Research And Implementation Of The Electromagnetic Environment Guarantee System In The Examination Room

With the development of radio communication technology,the problems of cheating on exams as well as jamming and even destroying the electromagnetic environment by illegal use of radio communication technology are becoming increasingly prominent.Therefore,it is of great theoretical and practical significance to study and realize an electromagnetic environment protection system which can effectively shield the examination rooms from cheating signals.To address this issue,this paper designs and realizes a novel electromagnetic environment protection system for examination rooms by studying the monitoring and blocking methods for cheating radio signals.In the aspect of cheating signal monitoring,this paper studies the FFT parallel algorithm,radio scanning spectrum signal extraction algorithm,signal bandwidth measuring method,communication signal modulation mode identification algorithm,and a cheating signal extraction method based on floating template comparison is then proposed,which greatly improves the automation of signal detection.The common modulation modes used by cheating signals,e.g.AM,FM,2ASK,2FSK and BPSK are classified and identified through statistical pattern recognition methods.The calculation methods of related characteristic parameters and the empirical values of the thresholds are introduced,and the main classification and identification flows are presented.In this paper,the proposed system integrates the scanning receiver and the monitoring receiver to enable the simultaneous operation of signal extraction and signal recognition,which has reduced the size of the device and improves the working efficiency of the system.In the aspect of blocking cheating signals,an interference signal source based on a simple vector signal generator is designed and realized using the HackRF software radio peripheral platform.Moreover,this paper employs MATLAB to implement the software modulation of AM,FM,2ASK,2FSK,BPSK signals and collect the corresponding baseband IQ data.The IQ data can be modulated and transmitted directly by HackRF,and can provide the best-match interference signal pattern for different types of cheating signals.In addition,HackRF is able to record signals and track transmission,which can impose deception jamming to the cheating signals.Finally,the validity of the system is proved by theoretical analysis and practical application.In an exam security protection action,the deceptive interference function successfully blocked a cheating device known as "Cloud VI",providing an important reference for fighting radio technology-based exam cheating.