| Based on the background of radio monitoring technology, studied the radio monitoring techniques based on software defined radio (SDR), radio direction finding technology based on MUSIC algorithm, and the radio position location technology based on TDOA (Time Difference of Arrival) architecture.Took the radio monitoring related technologies as its main research direction, this paper took an in-depth study on some of the key technologies. Here, radio monitoring mainly includes three levels. The first is the monitoring and measurement of modulated signals itself, including measurement of related parameters of modulated signals, demodulation, and automatic modulation recognition, etc. The second is the measurement of arrival direction for radio signals, which is to monitor the spatial distribution of radio energy, which is often called spatial spectrum estimation. The third is to monitor the source location of radio signals, and get the specific location of the signal source, in order to better grasp the radio environment of one region, and eliminating the interference, thus the normal communication business can be reconstructed as soon as possible.Based on the description above, the primary content of this paper is as follows:1. Radio monitoring technologies based on SDR. The objective of this part is to develop relevant algorithms for one company's mini type radio monitoring system, so that to strengthen its digital monitoring function, make full use of the resource already exist, and lay the foundation for system upgrades. Studied the following key technologies: the parameter measurement technology of radio signals, orthogonal demodulation, automatic modulation recognition, and synchronization, The flowing chart and corresponding simulation results were shown. Where, parameter measurement has been implemented on the system successfully, while developed simulation software for orthogonal demodulation and AMR technology.2. Radio direction finding (DF) technologies based on MUSIC algorithm. Mainly studied the application of MUSIC algorithm in uniform linear array (ULA) and uniform circular array (UCA), against the multi-path signal environment, also studied the process of coherent and correlated arriving signals. MUSIC algorithm needs to foreknow the number of arrivals, so studied AIC and MDL criterions to estimate the number of arrivals.3. Radio position location (PL) technologies based on TDOA architecture. Mainly studied the localization algorithms of TDOA architecture and its basic PL principles were analyzed. Conducted a comparative study on some of the PL algorithms already proposed, the simulation results and performance of these algorithms were shown. Simulation results show that Chan's method has some comparative advantages, and is more suitable for the current site layout of the monitoring stations.The creative works of this paper are as follows:1,In the AMR part, in view of the phase characteristic of DSB signals, a new feature parameter was proposed, which can achieve good recognition effect. When SNR=5dB, the success rate is larger than 97%, and moreover, this parameter is insensitive to carrier phase.2,In demodulation part, in view of the linear characteristic of the phase of FSKsignals, proposed to demodulate FSK signals via linear fitting algorithm. Simulationresults have shown the feasibility of this algorithm.3,In TDOA part, against the inherent ambiguity property of Chan's method proposed an object function, simulation results have shown that it can solve this ambiguity problem fairly. |
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