Design Of Automatic Detection System For Radio Spectrum Based On GNU Radio

With the wide application of the new technology and business of radio, and the numberof radio stations increase drastically, the phenomenon of radio interference is becomingincreasingly serious. Especially the interference to civil aviation, maritime communicationsand the other safety businesses. It is a direct threat to social stability, national security and thesafety of people’s lives and property. Due to the limited height of receiving antenna and thegreat path loss, it is difficult for the existing direction-finding technology(such asdirection-finding technology based on MUSIC algorithm) and positioning technology (suchas TDOA) to catch the area coverage of interfering signal in civil aviation. To resolve thisproblem, the State Radio Monitoring Center provided a method to locate interfering sourceby using the Doppler frequency Shift of scattering signals of civil airplanes. In this method,based on the Doppler frequency Shift of interfering signal, a mathematical expression is builton the coordinate of interfering source.The area range of interfering source can bedetermined on the basis of solving the mathematical expression, so this method provides akey basis to hunt the interfering source.In this paper, the major work is to research the methods to detect interfering signal andprecisely estimate carrier frequency of the received interfering signal. To detect interferingsignal, two methods of detection are studied, one is based on "the database of frequency" andthe other is based on "threshold". To estimate carrier frequency of the received interferingsignal, three methods include MUSIC algorithm, PLR algorithms and NLS algorithm arecompared in this paper. In addition to relevant theoretic research and MATLAB simulation,this article also puts forward specific engineering realization method. An automatic detection system for radio frequency is constructed by using GNU Radio（GNU ’s Not Unix Radio）andthe USRP2(The second-generation Universal Software Radio Peripheral).With energydetection method, the system can detect power spectrum in certain real time, and captureinterfering signal quickly, at the same time, the system will record its bandwidth, centerfrequency, beginning time, ending time and IQ data, while, precisely estimate carrierfrequency of the received interfering signal, at last, the interfering source can be foundaccording to the previous parameters. The actual tests show that the system is simple withfast detection speed, high accuracy, certain reliability and practicability.