KEYWORDS: Time-frequency analysis, Fourier transforms, Nonlinear optics, Signal processing, Signal analyzers, Modulation, Frequency modulation, Wavelets, Signal detection
The synchrosqueezing transform(SST), a kind of reassignment method, aims to sharpen the time-frequency representation. In this paper, we consider synchrosqueezing transform based short-time fourier transform with instantaneous frequency rate of change to analyze nonlinear and nonstationary signal, called the adaptive synchrosqueezing transform (ASST). Compared with SST, the window width of ASST is adaptively adjusted with the instantaneous frequency rate estimation which is extracted at the signal ridge. The proposed method can generate a more energy concentrated TF representation for the non-stationary signals with fast-varying frequencies. Simulation results are provided to demonstrate the effectiveness of the proposed method.
KEYWORDS: Signal to noise ratio, Detection and tracking algorithms, Chemical elements, Statistical analysis, Signal processing, Radar signal processing, Radar, Lithium, Computer simulations
This paper presents a novel matrix completion algorithm, penalty decomposition method based augmented Lagrange multipliers (PD-ALM), to improve the performance of Direction Of Arrival (DOA) in sparse array. In PD-ALM algorithm, we apply the penalty decomposition method to solve low-rank matrix completion problem directly. Firstly, we reconstruct a low rank matrix using the special structure of received signals of uniform linear array (ULA). Then, PD-ALM algorithm is used to complete the received signals of the sparse array. Finally, we apply Multiple Signal Classification (MUSIC) algorithm to estimate direction of arrival. The numerical experiments are provided to validate the effectiveness of the proposed algorithm.
Controlling the polarization state of light has important applications in optical communications, imaging, and detection. The latest developments in metamaterials can miniaturize optical components to the sub-wavelength range. The previous work cannot simultaneously take into account the two aspects of simple structure and high efficiency. Here, we propose a simple and effective circular polarization converter, which is composed of three layers of rotated gold split-rings and SiO2 substrate. It can convert LCP and RCP into orthogonally polarized light in two adjacent bands, with conversion efficiencies of 70% and 52%, respectively. Meanwhile, an asymmetric transmission of about 0.5 is achieved efficiently. The error caused by allowable changes of structural parameters will not affect the efficiency of asymmetric polarization conversion, indicating the high stability of our converter. As an ultra-thin planar optical element, the proposed metasurface can be used in integrated photonics, optical sensing and other fields. The asymmetric transmission in adjacent frequency bands may contribute to information encoding and decoding in applications of optical communication.
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