Phase-error performance of multi-focal and non-focal two-dimensional Rotman lens designs

2010 ◽  
Vol 4 (12) ◽  
pp. 2097 ◽  
Author(s):  
J. Dong ◽  
A.I. Zaghloul ◽  
R. Rotman
Keyword(s):  
Phase Error ◽  
Two Dimensional ◽  
Error Performance

The Two-Dimensional Histogram as a Constraint for Protein Phase Improvement

1998 ◽  
Vol 54 (6) ◽  
pp. 1230-1244 ◽  
Author(s):  
Alexandra Goldstein ◽  
Kam Y. J. Zhang
Keyword(s):  
Standard Deviation ◽  
Correlation Coefficient ◽  
Electron Density ◽  
Joint Distribution ◽  
Phase Error ◽  
Temperature Factor ◽  
Two Dimensional ◽  
Average Correlation ◽  
Phase Selection ◽  
2D Histogram

The joint distribution of electron density and its gradient in a protein electron-density map was examined. This joint distribution was represented by a two-dimensional histogram (2D histogram) of electron-density values and the modulus of the gradient. 16 structures representing distinct protein-fold families were selected to study the dependence of the 2D histogram on resolution, overall temperature factor, structural conformation and phase error. The similarity between the histograms for a pair of structures was measured by correlation coefficient, and the residual provided a measure of the difference. The 2D histogram was found to vary with resolution and overall temperature factor, but was found to be insensitive to structure conformation. The average correlation coefficient between pairs of 2D histograms at three different resolutions examined was 0.90 with a standard deviation of 0.04. The average residual for the same condition was 0.13 with a standard deviation of 0.03. The 2D histogram was also found to be sensitive to phase error. The average correlation coefficient and residual between 2D histograms with 10° phase difference are 0.71 and 0.18, respectively. The variation of the 2D histogram resulting from structure-conformation changes was estimated to be equivalent to that of a 4° phase error. This establishes the minimal phase error that a 2D histogram-matching method could achieve. The conservation of the 2D histogram with respect to structure conformation enables the prediction of the ideal 2D histogram for unknown structures. The sensitivity of the 2D histogram to phase error suggests that it could be used as a target for the density-modification method and also could be used as a figure of merit for phase selection in ab initio phasing.

Two-dimensional projection histogram assisted with low-overhead pilots for the common phase error compensation in CO-OFDM system

2020 ◽  
Vol 54 ◽  
pp. 102131
Author(s):  
Meihua Bi ◽  
Weisheng Ye ◽  
Guowei Yang ◽  
Yang Lu ◽  
Xuefang Zhou ◽  
...  
Keyword(s):  
Error Compensation ◽  
Phase Error ◽  
Two Dimensional ◽  
Ofdm System ◽  
The Common

scholarly journals Robust Two-Dimensional Spatial-Variant Map-Drift Algorithm for UAV SAR Autofocusing

2019 ◽  
Vol 11 (3) ◽  
pp. 340 ◽  
Author(s):  
Guanyong Wang ◽  
Man Zhang ◽  
Yan Huang ◽  
Lei Zhang ◽  
Fengfei Wang
Keyword(s):  
Cross Correlation ◽  
Phase Error ◽  
Synthetic Aperture ◽  
Two Dimensional ◽  
Spatial Variance ◽  
Phase Errors ◽  
Residual Phase ◽  
Aerial Vehicle ◽  
Sar Imagery ◽  
The One

Autofocus has attracted wide attention for unmanned aerial vehicle (UAV) synthetic aperture radar (SAR) systems, because autofocus process is crucial and difficult when the phase error is spatially dependent on both range and azimuth directions. In this paper, a novel two-dimensional spatial-variant map-drift algorithm (2D-SVMDA) is developed to provide robust autofocusing performance for UAV SAR imagery. This proposed algorithm combines two enhanced map-drift kernels. On the one hand, based on the azimuth-dependent phase correction, a novel azimuth-variant map-drift algorithm (AVMDA) is established to model the residual phase error as a linear function in the azimuth direction. Then the model coefficients are efficiently estimated by a quadratic Newton optimization with modified maximum cross-correlation. On the other hand, by concatenating the existing range-dependent map-drift algorithm (RDMDA) and the proposed AVMDA in this paper, a phase autofocus procedure of 2D-SVMDA is finally established. The proposed 2D-SVMDA can handle spatial-variance problems induced by strong phase errors. Simulated and real measured data are employed to demonstrate that the proposed algorithm compensates both the range- and azimuth-variant phase errors effectively.

Common Phase Error Compensation in Coherent Optical OFDM System with Two-Dimensional Projection Histogram-Based and Pilot-Aided Method

2019 ◽  
Vol 39 (11) ◽  
pp. 1106001
Author(s):  
杨国伟 Yang Guowei ◽  
叶玮胜 Ye Weisheng ◽  
毕美华 Bi Meihua ◽  
滕旭阳 Teng Xuyang ◽  
曾然 Zeng Ran ◽  
...  
Keyword(s):  
Error Compensation ◽  
Phase Error ◽  
Two Dimensional ◽  
Ofdm System ◽  
Optical Ofdm

scholarly journals Refocusing of Moving Ships in Squint SAR Images Based on Spectrum Orthogonalization

2021 ◽  
Vol 13 (14) ◽  
pp. 2807
Author(s):  
Xuyao Tong ◽  
Min Bao ◽  
Guangcai Sun ◽  
Liang Han ◽  
Yu Zhang ◽  
...  
Keyword(s):  
Phase Error ◽  
Bp Algorithm ◽  
Synthetic Aperture ◽  
Two Dimensional ◽  
Back Projection ◽  
Image Sharpness ◽  
Sar Images ◽  
Simulation Experiments ◽  
Geometric Deformation ◽  
Wavenumber Spectrum

Moving ship refocusing is challenging because the target motion parameters are unknown. Moreover, moving ships in squint synthetic aperture radar (SAR) images obtained by the back-projection (BP) algorithm usually suffer from geometric deformation and spectrum winding. Therefore, a spectrum-orthogonalization algorithm that refocuses moving ships in squint SAR images is presented. First, “squint minimization” is introduced to correct the spectrum by two spectrum compression functions: one to align the spectrum centers and another to translate the inclined spectrum into orthogonalized form. Then, the precise analytic function of the two-dimensional (2D) wavenumber spectrum is derived to obtain the phase error. Finally, motion compensation is performed in the two-dimensional wavenumber domain after the motion parameter is estimated by maximizing the image sharpness. This method has low computational complexity because it lacks interpolation and can be implemented by the inverse fast Fourier translation (IFFT) and fast Fourier translation (FFT). Processing results of simulation experiments and the GaoFen-3 squint SAR data validate the effectiveness of this method.

Spectrophotometric measurements of objective-prism spectra

1966 ◽  
Vol 24 ◽  
pp. 118-119
Author(s):  
Th. Schmidt-Kaler
Keyword(s):  
Progress Report ◽  
Two Dimensional ◽  
Objective Prism ◽  
Made In

I should like to give you a very condensed progress report on some spectrophotometric measurements of objective-prism spectra made in collaboration with H. Leicher at Bonn. The procedure used is almost completely automatic. The measurements are made with the help of a semi-automatic fully digitized registering microphotometer constructed by Hög-Hamburg. The reductions are carried out with the aid of a number of interconnected programmes written for the computer IBM 7090, beginning with the output of the photometer in the form of punched cards and ending with the printing-out of the final two-dimensional classifications.

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