The Design And Implementation Of Signal Transmitting Module Based On DDS For Perimeter Detection System

The perimeter intruder detection system based on leaky cable has the advantages of good concealment,all-weather work,long monitoring distance,follow-up installation and so on,which has broad application prospects in civil and national defense fields.Signal transmitting module is one of the important components of the perimeter intruder detection system based on leaky cables.The working stability of signal transmitting module and quality of the transmitting signal is the key factor affecting the sensitivity and false alarm rate of the system.The integrated signal transmitting module based on DDS has the advantages of small size,stable performance,strong anti-interference and good quality of the transmitting signal,so it is of great significance to develop the integrated signal transmitting module based on DDS.The topic of this dissertation comes from the application basic research project of " Research on Key Technologies of Perimeter Intruder Detection System Based on Leaky Coaxial Cable".It aims at generating the transmitting signal needed by Perimeter Intruder Detection System and realizing the hardware integration of signal transmitting module.This dissertation first demonstrates the signal transmitting scheme,then designs the single module of AD9910 signal source and driver amplifier,and finally completes the hardware integration of the signal transmitting module by interconnect the single module.The main research work and innovative product are as follows1?The transmitting signal was given and the signal transmitting scheme was put forward.The working principle and function of the perimeter intruder detection system was introduced in detail.It was given that the signal transmitting module needed to transmit a single carrier frequency pulse with a central frequency of 100 MHz and provided receiver with a local oscillator signal of 100 MHz.The peak power of the transmitting signal reached the driving level of 10 d Bm.In this dissertation,two signal transmitting schemes,AD834 multiplier modulation and AD9910 modulation,were compared and analyzed.At the point of view of system stability and anti-interference ability,the signal transmitting scheme using AD9910 modulation was choosed.2?A signal transmitting module based on AD9910 was developed.The working principle and function of AD9910 were briefly introduced.The design process of the peripheral circuit of AD9910 signal source module and the design process of the driving amplifier circuit with 15 d B gain were analyzed in detail.The integrated circuit schematic diagram was completed by interconnecting two AD9910 signal source module circuits with two driving amplifier module circuits.Referring to the integrated schematic diagram,the PCB layout of the signal transmitting module was completed in Allegro PCB editor and the PCB was made.3?The VHDL program of signal transmitting module based on AD9910 was designed.The VHDL program was designed by state machine and was simulated by Modelsim simulation software.The simulation results showed that the waveform of the control signal conformed to the SPI serial timing of AD9910.The output signal of the signal transmitting module was tested by using oscilloscope and spectrum analyzer.The results showed that the expected waveform was generated under the control of FPGA.The carrier's spurious free dynamic range was larger than 48 d B,the frequency stability was better than 1ppm,the frequency accuracy was less than 1KHz,the spurious emission of single carrier frequency pulse was less than-40 d Bc,and the output power of the signal transmitting module could reach 10 d Bm.The range of power regulation was larger than 20 d B.The pulse width and period of single carrier frequency pulse could be adjusted.The transmitting signal meeted the design requirements...