Study On The Key Technique Of Frequency Modulation Microwave Ranging System Based On Phase Measurement

Through three-dimensional deformation/displacement monitoring on largebuildings, changes in the building structure, and local damage of buildings can beknown. Early warning on the possible collapse of the building can avoid the majorincident and ensure safety of life and property of the people. In the actual buildingthree-dimensional displacement/deformation monitoring, the all-weather measurements,measuring range, measurement accuracy and the measurement cost are required to befully considered. Currently total station instrument and GPS system are the most widelyused three-dimensional displacement monitoring methods. They used distancemeasurement as the basis to achieve the displacement measurement. The accuracy ofdistance measurement will directly affect the accuracy of the displacement measurement.However, due to the laser ranging of the total station cannot meet the requirement ofmeasurements in all-weather, and the ranging of GPS cannot meet the measurementaccuracy, they cannot fully meet the actual measurement requirements. Usingmicrowave phase ranging method can simultaneously combine the advantages of TotalStations and GPS. However, due to price, technology, size and other aspects of themicrowave phase range finders, it has been replaced by a laser rangefinder graduallysince the1990s. There are almost no commercial products currently. Because theelectronic devices have been very mature, the price is relatively reasonable, whichprovide the basis for the studying of low-cost, high-precision microwave phaserangefinder. Therefore, according to the actual three-dimensionaldisplacement/deformation monitoring requirements, and using existing maturemicrowave transmitting and receiving devices, and signal conditioning devices, designand construction microwave phase ranging system.The main contents of the essay are as follows:①Analyzed and compared the distance measurement methods used in the currentthree-dimension displacement/deformation monitoring. According to the requirementson the all-weather measurements, measuring range, measurement accuracy and themeasurement cost of three-dimensional displacement/deformation monitoring in actualengineering, the microwave ranging method with phase difference measurement isdetermined.②The phase ranging method, frequency modulation demodulation and differential frequency of phase measuring in the phase microwave ranging system are discussed.The theoretical feasibility of phase microwave ranging method is verified.③According to the principle of microwave phase ranging system, the rangingsystem has been designed including the transmitting and receiving devices for rangingsystem, signal processing module, and phase measurement module. The modulesperformance tests have been conducted.④Analyzed the effect of ambient temperature on the range accuracy theoreticallyand experimentally. Theoretical analysis showed that when the temperature changed, themeasured distance had a cubic function to temperature. The correct of the theoreticalanalysis has been verified through the experiment. Based on the results, add a heat sinkto prevent temperature change caused by heat within the system electronics, so that thesystem is in a relatively stable low temperature environment.⑤Distance measurement experimental system has been set up in the outdoor andthe measurement range and measurement accuracy have been tested.