MODEM QPSK, MODIFIED WITH PURPOSE OF SIGNIFICANT IMPROVEMENT OF RECEIVER SENSITIVITY Russian patent published in 2017 - IPC H04L27/18 

FIELD: radio engineering, communication.

SUBSTANCE: modem (modulator-demodulator) is characterized by the fact that in the modulator (on the transmitting side) the transmitter signal at the output of the modulator is exposed to an additional phase of manipulation on 180° digital signal type meander with a period equal to the duration of informational character and in the demodulator (on the receiving side) - demanipulation at the demodulator input, eliminating additional phase manipulation of the signal transmitter, followed by narrowband filtering with a strip bandwidth significantly (by an order of magnitude or more) less than the width of the signal spectrum at the first zeros, after which the signal is processed in the mode of quadrature phase shift manipulation. The above energy gain is ensured by the combined use of additional manipulation and narrowband filtering.

EFFECT: increasing the sensitivity of the receiver without noise-proof coding by, at least, 20 dB by reducing the requirements for the signal-to-noise ratio when receiving phase-shifted signals in quadrature phase shift manipulation, binary phase shift manipulation.

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