Showing papers on "Phased array published in 2015"
TL;DR: An unambiguous approach for joint range and angle estimation is devised for multiple-input multiple-output (MIMO) radar with frequency diverse array (FDA), which is capable of employing a small frequency increment across the array elements.
Abstract: Phased array is widely used in radar systems with its beam steering fixed in one direction for all ranges. Therefore, the range of a target cannot be determined within a single pulse when range ambiguity exists. In this paper, an unambiguous approach for joint range and angle estimation is devised for multiple-input multiple-output (MIMO) radar with frequency diverse array (FDA). Unlike the traditional phased array, FDA is capable of employing a small frequency increment across the array elements. Because of the frequency increment, the transmit steering vector of the FDA-MIMO radar is a function of both range and angle. As a result, the FDA-MIMO radar is able to utilize degrees-of-freedom in the range-angle domains to jointly determine the range and angle parameters of the target. In addition, the Cramer–Rao bounds for range and angle are derived, and the coupling between these two parameters is analyzed. Numerical results are presented to validate the effectiveness of the proposed approach.
316 citations
TL;DR: In this article, an acoustic phased array using a metascreen that transmits sound energy from a single source and steers the outgoing wavefront in the desired direction is presented.
Abstract: Manipulating sound waves is key in applications such as ultrasound imaging and nondestructive testing. To this end, the authors present an acoustic phased array using a metascreen that transmits sound energy from a single source and steers the outgoing wavefront in the desired direction. Significantly, this metascreen does not itself contain any source of sound, unlike a conventional phased array with many individual sources. This passive array is therefore notably appealing for its simplicity, low cost, and good acoustic performance.
285 citations
TL;DR: This work reports the first monolithic optical phased array transceiver with independent control of amplitude and phase for each element using electronic circuitry that is tightly integrated with the nanophotonic components on one substrate using a commercial foundry CMOS SOI process.
Abstract: Monolithic microwave phased arrays are turning mainstream in automotive radars and high-speed wireless communications fulfilling Gordon Moores 1965 prophecy to this effect. Optical phased arrays enable imaging, lidar, display, sensing, and holography. Advancements in fabrication technology has led to monolithic nanophotonic phased arrays, albeit without independent phase and amplitude control ability, integration with electronic circuitry, or including receive and transmit functions. We report the first monolithic optical phased array transceiver with independent control of amplitude and phase for each element using electronic circuitry that is tightly integrated with the nanophotonic components on one substrate using a commercial foundry CMOS SOI process. The 8 × 8 phased array chip includes thermo-optical tunable phase shifters and attenuators, nano-photonic antennas, and dedicated control electronics realized using CMOS transistors. The complex chip includes over 300 distinct optical components and over 74,000 distinct electrical components achieving the highest level of integration for any electronic-photonic system.
185 citations
TL;DR: In this paper, a frequency diverse array (FDA) antenna with a small frequency increment, as compared with the carrier frequency, across array elements is proposed for range-dependent energy control.
Abstract: i»?Phased-array antennas are known for their capability to electronically steer a beam with high effectiveness, but beam steering is fixed in an angle for all range cells. This paper reviews frequency diverse array (FDA) antennas. Different from a phased array, an FDA uses a small frequency increment, as compared with the carrier frequency, across array elements. The use of a frequency increment generates an array factor that is a function of the angle, the time, and the range, allowing the FDA antenna to transmit the energy over the desired range and angle. In addition to analyzing FDA factor characteristics, this paper investigates FDA potential applications in range-dependent energy control and technical challenges in system implementation, with an aim to call for further investigations on the FDA.
173 citations
TL;DR: In this paper, a novel partially reflective surface (PRS) antenna with the capability of beam steering is presented, which is realized by employing a reconfigurable PRS structure to achieve a changeable reflection phase as well as using a phased array as the source to excite the PRS antenna.
Abstract: The design of a novel partially reflective surface (PRS) antenna with the capability of beam steering is presented in this paper. The beam steering is realized by employing a reconfigurable PRS structure to achieve a changeable reflection phase as well as using a phased array as the source to excite the PRS antenna. A prototype antenna including the biasing network is fabricated and measured. It achieves a consistent beam steering from – 15° to 15° with respect to the broadside direction across an overlapped frequency range from 5.5 to 5.7 GHz with measured realized gains over 12 dBi. Good agreement between the simulated and measured results for the input reflection coefficients and radiation patterns is achieved, which validates the feasibility of the design principle. Compared with other beam steering PRS antennas, the proposed one enables a larger beam steering angle with comparable gains, requires a simpler biasing network, and is more compact.
149 citations
Patent•
16 Mar 2015
TL;DR: In this paper, access point (AP) antenna apparatuses for communicating with one or more station devices by assigning a particular directional beam to each access point, and communicating with each station device using the assigned directional beam.
Abstract: Multi-directional antenna apparatuses, including phased array antennas and/or arrays of multiple antennas, and methods for operating them. In particular, described herein are access point (AP) antenna apparatuses for communicating with one or more station devices by assigning a particular directional beam to each access point, and communicating with each station device using the assigned directional beam. Methods and apparatuses configured to optimize the assignment of one or more directional beam and for communicating between different station devices using assigned directional beams are described. Also described are compact lacunated RF lenses that may be used with the multi-directional antenna apparatuses described herein, having a plurality of holes/openings through the lens body so that an electromagnetic signal entering the lens body from any of the input ports into the lens will exit from each of the output ports at a time delay corresponding to a predetermined steering angle.
132 citations
TL;DR: In this article, a wide-beam antenna and a planar phased array with wide-angle scanning performance based on image theory are proposed. But the main beam direction of the array can scan from the broadside direction to the end-fire direction.
Abstract: A wide-beam antenna and a planar phased array with wide-angle scanning performance based on image theory are proposed. To solve the wide-angle scanning problem, a summative evaluation of basic types of carrier-based antennas is given and the antenna types available for wide-angle scanning arrays or end-fire arrays are pointed out. Afterward, a wide-angle scanning array with an artificial magnetic conductor (AMC) ground is proposed. The main beam direction of the array can scan from $- \mathbf{ 89}^\circ \;\mathbf{ to}\;\mathbf{ 90}^\circ $ in the H-plane with a gain fluctuation less than 3 dB and the scanning 3-dB beamwidth can cover a range from $- \mathbf{ 105}^\circ \;\mathbf{ to}\;\mathbf{ 105}^\circ $ . An excellent wide-angle scanning performance from the broadside direction to the end-fire direction can be obtained by the proposed method, which can be used to guide the design of wide-angle scanning arrays.
127 citations
TL;DR: A new concept for phased-array sources at infrared frequencies based on metamaterial nanocavities coupled to a highly nonlinear semiconductor heterostructure is proposed, which will enable such phased arrays to span most of the infrared spectrum.
Abstract: Coherent superposition of light from subwavelength sources is an attractive prospect for the manipulation of the direction, shape and polarization of optical beams. This phenomenon constitutes the basis of phased arrays, commonly used at microwave and radio frequencies. Here we propose a new concept for phased-array sources at infrared frequencies based on metamaterial nanocavities coupled to a highly nonlinear semiconductor heterostructure. Optical pumping of the nanocavity induces a localized, phase-locked, nonlinear resonant polarization that acts as a source feed for a higher-order resonance of the nanocavity. Varying the nanocavity design enables the production of beams with arbitrary shape and polarization. As an example, we demonstrate two second harmonic phased-array sources that perform two optical functions at the second harmonic wavelength (∼5 μm): a beam splitter and a polarizing beam splitter. Proper design of the nanocavity and nonlinear heterostructure will enable such phased arrays to span most of the infrared spectrum.
126 citations
TL;DR: A pulsed-FDA is proposed with an aim to generate quasi-static beampattern and the corresponding constraint is derived together with the method to control the mainbeam direction.
Abstract: Different from the conventional phased array, frequency diverse array (FDA) can provide electronic beam scanning without phase shifters and its beam steering is range-angle-dependent. Nevertheless, reported studies on FDA are most in continuous waveforms and the corresponding beampattern is time-variant, which increases difficulty in controlling the mainbeam direction and complexity of signal processing. To alleviate this problem, a pulsed-FDA is proposed with an aim to generate quasi-static beampattern in this communication. The corresponding constraint is derived together with the method to control the mainbeam direction. Moreover, the range-angle-dependent characteristics of the quasi-static transmit/receive beampattern are addressed considering the radar applications. Besides, range-angle-dependent beampattern significantly enhances the flexibility of beam scanning and its signal processing. Simulation results are in good agreement with the theoretical analysis.
118 citations
TL;DR: In this paper, the authors proposed an ultra-thin metasurface composed of a sheet of split-ring resonators (SRRs) to improve the scanning characteristics of a dipole phased array.
Abstract: The effects of mutual coupling impact the performance of phased arrays as the beam is scanned off broadside. Wide-angle impedance matching (WAIM) alleviates this problem from a transmission-line impedance matching viewpoint, increasing the useable scan range of the array. Traditionally, a dielectric slab is placed at some distance above the array, resulting in a match at some given angle off broadside. We propose a simpler and more effective solution, replacing the dielectric slab with an ultra-thin metasurface composed of a sheet of split-ring resonators (SRRs) to improve the scanning characteristics of a dipole phased array. It is shown that the presence of the metasurface results in significant improvements in multiple scan planes. A generalized equivalent transmission-line model is introduced for the classical WAIM configuration and adapted for the metasurface. A quasi-analytical model based on the equivalent transmission-line model and the extracted scattering parameters of the metasurface properly predicts the scan range of the full structure, and allows for an accelerated design process.
103 citations
TL;DR: In this article, the authors theoretically demonstrate the tunability of infrared scattering phase and radiation patterns in low-loss, high-index dielectric resonators using free carrier refraction.
Abstract: Phased-array metamaterial systems are enabling new classes of refractive and diffractive optical elements through spatial-phase engineering. In this article, we develop design principles for reconfigurable optical antennas and metasurfaces. We theoretically demonstrate the tunability of infrared scattering phase and radiation patterns in low-loss, high-index dielectric resonators using free carrier refraction. We demonstrate reconfigurable endfire antennas based on interference between multiple elements. Within single resonators, we demonstrate reconfigurable broadside antenna radiation lobes arising from interfering electric and magnetic dipole resonances. Extending this concept to infinite arrays, we design ideal Huygens metasurfaces with spectrally overlapping electric and magnetic dipole resonances. By introducing free charge carriers into these metasurfaces, we demonstrate continuously tunable transmission phase between 0 and 2π with less than 3 dB loss in intensity. Such tunable metasurfaces may for...
TL;DR: This chip presents the first fully integrated terahertz phased array on silicon and the output power is higher than any lens-less silicon-based source above 200 GHz and the phase noise is lower than all silicon radiating sources above 100 GHz.
Abstract: This work introduces a 2-D phased array architecture that is suitable for high power radiation at mm-Wave and Terahertz frequencies. We address the challenge of signal generation above the cut-off frequency of transistors by presenting a radiation method based on the collective performance of a large number of synchronized sources. As theory shows, both frequency locking/tuning and beam steering can be independently achieved by manipulating the local coupling between the nearest neighbors. This control method results in a dynamical network that is insensitive to array dimensions and is scalable to the point that can achieve a level of output power and spectral purity beyond the reach of conventional sources. To demonstrate the concept, we implement a 4 $\times$ 4 version of this phased array at 340 GHz using a 65 nm bulk CMOS process. The paper presents the design and implementation of the oscillators, couplings and the integrated antennas. The measured results at 338 GHz reveal a peak equivalent isotropically radiated power (EIRP) of +17.1 dBm and a phase noise of -93 dBc/Hz at the 1 MHz offset frequency. This chip presents the first fully integrated terahertz phased array on silicon. Furthermore, the output power is higher than any lens-less silicon-based source above 200 GHz and the phase noise is lower than all silicon radiating sources above 100 GHz.
TL;DR: In this paper, a new in-phase/quadrature (I/Q) complex modulation technique to realize single-sideband time-modulated phase-only weighting on an array antenna is proposed.
Abstract: A new in-phase/quadrature (I/Q) complex modulation technique to realize single-sideband time-modulated phase-only weighting on an array antenna is proposed. Based on modulating rectangular pulses and trapezoidal pulses, the theories of generating a scanning beam at the single positive sideband are presented. It was found that using trapezoidal pulse modulation can obtain excellent performance in power efficiency and undesired sideband level than using rectangular pulse modulation. Unlike conventional time-modulated antenna array where each array element is connected to a RF switch, in the proposed scheme, each element is connected to an I/Q channel modulator which is composed of two Wilkinson power dividers, two RF switches, two $0/\pi $ phase shifters in RF channels, and one $\pi/2 $ fixed-phase shifter in the control circuit. By properly controlling both the phase shifters and the switches in time domain, the single-sideband modulation can be realized with the uniform amplitude and variable phase in frequency domain. The I/Q modulator acts as a phase shifter and can be used to form a phased array. In this paper, the main efforts have been paid to find the pulse sequences to suppress the spurious bands. To validate the proposed technique, simulated results of an eight-element single-sideband time-modulated linear array obtained from the array factor and full-wave analysis are reported. In the case of using rectangular pulses, the power efficiency of the scanning beam is 91.47% and the peak level of the highest undesired harmonic is $-13.98\;\mathrm{dB} $ . In the case of using trapezoidal pulses, the best values can reach 99.79% and $-27.98\;\mathrm{dB} $ .
TL;DR: In this article, a 3D printed RF front end for a 2.45 GHz unit cell is presented, which includes a circularly-polarized dipole antenna, a miniaturized capacitive-loaded open-loop resonator filter and a 4-bit phase shifter.
Abstract: This paper reports on the design, fabrication and characterization of a 3-D printed RF front end for a 2.45 GHz phased array unit cell. The printed unit cell, which includes a circularly-polarized dipole antenna, a miniaturized capacitive-loaded open-loop resonator filter and a 4-bit phase shifter, is fabricated using a direct digital manufacturing (DDM) approach that integrates fused deposition of thermoplastic substrates with micro-dispensing for deposition of conductive traces. The individual components are combined in a passive phased array antenna unit cell comprised of seven stacked substrate layers with seven conductor layers. The measured return loss of the unit cell is ${>}12$ dB across the 2.45 GHz ISM band and the measured gain is ${-}11$ dBi including all components. Experimental and simulation-based characterization is performed to investigate electrical properties of as-printed materials, in particular the inhomogeneity of printed thick-film conductors and substrate surface roughness. The results demonstrate the strong potential for fully-printed RF front ends for light weight, low cost, conformal and readily customized applications.
TL;DR: 3-D SWE based on ultrafast volumetric imaging in a clinically applicable configuration is demonstrated based on a 32 × 32 matrix phased array driven by a customized, programmable, 1024-channel ultrasound system to perform 4-D shear-wave imaging.
Abstract: Over the last ten years, shear wave elastography (SWE) has seen considerable development and is now routinely used in clinics to provide mechanical characterization of tissues to improve diagnosis. The most advanced technique relies on the use of an ultrafast scanner to generate and image shear waves in real time in a 2-D plane at several thousands of frames per second. We have recently introduced 3-D ultrafast ultrasound imaging to acquire with matrix probes the 3-D propagation of shear waves generated by a dedicated radiation pressure transducer in a single acquisition. In this study, we demonstrate 3-D SWE based on ultrafast volumetric imaging in a clinically applicable configuration. A 32 × 32 matrix phased array driven by a customized, programmable, 1024-channel ultrasound system was designed to perform 4-D shear-wave imaging. A matrix phased array was used to generate and control in 3-D the shear waves inside the medium using the acoustic radiation force. The same matrix array was used with 3-D coherent plane wave compounding to perform high-quality ultrafast imaging of the shear wave propagation. Volumetric ultrafast acquisitions were then beamformed in 3-D using a delay-and-sum algorithm. 3-D volumetric maps of the shear modulus were reconstructed using a time-of-flight algorithm based on local multiscale cross-correlation of shear wave profiles in the three main directions using directional filters. Results are first presented in an isotropic homogeneous and elastic breast phantom. Then, a full 3-D stiffness reconstruction of the breast was performed in vivo on healthy volunteers. This new full 3-D ultrafast ultrasound system paves the way toward real-time 3-D SWE.
TL;DR: An iterative strategy is implemented by combining a fast EM modeling tool for the computation of the voltage reflection coefficient at the array surface and a solution-space sampling loop driven by the set of physical constraints describing both the synthesis objectives and the range boundaries for the degrees-of-freedom (DoFs) of the problem at hand.
Abstract: The synthesis of multilayer wide-angle impedance-matching (WAIM) structures for waveguide-fed planar phased array antennas is addressed. Under multifrequency constraints and assuming arbitrary array layouts, the synthesis problem is formulated within the system-by-design (SbD) framework. An iterative strategy is implemented by combining a fast EM modeling tool for the computation of the voltage reflection coefficient at the array surface and a solution-space sampling loop driven by the set of physical constraints describing both the synthesis objectives and the range boundaries for the degrees-of-freedom (DoFs) of the problem at hand. Thanks to the effectiveness and the reliability of such an integrated approach, it is possible to deal with multilayer multifrequency WAIM structures with uniaxially anisotropic permittivity and permeability tensors. Selected numerical results are presented to assess the potentialities and the reliability of the proposed approach also in comparison with state-of-the-art techniques.
TL;DR: In this article, an improved phased array using pattern reconfigurable antenna elements in this communication is proposed to realize wide-angle scanning performance with low gain fluctuation, where the antenna array is a microstrip Yagi antenna with its parasitic strips loaded with varactors.
Abstract: An improved phased array using pattern reconfigurable antenna elements in this communication is proposed to realize wide-angle scanning performance with low gain fluctuation. The pattern reconfigurable element is a microstrip Yagi antenna with its parasitic strips loaded with varactors. The reconfigurability of radiation pattern from the element is enabled by tuning the capacitive reactance of the varactors. Five elements were arranged in an equally spaced linear array, and the effects of several key parameter variations on the radiation characteristics of the array are provided. The proposed array is fabricated and experimentally verified. It is seen from the measured results that the main beam of the array can scan from $- 70^\circ $ to 70° in the $H$ -plane with a gain fluctuation less than 2 dB. Meanwhile, the coverage of 3-dB beamwidth of the array is from about $- 87^\circ $ to 87°. The agreement between simulated and measured results validates our design exhibiting a good performance of wide-angle scanning.
TL;DR: In this paper, a 77 GHz transmit-array on dual-layer printed circuit board (PCB) is proposed for automotive radar applications, where coplanar patch unit-cells are etched on opposite sides of the PCB and connected by through-via.
Abstract: A 77-GHz transmit-array on dual-layer printed circuit board (PCB) is proposed for automotive radar applications. Coplanar patch unit-cells are etched on opposite sides of the PCB and connected by through-via. The unit-cells are arranged in concentric rings to form the transmit-array for 1-bit in-phase transmission. When combined with four-substrate-integrated waveguide (SIW) slot antennas as the primary feeds, the transmit-array is able to generate four beams with a specific coverage of $\pm 15^{\circ}$ . The simulated and measured results of the antenna prototype at 76.5 GHz agree well, with gain greater than 18.5 dBi. The coplanar structure significantly simplifies the transmit-array design and eases the fabrication, in particular, at millimeter-wave frequencies.
TL;DR: In this paper, a waveguide hybrid phased array (HPA) for mobile satellite communications operating in the Ku-band is proposed, which adopts an electrical scan in elevation and mechanical scan in azimuth to track satellites.
Abstract: This paper introduces a novel waveguide hybrid phased array (HPA) for mobile satellite communications operating in Ku-band. The array is low profile and low cost, adopting an electrical scan in elevation and mechanical scan in azimuth to track satellites. High directivity and wide bandwidth impedance is provided by a dual linear polarized waveguide radiating element that covers both Rx and Tx frequencies within the band. The vertical and horizontal polarizations are excited by direct feeding and slot coupled aperture feeding, respectively. The array structure of $32 \times 12$ elements is split into inclined and interlaced 12 subarrays 225 mm in height. The feed networks and duplexers are designed in unconventional waveguide sizes. In the system, there are 12 independent receiving (Rx) and transmitting (Tx) modules with phased shifter components, which realize beam and polarization tracking. The system is designed to track satellites by scanning $15^\circ{-}75^\circ$ (relative to the ground plane) electrically in the elevation and $0^\circ{-}360^\circ$ mechanically in the azimuth. The array has been successfully developed and measured. The maximal gain loss in scanning range is about 4.0 dB.
TL;DR: In this article, an efficient decoupling network is developed to reduce the mutual coupling between adjacent elements for wide-angle impedance matching (WAIM), and a linear microstrip phased array has been designed and fabricated for experimental verification.
Abstract: The active impedance of each element in a phased array changes substantially with scan angle due to mutual coupling. Therefore, a key challenge in the design of wide-angle scanning phased array is to achieve wide-angle impedance matching (WAIM). In this communication, an efficient decoupling network is developed to reduce the mutual coupling between adjacent elements for this purpose. A complete scattering matrix analysis of the decoupling network is given and the design procedure is summarized. A ${1} \times {16}$ linear microstrip phased array has been designed and fabricated for experimental verification. Good agreement is obtained between measured and simulated results. The measured mutual coupling between adjacent elements is reduced to lower than $- {35}\; \text{dB}$ at the center frequency. Due to the reduced mutual coupling, the array can experimentally scan to 66° with a gain reduction of only 3.04 dB.
TL;DR: In this article, a near-field magnetically coupled resonator is used to determine the optimal magnitude and phase of each transmitter to deliver power to one or more receivers in a phased array wireless power transfer system.
Abstract: Efficient wireless power transfer and precise control of power delivery and leakage field strength can be achieved using a phased array wireless power transfer system. This has particular importance for charging multiple devices simultaneously, or charging devices in environments where humans or foreign objects will be in close proximity. The phased array wireless power system consists of two or more phase-synchronized power amplifiers each driving a respective transmit coil. The system can maximize power delivery to an intended receiver in one location while simultaneously minimizing power delivery and leakage fields in other locations. These functions are possible by varying the amplitude and phase of each transmitter. This paper provides an analysis of a phased array wireless power transfer system using near-field magnetically coupled resonators, and derives parameters that can be used to automatically determine the optimal magnitude and phase of each transmitter to deliver power to one or more receivers. Experimental results verify the theoretical analysis and additional features of the full system are demonstrated.
TL;DR: The benefits and challenges associated with the design of multi-function scalable phased arrays at millimeter wave frequencies are discussed, and a solution based on SiGe ICs and organic packages for a 64-element dual-polarized 94 GHz phased array is described.
Abstract: This article discusses the benefits and challenges associated with the design of multi-function scalable phased arrays at millimeter wave frequencies. First, applications for phased arrays with tens to hundreds of elements are discussed. Existing solutions for scaling silicon-based phased arrays from microwave to terahertz frequencies are reviewed. The challenges and tradeoffs associated with multiple integration options for W-band phased arrays are analyzed, with special consideration given to packaging and antenna performance. Finally, a solution based on SiGe ICs and organic packages for a 64-element dual-polarized 94 GHz phased array is described, along with associated measurement results.
TL;DR: In this paper, an efficient decoupling feeding network is proposed, which is composed of two directional couplers and two sections of transmission line for connection use, which can be used to cancel out the direct coupling caused by space waves and surface waves between array elements.
Abstract: An efficient decoupling feeding network is proposed in this letter. It is composed of two directional couplers and two sections of transmission line for connection use. By connecting the two couplers, an indirect coupling with controlled magnitude and phase is introduced, which can be used to cancel out the direct coupling caused by space waves and surface waves between array elements. To demonstrate the method, a two-element microstrip antenna array with the proposed network has been designed, fabricated and measured. Both simulated and measured results have simultaneously proved that the proposed method presents excellent decoupling performance. The measured mutual coupling can be reduced to below $-58 ~\hbox{dB}$ at center frequency. Meanwhile it has little influence on return loss and radiation patterns. The decoupling mechanism is simple and straightforward which can be easily applied in phased array antennas and MIMO systems.
28 Dec 2015
TL;DR: A new technique for dual-function radar-communications in a transmit multi-sensor array where information embedding is achieved using phase-rotational invariance and is inherently secure against interception from directions other than the desired communication direction.
Abstract: In this paper, we develop a new technique for dual-function radar-communications in a transmit multi-sensor array where information embedding is achieved using phase-rotational invariance. A sequence of Q bits is first mapped into a dictionary of 2Q phase rotations. Then, one pair of transmit orthogonal waveforms is used in tandem with 2Q pairs of transmit beamforming weight vectors for embedding a certain entry of the phase-rotation dictionary during each radar pulse. The same pair of waveforms is used during all pulses while the pair of transmit beamforming weight vectors changes from pulse to pulse based on which entry of the phase-rotation dictionary is embedded. During each pulse, the receiver detects the embedded phase rotation and employ it to decipher the transmitted bit sequence. The proposed information embedding technique is angle-dependant and, therefore, the communication process is inherently secure against interception from directions other than the desired communication direction. The performance of the proposed technique is investigated in terms of the bit error rate (BER).
08 Jun 2015
TL;DR: A channel model is developed that reveals coupling between the spatial and temporal dimensions that is not captured by conventional separable models and leads to new B-SIMO transceivers that use on the order of Δch beams to deliver near-optimal performance with dramatically low complexity compared to the optimal receiver.
Abstract: Wideband high-dimensional antenna arrays are expected to play a key role in future 5G wireless systems. Due to narrow beamwidths, phased array/beamforming methods are the natural choice for design and analysis of high-dimensional MIMO systems. However, conventional methods are based on the narrowband assumption which is violated as the bandwidth and array dimension increase. In this paper we revisit the use of high-dimensional arrays in line-of-sight single-input multiple-output (SIMO) systems. We develop a channel model that reveals coupling between the spatial and temporal dimensions that is not captured by conventional separable models. We then apply beamspace MIMO (B-MIMO) theory - system representation with respect to orthogonal spatial beams - to analyze system performance. Our analysis reveals a key dispersion factor Δ ch that captures the impact of array dimension and bandwidth on performance. We show that Δ ch characterizes the magnitude of the coupled signal dispersion in spatial angle and time. This leads to new B-SIMO transceivers that use on the order of Δ ch beams to deliver near-optimal performance with dramatically low complexity compared to the optimal receiver. We present results that demonstrate the significant losses incurred by phased array receivers, and the near-optimal performance of low-complexity B-SIMO transceivers. Extension of the new wideband LoS SIMO model to MISO, MIMO, and multipath scenarios is outlined.
TL;DR: The work demonstrates the value of the dual astronomy-simulation approach in upcoming SKA design work and presents array sensitivity and beam pattern characterization results and compare to detailed full-wave simulation.
Abstract: We report characterization results for an engineering prototype of a next-generation low-frequency radio astronomy array. This prototype, which we refer to as the Aperture Array Verification System 0.5 (AAVS0.5), is a sparse pseudorandom array of 16 log-periodic antennas designed for 70–450 MHz. It is colocated with the Murchison widefield array (MWA) at the Murchison radioastronomy observatory (MRO) near the Australian square kilometre array (SKA) core site. We characterize the AAVS0.5 using two methods: in situ radio interferometry with astronomical sources and an engineering approach based on detailed full-wave simulation. In situ measurement of the small prototype array is challenging due to the dominance of the Galactic noise and the relatively weaker calibration sources easily accessible in the southern sky. The MWA, with its 128 “tiles” and up to 3 km baselines, enabled in situ measurement via radio interferometry. We present array sensitivity and beam pattern characterization results and compare to detailed full-wave simulation. We discuss areas where differences between the two methods exist and offer possibilities for improvement. Our work demonstrates the value of the dual astronomy–simulation approach in upcoming SKA design work.
TL;DR: A successful measurement campaign has demonstrated that a UAV-mounted test source provides a means to accurately validate and calibrate the full-polarized response of an antenna/array in operating conditions, including consequently effects like mutual coupling between the array elements and contribution of the environment to the antenna patterns.
Abstract: One of the most challenging aspects of the new-generation Low-Frequency Aperture Array (LFAA) radio telescopes is instrument calibration. The operational LOw-Frequency ARray (LOFAR) instrument and the future LFAA element of the Square Kilometre Array (SKA) require advanced calibration techniques to reach the expected outstanding performance. In this framework, a small array, called Medicina Array Demonstrator (MAD), has been designed and installed in Italy to provide a test bench for antenna characterization and calibration techniques based on a flying artificial test source. A radio-frequency tone is transmitted through a dipole antenna mounted on a micro Unmanned Aerial Vehicle (UAV) (hexacopter) and received by each element of the array. A modern digital FPGA-based back-end is responsible for both data-acquisition and data-reduction. A simple amplitude and phase equalization algorithm is exploited for array calibration owing to the high stability and accuracy of the developed artificial test source. Both the measured embedded element patterns and calibrated array patterns are found to be in good agreement with the simulated data. The successful measurement campaign has demonstrated that a UAV-mounted test source provides a means to accurately validate and calibrate the full-polarized response of an antenna/array in operating conditions, including consequently effects like mutual coupling between the array elements and contribution of the environment to the antenna patterns. A similar system can therefore find a future application in the SKA-LFAA context.
TL;DR: In this article, a radar sensor system for real-time blast furnace burden surface imaging inside a fully operative blast furnace, called BLASTDAR, the blast furnace radar, was presented, which operates in the frequency band around 77 GHz and consists of several nonuniformly spaced receive and transmit antennas.
Abstract: In this paper, we present a radar sensor system for real-time blast furnace burden surface imaging inside a fully operative blast furnace, called BLASTDAR, the blast furnace radar. The designed frequency-modulated continuous-wave (FMCW) radar sensor array operates in the frequency band around 77 GHz and consists of several nonuniformly spaced receive and transmit antennas, making it a multiple-input multiple-output radar system with large aperture. Mechanical steering is replaced by digital array processing techniques. Off-the-shelf automotive-qualified multichannel monolithic microwave integrated circuits are used. By means of this configuration, a virtual antenna array with 256 elements was developed that guarantees the desired angular resolution of better than 3°, and a range resolution of about 15 cm. Based on the single-channel FMCW signal model, this paper will derive a multichannel signal model in combination with a digital beamforming approach and further advanced signal processing algorithms. The implementation of a simulation tool covering the whole design process is shown. Based on these simulation results, a system configuration is chosen and the obtained setup is defined and presented. A description of the manufactured cost-efficient radio frequency and baseband boards together with the housing design shows the practical implementation of the sensor. For the system calibration, two different methods are listed and compared regarding their performance. Verification measurements confirm the predicted performance of the developed sensor. Several measurements inside a fully operational blast furnace demonstrate the proper long-term functionality of the system, to the best of our knowledge, for the first time worldwide. It is in continuous operation since about two years in blast furnace #5 of voestalpine Stahl GmbH, Linz.
01 Nov 2015
TL;DR: The proposed phased array antenna has good gain, efficiency, and 3D beam steering characteristics in the entire operation band, which makes it suitable for millimeter-wave 5G communications.
Abstract: This manuscript proposes a new design of phased array antenna for future fifth generation (5G) cellular communications. The proposed phased array antenna is designed on a low-cost N9000 PTFE substrate with overall size of 60×130×0.8 mm3. It consists of eight 28-GHz Vivaldi antenna elements used to form a linear phased array in the edge region (top-side) on a mobile phone PCB. The simulated results show that the antenna has the reflection coefficient (S11) less than −10 dB in the frequency range of 27.4 to 28.6 GHz. The proposed phased array antenna has good gain, efficiency, and 3D beam steering characteristics in the entire operation band, which makes it suitable for millimeter-wave 5G communications. In addition, the performance of the antenna in the vicinity of user's hand has been investigated in this study.
TL;DR: It is shown that far fields can be obtained from limited, experimentally obtained knowledge of the near fields, paving the way for experimental near-field characterization of metasurfaces and other optical nanostructures and prediction of their far fields from the near- field measurements.
Abstract: Phased-antenna metasurfaces can impart abrupt, spatially dependent changes to the amplitude, phase, and polarization of light and thus mold wavefronts in a desired fashion. Here we present an experimental and computational near-field study of metasurfaces based on near-resonant V-shaped antennas and connect their near- and far-field optical responses. We show that far fields can be obtained from limited, experimentally obtained knowledge of the near fields, paving the way for experimental near-field characterization of metasurfaces and other optical nanostructures and prediction of their far fields from the near-field measurements.