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Diffraction gratings and photonic crystals are widely used to control light. However, their capabilities are less effective in the case of extreme ultraviolet (XUV) radiation due to the high absorption of the optical material in this frequency range. In this work, we study the possibility of enhancing the angular dispersion of XUV radiation due to scattering by plasma clusters whose dimensions are smaller than the incident radiation wavelength. An analytical model was developed using the plasma Drude dielectric function and the Mie scattering theory in the quasi-static approximation. The resonant parameters of the target for the tenth harmonic of the Ti:Sa-laser are determined, and a significant enhancement of the scattered field in this case compared to the laser one is shown. Under resonance conditions for one cluster, the diffraction of radiation by an array of such clusters is simulated using the CELES code. The results obtained show a significant enhancement of the scattered field in the resonance case for large angles corresponding to the theory of Bragg–Wulf diffraction, which makes it possible to control high harmonics of laser radiation in the XUV range using ionized cluster gas. [ABSTRACT FROM AUTHOR]

Free-space transmission of terahertz (THz) waves opens great opportunities for wireless applications including sensing and communication in the 6G era and beyond. Owing to their wider bandwidths and shorter wavelengths, the use of THz waves enhances information capacity and spatial resolution while downsizing aperture sizes compared to microwaves. On the other hand, the shorter wavelengths of THz waves can involve severe path loss. To compensate for the path loss, directional transmission based on beam steering is indispensable. In this article, we review the development of THz beam steering, which has been a longstanding challenge as well as the generation of high-power THz waves. While the use of active or passive phased arrays is the predominantly utilized approach to implement beam steering, other approaches based on variable diffractive structures and frequency dispersive structures offer low-cost alternatives. We also emphasize that application-driven system design approaches, in which THz beam steering is tightly coupled to signal processing, have been emerging to overcome hardware limitations. [ABSTRACT FROM AUTHOR]

In the paper, observation results of the magnetar SGR 1935+2154 at the frequency 111 MHz by the LPA (BSA) FIAN radio telescope are presented. For the search of single non-periodic pulses, we used data recorded in the six-frequency channel mode with a temporal resolution of 0.1 s in the receiver band 110.25 ± 1.25 MHz. As a result of data analysis for the period from September 1, 2019 to March 1, 2021, a pulse was detected with a dispersion measure pc/cm3, scattering value ms, and a fluence Jy ms. To search for periodic pulses, we used data recorded in the 32-channel mode in the receiver band 109–111.5 MHz in January–February and October–December, 2020. As a result, in two sessions, periodic radiation was found with a period of 3.247 s, an amplitude of 40 mJy, and dispersion measure DM = 320 pc/cm3. [ABSTRACT FROM AUTHOR]

This paper proposes a new data-dependent beamforming strategy to adaptively maximize the output power, while nulling preset directions-of-arrival. This new beamformer needs no iterative computation and needs no prior information of the signals-of-interest's incident directions nor temporal waveforms. Surprisingly, this proposed beamformer can "blindly" null any dominant interferences with no prior information of their incident directions nor of their waveforms, even as this beamformer simultaneously preserves the signals-of-interest as mentioned above. Monte Carlo simulations verify this new method's superior array gain relative to the "linearly constrained minimum-variance" beamformer's. [ABSTRACT FROM AUTHOR]

A possibility of sustaining a stable 3D-levitation of a collection of particles in an acoustic field under the conditions of all-around irradiation by monochromatic ultrasonic waves in air is investigated. The levitation of particles is ensured by placing them into a field of standing waves of a particular configuration. The particles are controlled in the field in the horizontal plane by varying the phase relations of the radiating arrays. It is shown theoretically and experimentally that it is possible to apply a monochromatic field to sustain a stable levitation of particles in a volume. A multiple-channel system of control over the phased arrays of ultrasonic vibrators is shown, which is based on a 1-bit DA-converter for application in a facility of ultrasonic levitation in air. [ABSTRACT FROM AUTHOR]

A method of control for an ordered group of particles that levitate in an ultrasonic field and structures of rectilinear segments is proposed. An ultrasonic field in air at a frequency of 40 kHz and particles whose dimensions are less than a quarter of a wavelength or thin cylindrical objects with diameters of less than a quarter of a wavelength are considered. The ultrasonic field is formed using four phased arrays of radiators that are placed oppositely on lateral faces of a rectangular parallelepiped. The radiators form a distribution of the standing wave field in the plane, which provides levitation of particles in a rectangular grid in a plane layer. With the use of numerical simulation and experimentally, it has been shown that the obtained distribution is stabilized and the particles remain immobile at local minimums of the Gor'kov potential. Moreover, regulation of the phase difference of opposite radiators provides controlled motion of a group of particles in a horizontal plane and a change in the focusing plane of side radiators provides controlled motion of a group of particles along the vertical plane. It has been shown experimentally that not only small particles but also structures assembled of rectilinear segments whose length is much greater than the wavelength can levitate in this field distribution. [ABSTRACT FROM AUTHOR]

Real-time imaging, using ultrasound techniques, is a complex task in non-destructive evaluation. In this context, fast and precise control systems require design of specialized parallel architectures. Total focusing method (TFM) for ultrasound imaging has many advantages in terms of flexibility and accuracy in comparison to traditional imaging techniques. However, one major drawback is the high number of data acquisitions and computing requirements for this imaging technique. Due to those constraints, the TFM algorithm was earlier classified in the field of post-processing tasks. This paper describes a multi-FPGA architecture for real-time TFM imaging using the full matrix capture (FMC). In the acquisition process, data are acquired using a phased array and processed with synthetic focusing techniques such as the TFM algorithm. The FMC-TFM architecture consists of a set of interconnected FPGAs integrated on an embedded system. Initially, this imaging system was dedicated to data acquisition using a phased array. The algorithm was reviewed and partitioned to parallelize processing tasks on FPGAs. The architecture was entirely described using VHDL language, synthesized and implemented on a V5FX70T Xilinx FPGA for the control and high-level processing tasks and four V5SX95T Xilinx FPGAs for the acquisition and low-level processing tasks. The designed architecture performs real-time FMC-TFM imaging with a good characterization of defects. [ABSTRACT FROM AUTHOR]

This paper presents the design of a millimeter-wave wideband receiver front-end in a 0.13 μm SiGe BiCMOS technology for phased array applications. The receiver front-end is suitable for a phased array time-division duplexing communication system where both the transmitter and the receiver share the same antenna. The monolithic microwave integrated circuit front-end comprises of quarter-wave shunt switches, a low-noise amplifier (LNA), an active phase shifter and a buffer amplifier. The quarter-wave shunt switch is designed using reverse-saturated SiGe HBTs. The transformer-based LNA utilizes a common-emitter amplifier at the first stage and a cascode amplifier at the second stage to exploit the advantages of both common-emitter and cascode topologies. The designed switch is incorporated in the input matching network of the LNA. The active phase shifter consists of variable gain amplifiers driven by a polyphase filter-based quadrature generator. The receiver front-end achieves a measured gain of 18.5 dB and a noise figure of 9 dB with a 3 dB bandwidth of 23 GHz from 56 to 79 GHz. The receiver phase can be tuned continuously from 0∘ to 360∘. An output referred 1-dB compression point of - 7.4 dBm is achieved at 70 GHz. The receiver consumes 116 mW of DC power and occupies a core area of 1800μm×475μm. [ABSTRACT FROM AUTHOR]

This paper presents a four channel phased array transmitter at 15 GHz aimed for the upcoming 5G wireless systems. The circuit is designed and fabricated using 45 nm  CMOS silicon on insulator technology. The design is programmable with exhaustive digital controls available for parameters such as bias voltage, resonance frequency, and gain. The phase shift required for the phased array is provided at RF using an IQ vector modulator (IQVM) topology, which provides both amplitude and phase control. Based on the measurement results, the IQVM provides 360° of phase shift and 15 dB of gain variation. Both phase and amplitude information are encoded in a 10 bit control word. The mean angular separation provided by the IQVM is 3° at optimum amplitude levels. Active area occupied is 2.88 square millimeter. Total DC power consumed by one transmit channel from 1 and 2.6 V supply is 268 mW. The maximum RF output power from one transmit channel is 1dBm. Measured EVM for a 256 QAM modulated signal is as low as 2.0%. All results include the impact of printed circuit board traces and pad parasitics. Based on the achieved results, the proposed architecture is well suited for the next generation of the wireless systems. [ABSTRACT FROM AUTHOR]

Applying ultrasonic-tomography systems makes it possible to precisely determine the shape and dimensions of flaws with the aim of establishing the degree to which the flaws influence safe operation of tested objects. This problem is solved by using special algorithms that make use of echo-signals recorded by an ultrasonic transducer to generate synthesized images of flaws in the sample. The use of phased arrays in ultrasonic tomography is explained by their ability to provide exhaustive data about the internal structure of a test object, thus allowing formation of the high-quality synthesized images of flaws in the object. Increasing the speed of ultrasonic tomography by using phased arrays necessitates the development and implementation of fast data-processing algorithms. In this connection, of interest are calculation algorithms in the frequency domain, which ensure the high speed of producing synthesized images. An ultrasonic-tomography algorithm is proposed that is based on calculations in the frequency domain. The algorithm takes the complex nature of the propagation of ultrasonic waves into account and is connected with the presence of media with different acoustic properties (e.g., in the case of immersion tests). Possibilities offered by the algorithm are investigated by computer simulations using the licensed CIVA 2016 software package and experimentally. [ABSTRACT FROM AUTHOR]

In this paper we present the electromagnetic modeling and beam pattern measurements of a 16-elements ultra wideband sparse random test array for the low frequency instrument of the Square Kilometer Array telescope. We discuss the importance of a small array test platform for the development of technologies and techniques towards the final telescope, highlighting the most relevant aspects of its design. We also describe the electromagnetic simulations and modeling work as well as the embedded-element and array pattern measurements using an Unmanned Aerial Vehicle system. The latter are helpful both for the validation of the models and the design as well as for the future instrumental calibration of the telescope thanks to the stable, accurate and strong radio frequency signal transmitted by the UAV. At this stage of the design, these measurements have shown a general agreement between experimental results and numerical data and have revealed the localized effect of un-calibrated cable lengths in the inner side-lobes of the array pattern. [ABSTRACT FROM AUTHOR]

We present results from pulsar observations using the Giant Metrewave Radio Telescope (GMRT) as a phased array with infield phasing. The antennas were kept in phase throughout the observation by applying antenna based phase corrections derived from visibilities that were obtained in parallel with the phased array beam data, and which were flagged and calibrated in real time using a model for the continuum emission in the target field. We find that, as expected, the signal to noise ratio (SNR) does not degrade with time. In contrast observations in which the phasing is done only at the start of the observation show a clear degradation of the SNR with time. We find that this degradation is well fit by a function of the form SNR $(\tau ) = \alpha + \beta e^{-(\tau /\tau _{0})^{5/3}}$ , which corresponds to the case where the phase drifts are caused by Kolmogorov type turbulence in the ionosphere. We also present general formulae (i.e. including the effects of correlated sky noise, imperfect phasing and self noise) for the SNR and synthesized beam size for phased arrays (as well as corresponding formulae for incoherent arrays). These would be useful in planning observations with large array telescopes. [ABSTRACT FROM AUTHOR]

The performance of an in-room MIMO system is investigated with the use of elevation-directional access point (AP) antennas which emphasize wall-reflected NLOS components instead of non-directional antennas. Simulation results suggest that the mean MIMO capacity throughout an idealised in-room environment can be improved on the order of 14% coupled with a 3% increase in mean relative MIMO gain if the appropriate main-lobe elevation direction is selected. The associated antennas are omnidirectional in azimuth and exhibit directivities and elevation half-power beamwidths on the order of 6 dBi and 28°, respectively. Experimental results obtained via channel measurements reveal more modest improvements due to the increased multipath richness exhibited by the real environment; a mean capacity improvement of approximately 5% is achieved, but this is accompanied by a minor reduction in relative MIMO gain. This level of performance may not be significant enough to warrant switching to elevation-directional AP antennas; however, the measured results provide qualitative verification of the simulation model. In any case, the results quantify the modest in-room MIMO performance gains one should expect when considering only wall reflections in the design of elevation-directional AP antennas at microwave frequencies. [ABSTRACT FROM AUTHOR]

This paper presents the performance analysis of a cognitive phased array radar with online tracking capability. The versatile model has the ability to sense the environment for adaptive selection of active number of array elements in the transmitter, as well as, in receiver arrays. An online extended Kalman filter with a kernel recursive least squares observer has been used to predict the future direction of target. The proposed radar avoids continuous scanning of the surveillance region. Instead, the transmitter, based on the feedback from the receiver, ensures maximum power in the target future direction. It saves a lot of power. Likewise, the intelligent selection of transmitting and receiving array elements, at each scan, results in less computational complexity and improved detection probability along with signal to interference plus noise ratio than that of a conventional phased array. Monte-Carlo based simulations have been conducted to validate the performance of the design. [ABSTRACT FROM AUTHOR]

An effective non-revisiting artificial bee colony (NrABC) algorithm based on the paradigm of artificial bee colony (ABC) is developed in this paper. NrABC is applied to tackle the synthesis of phased linear arrays. Pros and cons of NrABC is provided along with a comparison to standard ABC. Binary space partitioning tree structure is used to record history evolutionary information. Non-revisiting scheme assures NrABC keeping good diversity of population. Moreover, scout bee stage is discarded in NrABC which also removes an algorithmic parameter of standard ABC. Three phased array synthesis examples are employed to study the performance of NrABC. It turns out that under the same experimental configuration, NrABC outperforms standard ABC in terms of both solution quality and reliability in repeated runs. [ABSTRACT FROM AUTHOR]

In this article, a compact W-band differential I-Q phase shifter is designed and implemented using 28-nm CMOS technology. The phase shifter is capable of achieving phase shifts ranging from 45° to 315° with a resolution of 90°. The design employs transmission-line baluns for creating a differential signal, Gilbert-cell-type active switches for generating 0° and 180° phase shifts and a 90° differential hybrid for obtaining differential I-Q signals. The hybrid is developed using capacitive-loaded slow-wave differential lines, thereby making it 75 % smaller than a conventional 90° hybrid. Furthermore, the modelling of a slow-wave differential line for odd-mode and even-mode propagation is explained. The phase shifter exhibits 12 dB of insertion loss, and the root-mean-square (RMS) gain and phase error are 0.55 dB and 16.6°, respectively, at 100 GHz. The total power consumption is 39 mW when using a 1-V supply. The chip size of the implemented design is 0.48 mm including the probing pads. The phase shifter design is further modified by replacing the baluns with single-stage differential buffer amplifiers to mitigate the signal loss. This modified version of the design shows +1 dB insertion gain with a total power consumption of 122.9 mW from a 1-V supply and realized at 0.565 mm. A 13-dB gain improvement is obtained from the modified version and the measured RMS gain and phase error are 1.5 dB and 13°, respectively, at 100 GHz. After redesigning the layout, a minimum RMS phase error of 1.7° is expected in the simulations. [ABSTRACT FROM AUTHOR]

This paper presents a front-end architecture for fully integrated 60 GHz phased array receivers. It employs LO-path beamforming using a phase controlled phase-locked loop (PC-PLL). To demonstrate the architecture a circuit is implemented featuring a two stage low noise amplifier, two cascaded active mixers, and a PC-PLL. The receiver downconverts the 60 GHz signal in two steps, using LO signals from the 20 GHz QVCO of the PLL. A differential 2nd-order harmonic is coupled from the sources of the current commutating pairs of the QVCO, feeding the LO-port of the first mixer and downconverting the 60 GHz RF signal to a 20 GHz intermediate frequency. Quadrature 20 GHz LO signals are then used in the second mixer to down-convert the IF signal to baseband. The PLL is locked to a relatively high reference frequency, 1.25 GHz, which reduces the size of the PLL loop filter and enables a compact layout. The measurements show an input return loss better than −10 dB between 57.5 and 60.8 GHz, a 15 dB voltage gain, and a 9 dB noise figure. Two-tone measurements show −12.5 dBm IIP3, 29 dBm IIP2, and −24 dBm ICP1. The PC-PLL phase noise is −105 dBc/Hz at 1 MHz offset from a 20 GHz carrier, and the phase of the received 60 GHz signal is digitally controllable with a resolution of 3.2°, covering the full 360° range with a phase error smaller than 1°. The chip consumes 80 mA from a 1.2 V supply, and measures 1,400 μm × 660 μm (900 μm × 500 μm excluding pads) including LNAs, mixers, and PC-PLL in a 90 nm RF CMOS process. [ABSTRACT FROM AUTHOR]

The Ultrasonic Pulse-Echo inspection method is extremely capable of detecting cracks that limit the structural integrity of loaded technical components and systems. However, the applied principles of ultrasonic material testing do not in general allow the characterization of flaws and the required measurement of crack dimensions. Appropriate wave field data sampling at the scanned surface with the subsequent field reconstruction improves both the resolution and the contrast sensitivity of inspection results. We use arrays with elements adapted for the inspection task with an optimized arrangement and element apertures of point source character. First results have been received applying linear arrays that are promising for the quantitative assessment of flaws by high-resolved high contrast imaging of inspection results in real-time. [ABSTRACT FROM AUTHOR]

The well-known method of focusing ultrasonic signals to a point implemented using phased antenna arrays is considered as applied to problems of tomography of products manufactured from complexly structured materials. The features of applying broadband ultrasonic complexly modulated signals in phased antenna arrays and the limits of applicability of this method in constructing an image of a reflecting surface are discussed. [ABSTRACT FROM AUTHOR]