| Popis: |
[For the English abstract and full text of the article please see the attached PDF-File (English version follows Russian version)].ABSTRACT New versions of the modulator and demodulator (modem) for the digital railway radio communication system GSM-R have been developed, which increase the noise immunity twofold. To realize «cos» and «sin» blocks, a phase modulator is used, two coherent quadrature demodulators are connected to its output in parallel. It is shown that «cos» block generates the signal cos [msinφ(t)], which is transferred to the operating frequency of the transmitter by means of subsequent blocks representing the structure of the one-side amplitude modulation driver, forming the final phase-modulated signal. It is proposed to detect an FM signal not from the modulation envelope, as it is done customary, but coherently, which excludes the quadrature component of the interference. Keywords: railway, radio communication, digital signal, Gaussian filter, modulation, coherent FM signal detector, noise immunity, frequency efficiency. |
