scholarly journals Strip-Mode Microwave Staring Correlated Imaging with Self-Calibration of Gain–Phase Errors

Sensors ◽  
2019 ◽  
Vol 19 (5) ◽  
pp. 1079 ◽  
Author(s):  
Rui Xia ◽  
Yuanyue Guo ◽  
Weidong Chen ◽  
Dongjin Wang
Keyword(s):  
Error Estimation ◽  
Phase Error ◽  
Super Resolution ◽  
Image Splicing ◽  
Initial Value ◽  
Self Calibration ◽  
Phase Errors ◽  
Imaging Model ◽  
Multiple Imaging ◽  
Imaging Performance

Microwave staring correlated imaging (MSCI) can realize super resolution imaging without the limit of relative motion with the target. However, gain–phase errors generally exist in the multi-transmitter array, which results in imaging model mismatch and degrades the imaging performance considerably. In order to solve the problem of MSCI with gain–phase error in a large scene, a method of MSCI with strip-mode self-calibration of gain–phase errors is proposed. The method divides the whole imaging scene into multiple imaging strips, then the strip target scattering coefficient and the gain–phase errors are combined into a multi-parameter optimization problem that can be solved by alternate iteration, and the error estimation results of the previous strip can be carried into the next strip as the initial value. All strips are processed in multiple rounds, and the gain–phase error estimation results of the last strip can be taken as the initial value and substituted into the first strip for the correlated processing of the next round. Finally, the whole imaging in a large scene can be achieved by multi-strip image splicing. Numerical simulations validate its potential advantages to shorten the imaging time dramatically and improve the imaging and gain–phase error estimation performance.

scholarly journals Knowledge-Aided Doppler Beam Sharpening Super-Resolution Imaging by Exploiting the Spatial Continuity Information

Sensors ◽  
2019 ◽  
Vol 19 (8) ◽  
pp. 1920 ◽  
Author(s):  
Hongmeng Chen ◽  
Zeyu Wang ◽  
Jing Liu ◽  
Xiaoli Yi ◽  
Hanwei Sun ◽  
...  
Keyword(s):  
Dwell Time ◽  
Spatial Coherence ◽  
Super Resolution ◽  
Data Set ◽  
Spatial Continuity ◽  
Range Resolution ◽  
Imaging Model ◽  
Equivalent Number ◽  
The Cross ◽  
Imaging Performance

This paper deals with the problem of high cross-range resolution Doppler beam sharpening (DBS) imaging for airborne wide-area surveillance (WAS) radar under short dwell time situations. A knowledge-aided DBS (KA-DBS) imaging algorithm is proposed. In the proposed KA-DBS framework, the DBS imaging model for WAS radar is constructed and the cross-range resolution is analyzed. Since the radar illuminates the imaging scene continuously through the scanning movement of the antenna, there is strong spatial coherence between adjacent pulses. Based on this fact, forward and backward pulse information can be predicted, and the equivalent number of pulses in each coherent processing interval (CPI) will be doubled based on the autoregressive (AR) technique by taking advantage of the spatial continuity property of echoes. Finally, the predicted forward and backward pulses are utilized to merge with the initial pulses, then the newly merged pulses in each CPI are utilized to perform the DBS imaging. Since the number of newly merged pulses in KA-DBS is twice larger than that in the conventional DBS algorithm with the same dwell time, the cross-range resolution in the proposed KA-DBS algorithm can be improved by a factor of two. The imaging performance assessment conducted by resorting to real airborne data set, has verified the effectiveness of the proposed algorithm.

scholarly journals Antenna Phase Error Compensation for Terahertz Coded-Aperture Imaging

Electronics ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 628
Author(s):  
Xingyue Liu ◽  
Chenggao Luo ◽  
Fengjiao Gan ◽  
Hongqiang Wang ◽  
Long Peng ◽  
...  
Keyword(s):  
Error Compensation ◽  
Phase Error ◽  
Radar System ◽  
Coded Aperture ◽  
Aperture Antenna ◽  
Imaging Radar ◽  
Phase Errors ◽  
Coded Aperture Imaging ◽  
Imaging Model ◽  
Antenna Phase

Coded-aperture antenna plays an important role in terahertz coded-aperture imaging radar system. However, the performance of a system is inevitably affected by the phase errors introduced by the coded-aperture antenna elements. In this paper, we propose a phase error compensation method by deducing a formula to compute all element phase errors accurately. According to the formula, the phase errors can be calibrated by using a calibrator and can be used to compensate the imaging model of the system. Numerical simulations demonstrate that the proposed method can effectively improve the imaging quality when the elemental phase error exceeds 10 ∘ .

scholarly journals Three-Dimensional Imaging Method for Array ISAR Based on Sparse Bayesian Inference

Sensors ◽  
2018 ◽  
Vol 18 (10) ◽  
pp. 3563
Author(s):  
Zekun Jiao ◽  
Chibiao Ding ◽  
Longyong Chen ◽  
Fubo Zhang
Keyword(s):  
Bayesian Inference ◽  
3D Imaging ◽  
Three Dimensional ◽  
Super Resolution ◽  
Information Criterion ◽  
Radar Data ◽  
Imaging Method ◽  
Model Order Selection ◽  
Imaging Model ◽  
Imaging Performance

The problem of synthesis scatterers in inverse synthetic aperture radar (ISAR) make it difficult to realize high-resolution three-dimensional (3D) imaging. Radar array provides an available solution to this problem, but the resolution is restricted by limited aperture size and number of antennas, leading to deterioration of the 3D imaging performance. To solve these problems, we propose a novel 3D imaging method with an array ISAR system based on sparse Bayesian inference. First, the 3D imaging model using a sparse linear array is introduced. Then the elastic net estimation and Bayesian information criterion are introduced to fulfill model order selection automatically. Finally, the sparse Bayesian inference is adopted to realize super-resolution imaging and to get the 3D image of target of interest. The proposed method is used to process real radar data of a Ku band array ISAR system. The results show that the proposed method can effectively solve the problem of synthesis scatterers and realize super-resolution 3D imaging, which verify the practicality of our proposed method.

Error estimation and bias correction in phase-improvement calculations

1999 ◽  
Vol 55 (9) ◽  
pp. 1555-1567 ◽  
Author(s):  
Kevin Cowtan
Keyword(s):  
Error Estimates ◽  
Error Estimation ◽  
Bayesian Methods ◽  
Bias Correction ◽  
Phase Error ◽  
Acta Cryst

With the rise of Bayesian methods in crystallography, the error estimates attached to estimated phases are becoming as important as the phase estimates themselves. Phase improvement by density modification can cause problems in this environment because the quality of the resulting phases is usually overestimated. This problem is addressed by an extension of the γ correction [Abrahams (1997). Acta Cryst. D53, 371–376] to arbitrary density-modification techniques. The degree to which the improved phases are biased by the features of the initial map is investigated in order to determine the limits of the resulting procedure and the quality of the phase-error estimates.

An Adaptive Phase Tracking Scheme of OFDM Wireless Communication System

2013 ◽  
Vol 336-338 ◽  
pp. 1798-1803
Author(s):  
Qian Du ◽  
Wen Wu Xie
Keyword(s):  
Kalman Filter ◽  
Wireless Communication ◽  
Channel Estimation ◽  
Error Estimation ◽  
Communication System ◽  
Phase Error ◽  
Basic Structure ◽  
Adaptive Kalman Filter ◽  
Phase Tracking ◽  
New Phase

This paper proposes a new phase tracking algorithm for the 802.11a system. Since this system illuminates the basic structure of 802.11a system, and introduces the OFDM frame generation principle based the transmitter, phase error estimation and channel estimation. On the basis of this, this paper presents a phase tracking scheme based on adaptive Kalman filter, and then simulates the process based on 802.11a system. The result indicates that the BER has been improved because of this adaptive phase tracking scheme.

scholarly journals Customizable live-cell imaging chambers for multimodal and multiplex fluorescence microscopy

2020 ◽  
Vol 98 (5) ◽  
pp. 612-623
Author(s):  
Adam Tepperman ◽  
David Jiao Zheng ◽  
Maria Abou Taka ◽  
Angela Vrieze ◽  
Austin Le Lam ◽  
...  
Keyword(s):  
Live Cell Imaging ◽  
Cell Imaging ◽  
Super Resolution ◽  
Live Cell ◽  
Imaging Modalities ◽  
Experimental Conditions ◽  
Microscopy Imaging ◽  
Glass Coverslip ◽  
Multiple Imaging ◽  
Microscopy Techniques

Using multiple imaging modalities while performing independent experiments in parallel can greatly enhance the throughput of microscopy-based research, but requires the provision of appropriate experimental conditions in a format that meets the optical requirements of the microscope. Although customized imaging chambers can meet these challenges, the difficulty of manufacturing custom chambers and the relatively high cost and design inflexibility of commercial chambers has limited the adoption of this approach. Herein, we demonstrate the use of 3D printing to produce inexpensive, customized, live-cell imaging chambers that are compatible with a range of imaging modalities, including super-resolution microscopy. In this approach, biocompatible plastics are used to print imaging chambers designed to meet the specific needs of an experiment, followed by adhesion of the printed chamber to a glass coverslip, producing a chamber that is impermeant to liquids and that supports the growth and imaging of cells over multiple days. This approach can also be used to produce moulds for casting microfluidic devices made of polydimethylsiloxane. The utility of these chambers is demonstrated using designs for multiplex microscopy, imaging under shear, chemotaxis, and general cellular imaging. Together, this approach represents an inexpensive yet highly customizable approach for producing imaging chambers that are compatible with modern microscopy techniques.

DOA and Phase Error Estimation for a Partly Calibrated Array With Arbitrary Geometry

2020 ◽  
Vol 56 (1) ◽  
pp. 497-511 ◽  
Author(s):  
Xuejing Zhang ◽  
Zishu He ◽  
Xuepan Zhang ◽  
Yue Yang
Keyword(s):  
Error Estimation ◽  
Phase Error ◽  
Arbitrary Geometry

scholarly journals Controlling the non-linear emission of upconversion nanoparticles to enhance super-resolution imaging performance

Nanoscale ◽  
2020 ◽  
Vol 12 (39) ◽  
pp. 20347-20355
Author(s):  
Simone De Camillis ◽  
Peng Ren ◽  
Yueying Cao ◽  
Martin Plöschner ◽  
Denitza Denkova ◽  
...  
Keyword(s):  
Super Resolution ◽  
Upconversion Nanoparticles ◽  
Non Linear ◽  
Resolution Imaging ◽  
Imaging Performance ◽  
Luminescence Characteristics

Convenient design of fully Yb-based upconversion nanoparticles enables control of their luminescence characteristics and enhances super-resolution imaging performance.

scholarly journals A Novel 2-D Geometry Reconstruction Approach for Space Debris via Interpolation-Free Operation under Low SNR Conditions

2020 ◽  
Vol 12 (12) ◽  
pp. 2059
Author(s):  
Xi Luo ◽  
Lixin Guo ◽  
Dong Li ◽  
Hongqing Liu ◽  
Mengyi Qin
Keyword(s):  
Signal To Noise Ratio ◽  
Computational Cost ◽  
Low Snr ◽  
Phase Errors ◽  
Isar Imaging ◽  
Key Issues ◽  
Imaging Mode ◽  
Imaging Performance ◽  
Low Computational Cost ◽  
Spinning Targets

Two unsolved key issues in inverse synthetic aperture radar (ISAR) imaging for non-cooperative rapidly spinning targets including high computational complexity and poor imaging performance in the case of low signal-to-noise ratio (SNR) are addressed in this work. In the strip-map imaging mode of SAR, it is well known that azimuth spatial invariant characteristics exist, and inspired by this, we propose a fast ISAR imaging approach for spinning targets. Our approach involves two steps. First, a precise analytic expression in the range-Doppler (RD) domain is produced using the principle of stationary phase (POSP). Second, a novel interpolation kernel function is designed to remove two-dimensional (2-D) spatial-variant phase errors, and the corresponding fast implementation steps that only require Fourier transform and multiplications are also presented. Finally, a well-focused ISAR image is obtained by compensating the azimuth high-order terms. Compared with current imaging methods, our approach avoids multi-dimensional search and interpolation operations and exploits the 2-D coherent integrated gain; the proposed method is of low computational cost and robustness in the low SNR condition. The effectiveness of the proposed approach is confirmed by numerically simulated experiments.

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