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This paper proposes a deep neural network (DNN)-based approach for radiation pattern synthesis of 8 elements phased array antenna. For this purpose, 181 points of a desired radiation pattern are fed as input to the DNN and phases of array elements are extracted as the outputs. Existing DNN techniques for radiation pattern synthesis are not directly applicable to higher-order arrays as the dataset size grows exponentially with array dimensions. To overcome this bottleneck, we propose novel and efficient methods of generating datasets for DNN. Specifically, by leveraging the constant phase-shift characteristic of the phased array antenna, dataset size is reduced by several orders of magnitude and made independent of the array size. This has considerable advantages in terms of speed and complexity, especially in real-time applications as the DNN can immediately learn and synthesize the desired patterns. The performance of the proposed methods is validated by using an ideal square beam and an optimal array pattern as reference inputs to the DNN. The results generated in MATLAB as well as in CST, demonstrate the effectiveness of the proposed methods in synthesizing the desired radiation patterns. [ABSTRACT FROM AUTHOR]

This paper introduces a novel, small-sized, highly integrated, circularly polarized wide-angle scanning antenna using substrate-integrated waveguide (SIW) technology at millimeter-wave frequencies. The antenna unit addresses requirements for high data transmission rates, wide spatial coverage, and strong interference resistance in communication systems. By integrating radiating square waveguides, circular polarizers, filters, and matching loads, the antenna enhances out-of-band suppression, eliminates cross-polarization, and reduces manufacturing complexity and costs. Utilizing this antenna unit as a component, a 4 × 4 phased array antenna with a two-dimensional ±60° scanning capability is designed and simulated. The simulation and measurement results confirm that the phased array antenna achieves the desired scan range with a gain reduction of less than 3.9 dB. [ABSTRACT FROM AUTHOR]

The next generation phased array radio telescopes, such as the Square Kilometre Array (SKA) low frequency aperture array, suffer from RF interference (RFI) because of the large field of view of antenna element. The classical station beamformer used in SKA-low is resource efficient but cannot deal with the unknown sidelobe RFI. A real-time adaptive beamforming strategy is proposed for SKA-low station, which trades the capability of adaptive RFI nulling at an acceptably cost, it doesn't require hardware redesign but only modifies the firmware accordingly. The proposed strategy uses a Parallel Least Mean Square (PLMS) algorithm, which has a computational complexity of 4 N + 2 and can be performed in parallel. Beam pattern and output SINR simulation results show deeply nulling performance to sidelobe RFI, as well as good mainlobe response similar to the classical beamformer. The convergence performance depends on the signal-and-interference environments and step size, wherein too large a step size leads to a non-optimal output SINR and too small a step size leads to slow convergence speed. FPGA implementation demonstrations are implemented and tested on a NI FPGA module, and test results demonstrate good real-time performance and low slice resource consumption. [ABSTRACT FROM AUTHOR]

True time delay digital beamforming enables large squint-free bandwidths and high beamcounts, ideal for Low Earth Orbit (LEO) satellite communication links. This work proposes a true time delay architecture using Variable Fractional Delay (VFD). True time delay eliminates many analog beamforming performance constraints including inaccurate beam steering and limited beamcounts, while managing system quantization error. This article presents a method of implementing true time delay using a VFD digital filter with sufficient time resolution to minimize quantization error and enable both gigahertz bandwidths and sampling frequencies. Simulations of antenna patterns utilizing the proposed VFD digital filters demonstrate satisfactory LEO beamforming performance with only a 29-tap filter. The VFD filter was implemented using a Xilinx Virtex Ultrascale FPGA and demonstrated a 1077% reduction in dynamic power and a minimum 498% reduction in logic resources, with only a modest increase in multipliers required when compared to Farrow-based architectures previously proposed in the literature. [ABSTRACT FROM AUTHOR]

This paper studies the performance of hybrid digital-analog multi-user multipleinput multiple-output (MU-MIMO) downlink communication based on various antenna systems for 5G applications. The analysis is focused on comprehensive numerical simulations comparing hybrid beamforming schemes for collocated vs distributed phased array antennas (PAA) deployments in two indoor office environments. This study uses measured beamforming radiation patterns from two 28 GHz state-of-the-art PAAs. The channel models employed are the standardized statistical 3GPP 38.901 indoor channel models implemented in the QuaDRiGa software. A beam selection algorithm is implemented to maximize the achievable sum rate, assuming either matched-filtering or zero-forcing precoding. The evaluated figures of merit are the gain of the RF power amplifier, the per-user signal-to-interference-plus-noise ratio (SINR), and the resulting achievable sum-rate capacity. Based on the results, the distributed deployment scenario always shows a higher SINR and achievable sum-rate capacity at the user locations while requiring a lesser amplification of the conducted power. Specifically, the largest PAA with slant-polarized 16 x 4 elements producing 16 horizontal analog beams in combination with zeroforcing digital precoding proved to be the best solution in both open and mixed indoor office environments in absolute values. On the other hand, the array based on the same type of elements but in a more compact realization with 4 x 4 elements, but with beams arranged as 8 horizontal times 2 vertical, offered the most significant relative gains. [ABSTRACT FROM AUTHOR]

This paper proposes a deep neural network (DNN)-based approach for radiation pattern synthesis of 8 elements phased array antenna. For this purpose, 181 points of a desired radiation pattern are fed as input to the DNN and phases of array elements are extracted as the outputs. Existing DNN techniques for radiation pattern synthesis are not directly applicable to higher-order arrays as the dataset size grows exponentially with array dimensions. To overcome this bottleneck, we propose novel and efficient methods of generating datasets for DNN. Specifically, by leveraging the constant phase-shift characteristic of the phased array antenna, dataset size is reduced by several orders of magnitude and made independent of the array size. This has considerable advantages in terms of speed and complexity, especially in real-time applications as the DNN can immediately learn and synthesize the desired patterns. The performance of the proposed methods is validated by using an ideal square beam and an optimal array pattern as reference inputs to the DNN. The results generated in MATLAB as well as in CST, demonstrate the effectiveness of the proposed methods in synthesizing the desired radiation patterns.

This paper presents the design, development, and performance evaluation of a compact wideband phased array active helical antenna for monitoring HF interference. Traditional multi-element HF antenna designs are often subjected to size restrictions. The front-to-back ratio of the proposed circularly polarized phased array exceeds 20 dB across the operating range. This array enables the simultaneous monitoring of vertically and horizontally polarized signals, offering a practical alternative to larger antennas, particularly in space-constrained scenarios. Through advanced low-noise amplifier design, efficiency and bandwidth are optimized while mitigating mutual coupling effects. Optimal beamformer design enhances array performance with respect to more traditional array design approaches. The test results verify exceptional performance with an average axial ratio of 2 dB and a high front-to-back ratio beyond the desired frequency range. This study offers valuable insights into the design and deployment of compact wideband phased array antennas, providing an effective solution for monitoring HF interference. [ABSTRACT FROM AUTHOR]

A wide-angle scanning phased array with dual circular polarization in the Ka-band is presented in this paper. To improve the scanning capability of the phased array, the microstrip element is modified by loading many metal posts at its center and periphery. In addition, a stripline coupler is designed to achieve dual circularly polarized (CP) radiation, and the inner conductor of the subminiature micro-push-on (SSMP) connectors for feeding the coupler is extended to the top layer of the multilayer element by introducing an open stub, which simplifies the assembly process between the SSMP connector and multilayer printed circuit board (PCB) due to through-hole soldering instead of blind-hole soldering. The proposed element can cover a frequency range from 28 GHz to 30.5 GHz with a relative bandwidth of 8.5% in the Ka-band. An 8 × 8 phased array is constructed based on this proposed element, and a wide-angle scanning range from −65° to +65° is obtained for the dual circular polarization. The proposed array has a gain fluctuation of 5.1 dB and an axial ratio (AR) of less than 3.3 dB during beam-steering. The prototype is fabricated and measured, with a good agreement between the measured and simulated results. The proposed phased array can be applied in a Ka-band millimeter-wave (MMW) communication system. [ABSTRACT FROM AUTHOR]

In this paper, a wide-band, low-profile antenna is presented for a high-integration phased array system. The proposed antenna, implemented using a tightly coupled array, operates over roughly the X-K frequency band and is performant at 8 GHz–18.5 GHz. The antenna can scan to ± 60 degrees in both the E- and H-planes. Compared to previous tightly coupled antennas with smaller element spacing, the antenna in this paper reaches 9.4 mm, which corresponds to 0.58   λ of high frequency, suitable for engineering application conditions in production. The antenna can be soldered to BGA T/R chips in this space. Additionally, to facilitate flexible assembly for large arrays, the antenna is manufactured modularly using four elements and its parasitic radiation is analyzed. Then, a method for repressing parasitic radiation is presented. Finally, the antenna is fabricated and measured in a microwave chamber, exhibiting an excellent pattern and scanning radiation. The measured performance agrees with the full-wave finite array simulations. [ABSTRACT FROM AUTHOR]

This review encompasses additive manufacturing techniques for crafting 5G electronics, showcasing how these methods innovate device creation with novel examples. A wearable phased array device on commonplace 3D printed material is described, with integrated microfluidic cooling channels used for thermal regulation of integrated circuit bulk components. Mechanical and electrical tunability are exemplified in an origami-inspired phased array structure. A 3D printed IoT cube structure shows the flexibility in the number of geometries additively manufactured 5G devices can adhere to. Finally, integrating 3D optical lenses with 5G electronics is shown. [ABSTRACT FROM AUTHOR]

Summary: In this paper, a vector‐sum phase shifter (VSPS) integrated with a wideband high‐gain low‐noise amplifier (LNA) for Ka‐band phased‐array receivers is presented. The digitally controlled VSPS based on the RF phase shifting architecture consists of a modified I/Q signal generator with additional inductor resonance and a programmable variable gain amplifier (VGA) based on Four 3 × 4 transistor arrays. Besides the reduced parasitic effect of the I/Q signal generator, an Equidistant Contraction Technology (ECT) is used in the VGA, to maintain higher phase shift accuracy of the VSPS. A multistage LNA with series inductor peaking is adopted to fulfill the flat wideband gain, where LC resonance networks are used as interstage matching to compensate for gain roll‐off at a higher frequency. Based on simulations in 65 nm CMOS technology, the presented LNA‐Phase shifter has achieved an average NF of 3.24–3.66 dB, and an average gain of 13.1–23.6 dB. Moreover, an RMS phase error of 1.1–12.6°, an RMS gain error of 4.2–5.6 dB, and an RMS magnitude error of 2.1–2.8 dB are maintained across 27–40 GHz, with a 360° phase shift coverage in steps of approximately 2.8125°. The chip consumes 16.83 mW from a 1.2 V supply voltage, and the occupied area is 0.65 mm2. [ABSTRACT FROM AUTHOR]

Copyright of Telecommunications Science is the property of Beijing Xintong Media Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The probability of antenna array failure or malfunctioning cannot be ruled out, and hardware replacement of faulty elements is not always a viable solution. Therefore, academic and industrial interest in self-healing phased arrays are on the rise. In this work, the phase-only genetic algorithm (GA) optimization flow for the radiation pattern correction of a 4 × 4 phase faulty planar antenna array is proposed. Initially, a reference array pattern at the desired scan angle is generated. Then random phase faults are introduced across the 1 × 4 antenna elements in any one of 4 sub-arrays to produce maximum distortion in the reference radiation pattern of 4 × 4 planar array. The proposed GA re-computes the new excitation weights for the remaining non-faulty 3 sub-arrays to correct the overall radiation pattern of 4 × 4 array. This is achieved by calculating the array output power for reference and GA computed weights. The GA corrected patterns fairly follow the desired array patterns in terms of peak gain and reducing sidelobe levels for the desired scan angle. The efficiency of the optimized radiation patterns was evaluated in full-wave HFSS model and measurements validation. In this way, maintenance cost can be reduced with recovery of acceptable level of radiation pattern using software instead of physically replacing faulty antenna elements in the array.

We report the fabrication and characterization of a plasmonic metasurface comprising electrically-contacted sub-wavelength gold dipole nanoantennas, conformally coated by a thin hafnia film, an indium tin oxide layer and a backside mirror, forming metal–oxide–semiconductor (MOS) capacitors, for use as an electrically-tunable reflectarray or metasurface. By voltage biasing the nanoantennas through metallic connectors and leveraging the carrier refraction effect in the MOS capacitors, our measurements demonstrate phase control in reflection over a range of about 30°, with a constant magnitude of reflection coefficient of 0.5, and the absence of secondary lobes. Comprehensive electromagnetic and quantum carrier models of the structure are developed and are in excellent agreement with the measurements. The metasurface holds promise for use as an optical phased array.

Focusing electromagnetic energy into a narrow sliver of space (beamforming) and directing this energy to desired areas (beam steering), which have been conventionally achieved using phased array antennas, allow for mitigating the propagation loss of energy and are critical for emerging communication and radar systems. This work presents a novel beamforming and steering technique which is based on the superposition of circular waveguide transverse electric (TEn1) modes. In this technique, a plurality of superposed omnidirectional circular polarized (CP) TEn1 waves, where each wave has a specific azimuthal radiation phase profile, is created. The unique phase profile of each wave is leveraged for CP beamforming and 360° beam steering. The proposed beamforming and steering approach can be realized using a single antenna structure with a relatively small dimension. It can be integrated into user mobile equipment, vehicles, base stations, repeaters, and radars, and due to its CP radiation, would be more immune to multipath fading and multiple reflections. It can also eliminate the requirement of a precise alignment for transmitting and receiving antennas. A CP beamformer antenna performing based on the proposed method is designed and fabricated for operation within 26.5-29.5 GHz which covers n257 and n261 bands for 5G systems. The test results verify the functionality of the proposed CP beamforming and steering technique. This technique can also be adapted for high-resolution automotive radars by employing a rotating antenna, and preliminary simulation and measurement results are also presented.

This paper presents a novel approach for linear to circular polarization (LP-CP) conversion in transmitarray antennas. The proposed conversion mechanism differs significantly from previous published realizations. The concept utilizes a transmission line modeling-based excitation technique, in which a centralized via excitation is split into two striplines carefully designed to balance excitations and guarantee a phase quadrature. The striplines are embedded at the center of the patch antenna allowing a compact footprint and a simple design structure. The applied true-time delay (TTD) technique assures the radiation of a wideband and low axial ratio circularly polarized (CP) field. To optimize bandwidth and transmission efficiency, a stacked patch configuration is also employed, allowing for simultaneous high polarization conversion and transmission efficiency. The unit-cell design methodology is detailed, and two transmitarray designs are realized in both X and Ka bands. Experimental results from a fabricated X-band $20 \times 20$ cell array prototype demonstrate a peak aperture efficiency of 30%, accompanied by a simultaneous 16% -1 dB gain and 1 dB axial ratio bandwidths. Furthermore, the measured wideband and highly efficient Ka-band transmitarray with a $70 \times 70$ cell array confirmed a remarkable gain of 39.8 dB and 55% aperture efficiency at 29 GHz, surpassing previous LP-CP transmitarray antennas, while maintaining axial ratio values below 1 dB in a bandwidth larger than 26%.

The demand for high-quality network services has increased due to the widespread use of wireless devices and modern technologies. To address the growing demand, 5G technology is being implemented at a larger scale. Small-cell Base Station (SBS) antennas are crucial for exploring the full potential of 5G networks by expanding the network in urban areas, densely populated regions, indoor environments, and low-coverage zones. This paper analyses the literature on the 5G sub-6 GHz and Millimeter wave SBS antennas, including their state-of-the-art designs and encompassing several parameters like bandwidth, gain, radiation pattern, and polarization. The integration of advanced technologies and designs, such as reconfigurable antennas, metamaterials, beam forming, phased array and massive MIMO has been given special consideration due to its importance in SBS antenna. While traditional base stations have been widely studied and implemented with multiple antenna techniques, the use of these techniques in SBSs is still developing. As networks become more complex and 5G systems require more network coverage, implementing several antenna designs in SBSs presents unique challenges related to performance and compactness. This paper discusses 5G SBS antenna designs that have been proposed recently and studies their characteristics with the parameters that enhance the performance. In addition, comparison tables analyzing the antenna designs are given to comprehend the nuances of design and implementation.

This paper aims to introduce a new strategy for the detection of faulty elements in phased array antennas. The approach takes advantage on the possibility in phased array to introduce the steering diversity. Accordingly, by collecting the radiated field over the measurement aperture while steering the beam, an approach inspired by the Time reversal MUSIC (TR-MUSIC) algorithm is exploited to achieve the diagnostics. At first, it is shown that such an algorithm allows the detection of only completely turned-off elements as long as the number of defective elements is relatively (depending on the configuration parameters) high. To overcome such a limitation, the difference model is built and the approach succeeds in detecting any failure (amplitude and phase failure) by a reduced set of data, mainly depending on the number of faulty elements. In addition, from the mere knowledge of the geometric parameters of the measurement configuration and by invoking the theory of degrees of freedom, the conditions for which the algorithm succeeded in the diagnostics are analytically derived. Furthermore, it is highlighted that the proposed algorithm achieves the diagnostics even when both the spacing between the array elements and the element factor is not a priori known. An extensive Montecarlo numerical analysis is included to show the capability of the approach to achieve a high probability of detection with a reduced set of data. Finally, full-wave simulations are also included.

This paper presents the construction and measurement of a phased array BPSK transmitter system operating at 246 GHz with tested data rates of up to 32 Gbit s-1. The system is built using custom monolithic microwave integrated circuit (MMIC) and a novel packaging solution. The construction showcases the flexibility in the chosen approach, paving a path for future systems. It is the first TX array with significant beam steering capabilities tested above a pure antenna pattern stage above 200 GHz. The system is tested for realistic usage scenarios. Bit-error-rate (BER) measurements are used to showcase real-world usability. BER over angle and BER over steering angle are measured to verify the operation of the transmitter.

A circuit-based calibration system is presented for active phased arrays. In particular, to achieve the desired (and corrected) consecutive phase differences and relative magnitudes between RF channels, a computer controlled circuit system was developed for dynamic adjustment. The proof-of-concept demonstrator uses a phase sensor, phase shifters (PSs), and variable gain amplifiers, along with other active hardware, to realize a self-calibrating circuit system which achieves the required magnitude and phase for each array element. In addition, measured magnitude and phase imbalances are less than 0.10 dB and 3$^\circ$, respectively. The computer-controlled feed network is then used to demonstrate that the system can automatically calibrate an active antenna array for various beam steering examples. Also, the S-band feed system can self-calibrate due to any monitored magnitude and phase drifts due to temperature changes and practical component ageing, or, other general channel offsets. This can be considered advantageous and simpler when compared to more established approaches which characterize the coupling between elements or the response of the entire array in the near- or far-field for example.

Calibration is essential to optimize the performance of any radio transceiver during its development and manufacturing processes. This paper proposes over-the-air (OTA) calibration methods based on measuring and calibrating the phases of phased array transceiver paths. The phase responses of each signal path with all phase shifter states were characterized using an OTA radio link in the transmission and reception modes. Scattering parameter measurements give amplitude and phase responses over the frequency range, which can be converted to the delay domain with the Fourier transform. In this paper, two new delay domain phase calibration methods are presented and compared with a previously presented frequency domain method. The best performance was achieved with the relative phase calibration method in the delay domain which uses all measurement data to find the calibration values. The other two methods, i.e., the absolute phase calibration method in the delay domain and in the frequency domain, use the average phase as the calibration value. OTA radiation pattern measurements from two prototype 5G millimeter wave transceivers were used to compare the RF performances of the calibration methods, and measurements were performed with a 100 MHz 5G new radio waveform. The radiation patterns were analyzed based on direction accuracy, power level, and side lobe level, to give a few examples. The transceiver units were calibrated using the three studied methods, and while having significantly different uncalibrated performances, after calibration, both transceivers were tuned to similar performance levels.

The mutual coupling between the elements of an aperture-fed, dual-polarized, low cross-polarization, scanning phased array microstrip antenna is investigated and a simple rectangular planar resonator between the elements is proposed to reduce the mutual coupling. The mutual coupling effect on antenna performance is studied based on active reflection coefficient. The rectangular resonating structure is positioned on the antenna top layer between patch elements, with dimensions optimized for resonance within the desired frequency range without significantly compromising cross-polarization performance. The antenna is a $2\times 8$ planar-phased array operating in the frequency range of 2.77 - 3.10 GHz using the aperture-coupled dual-polarization elements. Based on simulations and measurements, it is observed that the resonator effectively suppresses mutual coupling between antenna elements by 6 and 7 dB for V- and H-polarizations, respectively while maintaining cross-polarization levels below −35 dB for both polarizations within the required scan angle range. The reduced mutual coupling allows for elements to be placed at a distance of $0.45\lambda $ which in turn supports a scan angle range of −60° to 60° as verified by measurements and simulations. The design is simple enough such that the array size can be increased to achieve very fine beamwidth and high gain needed for polarimetric weather radar applications.

Millimeter (mmWave) 5G phased arrays require multiple simultaneous features for reliable high data-rate communication. However, it is challenging to simultaneously achieve a true wideband operation for all parameters due to mutual coupling and grating lobe issues. A $5\times5$ -stacked patch rectangular phased array was designed and fabricated in a 15-layer low-temperature co-firing ceramic (LTCC) substrate. This work utilized multiple design strategies, such as employing stacked patch topology, electromagnetic band gap (EBG) structures, and the rotation of elements to obtain a true wideband performance. The single element of the phased array was a dual linear polarized stacked patch antenna with notched corners. Compared to a standard patch antenna, the bandwidth was enhanced by 15.3%. The undesired mutual coupling between elements was minimized by rotating nearby elements and introducing EBG structures between the adjacent elements. A wideband beamforming network composed of a Rotman lens and a 5-way Wilkinson power divider (WPD) was also designed and fabricated. The proposed phased array achieved 6 GHz of bandwidth, covering 24 to 30 GHz and achieving a maximum gain of 17.5 dBi and a wide beam-scanning range from–50 to +50 degrees. This work also introduced a figure of merit (FoM) based on all critical performance parameters for objective comparison with state-of-the-art designs. The proposed design achieved the highest FoM (0.451), whereas most similar 5G phased array designs achieved much lower FoM value.

Copyright of Telecommunication Engineering is the property of Telecommunication Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper proposes a budget-friendly, highly integrated, and low-profile wideband simultaneous dual circularly polarized phased array subarray with scalable characteristics for satellite communications. In order to achieve wideband, the antenna unit is not only fed by double-fed point probe contact, but also by electromagnetic coupling. Moreover, the dual circularly polarized radiation of the antenna unit is realized by a miniaturized 3 dB bridge-type phase-shift network. In addition, the phased array subarray uses metalized vias to reduce inter-element crosstalk, which effectively improves the active voltage standing wave ratio (VSWR) and beam steering characteristics. Also, the subarray has interchangeability and versatility, enabling convenient twodimensional expansion to form a tile-type phased array antenna. Besides, the phased array subarray can be used to achieve two-dimensional ±40° beam scanning in both the azimuth and elevation planes. Within ±40° beam scanning, the active VSWR of the subarray is less than 2.5 in 9.55 - 14.35 GHz (40.17%). At 12.1 GHz, the twodimensional gain decreases by less than 2.1 dB and 1.95 dB, respectively. The proposed antenna exhibits good performance in terms of matching and beam steering characteristics, which make it suitable for use in future 5G/6G phased array antenna systems. [ABSTRACT FROM AUTHOR]

Radiation patterns of a phased array tend to be affected by random excitation errors. In this paper, a unified neural network (UNN) architecture is presented to study the statistical characteristics of radiation patterns. Benefited from the inherent symmetry of the array manifolds and efficient data preprocessing, the UNN architectures are almost identical for planar arrays consisting of 4–10 000 elements except for a slight difference existed in the output layer. Therefore, this merit avoids repetitive selections of training hyperparameters and network architectures. This method can efficiently treat the problems with multiple observation points in order to obtain statistical radiation patterns, and an analytic or closed‐form solution is not required. Moreover, it can combine with the method of moments (MoM), which takes account of the element pattern and mutual coupling effects. The trained UNN models can predict the probability density function (PDF) of radiation characteristics at any spatial location. Numerical results show that the UNN and Monte Carlo (MC) results are comparable in accuracy. [ABSTRACT FROM AUTHOR]

This paper presents a 66–76-GHz sparsely-excited phased array antenna with the array of array (AoA) architecture for eliminating the blindness and suppressing the grating lobe when scanning. For the array antennas printed on the thick dielectric layers with high relative permittivity, scanning blindness appears and seriously impacts the radiation performance. To address this issue, the AoA topology is developed first. It finds that the scanning blindness appears due to the coupling of the radiating Floquet modes to the non-radiating surface wave (SW) modes. Therefore, the array is divided into two types of domino subarrays. The inner-phase distributions are introduced into the domino subarrays to break the one-to-one relationship between the Floquet mode and the SW mode. Then, the blindness inside ±60° scanning volume is eliminated by the aperiodic subarrays. Meanwhile, the aperiodic inner-phase distributions enhance the aperiodicity of the array and contribute to suppressing the grating lobe when scanning. Next, the meta-surface-based dipole with the shorted post is chosen as the unit cell for the proposed aperiodic array. Based on these methods, the array achieves the wide-scanning performance of ±60° in the E-plane and ±30° in the H-plane, without the blindness and the grating lobe. Finally, the 16×16 array is built and simulated with the dimension of 32 mm × 32 mm. At the highest operating frequency, the simulated gains are 28.42, 25.17, and 24.01 dBi when scanning to the broadside, 50° in the E-plane, and 30° in the H-plane, respectively. Compared to the ideal gain, it shows that the simulated radiation efficiency is about 84.13%, 62.08%, and 35.23% when scanning to the broadside, 50° in the E-plane, and 30° in the H-plane, respectively. The worst transmission coefficient, i.e., the worst isolation, is −11.97 dB between the central element and its two adjacent elements in the E-plane. The array prototypes are fabricated, and the experiments are carried out to verify the correctness of the principle and design. Compared to existing antenna array designs, due to the employment of the AoA architecture, the proposed antenna achieves 51.30% channel reduction with both blindness-free and grating-lobe-free performance. Meanwhile, due to the regular and periodic subarray spacing, the best realizability is achieved for the sparsely-excited phased array at the millimeter-wave bands. This is valuable for the wide-scanning phased array antennas in the sixth-generation (6G) highly-integrated communication systems at the millimeter-wave bands. [ABSTRACT FROM AUTHOR]

A mm-wave phased array antenna used in mobile devices for 5G wireless communication provides better data transmission than 4G networks due to the fast expansion of 5G radio frequency technology. The frequency spectrum limit is specified in brief in a number of standard organizations. The EMF [Electromagnetic Field] exposure of radio frequency in millimeter-wave bandwidth frequency range of 10 GHz to 200 GHz evaluates the power density in free space and takes into account the impact of electromagnetic field exposure in the region of frequency, distance, and different phase shift angle instead of using the SAR (Specific Absorption Rate) value. The digital architecture of the beam shape and the impact of beam steering on power density are covered in this study by the phase array antenna. The suggested array antenna's bandwidth frequency of 28 GHz is acknowledged as a potential spectrum for determining the power density attribute. Include a comparison of the various array antenna element configurations as well. This article presents the simulation results based on the theoretical and numerical explanation of phased array antenna. [ABSTRACT FROM AUTHOR]

The simultaneous transmit and receive (STAR) array system provides higher radiation gain and data rate compared to traditional radio system. Because of the various mutual couplings between each pair of transmit and receive elements, it is a great challenge to suppress the incident self-interference power at multiple receive elements, which is usually much higher than the desired signal of interest (SoI) power and causes the saturation of receive links and the distortion of the digital SoI. In this paper, we propose an optimized method for transmit beamforming based on radiation power constraints and transmit power control. Through adaptive transmit beamforming, high isolation between the transmit array and each receive link is achieved, minimizing the self-interference power at each receiving element. This method effectively reduces the self-interference power, avoiding distortion of the SoI digital signal caused by limited-bit analog-to-digital converters (ADCs). Simulation results demonstrate that this optimized transmit beamforming method can achieve more than 100 dB effective isotropic isolation (EII) on a 32-element two-dimensional phased array designed in HFSS, reducing the maximum incident self-interference power at the receive channels by approximately 35 dB, while effectively controlling the attenuation of the transmit gain. We also present the advantages in receive subarray isolation and lower ADCs digits under the transmit ABF method. [ABSTRACT FROM AUTHOR]

In this letter, a dual-polarized metal Vivaldi phased array antenna composed of independent structural elements is proposed, covering 6–18 GHz. By designing Vivaldi elements with a flexible and complementary structure, arrays of arbitrary shapes and scales can be constructed. The resonance caused by structural discontinuity is critically studied and eliminated to ensure good performance across the entire band. The antenna elements are fed by 50-Ohm SSMP connectors and manufactured from 2A12 aluminum alloy. An array prototype consisting of 8 × 8 dual-polarized metal has been fabricated and tested with active transmit/receive (T/R) modules to demonstrate the design concept. The array exhibits excellent beam-scanning characteristics in both the E-plane and H-plane, within the scanning range without grating lobes, which shows good agreement with the simulated results. The measured gain results are within the range of 15.2 to 24.8 dBi, and the aperture efficiencies are greater than 91% in the entire operating band. The wideband antenna technology involved in this study can effectively help increase the capacity of communication systems and meets the intentions of the Special Issue. [ABSTRACT FROM AUTHOR]

Satellite communication (satcom) is experiencing increased interest to cover the connectivity gaps of terrestrial networks. To ensure high performance and throughput for the user—and even more so in Communications-On-The-Move(COTM) systems, e.g., in aeronautics—steerable antennas such as phased arrays are required to adjust the beam so as to follow the satellite's trajectory. The mutual movement of terminals and satellite in COTM systems calls for a broad Field of View (FoV) and, hence, poses a challenge to common planar systems. For improving the FoV, common solutions require ad hoc designs, such as multi-mode antennas, wide half-power-beamwidth antennas or metasurfaces. By contrast, 3D arrays are able to cover a wider angular region by the 3D allocation of the antennas. In this paper, the benefits and drawbacks of moving from 2D (planar) arrays to 3D phased arrays are investigated. Multiple geometrical configurations are analyzed, keeping in mind the size requirements of aeronautic terminals. The best configuration is, hence, an array capable of enhancing the FoV of the terminal. The proposed antenna architecture offers a good trade-off between design complexity and performance, and it could be further developed to become an aeronautic-grade terminal aperture. [ABSTRACT FROM AUTHOR]

This paper introduces a novel single-layer microstrip patch element designed to achieve a wide beamwidth, in order to address the growing demand for wide-angle scanning capabilities in modern phased array systems. The proposed element, comprising a slot-etched circular patch and an array of metallized holes arranged in square rings, offers a unique approach to beam shaping. By carefully adjusting parameters such as the slot structure and feeding position, our element is engineered to simultaneously excite both the TM01 and TM21 modes, a key feature that contributes to its wide beamwidth characteristics. Through the constructive interference of these modes, our element demonstrates a remarkable 3 dB beamwidth of approximately 150° in both principal planes, showcasing its potential for wide-angle scanning applications. To validate the practical performance of this proposed element, two linear phased arrays are manufactured and experimentally evaluated. The simulation results confirm the wide-angle scanning capability of the antennas in both the E-plane and H-plane. Furthermore, the experimental assessment demonstrates that these linear phased arrays can effectively generate scanning beams within a frequency range of 25 GHz to 28 GHz, covering a wide angular range from −60° to 60°, while maintaining a gain loss within 3 dB. This innovative design approach not only offers a promising solution for achieving a wide beamwidth in microstrip patch elements, but also holds significant potential for the development of cost-effective phased arrays with wide-angle scanning capabilities, making it a valuable contribution to the advancement of phased array technology. [ABSTRACT FROM AUTHOR]

This paper studies the performance of hybrid digital-analog multi-user multiple-input multiple-output (MU-MIMO) downlink communication based on various antenna systems for 5G applications. The analysis is focused on comprehensive numerical simulations comparing hybrid beamforming schemes for collocated vs distributed phased array antennas (PAA) deployments in two indoor office environments. This study uses measured beamforming radiation patterns from two 28 GHz state-of-the-art PAAs. The channel models employed are the standardized statistical 3GPP 38.901 indoor channel models implemented in the QuaDRiGa software. A beam selection algorithm is implemented to maximize the achievable sum rate, assuming either matched-filtering or zero-forcing precoding. The evaluated figures of merit are the gain of the RF power amplifier, the per-user signal-to-interference-plus-noise ratio (SINR), and the resulting achievable sum-rate capacity. Based on the results, the distributed deployment scenario always shows a higher SINR and achievable sum-rate capacity at the user locations while requiring a lesser amplification of the conducted power. Specifically, the largest PAA with slant-polarized 16 × 4 elements producing 16 horizontal analog beams in combination with zero-forcing digital precoding proved to be the best solution in both open and mixed indoor office environments in absolute values. On the other hand, the array based on the same type of elements but in a more compact realization with 4 × 4 elements, but with beams arranged as 8 horizontal times 2 vertical, offered the most significant relative gains.

The next generation phased array radio telescopes, such as the Square Kilometre Array (SKA) low frequency aperture array, suffer from RF interference (RFI) because of the large field of view of antenna element. The classical station beamformer used in SKA-low is resource efficient but cannot deal with the unknown sidelobe RFI. A real-time adaptive beamforming strategy is proposed for SKA-low station, which trades the capability of adaptive RFI nulling at an acceptably cost, it doesn’t require hardware redesign but only modifies the firmware accordingly. The proposed strategy uses a Parallel Least Mean Square (PLMS) algorithm, which has a computational complexity of 4N+2 and can be performed in parallel. Beam pattern and output SINR simulation results show deeply nulling performance to sidelobe RFI, as well as good mainlobe response similar to the classical beamformer. The convergence performance depends on the signal-and-interference environments and step size, wherein too large a step size leads to a non-optimal output SINR and too small a step size leads to slow convergence speed. FPGA implementation demonstrations are implemented and tested on a NI FPGA module, and test results demonstrate good real-time performance and low slice resource consumption.

In this paper, we utilize micro-computed tomography (micro-CT) to obtain micro-CT images with a resolution of 60 μm and establish a micro-CT model based on the k-wave toolbox, which can visualize the microstructures in trabecular bone, including pores and bone layers. The transcranial ultrasound phased array focusing field characteristics in the micro-CT model are investigated. The ultrasonic waves are multiply scattered in skull and time delays calculations from the transducer to the focusing point are difficult. For this reason, we adopt the pulse compression method and the linear frequency modulation Barker code to compute the time delay and implement phased array focusing in the micro-CT model. It is shown by the simulation results that ultrasonic loss is mainly caused by scattering from the microstructures of the trabecular bone. The ratio of main and side lobes of the cross-correlation calculation is improved by 5.53 dB using the pulse compression method. The focusing quality and the calculation accuracy of time delay are improved. Meanwhile, the beamwidth at the focal point and the sound pressure amplitude decrease with the increase in the signal frequency. Focusing at different depths indicates that the beamwidth broadens with the increase in the focusing depth, and beam deflection focusing maintains good consistency in the focusing effect at a distance of 9 mm from the focal point. This indicates that the phased-array method has good focusing results and focus tunability in deep cranial brain. In addition, the sound pressure at the focal point can be increased by 8.2% through amplitude regulation, thereby enhancing focusing efficiency. The preliminary experiment verification is conducted with an ex vivo skull. It is shown by the experimental results that the phased array focusing method using pulse compression to calculate the time delay can significantly improve the sound field focusing effect and is a very effective transcranial ultrasound focusing method. [ABSTRACT FROM AUTHOR]

The problem of accurate source localization has been an area of focus in high-frequency surface wave radar (HFSWR) applications. However, antenna pattern distortion (APD) decreases the direction-of-arrival (DOA) estimation performance of the multiple signal classification (MUSIC) algorithm. Up to now, limited studies have been conducted on the calibration of antenna pattern distortion for phased arrays in HFSWR. In this paper, we first analyze the effect of APD on the performance of the MUSIC algorithm through estimation of accuracy and angular resolution. We demonstrate that using the actual pattern (or say APD) can improve DOA estimation performance. Based on this proposition, we propose a novel iterative calibration method that employs the first-order sea clutter data and can jointly estimate DOA and APD in an iterative way. To obtain available calibration points, we introduce the extraction methods of the first-order sea clutter spectrum and single-DOA spectrum points. Meanwhile, in each iteration, the Beamspace MUSIC algorithm and artificial hummingbird algorithm (AHA) are utilized to estimate the DOA and APD, respectively. Numerical results reveal a good coincidence between the actual pattern and the estimated APD. We also apply this method to process the experimental data of HFSWR. We obtain the APD vector of the real phased array and improve the direction-finding performance of several real ship targets using this vector. Both numerical and experimental results prove the correctness of our proposed calibration method. [ABSTRACT FROM AUTHOR]

Considering the background of civilian and personnel safety as well as supply chain reliability, it is necessary to develop complex rail testing protocols that are capable of validating crack growth rate models, thereby increasing the safety, reliability, and efficiency of railway operations. The objective of the research herein is to consider a common approach to rail testing, which involves the non-destructive evaluation of internal rail cracks using phased array ultrasonic testing (PAUT). This paper focuses on our efforts to utilize PAUT methodology to nondestructively measure internal crack geometry during long term multiaxial cyclic loading of rails with growing internal cracks. Our methods include the employment of a hydraulically powered apparatus that is capable of simultaneously applying both constant axial load and dynamic bending moment to the irregular geometry of a rail head. Then tracking progressive crack growth using a PAUT system in addition to the algorithm developed herein. In this paper we present an overview of our experimental results to date as well as our efforts to improve this critical testing methodology for assessing crack growth rates in rails subject to cyclic loading. Our efforts have in some cases resulted in anomalous measurements of crack geometry, thereby impacting the accuracy of the results in these complex experiments. The results to date suggest the conclusion that additional systems need be implemented in order to standardize the readings in this complex loading environment, including standardization of the initiation point, couplant uniformity, and matching the irregular curvature of the rail head itself. [ABSTRACT FROM AUTHOR]

A strip‐typed patch antenna covered with a dielectric is studied. The antenna is excited with a differential feeding mechanism to obtain a low cross‐polarization level. When the patch antenna is totally covered with a dielectric, it can be operated at lower frequencies without tuning antenna dimensions. The simulated results show that as the relative permittivity of the dielectric is increased from 1 to 9.2, the antenna operation frequency is reduced from 4.25 to 2.38 GHz, and the cross‐polarization level is lower than −25 dB for each operation frequency. Based on such an antenna, a 1 × 8 dual‐polarized phased array is developed. The simulated results indicate that for each polarization mode, the gain variations of the array are less than 2 dB when the main beam is scanned from 60° to −60°; bedsides, a cross‐polarization level of less than −20 dB is also achieved. An array prototype is constructed, and measured data validate the simulated results. [ABSTRACT FROM AUTHOR]

This paper furnishes a compact modified hourglass-shaped aperture-coupled antenna for radar applications. The effect of slots of various shapes and various slot lengths on the input impedance, radiation pattern, and gain of the antenna are analyzed. The proposed antenna, designed using a modified hourglass-shaped aperture, offers a gain of 8.214 dBi for an compact antenna with a dimension of 20.4 × 20.4 × 1.041 mm3 and an aperture area of 2.495 mm2. Implementation of this proposed modified hourglass-shaped aperture offers a high gain per unit radiating patch area of 40.26 dB/ $\lambda _g ^2$ and a high gain per unit aperture area of 1324.84 dB/ $\lambda _g ^2$. The proposed aperture feeds a circular patch which radiates at its resonant frequency of 10.5 GHz. The proposed design is fabricated and the simulated results are verified experimentally. Equivalent circuit analysis is also done. A measured gain of 7.2 dBi is observed at 10.5 GHz. The physical area of the antenna is reduced without compromising the gain by judiciously choosing the shape of slot with more degree of freedom for impedance matching. The proposed antenna is well suited for the unit cell of phased array antennas for X-band missile radar applications. [ABSTRACT FROM AUTHOR]

This paper presents a Ka-band variable gain phase shifter with a non-linear DAC comprising an IQ generator, a pair of vector generators with a 180° phase difference, and a vector summation circuit. Non-linear DACs are used to simplify the phase control DACs and reduce phase errors. Between 29 GHz and 33 GHz, the insertion loss and total root mean square phase error are less than 5.02 dB and 1.71°, respectively. The device, which measured 0.259 mm² in size including the DACs, was fabricated using the 65-nm RF CMOS process. [ABSTRACT FROM AUTHOR]

The study of ionospheric effects1 on the satellite-based communication signals has been a continued topic of interest both for academic interest and global positioning system aided navigation applications. These communication signals are affected by the fieldaligned irregularities, suffers from fading and range spreading when they pass through the ionosphere.2 To study the low latitude ionospheric plasma irregularities, dedicated radar with wide beam steering capabilities is required. Recently Gadanki Ionospheric Radar Interferometer, which operates at 30 MHz frequency, has been realized at National Atmospheric Research Laboratory, Gadanki, to scan a larger part of the sky up to -50°C in East-West direction. The radar system employs a 160 element phased antenna array, antenna system, state-of-the-art 8 kW high power solid-state transmit-receive modules, and direct digital receiver. In order to carryout round-the-clock scientific observations, highly reliable, robust designs are required to realize the high power transmit-receive modules. Detailed design philosophies are described with modular concept and better thermal designs in this paper to achieve the high power requirements. Performance results of the transmit-receive module and the sample scientific results obtained by employing these transmit-receive modules are presented in this paper. [ABSTRACT FROM AUTHOR]

Background. In the medical field, work is underway to develop a special device designed to receive and process data from ultrasound sensors. This device aims to detect diseases at an early stage. Materials and methods. Ultrasound is used to measure the thickness of the walls of blood vessels and veins, which makes it possible to assess the state of the cardiovascular system. Ultrasonic sensors are placed on the patient's body in the form of a phased array, which helps to increase the accuracy and measurement area. Results and conclusions. The creation of a device for collecting and processing data from ultrasound sensors has great potential for early diagnosis of diseases of the human cardiovascular system.

This paper presents the design, development, and performance evaluation of a compact wideband phased array active helical antenna for monitoring HF interference. Traditional multi-element HF antenna designs are often subjected to size restrictions. The front-to-back ratio of the proposed circularly polarized phased array exceeds 20 dB across the operating range. This array enables the simultaneous monitoring of vertically and horizontally polarized signals, offering a practical alternative to larger antennas, particularly in space-constrained scenarios. Through advanced low-noise amplifier design, efficiency and bandwidth are optimized while mitigating mutual coupling effects. Optimal beamformer design enhances array performance with respect to more traditional array design approaches. The test results verify exceptional performance with an average axial ratio of 2 dB and a high front-to-back ratio beyond the desired frequency range. This study offers valuable insights into the design and deployment of compact wideband phased array antennas, providing an effective solution for monitoring HF interference.