Digital Multi-beam Microwave Radiometer

Microwave radiometers are widely applied to the field of radio astronomy, remote sensing, target detection and tracing, guidance, medicine etc. Synthetic aperture technology is introduced to microwave radiometer in order to improve the space resolution. In this paper, digital multi-beam microwave radiometer is introduced. Based on digital adaptive beamforming technology, digital multi-beam microwave radiometer can utilize multiple beams to scan the space quickly and efficiently.Based on principle and theory of multi-beam forming, weight optimization and structure optimization of antenna arrays are studied in the paper. For weight optimization, the formula of optimal weight is derived and two traditional beamforming algorithms are theoretically analyzed. Two improved beamforming algorithms are also presented, one is searching the narrowest mainlobe given the ratio of mainlobe peak and sidelobe level, and another is searching the lowest uniform sidelobe given the width of mainlobe. The simulation results show that the improved algorithms can work effectively, quickly and stably. In structure optimization, this paper theoretically analyze the structure and pattern of an interferometric antenna arrays in radio astronomy, discuss the spacing of the mainlobe, and simulate the pattern of the interferometric antenna arrays. The simulation results tell us a feasible method that how to design a thinned array.Finally, the basic theory of digital multi-beam microwave radiometer is described and three digital multi-beam microwave radiometers are also presented, which are the digital multi-beam microwave radiometer with linear array, the digital multi-beam microwave radiometer with rectangular array and the multi-beam microwave radiometer with cross array. The formulas of the main parameter such as pattern and space resolution are derived and the detecting performance of the three digital multi-beam microwave radiometers is analyzed.