Design And Research Of The VHF/UHF Radio Monitoring Networks In The Complex Electromagnetic Environment

This thesis mainly focuses on the VHF/UHF radio monitoring systems in complex electromagnetic environment.First, optimal station site combination is investigated based on analysis about the coverage of monitoring stations in VHF/UHF band. According to the suggestion from the International Telecommunication Union ITU-R, reconnaissance and survey on thirteen mountains in Shenzhen are carried out. By means of analysis tool based on the Okumura-Hata propagation statistical model, the measurement data of the thirteen mountains are analysed, after which, seven of them are selected as monitoring station candidates. Afterwards, through WRAP covering computer simulation method, together with CRC computer mathematical propagation model, digital maps and geographical information system, covering performance of the mountain radio monitoring stations in Shenzhen are analyzed. The design result of four mountains is concluded as the optimal combination to build monitoring stations.Second, this dissertation studies the effect to VHF/UHF monitoring stations from complicated electromagnetic environment such as the strong radiation from electromagnetic sources and its countermeasure. Through comparison of the theoretical estimation results and real measured results of electromagnetic intensity of some electromagnetic sources that have strong radiation around the candidate stations, we studies the frequency spectrum, techniques and main performances of monitoring receivers, such as the noise coefficient, sensitivity, non-linearity and inter-modulation product, phase noise, dynamic area, interference rejection, and so on . Also, we research how to choose a suitable monitoring receiver of an VHF/UHF monitoring station that can properly work in strong electromagnetic environment, its possibility to work properly, and countermeasures. Then, we deeply research some countermeasures, such as advanced detection of direction techniques, passive antennas, prior monitoring receivers, equipped with external appropriative narrow band wave trap, and setting up the receivers according to the real measured results. In the end, we validate and compare the real results measured by VHF/UHF monitoring equipment in the mountains with each other.Finally, in this dissertation, we propose our viewpoints and the ways to design the layout of VHF/UHF radio monitoring networks in the typical complex electromagnetic environment.