Design Of Specialized Communication Signal Simulator

With the development of the digital technology in the fie ld of communication, commonly used digital modulation and the liner frequenc y modulation pulse signal are widely used in a variety of occasions. At present, the portable device with kinds of digital modulation signals and the pulse signal are applied in the signa l feature recognit ion, the field of information countermeasure and the teaching experiment. So the special communication signal simulator designed in this paper has the urgent need and significance.This thesis studies the producing theory of the LFM signal and six types of digital modulation signals inc luding ASK, FSK, BPSK, Q PSK, QAM, OFDM. Then it puts forward the technical requirement of the communication signal simulator, including the key parameters of carrier frequency, channel bandwidth, code rate, output mode and then presents the realization method of generation sc heme of LFM signal and modulation signal based on Direct Digital Frequency Synthesis.The design of dedicated communication signa l simulator includes two parts, hardware and software. The hardware circuit design uses FPGA as core controller, and the UART interface to communicate with the controller of screen. The wideband synthesizer is used for generating the input clock of DAC to realize the analog signal. Logic design of DDS IP core is the key technique to generate the carrier signal. The different modulation modules are used to take the digital signals onto the carrier. The software design includes display design and communication design. Using the tool of designer to achieve function of the control panel and write the generated document to the controller of the LC D screen. The self-design of the data structure completes the communication with FPGA through the serial port.At last, a portable specialized communication signal simulator is built with the signal generating board, the power module and the display screen. The oscilloscope and the spectrum analyzer are used to test the performance and function of the device. The result shows that the specialized communication signal simulator designed in this thesis can meet the requirements of the technical target of the signal. And the digital modulation signal and linear frequency modulation signal with controllable parameters can be achieved.