THz Atmospheric Limb Sounder (TALIS) is a microwave radiometer designed by the National Space Science Center (NSSC) of the Chinese Academy of Sciences (CAS) for sounding the vertical distribution of the atmosphere, focusing on measuring the temperature and the chemical composition of the middle and upper atmosphere. Fast Fourier transform spectrometer (FFTS) is the core component of TALIS back-end, which mainly undertakes the function of spectral analysis. In this paper, a new wideband, real-time FFTS design and implementation scheme is proposed to obtain the power spectrum of the signal through the core radix 16 real-time complex FFT algorithm. The analysis bandwidth and the number of channels of FFTS are 2 GHz and 1 k, respectively. The simulations and tests are performed using sinusoidal signals, and the results show that the effective number of bits (ENOB) is better than 3-bit, the signal-to-noise ratio (SNR) is better than 20 dB, and the spectral resolution is constant at 2.3 MHz. Moreover, the peak frequencies of the simulation and test are consistent, which can meet the requirements of the spectral line detection in TALIS.
Ice cloud parameters have an important influence on global climate research and weather forecast. According to the atmospheric radiation theory, THz is the best frequency band for ice cloud remote sensing. In this paper, the principle and research status of ice cloud remote sensing is analyzed. The detection capabilities of different ice cloud sounders are compared, and a THz ice cloud imager for the next generation meteorological satellite is designed. The THz ice cloud imager covers five detection frequencies of 183GHz, 243GHz, 325GHz, 448GHz and 664GHz, and uses cone scanning mode, with the spatial resolution better than 10km, noise temperature better than 3000K.
Radiometers are used in a various number of measurements applications. The output detector is the main element in the radiometer which determines its linearity and dynamic range. In this paper, the square-law detection principle of Schottky diode and multiplier is introduced. The multiplication detection module and the amplifer-filter circuits are designed. The multiplication detector takes the analog multiplier as the core, and the differential circuit is used at the signal input. The output linearity of 0.99999 is achieved in the bandwidth of 50 MHz ~ 2GHz and the dynamic range of -16dBm ~ 4dBm. Compared with the diode detector, the multiplication detector has the advantages of large effective bandwidth, wide dynamic range, high linearity and good stability.
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