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—Thin cloud detection for all-sky images is a challenge in ground-based sky-imaging systems because of low contrast and vague boundaries between cloud and sky regions. We treat cloud detection as a labeling problem based on the Markov random field model. In this model, each pixel is represented by a combined-feature vector that aims at improving the(More)
The theoretical expression is presented in this study to predict the early minus late power (EMLP) code tracking performance with residual frequency shift and finite front-end bandwidth. On basis of the expression and numerical simulation, the impact on the code tacking performance of Doppler hopping caused by radio frequency hopping of DS/FH signal for(More)
It becomes an emergent challenge how to retrieve the cloud image from a gigantic cloud image database because of the fast accumulation of digital cloud images in meteorological area. This paper puts forward the histogram descriptor based on gray level co-occurrence matrices to depict the texture characteristics of cloud images, and then applies the(More)
In order to meet the contradictory needs coming from dynamic and tracking accuracy, a novel 2-order Phase Lock Loop (PLL) with frequency and phase dual assistance is proposed based on the introduction of DFT phase difference algorithm. The frequency estimation is used to set the center frequency of NCO to make the PLL work in fast pull-in range. According(More)
Carrier delay ambiguity resolving is the essence to enable CEI (Connected Elements Interferometry) a high accurate measuring system. Two ways of resolving carrier delay ambiguity are discussed under different signal types in TT&C, including Δ DOR method and FX correlation method. According to 3σ rule, the requirement of difference phase(More)
The tracking accuracy of baseband Delay Locked Loop (DLL) with narrow loop band is studied. The equivalent phase discrimination model of code delay correlator is provided, and the correlation functions and power spectrum density functions of correlator output port noise and its equivalent noise at the input port are developed, then the simplified(More)
Because of the relation with Fourier transform, the bispectrum also has fence effect, and this brings error to frequency estimation based on bispectrum. To overcome this problem, bispectrum phase difference method is proposed. This method constructs two data sets from the sampled data and makes bispectrum analysis respectively. It uses their peak spectrum(More)
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