followed by a digital code correlator. Performance of tlie proposed system, expressed in probability of bit error and code miss probability, is similar to that of noncoherent FSK using codewords, if sullicient compression gain is used. In the overlay whcre chirp is used to overlay an FM-TV channel, two chirp signals with data rate up to 25 kbps could be overlaid in a 36 Mllz satellite transponder without signif~cant mutual interrercnce. Performance estimates for a VSAT earth station operating at C-band show that a 2.4 meter antenna and 300 mW transmitter could send a 2.4 kbps signal to a large central earth station over an occupied channel.