Design And Implementation Of The Signal Receiving Module For The Leaky Coaxial Cable Security System

The leaky cable security system is a system for intrusion detection,alarming and positioning by using a pair of parallel buried leakage coaxial cables as the receiving and transmitting antenna.It has the advantages of follow-up installation,high concealment,all-weather work,and full alertness.So the system has a wide range of application prospects in the security industry.As the front end of the signal receiving and signal processing of the system,the performance of signal receiving module directly determines the quality of the received signal quality,thereby affecting whether the application of this system on intrusion detection,alarm and positioning functions.So the design and implementation of the signal receiving module of the leaky cable security system has a very important significance.Based on the project “Key Technology Research for Perimeter Intrusion Detection System Based on Leaky Cables”,designed the receiving module of the leakage.cable security system by adopting system-level,circuit-level,and component-level design methods.As well as the design order of program determination,simulation design,hardware implementation,and testing.The main work of this article is as follows:1.Brief introduction about the structure and working principle of the leaky cable security system.Comparing and analyzing the advantages and disadvantages of super heterodyne structure,zero-IF structure,low-IF structure,image rejection structure,and digital IF structure.As well as the signal processing process.According to the characteristics of the transmission signal of this system and the signal processing method,using the signal receiving module scheme of zero IF structure.According to the characteristics of the transmit signal of this system and the signal processing method adopted,it is determined that a zeroIF structure scheme is used for design.The index requirement for the signal receiving module of this system is: the operating frequency is 40 MHz,100MHz or 200 MHz,the bandwidth is 5MHz,and the sensitivity is-85 d Bm.the noise figure is ?12d B,the dynamic range is 58~72d B,and the minimum carrier-to-noise ratio is 10 d B.2.According to the indicators of the signal receiving module,the device selection of each unit of the signal receiving module is completed,and the link simulation is performed.Link budget simulation and calculation results show: the sensitivity of the receiving module is- 95.98 d Bm,the noise figure is 1.02 d B,the power gain is 66.53 d B,the minimum carrier-tonoise ratio is 10 d B.Agree well with the indicator requirements for the signal receiving module of the leaky cable security system.Also,the circuit design,PCB layout design,physical production and testing of the low-noise amplifier,mixer,and baseband amplifier unit in the link are performed.The test results show that the physical object can meet the design requirements.3.The functional testing of the signal receiving module is performed on the leaky cable security system platform.The result shows that the receiving module can accomplish the positioning function,and then the signal receiving module designed in this paper can undertake the task of signal receiving and processing,and finally it is applicable to the project of the leaky cable security system.