Design And Implementation Of Pulse Signal Transmitting Module

With the development of science and technology,the use of radar is no longer confined to the military field,it is also extended to the national economy fields of resource exploration and security etc.In the security field,the leakage detection function of leaky coaxial cable and the characteristics of radar are combined to achieve a perimeter intrusion detection system with all-weather operation and high concealment unmanned warning function,which catches social attention a lot.This detection system needs a design of radar transmitter module with high performance and meeting the system's requirements.The property of the transmitter module directly affects the performance of the received signal and the positioning accuracy of the detection system.Based on the principle of perimeter intrusion detection system and it's specific requirements,a pulse transmitter module is designed through processes of the general scheme planning,design index distributing,simulating and producing.The transmitting module can transmit single frequency pulse or four-bit Barker code modulation pulse signal,the working frequency range is 50MHz~200MHz,the output signal power is close to 3W.The main working process of the transmitter module design can be divided into two parts,the definite contents of these two parts are as follow.The first part is intended to implement the function of the signal source to produce small signal waveform.The required signal is produced from the AD9910 chip controlled by the FPGA with the technology of DDS.The second part is intended to achieve the signal power amplification.For the Intrusion detection feature of the system,it needs to ensure the high-linearity and stability of the produced signal while the signal power is amplified.Based on the simulation of ADS software,the research of multistage amplification of transmitter signal is made,including the designs of driving amplifier and final power amplifier.The driving amplifier is to amplify the signal to drive the final power amplifier by using the Low noise and high gain chips.The final power amplifier is to amplify the signal power to meet the requirement;the stability is improved by the negative feedback in the circuit and the impedance matching is completed by load pull technique.The experiment testing results of the deigned transmitter show that the range of the transmitting signal produced is from 50 MHz to 200 MHz,and the power peak is up to 2.8W,which well satisfy the requirements of the intrusion detection system.