Multi-Channel Mommunication Signal Source Is Developed

As an important instrument signal sourcehas been widely used in the field of navigation,communication and testing,etc.In these applications,signal source is generally used to produce excitation signal and test the system.With the rapid development of electronic and communication technology,the system under test is increasingly complex and the requirements for the signal source performance are also more and more high,which mainly reflected in high frequency,wide band,high resolution,more modes and channels,etc.In addition,in order to improve the accuracy of the test and the generality of signal source,signal source must have the advantages of speedy parameters change,flexible methods of producing signal,stable and reliable system and highsignal frequency spectrum purity,etc.According to the characteristics of the demand of the signal source and based on the idea of software radio,this paper designed and implemented a kind of communication signal source of multi-channel and multi-mode.The real-time hardware platform of ARM+FPGA+DAC is architecture to realize the signal pattern,multi-channel digital phase shifting,ARM interface and storage control,system generated sequence and peripheral interface circuit.The signal source designed in this paper can simulate ultrashort wave communication signals(30 ~ 600 MHz)and satellite uplink communication signals(1600 ~ 1700 MHz),and realize the signals of QPSK,AM,FM,PSK,FSK,4FSK and frequency hopping,etc.With the multi-channel and power control to realize the functions of infield test in target azimuth and distance simulation,it is able to work in the modes of fixed frequency or and hopping frequency hopping.As to the signal generation technique,this paper firstly further studies the basic structure and working principle of the direct frequency synthesis technology(DDS).Secondly,this paper analyses the principle,hardware structure advantages and disadvantages of the direct waveform synthesis(DDWS)and direct frequency synthesis(DDFS)technology.And according to the their application conditions in arbitrary waveform synthesis,this thesis chooses DDFS technology to produce digital signals of high resolution and frequency,convenient phase modulation,fast conversion,and continuous waveform phase output.In order to further improve the signal source output frequency and bandwidth and in view of the actual device working clock,the digital end uses parallel DDFS technology and produces digital signal with low clock and high speed.By using the principle of ultra Nyquist,this paper analogs output signal to reconstruct high frequency wideband in the second domain Nyquist.In addition,this paper applies the communication modulation algorithm to produce the multimodal test signal of high precision.Combining the FPGA software reconstruction can realize the real-time variability of the parameters and forms of the signal source.Through the further study of interferometer principle,the reverse the phase difference of the interferometer signal simulation is used to simulate the azimuth of the target signal and test the performance of the system under test in detection and identification.And designing the module of phase feedback to realize the synchronization between channels through digital phase modulation.