Research On Multi-targets Distance Measurement Algorithm Based On Linear Frequency Modulation

With the rapid development of wireless communication technology,the distributed antenna system(DAS)has been widely used in the indoor environment as its advantages of coverage area,channel capacity and sloving transmission power issues.However,the feeders of the DAS are inside the wall or more secluded places,which makes the matters often occur that the feeders are stolen or the feeders' length can't meet the requirements because of cutting corners.As a result,it is necessary to monitor the DAS topology so that the feeder's length between each nodes in the DAS can be accurately measured.In the thesis,the author presents a way to monitor the DAS topology by the linear frequency modulation continuous wave(LFMCW)ranging radar based on sawtooth wave modulation,and makes a research on the algorithm of multi-targets' distance measurement in the passive DAS with the linear frequency modulation.The author introduces the system-related principles of DAS monitoring and analyzes the signal reflection caused by impedance discontinuity and the LFMCW radar model based on sawtooth wave modulation.Then,according to the above principles,the whole system framework is established and simulated.In the design,the author proposes a signal processing scheme in view of the particularity of DAS architecture.Firstly,the author clarifies the reasons of choosing the large-scale FFT comparing with the spectrum analysis method based on complex modulation(Zoom-FFT)which can enhance the resolution.Secondly,due to the big difference of the different beat-note signals energy corresponding to different targets in the system,the author chooses the Kaiser window to inhibit side lobe energy by comparing different widows.Furthermore,Constant False-Alarm Rate(CFAR)is applied in the design to deal with the clutter along with the signals,and the signal needs to be processed after CFAR because of the special of the system.Last but not least,the author designs the algorithm to match the nodes in the DAS and the feeder's length during monitoring the DAS topology.It is easy to match the nodes and the feeder's length as the nodes have some certain correlation.The corresponding specific algorithm needs to be implemented as it has been proposed.The signal processing algorithm is simulated by Matlab and implemented with Verilog HDL and Xilinx development tools Vivado14.4.Besides,the matching algorithm is implemented by the language C#.At the end,to verify the correctness and stability of the algorithm,the author provides the results of monitoring practical DAS with the whole radar system,which consists of the processing algorithm implementation module and the RF front module.