W-band Broadband Radiometer Channel Modeling And Experimental Study

As an important part of passive remote sensing, microwave radiometer has been widely applied in radio astronomy, remote sensing, missile guide and measurements of objective characteristics. Direct-detection total-power radiometer channel is implemented to meet the application requirements of the W-band multi-channel radiometer system, and which has many advantages such as small size, high-level integration and low power consumption, and so on.Three main contributions are achieved in this dissertation. Firstly, to overcome the disadvantages of the two kinds of present detector models, the equivalence principle is applied in the modeling of wideband detectors to model the frequency domain and time domain characteristics of the wideband detectors effectively. Secondly, based on the wideband detector model, wideband radiometer channel model is also established. At last, a correction formula of the effective bandwidth of radiometer is proposed with the influences of the characteristics of detector on the properties of radiometer system considered, and which is named"effective RF bandwidth".Based on the model of wideband radiometer channel and the formula of effective RF bandwidth, the influences of the characteristics of microwave devices on the properties of radiometer system is analyzed using ADS and MATLAB software. And in general, in-band flatness and consistency of operating bands are the key points of the characteristics of microwave devices for good system performances. Experiment platform of the radiometer channel is built, and performances of the microwave devices and the whole channel are measured. It is found that the measured results accord with the simulated.Based on the radiometer channel model, system performances can be analyzed for the known LNA and detector characteristics. Meanwhile, realistic parameters of the microwave devices can be introduced for known system features, such as the voltage sensitivity of detectors and the gain of amplifiers. Moreover, the simulation results are suitable for radiometers operating in other frequency bands with other structures.