HF modem design and implementation

Communication over HF has disadvantages as high error rates due to both characteristic properties of the waveforms and intensive communication exists on these frequency bands. Several algorithms like adaptive filters or coding methods developed to override these problematic situations. NATO has defined kinds of standarts to be able to communicate over HF bands. One of these standarts is STANAG 4285 which defines communication from 75 baud to 2400 baud coded and 1200 baud to 3600 baud without coding by using BPSK, QPSK and 8PSK modulation schemes. Furthermore, standart also purpose methods to recover signal for both analog and digital processes. In this thesis, 1200 baud is selected as modulation rate and QPSK modulation/demodulation has implemented as STANAG defines for this rate. Furthermore, for performance improvement, several methods as convolutional coding, interleaving, equalizer and viterbi decoding have implemented.