Large Phased Array Research Articles

Pushchino multibeam pulsar search – I. Targeted search of weak pulsars

ABSTRACT The search for pulsars in a sample of pulsar candidates found based on a multi-year survey conducted with low (six channels; sampling 0.1s) time-frequency resolution on declinations −9° < δ < +42° was carried out with the Large Phased Array of the Lebedev Physical Institute (LPA LPI). LPA is a transit telescope operating at 111 MHz with a bandwidth of 2.5 MHz. Search, analysis and evidence of pulsar detection were carried out using a visualization programme of summed up power spectra obtained from the survey data with high (32 channels; sampling 12.5 ms) time-frequency resolution. 11 new pulsars with periods P0 = 0.41–3.75 s and dispersion measure DM = 15–154 pc cm−3 have been discovered. In total, in the survey with a low-time-frequency resolution for the period 2016–2021 in a blind search 203 pulsars were found, among them 42 new and 161 known pulsars. It is shown that in the search on the data with high-time-frequency resolution accumulated over a time interval of seven years, pulsars with a flux density of 0.1–0.2 mJy at the frequency of 111 MHz can be detected. When searching for pulsars with regular (periodic) emission at declinations +21° < δ < +42o, all pulsars located outside the galactic plane having P0 ≥ 0.5 s, DM ≤ 100 pc cm−3, and the flux density S ≥ 0.5 mJy can be detected.

Revisiting the Pushchino RRAT search using a neural network

The search for rotating radio transients (RRAT) at declinations from −9° to +42° was carried out based on the semi-annual monitoring data obtained on the Large Phased Array (LPA) radio telescope at a frequency of 111 MHz. A neural network was used to search for candidates. Four new RRATs were detected; they have dispersion measures of 5–16 pc cm−3. A comparison with an earlier RRAT search that was conducted using the same data shows that the neural network reduced the amount of interference by 80 times. It is now down to 1.3% of the initial amount of interference. The loss of real pulsar pulses does not exceed 6% of their total number.

Ultrasonic Testing in Nuclear Plants

The approach for nondestructive testing inspections in nuclear power plants differs significantly from nonnuclear industries. In most industries, inspections are planned and specified by owners or insurance companies. Nuclear plant inspections are, however, regulated and must follow certain processes, regulatory requirements, and required codes. Codes classify components and specify inspection methods, coverage, and inspection intervals. With regard to ultrasonic testing (UT), there is a broad range of applications for nuclear plant components. Applications vary from simple corrosion/erosion scanning to more complex techniques that require UT of difficult-to-inspect materials. These include dissimilar metal welds of materials such as stainless steel, nickel alloy, and cast stainless steels. In addition, UT inspection can include tests of complex geometries such as nozzles and turbines. Furthermore, due to the nature of the nuclear plant operation, the inspection processes must be demonstrated to validate reliability and qualify equipment and personnel. Finally, this article highlights the importance of using notches as calibration reflectors when using refracted longitudinal waves and large aperture phased array probes to improve resolution.

A high‐precision and fast off‐line beamforming pattern estimation technique for active phased array antenna application

A detailed modeling method including all states of each active devices is proposed in this work, aiming to achieve high-precision and fast off-line estimation of beamforming pattern. Experimental verification of hundreds of radiating patterns shows that the beam steering angle accuracy is able to obtain 0.2% (Tx mode) and 0.19% (Rx mode) beam width in average, respectively; and the beam width accuracy is 0.2% (Tx mode) and 0.39% (Rx mode) in average, respectively. Also, SLL accuracy can reach 0.01 dB (Tx mode) and 0.1 dB (Rx mode), respectively. By adopting this technology, the optimal beam controlling codes of large active phased array antenna (APAA) could be quickly derived. Furthermore, measurement and online compensation works of enormous quantities of beams could be greatly simplified.

Low-frequency observations of giant pulses from ordinary pulsars

ABSTRACTWe present the results of an investigation of the giant radio pulse (GRP) generation rate from five radio pulsars (B0301+19, B0950+08, B1112+50, B1133+16, and B1237+25) and anomalous intensity pulse generation rate from B0809+74. All data used were obtained with the Large Phased Array radio telescope at the Pushchino Radio Astronomy Observatory at 111 MHz from 2012 to 2021. In addition to the analysis of the rate of generation of bright pulses, we analyse the distribution of bright pulses in the phase of the pulsar period and search for clusters of bright pulses – several bright pulses emitted in adjacent pulsar periods. It is found that pulsars B0301+19, B1112+50, B1133+16, and B1237+25 demonstrate different generation rates and generation of clusters. Pulsar B1112+50 generates GRP clusters more often than the other pulsars studied. The longest cluster of GRPs containing four single pulses is detected from this pulsar. GRPs from the pulsars studied are distributed along the longitudes of the main components of the average pulses of these pulsars. This distribution is 1.5–2 times narrower than the phase distribution of non-giant pulses. It is found that the distance between the components of the average GRP profile and the distance between the components of the average non-giant profile differ substantially for pulsars with multicomponent average profiles.

Conceptual design of cryostat for cryo-cooled 37 elements phased array radar system for space surveillance

The amount of space debris orbiting the earth is increasing. More than 700 000 objects with critical sizes of more than 1 cm have the potential to cause severe damage to space-based infrastructure. Improving the sensitivity of next generation space surveillance RADARs is necessary for the ability to detect space debris with sizes down to 1 cm. For a successful detection, a key parameter is the signal-to-noise ratio (SNR). Therefore the Fraunhofer Institute for High Frequency Physics and Radar Technique (FHR) analyses cryogenic cooled receivers for space surveillance RADAR systems. In addition to electrical frequency, the requirements of a mechanical design for a large cryo-cooled phased array receiver is challenging. In previous papers, an interim stage 7-element cryogenic receiver with cold antennas was mentioned as well as first studies of a scalable RF unit cell. The present paper shows the prototype and first results of a 37 – element phased array receiver, based on simulations. The design of a cryogenic phased array requires thermal and mechanical simulations in consideration with the modular design concept including the scalable unit cell. Referring to the German Space Surveillance Tracking RADAR (GESTRA) operating in L-band leads to the large receiver size due to the free-air wavelength of 23 cm. This paper presents our approach in the design of a 37 cryogenic phased array. It presents the simulation with focus on thermal transitions, heat loads and mechanical stress.

Dual Polarization and Bi-Directional Silicon-Photonic Optical Phased Array With Large Scanning Range

We propose a large scanning range silicon optical phased array (OPA), which is polarization multiplexed and bi-directional with only one waveguide grating antenna array. Mach-Zehnder interferometers (MZIs) and polarization splitter-rotator (PSR) are utilized to select the polarization states and propagation directions of the input light to the waveguide grating emitter array. By optimizing the parameters of the waveguide grating, the longitudinal far-field steering range is increased by four times compared to that of the conventional ones among the same wavelength range. The simulation results show that the 54.5° longitudinal scanning range could be realized with the tuning wavelength ranging from 1500 nm to 1600 nm. The high wavelength tuning efficiency is up to 0.545 °/nm. The beam steering range in the lateral direction is 77.8° via phase tuning.

Phase-only transmit beampattern design for large phased array antennas with multi-point nulling

Phase-only transmit beampattern design for large phased array antennas with multi-point nulling

MmWrite: Passive Handwriting Tracking Using a Single Millimeter-Wave Radio

In the era of pervasively connected and sensed Internet of Things, many of our interactions with machines have been shifted from conventional computer keyboards and mouses to hand gestures and writing in the air. While gesture recognition and handwriting recognition have been well studied, many new methods are being investigated to enable pervasive handwriting tracking. Most of the existing handwriting tracking systems either require cameras and handheld sensors or involve dedicated hardware restricting user convenience and the scale of usage. In this article, we present mmWrite, the first high-precision passive handwriting tracking system using a single commodity millimeter-wave (mmWave) radio. Leveraging the short wavelength and large bandwidth of 60-GHz signals and the radar-like capabilities enabled by the large phased array, mmWrite transforms any flat region into an interactive writing surface that supports handwriting tracking at millimeter accuracy. MmWrite employs an end-to-end pipeline of signal processing to enhance the range and spatial resolution limited by the hardware, boost the coverage, and suppress interference from backgrounds and irrelevant objects. We implement and evaluate mmWrite on a commodity 60-GHz device. The experimental results show that mmWrite can track a finger/pen with a median error of 2.8 mm and thus can reproduce handwritten characters as small as 1 cm × 1 cm, with a coverage of up to 8 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> supported. With minimal infrastructure needed, mmWrite promises ubiquitous handwriting tracking for new applications in the field of human-computer interactions.

Accelerating Simulations of Large Scale Phased-Array Systems

Next generation wireless communications systems operating at millimeter-wave frequencies are utilizing phased arrays of increasing electrical size to overcome path loss. The size of these arrays can make simulations become infeasible due to the amount of computation and memory required. Here we discuss parallelization and hardware acceleration methods to overcome these obstacles for large scale phased array systems. The acceleration of these methods was quantified using an orthogonal frequency division multiplexing frequency-domain simulator.

Two‐dimensional adaptive beamforming for large planar array antennas based on weight matrix reconstruction

Adaptive beamformers at the element level usually require a great number of training samples and the computational cost for calculating the weight vector for large phased array antennas is very high, which make it difficult for real-time applications. To address this problem, a two-dimensional (2-D) adaptive beamformer applicable to large planar array antennas that have low computational complexity and low training sample requirement is proposed. In the proposed method, the weight matrix is first reconstructed as a matrix that has the same or close columns and rows by utilising the special Kronecker property of the array steering matrix. Then, the weight vector is determined by adopting a bi-quadratic cost function and a bi-iterative algorithm. Experimental results show that the proposed method can achieve fairly good performance even when the training samples are small.

Compact 2 × 2 Circularly Polarized Aperture-Coupled Antenna Array for Ka-Band Satcom-on-the-Move Applications

This paper presents a novel design of a wideband circular polarization 2 × 2 microstrip antenna array working at Ka-band frequencies, from 27.5 to 31 GHz. This module is highly integrable with new silicon beamformer chips, creating a unit cell that can be part of a large electronically steerable antenna for compact, ultra-low-profile, Satcom-on-the-move (SOTM) platforms. A multi-layer structure fabricated in standard printed circuit board (PCB) technology with high-yield substrates has been used. The radiating elements consist of double-stacked circular patches housed in a cavity and fed by H-shaped aperture coupling. It achieves a bandwidth of 16.5 % with a wide beam-width of 95° in the desired band, which is necessary for wide scanning angles in a large phased array. In the 2 × 2 unit cell, the antenna elements are distributed by means of a sequential rotation technique where the separation between two of them is 5.3 mm in the XY-plane. Broadside beam-widths ranging from 53.4° at 27.5 GHz to 42.1° at 31 GHz are achieved, with boresight directivities from 10.7 to 12.9 dBi, respectively, in both the RHCP and LHCP polarization. Moreover, mutual coupling levels below −20 dB and an axial ratio less than 3 dB in the whole band guarantee a good circular polarization purity.

Array of Arrays: Optimizing Phased Array Tiles

This letter discusses some of the challenges for realizing large millimeter-wave phased array antennas using multiple scalable arrays (tiles). The letter uses the radiation pattern multiplication and the array of arrays concepts to analyze the effect of the tiling gap on the large array radiation pattern. Different techniques to mitigate the performance deterioration due to the tiling gap are proposed and analyzed. The proposed methods use either the elements’ spacing, or the amplitude excitation to minimize the tiling impact on the array performance.

Intersymbol Interference and Equalization for Large 5G Phased Arrays With Wide Scan Angles

Intersymbol interference (ISI) is introduced in a phased array when the beam is scanned. The cause of the ISI is demonstrated and its dependence on the phased array dimensions, scan angle, and symbol rate is derived. A mathematical model is created to simulate the ISI effects on transmitted (or received) symbols, and an equalizer model is introduced and achieves near-perfect equalization of the ISI. Also, for wideband signals, it is shown that large phased arrays result in amplitude modulation versus frequency. The effect of ISI on the error vector magnitude (EVM) is simulated using complex modulated signals, and the EVM before and after equalization is compared, using an adaptive 17-tap linear equalizer implemented in MATLAB. The results show that ISI in large phased arrays can be equalized regardless of the modulation, bandwidth, scan angle, and symbol rate. The EVM of 16-, 64-, and 256-quadrature amplitude modulation (QAM) signals is measured for a 256-element array in the transmit mode. The measurements verify the derivations, eliminating ISI and resulting in low EVM values after equalization. The effect of array tapering on EVM is also presented, and the results show no difference in the EVM for uniform and tapered excitations.

Use of graphics processors to cardinally acceleration the calculation procedure of large subaperture active phased antenna arrays radiation pattern

For traditional APAA with a rectangular and triangular grid of nodes, in which partial emitters are installed, simple analytical formulas are known that express the dependence of the array radiation pattern (ARP) on the angular coordinates. If the grid of nodes is irregular, or in a regular grid there are failures of individual digits in the control elements (phase shifters, attenuators, delay lines) or in power amplifiers, then these formulas are not applicable. Therefore, it is necessary to address to general relations of additive summation of the specific contribution to the ARP of the field generated by each emitter separately. In large arrays, their number can range from several to many tens or even hundreds of thousands. Further, if it is necessary to synthesize a given type of array RP, it is necessary to form special types of the amplitude-phase distribution of the signal on the emitters. The procedures for synthesizing such distributions require hundreds or even thousands of repeated calculations of the array RP, which may require several million angular points to analyze in the upper hemisphere of radiation. The article shows that using parallel computing with the help of programming technology on graphics processors (GPU), produced by NVIDIA and CUDA technology in a system designed to quickly create high-performance codes in the extended C language, C++ is able to speed up the calculations of the large antenna ARP by 2…3 orders of magnitude, even on standard office computers. When using modern CPUs (AMD Ryzen Threadripper PRO 3995 WX) and GPU (NVIDIA GeForce 3090), the acceleration in calculations can additionally increase by hundreds of times. At such computing speeds, even the problems of antenna synthesis and statistical analysis of the characteristics of the array RP will be solved almost in real time. An example of a statistical estimation of the ARP parameters of a large subaperture array with 1280 emitters, used in the COSMOSkyMed system, when random failures of the inverse type occur in the phase shifter digits. The use of graphics processors allows us to solve problems such as the synthesis of an array RP having a prescribed shape, and the statistical analysis of the characteristics of the array in the event of various failure options in its elements, as well as mechanical distortions of the aperture shape, in almost real time.

Observations of the gamma-ray pulsar J1836+5925 at 111 MHz

Abstract We describe the 10-day radio observations of the gamma-ray pulsar J1836+5925. Observations were carried out in the Pushchino Radio Astronomical Observatory at the frequency of 111 MHz using the Large Phased Array of the Lebedev Physical Institute.

Interleaved Parasitic Arrays Antenna (IPAA) for Active VSWR Mitigation in Large Phased Array Antennas With Wide-Angle Scanning Capacities

This paper explores a new concept for the design of high scanning-range phased array antennas: the Interleaved Parasitic Arrays Antenna or IPAA. In this concept, we use periodic parasitic elements and the generator impedance to control the Active Voltage Standing Wave Ratio (AVSWR) over a wide scanning range. This new array architecture comes with a design methodology enabling a smooth step-by-step design process aiming at reducing the need for full-wave calculations. First, a numerical dual-polarization design is presented in detail to illustrate the methodology and to give the design keys to the reader. Then, a prototype working in the 5G C-band between 3.4 and 3.8 GHz (11% bandwidth) was designed using this methodology and measured for a 36-element array. It is meant to demonstrate and validate the mutual coupling management done by the interleaved parasitic arrays and the design process accuracy. Good correspondence between measurements and simulation was found and the proposed unit cell with its corresponding tile can be integrated in a larger phased array with active modules to perform beam steering over an important scanning range without deteriorating the AVSWR. The proposed unit cell is designed for a high-scanning range going from $\theta =0^{\circ }$ to $\theta = 70^{\circ }$ for every $\varphi $ -directions and shows an active reflection coefficient for an infinite array below −13.6dB.

Pulsar B0531 + 21 in the Crab Nebula

The Crab Nebula and its pulsar PSR B0531 + 21 is the space laboratory for the study of fundamental physical processes. From the beginning of the current century up to date, the giant pulses of the pulsar in the Crab Nebula are regularly observed on the Large Phased Array of the Pushchino Radio Astronomy Observatory of the Lebedev Physical Institute at a frequency 111 MHz. The connection between the scattering time scale of radio pulses and the dispersion measure of the pulsar, which was established earlier together with Jodrell Bank, is confirmed. The observed variations in the scattering of radio pulses and their partial correlation with the dispersion measure are explained by the eclipse of the pulsar by dense plasma clouds with fluctuations in the electron density significantly exceeding the corresponding fluctuations in the interstellar medium. The question of a possible connection between period failers (glitches), dispersion measure variations, radio pulses scattering and gamma-ray flares is discussed.

Active Vibration Control of a Large Space Antenna Structure Using Cable Actuator

A large space antenna structure will inevitably vibrate due to the space thermal environment and maneuver actions of the satellite. Such vibration will last continuously and affect normal function of the antenna. Therefore, a proper vibration control method is vital to keep the shape accuracy of the structure within an acceptable range. The research object of this paper is a large deployable planar phased array antenna that uses cables as active actuators. Research contents include the optimization of actuator position and the design of control law: both of which have considered the unilateral and saturated constraints of the cable actuator. First, the finite element method is used to obtain the modal information of the structure. Then the actuator position optimization method is established by using the controllability principle and the particle swarm optimization algorithm. Second, a piecewise cost function is adopted to design the control law by combining a linear quadratic regulator with a bang–bang regulator. In the numerical simulation, the vibration control process of an antenna structure consisting of 18 lattices is simulated and analyzed. The results prove that the proposed actuator position optimization method and the control law could effectively suppress the vibration and maintain the shape accuracy of the antenna structure.

Design of Ambient Backscatter Training for Wireless Power Transfer

Wireless power transfer (WPT) using energy beamforming is a promising solution for low power Internet of Things (IoT) devices. In this work, we consider WPT from an energy transmitter (ET) employing retrodirective WPT using a large phased antenna array to an energy receiver (ER) capable of ambient backscatter. The advantage of retrodirective WPT is that no explicit channel estimation is needed at the ET and the use of ambient backscattering eliminates the need for active transmission at the ER. We propose a training sequence design, i.e., pattern of varying the reflection coefficient at the ER, to eliminate the direct-link interference from the ambient source. We show that when the ambient symbol duration is known, the ambient interference is fully cancelled by the proposed design. We analytically model the system and find the average harvested power at the ER considering Nakagami-m fading channels and non-linear energy harvesting model. Our results clearly show that the proposed solution is robust to a small timing offset mismatch at the correlator. When interference from undesired neighbouring sources in the ambient environment is not significant, the ER can successfully harvest tens to hundreds of μW of power, which is an important improvement for low-power IoT devices.