| Spaceborne microwave radiometer is an important remote-sensing technique for atmospheric sounding,ocean exploration,surface detection and deep space exploration.It can obtain the relatived critical parameters of the targets in all-weather and all day,realizing a continuous monitoring of the targets.In order to meet the demand of highly increased detection accuracy,such as the need for increased vertical resolution accuracy in atmospheric sounding,the research of hyperspectral microwave radiometer based on the broadband,multi-channel and high resolution IF signal processing technology becomes an active field.The spectrum subdivision detection technologies usually used in radiometer system mainly include analog filter bank spectrum analysis,acousto-optic detection spectrum analysis,autocorrelation spectrum analysis,FFT(Fast Fourier Transformation)spectrum analysis and CTS(Chirp Transform Spectrometer)spectrum analysis.These technologies have different measuring principle and implementation architecture,and the related radiometers also have different applications.Considering the complicated exterior environment of the space-borne system,Space-borne microwave radiometer has high requirements on volume,mass,power consumption and system stability.The CTS spectral analysis technology can not only realize broadband high resolution spectrum detection,it can also meet the requirement of small size,low power consumption and high stability.The CTS spectral analysis technology is quite suitable for the application in space-borne system.In this dissertation,we focused on the research of the CTS based broadband multi-channel intermediate frequency system.In order to meet the requirements of intermediate frequency processing bandwidth,channel number,power consumption,volume and stability of spaceborne microwave radiometer system,the structure design and verification of intermediate frequency system of space-borne broadband multi-channel microwave radiometer based on CTS technology are studied.The main research content and innovation includes three parts:(1)A fast digital pulse compression algorithm based on CTS technology is built,verified and analyzed.In order to deal with the large attenuation and non ideal dispersion characteristics of the surface acoustic wave filter,a fast digital pulse compression algorithm based on linear phase sampling and accumulation is proposed.The algorithm is verified by theoretical derivation,simulation and experimental analysis,and it is compared to the classic time-domain digital pulse compression technology with calculation accuracy,frequency resolution and computational complexity.The results show that the proposed algorithm can replace the surface acoustic wave filter to achieve pulse compression with high computational accuracy and low computational complexity.(2)Two novel CTS structures are designed for the CTS based spectrum subdivision technology in multichannel microwave radiometer.In order to solve the matching problem of components and link in the classical two-way push-pull CTS system,two novel single-channel structures are proposed: FCS M-C(Frequency Conversion Single-channel Multiplication-convolution)structures and TDS M-C(Time Delay Single-channel Multiplication-convolution)structures.The theoretical derivation,simulation,experimental verification and analysis of the two novel structures are carried out.The results show that the two novel structures have the advantages of few components,low weight and low power consumption.(3)A new spectrum subdivision intermediate frequency technology based on the novel CTS arrangements and fast digital pulse compression algorithm is built.A digital logic circuit based on fast digital pulse compression algorithm is designed and the designed circuit is verified by Vivado simulation and FPGA board level testing.FPGA board level verification of wideband multi-channel IF system is realized by combining TDS M-C and FCS M-C structures with fast digital pulse compression algorithm. |
PDF Full Text Request