The Calibration Algorithms Of Array Microwave Radiometer Based On Beamforming

Microwave radiometers are high sensitivity receivers, which are widely used in the field of passive remote sensing and target detection. To solve the problem of low space resolution of conventional microwave radiometers, traditional aperture antenna microwave radiometer needs to increase the size of antenna, but it is difficult in both manufacture and mechanism scanning. In order to solve these metters, an array microwave radiometer based on beamforming and its calibration algorithm are introduced in this paper.The main factors of errors in a DBF system, which are quantization errors, random errors in antenna arrays and nonlinearities in receivers, are analyzed in the thesis. Several calibration algorithms are also referred. Due to the little correlation value that caused by radiation signals, the last correlation outcome will be affected by the radiations from each direction. So, the calibration algorithms for multi-beam millimeterwave should consider the combined factors of pattern of an array, amplitude and phase errors of channel, as well as errors in the antenna element positions. Based on these theoretics, a new calibration algorithm using B matrix is proposed in this thesis. Letting the position of temporally calibration noise sources are N, the scanning fan beam can be shaped and the impulse response as the powerful noise source in these directions. Then a matrix will be got ,which contain the information of amplitude ,phase and the antenna element positions. Though this matrix, we can get the real brightness temperature distribution.A series of experiments for image reconstruction, such as noise source , building and chimney , were conducted by the system. The experiment results show that the quality of reconstruction image is improved using the method proposed in this thesis.