2. Origins of Spread Spectrum Communications
Initially, Spread Spectrum was known as Noise Modulation. This was because the spread spectrum signals look more like a noise to an ordinary AM/FM receivers due to spreading of signals over a large bandwidth (typically several 1000 times the signal bandwidth). Spread Spectrum techniques were used initially for military communications due to inherent coding (encryption) of SS Communications System. The initial use of spread spectrum was during World War , by using pulse-to-pulse frequency hopping radar called reisslans. The mid 1940s a matched filter concept was used for maximum signal-to-noise ratio pulse detection.