Modulation And Demodulation And Detection Module Design. Cars To Communication Systems

It is necessary to have modulation and demodulation carried out when digital baseband signal is transferred in wireless channel. To have this done, digital baseband signal needs to be carried onto high frequency signal, and sent to wireless channel by antenna. At the same time, signal received by receiver need to be modulated in order to obtain baseband signal.Modulation makes out three obvious effects. Firstly, transmit power can be increased by changing spectrum of baseband signal to a higher frequency. Secondly, baseband signals can be moved to unused carriers separately as to raise utilization of channels. Thirdly, bandwidth can be expanded to ensure the ability of anti-interference and anti-fading. In frequently used methods, sine wave is used as carrier with amplitude modulation (AM), frequency modulation (FM) and phase modulation (PM) implied.It indicates the modulation and demodulation plan of frequency-shift keying (FSK) under the practicality and minimization requirement of the 38GHz Communication System of Maglev Train, using continuous phase frequency shift keying (CPFSK) which is not sensitive to Doppler's frequency shift and tolerance while carrying out digital modulation by analog phase-locked loop modulation.The reliability of communication subsystem and control subsystem affects the reliability and safety of entire system for the maglev transportation system. As to the part of demodulation, non-coherent demodulation and multiplication phase detect are employed. In the meantime, this paper works out a detecting module used to test working condition of millimeter receiver and transmitter, in the way of sending working condition of millimeter receiver and transmitter to the following detection center.At last,the principle diagram and the circuit are provided as well as brief analysis and discussion of testing results.