Design And Implementation Of Circuit For Atmospheric Duct Measurement System

The detection principle of the radar is using of the scattering between the target and radiowave, the refraction which is caused by uneven atmosphere makes the radio wave bent, especially when the curvature of the ray is beyond the earth itself, some of the ray can spread forward in the duct layer. At the point the energy of electromagnetic wave propagation attenuation is very small, and it can propagate to a larger distance than the apparent range of target, that is it can reach over-the-horizon radar detection. At present using the atmospheric duct to reach over-the-horizon radar detection is not only becoming to an effective means to extend the radar detection range ,but also one of radar's hot topic in the field of research. To reach ver-the-horizon radar detection, the primary problem is to accurately measure the characteristic information of the atmospheric duct. Because the existing atmospheric duct forecasting model and meteorological instruments often used to measure usually have poor real-time, and can not reach online measurement accuracy, all always make the use of the atmospheric duct reach over-the-horizon in the theory stage and it can not meet the reality application needs. Basing on all-mentioned above, the paper gives the design, simulation and implementation of the circuit for atmospheric duct measurement system based on microwave cavity.The atmospheric duct depends on whether the presence of refractive index gradient, so the characteristics information of atmospheric duct measurement system is mainly the atmospheric refractive index on the different locations in the atmospheric environment. The paper introduces the characteristics of atmospheric environment and the general measurement method, on the basis is given the theory, composition and the main technical indicators of atmospheric duct measurement system for high accuracy measurement of online refractive index. Then each circuit element of composed atmospheric duct, such as crystal oscillators, the amplifier circuit, phase integral control circuit and PLL frequency synthesizer circuit, designed in detail. At the same time the designed circuit is simulated, optimized and produced. Finally, all the designed elements and microwave cavity are put together to compose the atmospheric duct to online performance test and the accuracy. The results show that design of each circuit element meets the overall design of atmospheric duct.