An adaptive chirp modem for medium data rates

The authors describe an experimental HF modem which uses serially transmitted chirp signals swept across a voice channel bandwidth. The modem is able to adaptively excise interference from other HF users, and has inherent tolerance to frequency selective fading and additive white Gaussian noise. A number of experimental signal formats have been incorporated so as to achieve data transmission at rates of 75, 150, 300 and 600 bits per second, and error correction via interleaved Golay code is included