Perimeter Intrusion Detection Methods Based On Leaky Coaxial Cable And Their Applications

The perimeter intrusion detection system based on leaky coaxial cable(LCX)has the advantages of security concealment,conformal laying,omni-directional vigilance and all-weather work.It satisfies the strong demand of the security defense in recent years.With the update of the latest science technology,software and hardware,it is urgent to use the new technologies and methods to meet the challenges of the sensor design,the weak disturbance signal detection,the detection system design and the accurate positioning algorithm.Combining with the scientific research project“Perimeter Intrusion Detection System Based on the LCX”,some key technologies are studied in this dissertation,and the design and implementation of the detection system are focused on the following aspects:1.The design method of LCX sensor and multi-mode positioning algorithm are proposed,which solve the problems of LCX sensor design and the detection signal forms optimization.A novel LCX sensor is designed in VHF frequency band according to basis theory of LCX,its structure parameter is optimized by modeling and simulation,the simulation and measurement results show that the LCX sensor has the advantages of 142MHz single-mode radiation bandwidth,0.75dB/100m transmission attenuation and great coupling loss,moreover,its transmission and radiation characteristics meet the reqirments of the detection system.The intrusion electromagnetic model is established by using CST MICROWAVE STUDIO~?,the mechanism of intrusion disturbance is studied thoroughly and systematically,then the signal optimization is realized.A multi-dimensional localization method is proposed by adjusting the sensor load and the radiation angles,which improves the detection modes and detection area.2.A high-precision positioning algorithm with environmental adaptability is proposed,and it is well known that the signal of intruder’s perturbation is difficult to recognize in the noisy environment of unstable background clutter and multipath reflection,however,the proposed algorithm can solve the problem mentioned above.The IQ demodulation,the pulse compression and the autocorrelation are used to verify the effectiveness of the pulse signals(single pulse,chirp,barker code pulse)in sequence.The detection positioning algorithm has the characteristics of the high positioning accuracy and better range resolution combined with the time delay location theory and the last two pulse signals.The pulse synchronous accumulation and the synchronous differential calculation are proposed to preprocess the echo signal on the basis of the useful signals coherence and noise randomness,and the results show that the positioning algorithm of pulse synchronous accumulation and synchronous differential calculation can increase the recognition probability of the weak and small signals,which also satisfy the environmental adaptability.3.The methods of the IQ demodulation vector summation,the complementary code summation,the threshold setting and the sliding time window are proposed to improve the echo signal quality.The methods optimize the rapid fluctuation and low signal noise ratio of the echo signal.The results show that the IQ demodulation vector summation method can avoid the problem of the blind zone in the single channel demodulation when the vector summation is set as the threshold value.Comparied with the autocorrelation results of the original codes,the autocorrelation results of the complement codes have the equivalent and inverse sidelobe.In this case,their summation algorithm can improve the main-side lobe ratio of the autocorrelation results and achieve the accurate acquisition of the delay time.The flexible threshold setting method can achieve better performance by eliminating the false alarm through secondary judgment,it also increases the alarm probability and reduces the false alarm rate.Moreover,the time domain processing algorithm of the sliding time window is proposed,which provides a better SNR of the echo signal.4.With the multi-mode positioning technique,the positioning algorithm and the echo signal quality improvement methods,a module integration scheme for the perimeter intrusion detection system based on the LCX sensor is proposed,then the engineering approach and the equipment test are carried out.The signal generation module adopts the type of DDS(Direct Digital Synthesizer)+RF,the echo signal receiving module is a zero-IF receiver,besides those two modules metioned above,there are also the DSP module,the host-slave computer and the relevant applications.The localization algorithms and system debugging are applied with the FPGA(Field Programmable Gate Array)and SingalTap II respectively,and the graphical display program is realized by the Labview platform and VISA interfaces.The measured results are in good agreement with the theoretical indicators,the integrated modular design not only can generate or receive the various signals,it also realizes the signal processing methods such as pulse compression and autocorrelation operation flexibly with the advantages of simple debugging and convenient maintenance.