Showing papers on "Phased array published in 2016"

Unconventional Phased Array Architectures and Design Methodologies—A Review

Abstract: The proliferation of wireless services is driving innovative phased array solutions that are able to provide better cost/performance tradeoffs. In this context, the use of irregular array architectures provides a viable solution. This paper reviews and highlights some of the most recent advances in this field, including clustered, thinned, sparse, and time-modulated arrays, and their proposed design methodologies.

The Evolution to Modern Phased Array Architectures

Abstract: Phased array technology has been evolving steadily with advances in solid-state microwave integrated circuits, analysis and design tools, and reliable fabrication practices. With significant government investments, the technologies have matured to a point where phased arrays are widely used in military systems. Next-generation phased arrays will employ high levels of digitization, which enables a wide range of improvements in capability and performance. Digital arrays leverage the rapid commercial evolution of digital processor technology. The cost of phased arrays can be minimized by utilizing high-volume commercial microwave manufacturing and packaging techniques. Dramatic cost reductions are achieved by employing a tile array architecture, which greatly reduces the number of printed circuit boards and connectors in the array.

Field-programmable beam reconfiguring based on digitally-controlled coding metasurface

Abstract: Digital phase shifters have been applied in traditional phased array antennas to realize beam steering. However, the phase shifter deals with the phase of the induced current; hence, it has to be in the path of each element of the antenna array, making the phased array antennas very expensive. Metamaterials and/or metasurfaces enable the direct modulation of electromagnetic waves by designing subwavelength structures, which opens a new way to control the beam scanning. Here, we present a direct digital mechanism to control the scattered electromagnetic waves using coding metasurface, in which each unit cell loads a pin diode to produce binary coding states of “1” and “0”. Through data lines, the instant communications are established between the coding metasurface and the internal memory of field-programmable gate arrays (FPGA). Thus, we realize the digital modulation of electromagnetic waves, from which we present the field-programmable reflective antenna with good measurement performance. The proposed mechanism and functional device have great application potential in new-concept radar and communication systems.

Generation of OAM Beams Using Phased Array in the Microwave Band

Abstract: A system is proposed to generate vortex electromagnetic (EM) beams in the microwave band, which generates high-order vortex beams at the X-frequency band for the first time. First, the orbital angular momentum (OAM)-generating system is designed and the signal model based on the uniform circular array is presented. Subsequently, the mathematical model with array error contributions is established and, comprehensively, numerical simulations are conducted to analyze how amplitude and phase errors affect the radiation field and the EM vortex imaging. The experimental results validate that the proposed system can readily generate vortex beams of high quality, which are in agreement with the simulated results. The work paves the way to applications of OAM-carrying beams as well as a novel information-rich radar paradigm.

Performance Analysis of Millimeter-Wave Phased Array Antennas in Cellular Handsets

Abstract: This letter discusses the usage of high-gain steerable antenna arrays operating at millimeter-wave (mmWave) frequencies for future cellular networks (5G). Based on the probable outline of the 5G networks, a method for characterizing phased array antennas in cellular handsets has been introduced. For analyzing the performance, the total scan pattern of the array configuration together with its respective coverage efficiency are essential to consider in order to compare different antenna designs and topology approaches with each other. Two design approaches and subarray schemes of these have been considered in order to illustrate the relevance of such a characterization method. The results show the importance of evaluating potential array antennas in such manners. The method can be applied to much more complex system models, where polarization diversity, hand and body effect, and statistical modeling of the channel may be included.

Benefits of Digital Phased Array Radars

Abstract: In this paper, an overview is given of the radar benefits of digital arrays in comparison with conventional phased arrays. Considered are passive and active phased arrays as well as subarray- and element-level digital arrays; their key differences are highlighted. A discussion of several radar attributes and performance measures follows to show the advantages and promise of element-level digital arrays as the newest generation architecture for radar and other electronic systems. Radar attributes considered are antenna patterns and beam control (including adaptive interference cancellation), dynamic range, in-band linearity, system phase noise, and angle measurement accuracy.

Overview of frequency diverse array in radar and navigation applications

Abstract: Different from phased array providing only angle-dependent transmit beampattern, frequency diverse array (FDA) employs a small frequency increment across its array elements to provide range-angle-dependent transmit beampattern. This enables the array beam to scan without the need of phase shifters or mechanical steering. Since FDA has received much attention in antenna and radar signal processing societies, it is necessary to make an overview on this interesting topic. This study introduces what FDA is and why it could be exploited for radar and navigation applications from a top-level system description and appeal to the radar signal processing and system engineering communities for more investigations on this promising array technique. The status of FDA studies is overviewed and the most recent advances of FDA radar are discussed. The basic FDA system architectures are introduced, along with performance compared to a conventional phased-array. Next, guidelines for choosing good system parameters and typical implementation schemes are provided. Finally, potential applications in range and angle estimation of targets, cognitive FDA radar and low probability of identification FDA radar are discussed, along with several technical challenges.

60-GHz 64- and 256-Elements Wafer-Scale Phased-Array Transmitters Using Full-Reticle and Subreticle Stitching Techniques

Abstract: This paper presents 60-GHz wafer-scale transmit phased arrays with 64- and 256-elements spaced $\lambda $ /2 apart in the $x$ - and $y$ -directions, and occupying an area of 21.4 $\times $ 22 mm2 (471 mm2) and 41.4 $\times $ 42 mm2 (1740 mm2), respectively. The 64-element phased array is built as a complete reticle and includes 64 independent transmit channels with 5-b phase control, 3-b (9 dB) amplitude control, a saturated output power of 3 dBm at the antenna port, a 1–64 distribution network with redundant line amplifiers, and a high-efficiency on-chip antenna at each element. In addition, redundant serial digital interface and power strips, dual series metal–insulator–metal capacitors, and multiple RF inputs are employed for improved yield. The 256-element array uses the same phased-array blocks as the 64-element design, but is built using a subreticle stitching technique so as to result in a chip which is larger than the standard reticle size (22 $\times $ 22 mm2). The 64- and 256-element arrays result in a half-power beamwidth of 12° and 6° in the $E$ - and $H$ -planes, a directivity of 23 and 29 dB, respectively, and scan to ±55° in the $E$ - and $H$ -planes with near-ideal patterns and a cross-polarization level of lesser than −30 dB. The measured equivalent isotropically radiated power (EIRP) of the 64-element array is 38 dBm at 62 GHz with a 3-dB bandwidth of 61–63 GHz, while that of the 256-element array is 45 dBm at 61 GHz with a 3-dB beamwidth of 58–64 GHz. A 1–4-Gb/s communication system is also demonstrated using the 64-element phased array up to ±45° scan angles, and at 4-, 30-, and 100-m ranges. To the best of our knowledge, this paper represents the first demonstration of large size (64- and 256-element) phased-array transmitters on a single wafer.

Photonic Multitasking Interleaved Si Nanoantenna Phased Array.

Abstract: Metasurfaces provide unprecedented control over light propagation by imparting local, space-variant phase changes on an incident electromagnetic wave. They can improve the performance of conventional optical elements and facilitate the creation of optical components with new functionalities and form factors. Here, we build on knowledge from shared aperture phased array antennas and Si-based gradient metasurfaces to realize various multifunctional metasurfaces capable of achieving multiple distinct functions within a single surface region. As a key point, we demonstrate that interleaving multiple optical elements can be accomplished without reducing the aperture of each subelement. Multifunctional optical elements constructed from Si-based gradient metasurface are realized, including axial and lateral multifocus geometric phase metasurface lenses. We further demonstrate multiwavelength color imaging with a high spatial resolution. Finally, optical imaging functionality with simultaneous color separation ha...

Multifunction Phased Array Radar for Aircraft and Weather Surveillance

Abstract: Multifunction phased array radar (MPAR) is a multiagency initiative to investigate the feasibility of replacing the aircraft surveillance and weather radar fleets in the US with a network of phased array radars based on a single, scalable architecture. The Federal Aviation Administration and the National Atmospheric and Oceanic Administration have been collaborating on MPAR risk reduction, which focuses on reducing cost, ensuring that the technology could accomplish all the missions within radar timelines, and developing dual polarization (dual pol) capability. The agencies have completed siting, cost, spectrum, dual pol, and back end studies, among others; have developed three dual pol architectures; and are building operational arrays to demonstrate that the technology can meet the basic needs of the agencies.

A Dual-Polarized 2–18-GHz Vivaldi Array for Airborne Radar Measurements of Snow

Abstract: This communication presents the experimental results of a ultrawideband 2–18-GHz dual-polarized Vivaldi antenna array for airborne radar measurements of snow. The antenna design is based on the previously reported all-metal flared-notch array by Kindt and Pickles for operation over the frequency range 0.7–9 GHz. An antenna array prototype consisting of $8 \times 8$ active dual-polarized elements was fabricated with precise aluminum machining and tested in the anechoic chamber. Beamsteering upto 30° was experimental demonstrated from 2 to 18 GHz. The measurement results are in a good agreement with the full-wave simulation results in both polarization configurations. Preliminary sample results from data collected using the Vivaldi array are also presented. The antenna array enables full polarimetric measurements of snow-over-sea-ice for estimating the snow-water-equivalent (SWE), as well as fine-resolution mapping of snow-air and snow-ice interfaces for estimating thickness.

Low RF-Complexity Technologies to Enable Millimeter-Wave MIMO with Large Antenna Array for 5G Wireless Communications

Abstract: Millimeter-wave (mmWave) MIMO with large antenna array has attracted considerable interests from academic and industry communities, as it can provide larger bandwidth and higher spectrum efficiency. However, with hundreds of antennas, the number of radio frequency (RF) chains required by mmWave MIMO is also huge, leading to unaffordable hardware cost and power consumption in practice. In this paper, we investigate low RF-complexity technologies to solve this bottleneck. We first review the evolution of low RF-complexity technologies from microwave frequencies to mmWave frequencies. Then, we discuss two promising low RF-complexity technologies for mmWave MIMO systems in detail, i.e., phased array based hybrid precoding (PAHP) and lens array based hybrid precoding (LAHP), including their principles, advantages, challenges, and recent results. We compare the performance of these two technologies to draw some insights about how they can be deployed in practice. Finally, we conclude this paper and point out some future research directions in this area.

Advanced Integration Techniques on Broadband Millimeter-Wave Beam Steering for 5G Wireless Networks and Beyond

Abstract: Recently, the desired very high throughput of 5G wireless networks drives millimeter-wave (mm-wave) communication into practical applications. A phased array technique is required to increase the effective antenna aperture at mm-wave frequency. Integrated solutions of beamforming/beam steering are extremely attractive for practical implementations. After a discussion on the basic principles of radio beam steering, we review and explore the recent advanced integration techniques of silicon-based electronic integrated circuits (EICs), photonic integrated circuits (PICs), and antenna-on-chip (AoC). For EIC, the latest advanced designs of on-chip true time delay (TTD) are explored. Even with such advances, the fundamental loss of a silicon-based EIC still exists, which can be solved by advanced PIC solutions with ultra-broad bandwidth and low loss. Advanced PIC designs for mm-wave beam steering are then reviewed with emphasis on an optical TTD. Different from the mature silicon-based EIC, the photonic integration technology for PIC is still under development. In this paper, we review and explore the potential photonic integration platforms and discuss how a monolithic integration based on photonic membranes fits the photonic mm-wave beam steering application, especially for the ease of EIC and PIC integration on a single chip. To combine EIC, for its accurate and mature fabrication techniques, with PIC, for its ultra-broad bandwidth and low loss, a hierarchical mm-wave beam steering chip with large-array delays realized in PIC and sub-array delays realized in EIC can be a future-proof solution. Moreover, the antenna units can be further integrated on such a chip using AoC techniques. Among the mentioned techniques, the integration trends on device and system levels are discussed extensively.

An Eight-Element 370–410-GHz Phased-Array Transmitter in 45-nm CMOS SOI With Peak EIRP of 8–8.5 dBm

Abstract: This paper presents a 370–410-GHz phased-array transmitter, which is based on a $W$ -band distribution network, amplifiers, and vector modulators, feeding a linear eight-element quadrupler array. The quadrupler outputs are connected to high-efficiency microstrip antennas. The design is scalable to a large number of elements, since most of the chip operates at $W$ -band frequencies. The chip is built using 45-nm CMOS silicon on insulator technology, which offers transistors with $f_{t}$ and $f_{\max }$ of 250–260 GHz referenced to the top metal. The phased array results an equivalent isotropic radiated power (EIRP) of >5 dBm at 375–405 dBm with a peak EIRP of 7–8.5 dBm at 380–400 GHz and with a pattern scan of +/−35° in one plane. To the best of our knowledge, this is one of the first demonstrations of a phased array operating at 400 GHz using CMOS technology and with wide operating bandwidth.

Forward facing sensing system for vehicle

Abstract: A forward facing sensing system comprises a windshield electronics module disposed in the interior cabin of a vehicle at and behind the windshield. A radar sensor device is disposed within the windshield electronics module and a forward facing image sensor is disposed within the windshield electronics module, and with both disposed behind or adjacent to an upper region of the windshield. A control comprising an image processor analyzes images captured by the forward facing image sensor in order to, at least in part, detect an object present forward of the vehicle in its direction of forward travel. The radar sensor device may utilize beam aiming or beam selection or may utilize digital beam forming or digital beam steering or may comprise an array antenna or a phased array antenna or the forward facing image sensor may comprise a pixelated imaging array sensor. The radar sensor device comprises a silicon germanium radar sensor.

Weather Radar Polarimetry

Abstract: This book presents the fundamentals of polarimetric radar remote sensing through understanding wave scattering and propagation in geophysical media filled with hydrometers and other objects. The text characterizes the physical, statistical, and electromagnetic properties of hydrometers and establishes the relations between radar observables and physical state parameters. It introduces advanced remote sensing techniques (such as polarimetric phased array radar) and retrieval methods for physical parameters. The book also illustrates applications of polarimetric radar measurements in hydrometer classification, particle size distribution retrievals, microphysical parameterization, and weather quantification and forecast.

Effect of Wideband Beam Squint on Codebook Design in Phased-Array Wireless Systems

Abstract: Analog beamforming with phased arrays is a promising technique for 5G wireless communication at millimeter wave frequencies. Using a discrete codebook consisting of multiple analog beams, each beam focuses on a certain range of angles of arrival or departure and corresponds to a set of fixed phase shifts across frequency due to practical hardware considerations. However, for sufficiently large bandwidth, the gain provided by the phased array is actually frequency dependent, which is an effect called beam squint, and this effect occurs even if the radiation pattern of the antenna elements is frequency independent. This paper examines the nature of beam squint for a uniform linear array (ULA) and analyzes its impact on codebook design as a function of the number of antennas and system bandwidth normalized by the carrier frequency. The criterion for codebook design is to guarantee that each beam's minimum gain for a range of angles and for all frequencies in the wideband system exceeds a target threshold, for example 3 dB below the array's maximum gain. Analysis and numerical examples suggest that a denser codebook is required to compensate for beam squint. For example, 54% more beams are needed compared to a codebook design that ignores beam squint for a ULA with 32 antennas operating at a carrier frequency of 73 GHz and bandwidth of 2.5 GHz. Furthermore, beam squint with this design criterion limits the bandwidth or the number of antennas of the array if the other one is fixed.

Moving-Target Tracking by Cognitive RF Stealth Radar Using Frequency Diverse Array Antenna

Abstract: Inspired by a cognitive radar in exploiting its environment to update current operation parameters and frequency diverse array (FDA) in offering a range-dependent beampattern due to the employment of frequency increments across the elements, this paper proposes a moving-target tracking approach to achieve cognitive radio frequency stealth using an FDA antenna for surveillance applications. Since surveillance systems are highly visible to intercept receivers, a traditional high-gain phased-array antenna beam is replaced by a series of low-gain FDA beams with spoiled frequency increments to reduce the system visibility, without degrading the surveillance system performance. Moreover, a cognitive closed-loop update scheme is presented to update the operation parameters in real time for improved moving-target tracking performance. All of the proposed methods are verified by simulation results.

An Eight-Element 2–16-GHz Programmable Phased Array Receiver With One, Two, or Four Simultaneous Beams in SiGe BiCMOS

Abstract: This paper presents an eight-element 2–16-GHz programmable phased array (PPA) receiver in a 0.13- $\mu \text{m}$ SiGe BiCMOS with the reconfigurable number of beams and with the digital beamforming (DBF) capabilities. The eight-element chip can be configured for one, two, or four simultaneous beams or as an element-level DBF receiver. This is achieved using reconfigurable input switching and output combining networks with wideband active switches and combiners. The phased array channel results in a 5-b performance at 3–14 GHz (rms error $P_{\text {1 dB}}$ of −20 dBm per channel when all channels are activated. The chip consumes 250 mW per channel, which is competitive knowing its bandwidth and linearity. The DBF function also results in a wideband response with a gain and an NF of 15–16 and 12–13 dB, respectively, and high linearity (input $P_{\text {1 dB}} = -16$ dBm) at 2–16 GHz. The programmable phased array receiver allows a single chip to be used over $S$ -, $C$ -, $X$ -, and $Ku$ -bands for a variety of applications such as satellite communications and point-to-point links. This results in faster and lower-cost phased array development since the same chip and its field-programmable gate array control can be reused from system to system, but with different antenna and grid spacing. The PPA removes the need to develop a different chip for every application and allows the development of phased arrays at commercial scales.

Radiating Elements for Shared Aperture Tx/Rx Phased Arrays at K/Ka Band

Abstract: A dual-band, Tx/Rx, self-diplexing phased array is presented. The antenna has been designed to cover Tx/Rx satellite communications at K/Ka band with a frequency ratio 1.5:1. To obtain dual-band operations with a single radiating surface, a novel dual-band radiator is adopted and placed in a configuration in which dual-band and single-band elements are interleaved. The proposed configuration reduces the number of radiating elements required by other solutions while avoiding the insurgence of grating lobes. The tightly packed arrangement of the elements poses many integration issues, which are solved with a novel integration technique. The array elements are optimized to scan the beam in excess of 50° in both bands. A subarray with 49 Rx elements and 105 Tx elements was built and measured confirming the results obtained in simulations.

Ultrasonic phased array detection of internal defects in composite insulators

Abstract: To reduce the risk imposed by use of defected composite insulators on the operation of power grids, this paper introduces a nondestructive ultrasonic phased array (UPA) technique that allows effectively test such insulators. The method offers a great potential by reducing inspection time as well as allowing for analyzing components characterized by a complex geometry. The UPA inspection system utilizes an openended rectangular waveguide sensor, operating at frequency of 2.5 MHz. The system is simple, safe and relatively inexpensive. In this work, samples of silicone rubber composite insulators with various types of detects are studied and the obtained results show that void defects in the bulk of the insulator housing are easiest to be detected. Holes under insulator sheds can also be detected by the edge of scanning range. For the defects near the core-shed interface, the detection becomes possible by comparisons with sample without defects.

Wide-Beam SIW-Slot Antenna for Wide-Angle Scanning Phased Array

Abstract: In order to enhance the scanning range of planar phased arrays, a planar substrate integrated waveguide slot (SIW-slot) antenna with wide beamwidth is proposed in this letter. The proposed antenna is fabricated on a single-layer substrate, which is fully covered with a metal ground on the back. The SIW works like a dielectric-filled rectangular waveguide working in the ${TE}_{10}$ mode. There are four inclined slots etched on the top metal layer following the rules of rectangular waveguide slot antenna. The electric fields in the slots work as equivalent magnetic currents. As opposed to normal microstrip antennas, the equivalent magnetic currents from the slots over a larger metal ground can radiate with a wide beamwidth. Its operating bandwidth is from 5.4 to 6.45 GHz with a relative bandwidth of 17.7%. Meanwhile, the 3-dB beamwidth in the ${x}{z}$ -plane is between 130° and 148° in the whole operating band. Furthermore, the SIW-slot element is employed in a ${1} \times {8}$ planar phased array. The measured results show that the main lobe of phased array can obtain a wide-angle scanning from $- {\hbox{71}}^\circ $ to 73° in the whole operating band.

Random Feeding Networks for Reducing the Number of Phase Shifters in Limited-Scan Arrays

Abstract: A new phased-array feeding network that results in low sidelobe levels (SLLs) over a limited scan region is demonstrated. The proposed concept groups the individual phased-array elements into random sequences of nonuniform subarrays and employs a single phase shifter (PS) for each subarray. When these random sequences are optimized, the resulting phased array can scan over a wide angle with low SLLs. A methodology for analyzing the random arrays is provided, multiple cases with different numbers of PSs and subarray groups are optimized, and design guidelines are presented. The performance of the random arrays is compared with conventional uniform subarrays and it is shown that random arrays reduce the number of PSs by up to 40% while preserving the same performance. A random array is demonstrated at 7.9 GHz for a 30-element linear design (scan in one direction) with 12 PSs and results in a half-power beamwidth of 4.1° with a scan angle up to ±14° and SLLs less than −15 dB. It is also shown that random arrays can be used in 2-D phased arrays with up to 60% reduction in the number of PSs. Application areas are in low-cost phased arrays with limited scan angles such as automotive radars or landing systems.

Microstrip Phased-Array In-Band RCS Reduction With a Random Element Rotation Technique

Abstract: The techniques of random antenna element distribution and rotation have been proposed to design a low sidelobe and low cross-polarization phased array or reflect array for a long time. In this communication, we demonstrate that the use of randomly rotated (RR) elements can provide random scattering phases and phase center distributions, which can lead to an in-band radar cross section (RCS) reduction for the array. To illustrate the effectiveness of the proposed method, three $8 \times 8$ circularly polarized (CP) microstrip arrays, 1) the uniform array without rotation; 2) sequentially rotated (SR) array; and 3) RR array, are compared and analyzed. Results indicate that the RCS of the RR array can be reduced significantly, even in the main beam region, while maintaining its high radiation performance.

A Ka-band digitally-controlled phase shifter with sub-degree phase precision

Abstract: We present a passive digital-to-phase converter with sub-degree phase precision for phased array frontends. The phase tuning approach is based on manipulating the electromagnetic properties of an artificially constructed transmission line. By simultaneously controlling dispersion, characteristic impedance, and loss across the structure, the phase shifter minimizes phase imprecisions while ensuring a flat amplitude response across different phase settings. The chip prototype is fabricated in a 130nm SiGe BiCMOS process, occupies an area of 0.18mm2, and consumes no power. The insertion loss is −9.3 dB ± 0.25 dB at 28 GHz. The phase control operates with 4.75 degree steps while maintaining an RMS phase error of 0.6 degrees across multiple chips and temperatures, demonstrating the best phase and amplitude accuracy when compared to state-of-the-art integrated microwave and mm-wave phase shifters.

High-Sensitivity Phased Array Receivers for Radio Astronomy

Abstract: Phased arrays have a long history in radio astronomy. Large, sparse synthesis arrays have been in use for decades to capture high-resolution images of deep space objects. More recent work has extended the range of applications to other types of arrays, including aperture arrays (AAs) and phased array feeds (PAFs) for multibeam reflector antennas. The extreme sensitivity required for astronomical instrumentation is driving advances in numerical electromagnetic modeling, design optimization of large arrays, low noise amplifiers, minimization of receiver noise, cryogenic PAFs, array calibration, optimal beamforming, interferometric imaging, and array signal processing algorithms for radio-frequency interference mitigation. We give an overview of research progress, current and planned array-based instruments, and open challenges in these areas related to the new generation of sparse arrays, PAFs, and AAs that are in development for astronomical observatories around the world.

A multi-frequency sparse hemispherical ultrasound phased array for microbubble-mediated transcranial therapy and simultaneous cavitation mapping

Abstract: Focused ultrasound (FUS) phased arrays show promise for non-invasive brain therapy. However, the majority of them are limited to a single transmit/receive frequency and therefore lack the versatility to expose and monitor the treatment volume. Multi-frequency arrays could offer variable transmit focal sizes under a fixed aperture, and detect different spectral content on receive for imaging purposes. Here, a three-frequency (306, 612, and 1224 kHz) sparse hemispherical ultrasound phased array (31.8 cm aperture; 128 transducer modules) was constructed and evaluated for microbubble-mediated transcranial therapy and simultaneous cavitation mapping. The array is able to perform effective electronic beam steering over a volume spanning (-40, 40) and (-30, 50) mm in the lateral and axial directions, respectively. The focal size at the geometric center is approximately 0.9 (2.1) mm, 1.7 (3.9) mm, and 3.1 (6.5) mm in lateral (axial) pressure full width at half maximum (FWHM) at 1224, 612, and 306 kHz, respectively. The array was also found capable of dual-frequency excitation and simultaneous multi-foci sonication, which enables the future exploration of more complex exposure strategies. Passive acoustic mapping of dilute microbubble clouds demonstrated that the point spread function of the receive array has a lateral (axial) intensity FWHM between 0.8-3.5 mm (1.7-11.7 mm) over a volume spanning (-25, 25) mm in both the lateral and axial directions, depending on the transmit/receive frequency combination and the imaging location. The device enabled both half and second harmonic imaging through the intact skull, which may be useful for improving the contrast-to-tissue ratio or imaging resolution, respectively. Preliminary in vivo experiments demonstrated the system's ability to induce blood-brain barrier opening and simultaneously spatially map microbubble cavitation activity in a rat model. This work presents a tool to investigate optimal strategies for non-thermal FUS brain therapy and concurrent microbubble cavitation monitoring through the availability of multiple frequencies.

A Wide-Angle Scanning and Low Sidelobe Level Microstrip Phased Array Based on Genetic Algorithm Optimization

Abstract: In order to obtain a wide-angle scanning and low sidelobe level (SLL) microstrip phased array with a finite metal ground, a novel microstrip phased array based on microstrip magnetic dipole is presented in this communication. Microstrip magnetic dipoles are employed as the driven elements in the phased array. Meanwhile, coupling patches are embedded between the adjacent driven elements, and coupling energy is transferred between driven elements by the coupling patches. Strong coupling has been constructed between elements as the driven element spacing is only about ${0}.\text{35}\; {\lambda}$ . With the influence of adjacent elements, the 3-dB beamwidth (BW) of each active element can reach over $\pm \text{80}^\circ $ in the elevation plane. From simulation and measurement, the main lobe scanning ranges of an 8-element and a 16-element phased arrays can both extend over $\pm \text{80}^\circ $ in the elevation plane with a gain fluctuation less than 3 dB. Furthermore, in order to keep the SLL low in the scanning, especially at the low elevation angles, genetic algorithm (GA) has been used, and the SLL has been decreased to the value of $- \text{9}\;\text{dB}$ in the full scanning range of $\pm \text{77}^\circ $ for the eight-element array.

EMF Exposure Study Concerning mmWave Phased Array in Mobile Devices for 5G Communication

Abstract: The electromagnetic field (EMF) exposure to millimeter-wave (mmWave) phased arrays in mobile devices for 5G communication is analyzed in this letter. Unlike the current cellular band, the EMF exposure in the mmWave band (10–200 GHz) is evaluated by the free-space power density instead of the specific absorption rate. However, current regulations have not been well defined for the mobile device application. In this letter, we present the power density property of phased arrays in mobile devices at 15 and 28 GHz. Uniform linear patch arrays are used, and different array configurations are compared. Suggestions for the power density evaluation are also provided.