Research On 8 Mm-Band Direct Detection Radiometer

Owing to the advantages of itself, Passive Millimeter Wave Imaging System, which is more and more important in the modern society, is irreplaceable in the field of Mag & Bag, and millimeter-wave radiometer is one of the most important part in PMMW. Millimeter wave radiometers are wireless receivers with high sensitivity. It has many characters for its special frequency, such as high sensitivity, low consumption, and small size and so on.Total power direct detection receiver was provided in the dissertation, it had been proved could be used in ka band through theoretical analysis and simulation study. Prototype system has been developed, and it display the excellent performance. It has been proved that the precept of total power direct detection receiver is feasible in PMMW. The detailed work includes:At first, for system design section, two types of radiometer system: total power and Dicke, were discussed. In practical application background, The advantage of total power structure was proved. On the based of total power structure, the parameters of system had been analyzed. To consider the practical application background, parameters of the components in this system were confirmed, establish the foundation for the entire research work.Secondly, the performance of radiometers were determined by the millimeter-wave front-end, so the front-end was studied as an important part. The method of design of LNA was studied. Square law detector was discussed, equivalent model of tiny signal has also been analyzed. Sensitivity of schottky diode was discussed. Then, circuit system was also been designed according to parameters of all components. Millimeter-wave LNA, square law detector, low-frequency amplifier and integral circuit were discussed. LNA components were chosen, the noise of system was also analyzed. Square law detector was discussed, the effect to radiometer was studied. Low-frequency amplifier and integral circuit were designed for system in low frequency domain.At last, the signal and noise of receiver were analyzed, the radiometer system was built up, and explored experiments of target detecting were performed.