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interferometric array configuration design for the expected UV-plane coverage

OPTIK 2018年 158卷 1443-1449页

作者： Huang, Siyu Guo, Youming Rao, Changhui Chinese Acad Sci Inst Opt & Elect Chengdu 610209 Sichuan Peoples R China Chinese Acad Sci Key Lab Adapt Opt Chengdu 610209 Sichuan Peoples R China Univ Chinese Acad Sci Beijing 100049 Peoples R China

UV-plane coverage (UVPC) represents the distribution of spatial frequency sampling of the interferometric array. This paper focuses on designing an interferometric array configuration for the expected UVPC. The method presented uses the array that can entirely sample the expected UVPC points as the initial array, and gradually deletes apertures to obtain a final array. The advantage of the method is that it can design an array configuration for any expected UVPC and the distribution of the generated UVPC can be quite similar to the expected one. Two examples are given to present the feasibility of the method. (C) 2018 Elsevier GmbH. All rights reserved.

关键词： interferometric array array configuration design UV-plane coverage Removing apertures

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interferometric array Design Under Regularized Antenna Placements for Interference Suppression 10

Interferometric Array Design Under Regularized Antenna Place...

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10th IEEE Sensor array and Multichannel Signal Processing Workshop (SAM)

作者： Wang, Xiangrong Amin, Moeness Aboutanios, Elias Beihang Univ Sch Elect & Informat Engn Beijing Peoples R China Villanova Univ Ctr Adv Commun Villanova PA 19085 USA Univ New South Wales Sch Elect Engn Sydney NSW Australia

ISBN: (纸本)9781538647523

Interference suppression is an important task in extensive sensor array applications, including large interferometric arrays in radio astronomy. The interferometric array design in terms of maximizing output signal-to-interference-plus-noise ratio (MaxSINR) calls for freely placing antennas on grid points without imposing any regularity conditions on the array structure. The configured sparse array exhibits multiple drawbacks, most notably, uncontrollable beampatterns with high sidelobes. To overcome these shortcomings, we add conventional beampattern sidelobe constraints in the design formulation. The resulting array is referred to as restricted beampattern array configuration (RBAC). Alternatively, we consider a new regularized placement array configuration (RPAC) strategy, where antenna position constraints are imposed as means for sidelobe control. In this case, the antenna selection is performed such that each segment of grid points must include one antenna, preventing very large inter-element spacing. We formulate the new RPAC problem and compare its solution to that of the RBAC.

关键词： interferometric array Regularized Sensor Placement Sidelobe Suppression Beampattern

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Low-Rank EM-Based Imaging for Large-Scale Switched interferometric arrays

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IEEE SIGNAL PROCESSING LETTERS 2025年 32卷 41-45页

作者： Wang, Jianhua El Korso, Mohammed Nabil Bacharach, Lucien Larzabal, Pascal Univ Paris Saclay SATIE F-91190 Gif Sur Yvette France Univ Paris Saclay L2S F-91190 Gif Sur Yvette France

Interferences and computational cost pose significant challenges in large-scale interferometric sensing, impacting the accuracy and numerical efficiency of imaging algorithms. In this letter, we introduce an imaging algorithm using antenna switching based on expectation-maximization (EM) to address both challenges. By leveraging the low-rank noise model, our approach effectively captures interferences in interferometric data. Additionally, the proposed switching strategy between different sub-arrays reduces significantly the computational complexity during image restoration. Through extensive experiments on simulated datasets, we demonstrate the superiority of the low-rank noise model over the Gaussian noise model in the presence of interferences. Furthermore, we show that the proposed switching approach yields similar imaging performance with fewer antennas compared to the full array configuration, thereby reducing computational complexity, while outperforming non-switching configurations with the same number of antennas.

关键词： Imaging Switches Antennas Computational modeling Antenna arrays Vectors Signal processing algorithms Radio interferometry Correlation Computational complexity Antenna array processing Barankin bound Cramer-Rao bound EM algorithm interferometric array

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Realization of a kind of interferometric imaging telescope with four apertures 10

Realization of a kind of interferometric imaging telescope w...

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Conference on Ground-Based and Airborne Telescopes X

作者： Zhang, Congcong Chen, Xinyang Zheng, Lixin Zhou, Dan Wang, Chaoyan Ding, Yuanyuan Hadjara, Massinissa Shen, Lurun Chen, Zhendong Cai, Jianqing Wang, Qi Zhu, Nenghong Chinese Acad Sci Shanghai Astron Observ Shanghai Peoples R China Chinese Acad Sci Nanjing Inst Astron Opt & Technol Nanjing Peoples R China

ISBN: (纸本)9781510675117;9781510675124

The Fizeau type interferometric telescope forms an array of several sub telescopes for direct imaging on the image plane based on the principle of optical interferometry. Compared to the optical long baseline interferometer, this kind of telescope can be used for real time imaging of celestial body due to some excellent characteristics such as sufficient spatial frequencies coverage, single mounting avoiding outer optical delay lines and so on. We have built an interferometric imaging telescope with four apertures. Although each aperture size is 100mm, but this telescope can reach the higher angular resolution which is equivalent to a monolithic telescope of 280mm aperture size through optimal array configuration. Some novel opto-mechanical structure design and error control methods have been applied to this telescope successfully. For example, in order to enhance the rigidity of mechanical system, a unique C-shape structure to replace the traditional azimuth axis is adapted. Piston, tip/tilt errors between all apertures can be detected at the same time by extracting signals from Modulation Transfer Function (MTF), so some classical beam splitters can be removed which will reduce light loss significantly. At present, we have finished the final assembly, co-phasing calibration and verifying of dynamic co-phasing close-loop methods at laboratory. The FWHM of far field image spot is 0.43 arcsecond which is consistent with theoretical values. The out-door astronomical observation will be carried out soon.

关键词： optical telescope interferometric array piston error tip tilt error imaging

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Non-redundant array configurations for optical interferometric systems combined with a large telescope

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OPTIK 2019年 178卷 343-350页

In this paper, we propose a method to design the configuration of the interferometric array working with a large telescope. It limits the array configuration region and minimum aperture distance to make sure baseline length is in a certain interval. And it gives aperture locations by "push" and "pull" operations. The UV-plane coverage obtained from this method has the advantage that there is no overlap between UV-plane coverage from the interferometric array and the large aperture telescope, and the overall UV-plane coverage is non-redundant and symmetric. Specifically, design results with varying diameters of the large telescope are provided.

关键词： interferometric array UV-plane coverage Configuration design

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Analysis and Experimental Validation of Direction Finding Systems for ELINT Applications

Analysis and Experimental Validation of Direction Finding Sy...

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IEEE International Symposium on Phased array Systems and Technology (PAST)

作者： Marcantoni, Daniele Ardoino, Riccardo Foglia, Goffredo Elettronica SpA Res & Innovat Dept Via Tiburtina Valeria Km 13-7 Rome Italy

ISBN: (数字)9781665441667

ISBN: (纸本)9781665441667

The Direction Finding (DF) problem is well known in the Electronic Support Measures (ESM) and Electronic signal Intelligence (ELINT) applications domain. The capability to achieve a high accuracy estimation of the angle of arrival (AOA) can be obtained by using interferometric techniques at the expense of phase ambiguity and phase errors due to the receiver unbalances. The paper presents the design implementation and experimental results of interferometric systems with a focus on wide band applications.

关键词： Direction finding angle of arrival phase ambiguity interferometric array phase error

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A New Metric for Estimating the Disparity of Antenna Patterns in Synthetic Aperture Imaging Radiometry

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IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE SENSING 2020年 13卷 5800-5806页

作者： Anterrieu, Eric Palacin, Baptiste Costes, Laurent Ctr Etud Spatiales BIOsphere F-31400 Toulouse France Ctr Natl Etud Spatiales F-31400 Toulouse France Airbus Def & Space F-31400 Toulouse France

The soil moisture and ocean salinity (SMOS) satellite has provided for about ten years systematic passive L-band measurements from space. For several months, phase 0 studies are conducted by the French space agency for a second-generation high resolution (HR) follow-on mission. This contribution is making the connection between this SMOShr project and the SMOS mission by revisiting the following problematic: the impact of the disparity of the antenna patterns on the reconstruction floor error observed in the retrieved brightness temperatures. This impact is revisited in light of the progress made since that time and a new metric is introduced for estimating the disparity between antenna patterns. It would be helpful for the design of future missions based on imaging by aperture synthesis with interferometric arrays comprising a large number of antennas.

关键词： Antenna measurements Brightness temperature Antenna arrays Instruments Antenna radiation patterns Aperture antennas Antenna pattern aperture synthesis imaging radiometry interferometric array

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LOFAR Operations: Lessons Learned and Challenges 7

LOFAR Operations: Lessons Learned and Challenges

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Conference on Observatory Operations - Strategies, Processes, and Systems VII

作者： Pizzo, Roberto. F. Netherlands Inst Radio Astron Postbus 2 NL-7990 AA Dwingeloo Netherlands

ISBN: (数字)9781510619623

ISBN: (纸本)9781510619623

LOFAR is the World's largest radio telescope which combines signals from 51 phased array antenna stations distributed in The Netherlands and across Europe. It covers the largely unexplored low-frequency range from 10240 MHz and provides several unique observing capabilities. Every second, tens of gigabytes of data flow through a massive ICT infrastructure from the stations to the correlation facility located in the north of The Netherlands. The post-correlator raw data is further processed on a supercomputer through a variety of processing pipelines. Final data products are shared with the community through a distributed long-term archive system, which hosts the largest astronomical data collection to date. In order to exploit the new frequency regime with unprecedented resolution and sensitivity, LOFAR faces several non-trivial technical and operational challenges. These are presented and discussed in this paper, along with the important lessons learned which will be important reference for next generation observing facilities.

关键词： Telescope operations low radio frequencies interferometric array data quality control monitoring systems resource management data sharing observing efficiency

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The SKA: Recent Developments

The SKA: Recent Developments

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IEEE Radio and Antenna Days of the Indian Ocean (RADIO)

作者： Taylor, Russ Univ Cape Town Dept Astron Cape Town Western Cape South Africa Univ Western Cape Dept Phys Cape Town Western Cape South Africa

ISBN: (纸本)9789990373394

The Square Kilometre array (SKA) is a global project to design and construct the next-generation international radio telescope operating at metre to cm wavelengths. The SKA will be an interferometric array with a collecting area of up to one million square metres and maximum baseline of at least 3000 km, and is designed to address fundamental questions in cosmology, physics and astronomy. The key science goals range from the epoch of re-ionization, dark energy, the formation and evolution of galaxies and large-scale structure, the origin and evolution of cosmic magnetism, strong-field tests of gravity and detection of gravity waves. The SKA project is now in the final design for an SKA Observatory to begin to be built in the latter half of this decade that will include facilities in South Africa and Western Australia. Precursor telescopes of the 1% SKA scale are currently under construction at both sites and will begin early science observations in late 2016. Scientific operations of the first 10% scale phase of the SKA is targeted for 2020.

关键词： interferometry radiotelescopes SKA Observatory SKA project early science observations interferometric array next-generation international radio telescope precursor telescopes square kilometre array arrays Australia Gravity Imaging Magnetic field measurement Radio astronomy Telescopes RADIO TELESCOPES Telescopes radio astronomy Magnetic field measurement Gravity interferometry Square kilometre Imaging arrays Catchment area South Africa

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Active and passive coherent beam combining of thulium-doped fiber lasers

Active and passive coherent beam combining of thulium-doped ...

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Conference on High-Power Lasers and Applications V

作者： Zhou, Pu Wang, Xiaolin Ma, Yanxing Ma, Haotong Han, Kai Xu, Xiaojun Liu, Zejin Natl Univ Def Technol Coll Optoelect Sci & Engn Changsha 410073 Hunan Peoples R China

ISBN: (纸本)9780819483737

Thulium-doped fiber laser (TFL), which emitted near 2 mu m laser beam, has become the latest revolution in high-power fiber laser technology. Further increasing the output power will face great challenges induced by nonlinear effects;coherent beam combining of TFL can increase laser output power while simultaneously maintaining beam quality. In this manuscript, we will present our detailed investigation on coherent beam combining of TFLs. Three different approaches, i.e., interferometric array, mutual injection locking and active phasing based on multi-dithering technique, are employed. In the interferometric array scheme, coherent combining is realized by using an intracavity fiber coupler in an all-fiber laser array configuration. Efficient coherent combining can be achieved by providing sufficient loss discrimination. High combining efficiency of 85% for two fiber laser has been obtained. In mutual injection locking scheme, mutual coherence between the two fiber lasers is established by means of mutual coupling through two 3dB couplers. High combining efficiency of 99% for two fiber laser has been obtained, and the fringe contrast of the intensity pattern at the receiving plane is as high as 93%. In active phasing scheme, when the phase control system is in the closed loop, the fringe contrast of far-field intensity pattern is improved by more than 75 % from 10 % in open loop, and the residual phase error is less than lambda/20.

关键词： Thulium-doped fiber laser coherent beam combining interferometric array mutual injection locking multi-dithering

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