| Atmospheric microwave sounding in geostationary orbit is a technical problem that needs to be overcome urgently in the field of meteorological remote sensing.When a microwave radiometer is used for observation in geostationary orbit,it needs to have high spatial resolution and high temperature sensitivity to meet the observation requirements.Compared with traditional real aperture radiometers,synthetic aperture microwave radiometers can improve spatial resolution while avoiding the processing difficulties of high-precision large-aperture antennas.Therefore,it has become the most promising technical approach for atmospheric microwave sounding in geostationary orbit.Antenna array arrangement and optimization is a key technology for synthetic aperture microwave radiometer.It determines the sampling distribution of the visibility function through the design of different baseline combinations,which in turn affects the sensitivity of the system and the final imaging quality.Compared with traditional two-dimensional antenna arrays,circular array is more suitable for rotating scanning time-sharing sampling imaging system.It can not only provide more efficient visibility function sampling coverage,but also be more convenient to take period outer-calibration for each receiver channel.Therefore,circular array is more suitable for atmospheric microwave sounding applications in geostationary orbit,and is considered to be the first choice for the configuration of synthetic aperture microwave radiometer antenna arrays in geostationary orbit.At present,the meteorological department has put forward higher observation requirements for atmospheric sounding in geostationary orbit,the resolution has been increased from 50 kilometers to 15 kilometers.Therefore,the design of antenna arrays has also put forward higher requirements.In this context,this article focuses on the arrangement and optimization of circular array for synthetic aperture microwave radiometers.Firstly,the relevant theories for optimization of synthetic aperture radiometer antenna array are described,and the optimization strategy of circular array and the relevant parameters to meet the application of atmospheric sounding in geostationary orbit are analyzed.Then,the arrangement of the low redundancy linear array(LRLA-2)with a minimum baseline of 2 is optimized.Compared with the traditional low-redundant linear array with a minimum baseline of 1,LRLA-2 can increase the aperture of the antenna element to improve temperature sensitivity while maintaining the same sampling density,so it can be used as the basis for the design of circular array of synthetic aperture radiometers in geostationary orbit.By using the difference evolution algorithm,the optimization results of LRLA-2 with N ?20 are obtained,according to these optimization results,the general structural rules of LRLA-2arrangement are summarized,and a rapid construction method based on the simplest "mother array" is proposed,which can quickly obtain a series of LRLA-2arrangements for large array elements.Finally,based on the optimization of LRLA-2,two-dimensional circular array is optimized,and periodic sub-arrayed circular array optimization method is established.In response to the application requirements of atmospheric sounding in geostationary orbit,the optimized design of circular array with different antenna sizes has been carried out.Compared with the traditional optimization method based on Cornwell objective function,this method does not need to calculate the position of each sampling point.It not only has the advantages of simplicity and fast calculation speed,but also applies to the optimization problem of circular array arrangement when the number of antenna elements is large.The main contributions of this paper can provide a new and efficient means for the optimal design of antenna arrays for the application of synthetic aperture microwave radiometers,and provide technical reference for the design of future satellite-borne synthetic aperture microwave radiometer systems in geostationary orbit. |
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