Maglev Car To Communication Systems If Modulator Developed

Along with the increasing development and broad application of the digital communication technology, the digital modulation technology as a very important part of this filed has being developed rapidly. In the digital mobile communication system, digital modulation is the key problem, so choosing a proper digital modulation blue print can make the radio wave transmit a higher signal bit rate in a limited bandwidth,transmit signal in a Rayleigh fading channel and can obtain a lower BER(bit error rate) when we demodulated the signal. It can satisfy the requirements of digital signal processing in so many communication fields by developing digital modulation technology and put it in action, and it has so practical significance to the Real-time data transmission.This thesis begin with the theories of the digital communication and the requirements of 38GHz communication system for maglev train, discussed and compared some common used methods of digital signal transmission by carrier wave. And focus on the principle, spectrum and improvement methods of the continuous phase frequency shift key which is propitious to mobile communication fields, has a constant envelopment and has a continuous phase trajectory.The writer study out a CPFSK blue print based on a PLL (phase lock loop) to fit the requirements of the communication system and did some necessary discussions and analysis of PLL.After that the writer designed and realized a CPFSK intermediate modulator. The work includes the software simulation, hardware designing and debugging, software designing and debugging for PLL and system united debugging.The modulator now is using in the 38GHz communication system for maglev train. It can modulated the 10.24Mbps data signal and a synchronous pulse which period is 1ms and pulse width is 10～12us.And it gets a good performance in the 1.5km experiment line for maglev train till the latest experiment.