Wideband Image Research Articles

MeerKAT discovery of a double radio relic and odd radio circle: connecting cluster and galaxy merger shocks

Abstract We present the serendipitous discovery of (1) a large double radio relic associated with the galaxy cluster PSZ2 G277.93+12.34 and (2) a new odd radio circle, ORC J1027–4422, both found in the same deep MeerKAT 1.3 GHz wide-band radio continuum image. The angular separation of the two arc-shaped cluster relics is ∼16′ or ∼2.6 Mpc for a cluster redshift of z ≈ 0.158. The thin southern relic, which shows several ridges/shocks including one possibly moving inwards, has a linear extent of ∼1.64 Mpc. In contrast, the northern relic is about twice as wide, twice as bright, but only has a largest linear size of ∼0.66 Mpc. Complementary SRG/eROSITA X-ray images reveal extended emission from hot intracluster gas between the two relics and around the narrow-angle tail (NAT) radio galaxy PMN J1033–4335 (z ≈ 0.153) located just east of the northern relic. The radio morphologies of the NAT galaxy and the northern relic, which are also detected with the Australian Square Kilometer Array Pathfinder (ASKAP) at 888 MHz, suggest both are moving in the same outward direction. The discovery of ORC J1027–4422 in a different part of the same MeerKAT image makes it the 4th known single ORC. It has a diameter of ∼90″ corresponding to 400 kpc at a tentative redshift of z ≈ 0.3 and remains undetected in X-ray emission. Supported by simulations, we discuss similarities between outward moving galaxy and cluster merger shocks as the formation mechanisms for ORCs and radio relics, respectively.

A 0.45‐V low‐power low‐noise amplifier using a wideband image‐rejection technology

AbstractA 0.45‐V low‐power wideband image‐rejection low‐noise amplifier (LNA) using Taiwan Semiconductor Manufacturing Company (TSMC) 0.18‐μm CMOS process has been proposed. The supply voltage, power consumption and chip area of the proposed LNA can be reduced using forward body biasing, folded cascode topology and a feedback capacitor. Moreover, a wideband gain‐enhancement‐and‐image‐rejection (WGEIR) circuit including a variable resonant LC tank and a common‐gate amplifier has been developed. The inductance of the variable resonant LC tank can enlarge the gain of the proposed LNA. The capacitance of the variable resonant LC tank can achieve the image rejection. Using the WGEIR circuit, gain enhancement and wideband image rejection can be achieved simultaneously. The variable inductors and capacitors are developed for suppressing wideband image signals and good image rejection ratio (IRR). The combination of the variable inductors and capacitors can achieve eight image‐reject frequencies under three control voltages. The proposed LNA shows the measured results including a 10‐dB power gain, a 3‐dB noise figure (NF) and a −11‐dBm input third‐order intercept point (IIP3) at 2.4 GHz, respectively. The measured IRR ranges from 18 to 23 dBc around 3.6–4.5 GHz, which is 900‐MHz image‐reject bandwidth. The measured proposed LNA using the mentioned techniques consumes 0.8‐mW power.

Parallel faceted imaging in radio interferometry via proximal splitting (Faceted HyperSARA) – II. Code and real data proof of concept

ABSTRACT In a companion paper, a faceted wideband imaging technique for radio interferometry, dubbed Faceted HyperSARA, has been introduced and validated on synthetic data. Building on the recent HyperSARA approach, Faceted HyperSARA leverages the splitting functionality inherent to the underlying primal-dual forward-backward algorithm to decompose the image reconstruction over multiple spatio-spectral facets. The approach allows complex regularization to be injected into the imaging process while providing additional parallelization flexibility compared to HyperSARA. This paper introduces new algorithm functionalities to address real data sets, implemented as part of a fully fledged matlab imaging library made available on GitHub. A large-scale proof of concept is proposed to validate Faceted HyperSARA in a new data and parameter scale regime, compared to the state of the art. The reconstruction of a 15 GB wideband image of Cyg A from 7.4 GB of Very Large Array data is considered, utilizing 1440 CPU cores on a high-performance computing system for about 9 h. The conducted experiments illustrate the reconstruction performance of the proposed approach on real data, exploiting new functionalities to leverage known direction-dependent effects, for an accurate model of the measurement operator, and an effective noise level accounting for imperfect calibration. They also demonstrate that, when combined with a further dimensionality reduction functionality, Faceted HyperSARA enables the recovery of a 3.6 GB image of Cyg A from the same data using only 91 CPU cores for 39 h. In this setting, the proposed approach is shown to provide a superior reconstruction quality compared to the state-of-the-art wideband clean-based algorithm of the wsclean software.

Parallel faceted imaging in radio interferometry via proximal splitting (Faceted HyperSARA): I. Algorithm and simulations

ABSTRACTUpcoming radio interferometers are aiming to image the sky at new levels of resolution and sensitivity, with wide-band image cubes reaching close to the petabyte scale for SKA. Modern proximal optimization algorithms have shown a potential to significantly outperform clean thanks to their ability to inject complex image models to regularize the inverse problem for image formation from visibility data. They were also shown to be parallelizable over large data volumes thanks to a splitting functionality enabling the decomposition of the data into blocks, for parallel processing of block-specific data-fidelity terms involved in the objective function. Focusing on intensity imaging, the splitting functionality is further exploited in this work to decompose the image cube into spatiospectral facets, and enables parallel processing of facet-specific regularization terms in the objective function, leading to the ‘Faceted HyperSARA’ algorithm. Reliable heuristics enabling an automatic setting of the regularization parameters involved in the objective are also introduced, based on estimates of the noise level, transferred from the visibility domain to the domains where the regularization is applied. Simulation results based on a matlab implementation and involving synthetic image cubes and data close to gigabyte size confirm that faceting can provide a major increase in parallelization capability when compared to the non-faceted approach (HyperSARA).

Illuminant Adaptive Wideband Image Synthesis Using Separated Base-Detail Layer Fusion Maps

In this study, we present a wideband image synthesis technique for day and night object identification. To synthesize the visible and near-infrared images, a base component and a detailed component are first decomposed using a bilateral filter, and the detailed component is synthesized using a local variance map. In addition, considering the difference in the near-infrared image characteristics between daytime and nighttime, the base components are synthesized using a luminance saturation region map and depth and penetration map using a joint bilateral filter. The proposed method overcomes the partial over- or under-exposure caused by sunlight and infrared auxiliary light, which is experienced variously in wideband imaging, and improves the identification of objects in various indoor and outdoor images compared with that achieved by existing methods by emphasizing detailed components.

Bio-inspired spherical compound eye camera for simultaneous wide-band and large field of view imaging.

Natural compound eyes have excellent optical characteristics, namely large field of view, small size, no aberration, and sensitive to motion. Some arthropods have more powerful vision. For example, the Morpho butterfly's compound eyes can perceive the near-infrared and ultraviolet light that the human eye cannot see. This wide-band imaging with a large field of view has great potential in wide-area surveillance, all-weather panoramic imaging, and medical imaging. Hence, a wide-band spherical compound eye camera inspired by the Morpho butterfly's eye was proposed. The wide-band spherical compound eye camera which can achieve a large field of view (360° × 171°) imaging over a wide range of wavelengths from 400nm to 1000nm, mainly consists of three parts: a wide-band spherical compound eye with 234 sub-eyes for light collection, a wide-band optical relay system for light transmission, and a wide-band CMOS image sensor for photoelectric conversion. Our experimental results show that the wide-band spherical compound eye camera not only captures a large field of view without anomalous blurring or aberrations but also perceives near-infrared light that is not recognized by the human eye. These features make it possible for distortion-free panoramic vision and panoramic medical diagnosis.

Accuracy of narrow-band spectral indices estimation by wide-band remote sensing data

Narrow-band spectral indices are quite informative and important in various applications of remote sensing – to assess the condition of vegetation, soils, water bodies and other land surface formations. However, direct measurement of narrow-band spectral indices requires hyperspectral imaging. But most of modern multispectral aerospace imaging systems are wide-band. Accordingly, it is not possible to calculate the narrow-band index directly from wide-band remote sensing data. This paper discusses approaches to the narrow-band spectral indices restoration by wide-band remote sensing data using statistical models of interrelations of narrow- and wide-band indices itself, of source wide-band and narrow-band signals in close spectral bands, as well as of land surface reflectance quasi-continuous spectra translation from wide bands to narrow ones.The experimental accuracy estimation of narrow-band spectral indices restoration by wide-band multispectral satellite image is performed. Three most complicated narrow-band spectral indices, which covering a range of spectrum from visible to short-wave infrared, were considered, namely – the transformed chlorophyll absorption in reflectance index (TCARI), the optimized soil-adjusted vegetation index (OSAVI) and the normalized difference nitrogen index (NDNI). All three mentioned methods for narrow-band spectral indices restoration are analyzed. The worst result is demonstrated for regression-restored signals in spectral bands, and the best result is for the spectra translation method. Therefore, the method on the basis of spectra translation is recommended for practical implementation.

Radar sensing of the sea surface using small spacecraft

The possibility of using a constellation of small spacecraft as receiving satellites, when “highlighting” the sea surface from existing (navigational, communication) or specially created spacecraft—to form a wide-area (about 1 000 km) radar survey zone at a given resolution (about 10 m)—is under consideration. Such a constellation could provide operational monitoring of fast-moving atmospheric cyclones, measuring directly the parameters of storm waves (altitude and orbital velocity)—which would replace the existing constellation of microwave scatterometers, providing operational monitoring of the World Ocean surface in the 3 H (H—altitude of the satellite’s orbit) field of view with a resolution of about 10 km—but with calibration of the received images by wind speed and direction, which leads to huge errors when trying to introduce altitude calibration in the Small spacecraft have many advantages over large satellites. For example, they are relatively inexpensive to build, take minimal time from design to launch, are easily modified to solve a specific problem, and create less radio interference. The approach under consideration consists in redistribution of tasks to be solved between the constellation of satellites in orbit. High orbiting navigation satellites, for example, can be used as transmitter carriers (of the illumination of the surface) that use the necessary broadband signal with acceptable periodicity. Receivers of reflected signals are placed on board small spacecraft, and at formation of wide-band radar image of sea surface with necessary resolution ∼10 m (that only on order exceeds acceptable on small spacecraft size of receiving antennas)—in flight direction is necessary to use synthesized aperture of receiving antenna. This work has the character of “staged” research.

Anti-interference small target tracking from infrared dual waveband imagery

For infrared small target detection and tracking, the challenge mainly contains dim targets, cluttered background, and infrared decoys. In the face of the above difficulties, traditional tracking algorithms focus on utilizing information of a single waveband is difficult to achieve good performance. In this paper, a tracking algorithm, which combines the Kernelized Correlation Filter (KCF) with a detection model, is presented to cope with these challenges on dual waveband imagery. Firstly, the Side Window Box Filter (SWBF) is utilized to suppress the background edge in the wide-band image, which contains much more detail than that in narrow-band image. Therefore, several filters are obtained in the first wide-band image processed by the SWBF. Subsequently, fused features for the KCF algorithm can be computed via convolution operation. In order to solve the migration problem referring to decoys, a detection model based on multi-frame association and image correlation is introduced to refind the target. Finally, experimental results demonstrate that the presented algorithm outperforms several relative algorithms in the accuracy and robustness. Besides, the multi-source information leads to improve the performance of tracking methods.

A Fully Integrated K-Band Dual Down-Conversion Receiver for Radar Applications in 90 nm CMOS

A fully integrated K-band dual down-conversion receiver for phased array radar applications in 90 nm CMOS is presented. The receiver utilizes the dual down-conversion architecture to achieve superior performance. The integrated 1.15 GHz image-rejection filter (IRF) provides enough wideband (22 MHz) image rejection ratio at 140 MHz offset before the second down-conversion by utilizing the Q-enhancing and frequency staggering techniques to compensate the component loss. The low noise amplifier realizes the single-to-differential-ended conversion at the input with a transformer and achieves good common-mode rejection. The 70 MHz intermediate frequency baseband consists of two cascaded 3rd-order band-pass active RC filters (BPFs) and one automatic gain control (AGC) loop, with the integrator frequency compensation technique to lower down the requirements on the embedded Op-Amps. Two phase-locked loop (PLL) frequency synthesizers are integrated to provide the local oscillation (LO) signals for the down-conversions, where the matching of the charge-pump is improved by adding one extra current compensation branch. The measurements of the prototype show that the receiver converts the targeted mm-wave signal to 70 MHz intermediate frequency while achieving 8.3 dB noise figure (NF), 51-95 dB variable gain range and >45 dB image rejection ratio at 140 MHz offset with >22 MHz signal bandwidth. The receiver draws 74 mA current (excluding 2 PLLs) from the 1.2 V power supplies and occupies a core area of 4.58 × 0.53mm 2 (excluding 2 PLLs).

Wideband super-resolution imaging in Radio Interferometry via low rankness and joint average sparsity models (HyperSARA)

ABSTRACT We propose a new approach within the versatile framework of convex optimization to solve the radio-interferometric wideband imaging problem. Our approach, dubbed HyperSARA, leverages low rankness, and joint average sparsity priors to enable formation of high-resolution and high-dynamic range image cubes from visibility data. The resulting minimization problem is solved using a primal-dual algorithm. The algorithmic structure is shipped with highly interesting functionalities such as preconditioning for accelerated convergence, and parallelization enabling to spread the computational cost and memory requirements across a multitude of processing nodes with limited resources. In this work, we provide a proof of concept for wideband image reconstruction of megabyte-size images. The better performance of HyperSARA, in terms of resolution and dynamic range of the formed images, compared to single channel imaging and the clean-based wideband imaging algorithm in the wsclean software, is showcased on simulations and Very Large Array observations. Our matlab code is available online on github.

Piston sensing of sparse aperture systems with a single broadband image via deep learning.

The pistons of sparse aperture systems need to be controlled within a fraction of a wavelength for the system's optimal imaging performance. In this paper, we demonstrate that deep learning is capable of performing piston sensing with a single wide-band image after appropriate training. Taking the sensing issue as a fitting task, the deep learning-based method utilizes a deep convolutional neural network to learn complex input-output mapping relations between the broadband intensity distributions and corresponding piston values. Given a trained network and one broadband focal intensity image as the input, the piston can be obtained directly and the capture range achieving the coherence length of the broadband light is available. Simulations and experiments demonstrate the validity of the proposed method. Using only in-focused broadband images as the inputs without defocus division and wavelength dispersion, obviously relaxes the optics complexity. In view of the efficiency and superiority, it's expected that the method proposed in this paper may be widely applied in multi-aperture imaging.

Analysis of Local Climate Variations Using Correlation between Satellite Measurements of Methane Emission and Temperature Trends within Physiographic Regions of Ukraine

Paper aimed to the description of the methods of analysis and measurements of atmospheric greenhouse gases (GHG), especially, methane concentration using satellite tools for climate change model improvement. The experimental accuracy estimation of narrow-band spectral indices restoration by the wide-band multispectral image is performed. Three methods for narrow-band spectral indices restoration are analyzed. The method on the basis of spectra translation is recommended for practical application.

A High-Fractional-Bandwidth, Millimeter-Wave Bidirectional Image-Selection Architecture With Narrowband LO Tuning Requirements

An image-selection, two-element transceiver is presented that operates over a large fractional bandwidth (FBW) covering both 71–76 and 81–86 GHz while requiring only 3 GHz of local oscillator (LO) tuning range at the RF mixer. A bidirectional sliding-intermediate frequency (IF) Weaver architecture allows operation in either transmit (TX) or receive (RX) modes. The sliding IF and narrow LO tuning range allow wideband image rejection using only a single-stage polyphase filter. The circuit is implemented in a 90-nm SiGe BiCMOS process and the RF and LO circuitry consume at most 150 and 250 mW, respectively. Measurements show less than ±0.75-dB gain variation over 10 GHz in the TX mode and less than ±1-dB variation over 10-GHz bandwidth in the RX mode. With 16- and 64-quadrature-amplitude modulation (QAM), the error vector magnitude is below −22 and −28.5 dB at the data rates of 12 and 9 Gb/s, respectively.

Suzaku and Chandra observations of CIZA J1700.8−3144, a cluster of galaxies in the Zone of Avoidance

Abstract We present the Chandra and Suzaku observations of 1RXS J170047.8−314442, located towards the Galactic bulge, to reveal a wide-band (0.3–10 keV) X-ray morphology and spectrum of this source. With the Chandra observation, no point source was found at the position of 1RXS J170047.8−314442. Instead, we revealed the presence of diffuse X-ray emission, via the wide-band X-ray image obtained from the Suzaku XIS. Although the X-ray emission had a nearly circular shape with a spatial extent of ∼3${^{\prime}_{.}}$5, the surface brightness profile was not axisymmetric; a bright spot-like emission was found at ∼ 1΄ away in the northwestern direction from the center. The radial profile of the surface brightness, except for this spot-like emission, was reproduced with a single β-model; β and the core radius were found to be 1.02 and 1${^{\prime}_{.}}$51, respectively. The X-ray spectrum of the diffuse emission showed an emission line at ∼6 keV, indicating an origin of a thermal plasma. The spectrum was well explained with an absorbed, optically-thin thermal plasma model with a temperature of 6.2 keV and a redshift parameter of z = 0.14 ± 0.01. Hence, the X-ray emission was considered to arise from the hot gas associated with a cluster of galaxies. Our spectroscopic result confirmed the optical identification of 1RXS J170047.8−314442 by Kocevski et al. (2007, ApJ, 662, 224): CIZA J1700.8−3144, a member of the cluster catalogue in the Zone of Avoidance. The estimated bolometric X-ray luminosity of 5.9 × 1044 erg s−1 was among the lowest with this temperature, suggesting that this cluster is far from relaxed.

Design and investigation of UV image detectors

The results of investigation of optical image detectors designed for the largest problem, near-VUV, range of the spectrum are presented. The possibility of using a dual-stage image detection system to appreciably lower the sensitivity threshold and make computer data processing feasible is considered. The integration of a UV module into a wideband image detector is studied.

High Performance Millimeter-Wave Image Reject Low-Noise Amplifier Using Inter-stage Tunable Resonators

A Q-band pHEMT image-rejection low-noise amplifier (IR-LNA) is presented using inter-stage tunable resonators. The inter-stage L-C resonators can maximize an image rejection by functioning as inter-stage matching circuits at an operating frequency () and short circuits at an image frequency (). In addition, it also brings more wideband image rejection than conventional notch filters. Moreover, tunable varactors in L-C resonators not only compensate for the mismatch of an image frequency induced by the process variation or model error but can also change the image frequency according to a required RF frequency. The implemented pHEMT IR-LNA shows 54.3 dB maximum image rejection ratio (IRR). By changing the varactor bias, the image frequency shifts from 27 GHz to 37 GHz with over 40 dB IRR, a 19.1 dB to 17.6 dB peak gain, and 3.2 dB to 4.3 dB noise figure. To the best of the authors' knowledge, it shows the highest IRR and of the reported millimeter/quasi-millimeter wave IR-LNAs.

A wideband on-chip millimeter-wave patch antenna in 0.18 μm CMOS

A wideband on-chip millimeter-wave patch antenna in 0.18 μm CMOS with a low-resistivity (10 Ω·bm) silicon substrate is presented. The wideband is achieved by reducing the Q factor and exciting the high-order radiation modes with size optimization. The antenna uses an on-chip top layer metal as the patch and a probe station as the ground plane. The on-chip ground plane is connected to the probe station using the inner connection structure of the probe station for better performance. The simulated S11 is less than −10 dB over 46–95 GHz, which is well matched with the measured results over the available 40–67 GHz frequency range from our measurement equipment. A maximum gain of −5.55 dBi with 4% radiation efficiency at a 60 GHz point is also achieved based on Ansoft HFSS simulation. Compared with the current state-of-the-art devices, the presented antenna achieves a wider bandwidth and could be used in wideband millimeter-wave communication and image applications.

Classification of visible point sources using hyperspectral chromotomosynthetic imagery

A hyperspectral chromotomosynthetic imaging (CTI) system is used to detect and classify a collection of 21 scattered, spectrally diverse point-like sources. The instrument operates in the visible to near IR (400 to 800 nm) and has the potential to collect spectral imagery at great than 10 Hz. A two-dimensional wideband spatial image of the target scene is used to detect and spatially characterize the targets leading to optimization of the three-dimensional (3-D) spatial/spectral reconstruction of the hyperspectral image cube. The instrument is assessed by directly comparing results to spatial data collected by a wideband image and hyperspectral data collected using a liquid crystal tunable filter (LCTF). Target classification using k-means clustering of observed spectra yielded 5 to 6 target classes for each methodology, indicating information obtained using CTI was similar to that collected by the LCTF. The wide-band spatial content of the scene reconstructed from the CTI data is of same or better quality in terms of background noise and target intensities as a single frame collected by the undispersed imaging system with projections taken at every 1 deg. Performance is dependent on the number of projections used, with projections at 5 deg producing adequate results in terms of target characterization. The CTI has 2 to 4 times the spectral resolution of the LCTF. The data collected by the CTI system can simultaneously provide spatial information of equal quality as a the bandpass imaging system, provide high-frame rate slitless one-dimensional spectra, and generate 3-D hyperspectral imagery which can be exploited to provide the same results as a traditional multiband spectral imaging system.

SpIOMM and SITELLE: Wide-field Imaging FTS for the Study of Galaxy Evolution

AbstractSpIOMM, a wide-field Imaging Fourier Transform Spectrometer attached to the Mont Mégantic 1.6-m telescope, is capable of obtaining the visible spectrum of every source of light in a 12 arcminute field of view, with a spectral resolution ranging from R = 1 (wide-band image) to R = 25 000, resulting in 1.7 million spectra with a spatial resolution of one arcsecond. SITELLE will be a similar instrument attached to the Canada-France-Hawaii telescope, and will be in operation in early 2013. We present a short description of these instruments and illustrate their capabilities to study nearby galaxies with the results of a data cube of M51.