| The paper introduces the history of BBADCP, discriminates the different among pulse-incoherent system , pulse-coherent system and pulse-pulse coherent system, analyzes the characteristic of BBADCP 's signal and explains how BBADCP works by reasoning. A BBADCP system model based on the method of baseband simulation is made in the computer and the theory of BBADCP is examined by simulation.Two methods are put forward to realize a BBADCP. For one , analog signal processing is in the majority , for the other, on the contrary, digital signal processing is in the majority . Computer simulations are done in both methods. A new DSP algorithm for Doppler frequency measurement is constructed in the second method, where the circuit configuration is simplified, the balanced I/Q channels can be available and the time for digital signal processing is reduced.In an attempt to measure SF6 gas concentration in air , a new technology to determine gas concentration in a binary gas mixture is investigated. The essential measurement formula and error formula of the technology are deduced and the application field of this method is also discussed. Applying this technology , an CPLD-based SF6 gas concentration detector is invented. It is tested and proved that the detector can emit sound and light alarm signals if the SF6 gas concentration is beyond 1000ppm, and if not, it can display the concentration according to three formats of 400 ppm, 600 ppm, and 800 ppm. Based on the research achievement, two patents of invention and new-type utility is being applied for, so some details can not be given in the thesis at present.
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