Study On Low Noise And High Sensitivity Technology Of Weak Signal Amplification

With the increase in insecurity.Outdoor perimeter intrusion detection system is required in banks,railways,borders and other open spaces for its security protection.In order to meet the requirements of good concealment,wide detection range and low false alarm rate,the intrusion detection system of leaky cable perimeter is studied and realized,and start the research based on this system.Whether the leaked cable intrusion detection system or other communication systems,the weak signal amplification is a necessary part.In order to enlarge the extremely weak signal with no distortion,the receiver front-end amplifier circuit with no distortion,appropriate gain,high sensitivity and good stability is needed in the link.According to the design scheme of leak cable detection system,in order to ensure its normal work,the key is to improve the sensitivity of the receiver front-end amplifier circuit Under the premise of suitable gain and stability.This paper aims to study the Low noise and high sensitivity technology of weak signal amplification then to ensure the normal operation of the system.Firstly,the background and significance of the whole research are expounded,and the basic structure of the leakage cable intrusion detection system,the characteristics of the leakage cable itself and the working principle of the leakage cable intrusion detection system are introduced.It is strict with the sensitivity of the receiver and the detection method of the system because the human body has little effect on the electromagnetic field in a wide range.Secondly,the function of the most important device(low noise amplifier)in the amplifier circuit is analyzed.Then the function,design method of the bias circuit and matching network are introduced.A low noise amplifier matching network based on microstrip line and adapted to dual band has proposed,and its theoretical simulation and verification have carried out.Then,in order to meet demand of sensitivity,noise figure of the receiver front-end amplifier circuit for intrusion detection system which gray-based,relatively large bandwidth.An improved band-pass filter has proposed,which combines the advantages of the m-type inductive filter,increases the passband interval,optimizes the circuit arm structure.So that in the case of ensuring a good transition zone,reduce the insertion loss and improve in-band flatness.Finally,on the basis of the improved band-pass filter,a low-noise and high-sensitivity receiver front-end amplifier circuit has realized.Mainly to broadband band-pass filter,ultra-low noise amplifier CMA5043,fixed amplification module Hmc580 and AGC AD8331 as the core.The entire receiver amplification to achieve 80 ~ 100 dB gain and adjustable,the sensitivity of-118 dBm.To ensure the sensitivity of the entire system,and ultimately the success of the human invasion of the detection and initial positioning.