FIELD: signals transmission equipment engineering.
SUBSTANCE: use of given method in systems for transmitting and receiving signals of quadrature amplitude modulation with low bearing frequency synchronization threshold makes it possible to decrease demodulation threshold due to provision of low synchronization threshold by bearing frequency. Result is achieved by adding to pack of M m-level quadrature amplitude modulation symbols of previously given symbols, part of which does not change from pack to pack, and another part is periodically inverted in some of packs. Due to that at receiving side components of quadrature amplitude modulation signals are singled out, appropriate for additional previously given symbols (frequency of which are known). On basis of these components, inversion frequency is determined, which provides for removal of ambiguousness in adjustment of receipt synchronization frequency, thus making it possible to approach Shannon threshold closely.
EFFECT: decreased demodulation threshold.
4 cl, 1 tbl, 9 dwg
