Showing papers on "Reflective array antenna published in 2013"

Circular antenna array for vehicular direction finding

Abstract: The circular antenna array for vehicular direction finding applications is a circular disc having a plurality of microstrip antennas radially spaced around the disc at equal angles. In one embodiment, the circular antenna array includes V-shaped antennas, and in another embodiment, the antennas are Yagi antennas. The circular antenna array can operate under two modes, switched and phased, in the 2.45 GHz band with an operating bandwidth of at least 100 MHz. The circular antenna array is configured to be installed in vehicles. Selective transmittal of an RF signal from a key fob generates a response signal from a specific antenna element receiving the RF signal in line with the direction of origin thereof. An LED panel indicates proximity and direction to the vehicle being located.

Antenna having split directors and antenna array comprising same

Abstract: An antenna is provided comprising a pair of driven elements and a pair of passive elements. The driven elements are disposed on opposite sides of a reference plane, and the passive elements are also disposed on opposite sides of the reference plane. One or both passive elements may be provided in a different plane than the driven elements. By varying placement of the passive elements the antenna radiation pattern can be altered. An antenna array is also provided, comprising two or more oppositely directed directional antennas at least one of which is as described above. The passive elements of the antennas can be adjusted for a desired coverage pattern of the array, such as an azimuthal omnidirectional pattern, for example through simulation. The antenna or array may be embodied on a printed circuit board.

Research on a Millimeter-Wave Phased Array With Wide-Angle Scanning Performance

Abstract: In order to extend the scanning range of a phased array and maintain the scanning gain flatness, a novel millimeter-wave phased array with four linearly-arranged pattern reconfigurable elements is presented in this communication. The phased array has been designed, fabricated, measured and analyzed. The active patterns of each reconfigurable element are measured at different reconfigurable modes and the pattern scanning performance of the phased array is synthesized by using these active patterns. Furthermore, a genetic algorithm is used to lower the level of side lobes of the proposed phased array. The results show that the phased array can scan its main lobe from -75° to +75° in the elevation plane with a gain fluctuation less than 3 dB.

A 108–114 GHz 4 $\,\times\,$ 4 Wafer-Scale Phased Array Transmitter With High-Efficiency On-Chip Antennas

Abstract: This paper presents a W-band wafer-scale phased- array transmitter with high-efficiency on-chip antennas. The 4 × 4 array is based on an RF beamforming architecture with an equiphase distribution network and phased shifters placed on every element. The differential on-chip antennas are implemented using a 100 μm thick quartz superstrate and with a simulated efficiency of ~ 45% at 110 GHz. The phased array is designed with low mutual coupling between the elements and results in a stable active antenna impedance versus scan angle. The phased array is built in the Jazz SBC18H3 SiGe BiCMOS process, and is 6.5 × 6.0 mm2. Measurements show two-dimensional pattern scanning capabilities with a directivity of 17.0 dB, an array gain of ~26.5 dB at 110 GHz, and an EIRP of 23-25 dBm at 108-114 GHz. The power consumption is 3.4 W from a 1.9 V supply. To our knowledge, this work represents the first W-band wafer-scale phased array to-date. The application areas are in point-to-point communication systems in the 100-120 GHz range.

A Self-Adapting Flexible (SELFLEX) Antenna Array for Changing Conformal Surface Applications

Abstract: A phased-array test platform for studying the self-adapting capabilities of conformal antennas is developed and presented. Specifically, a four-port 2.45-GHz receiver with voltage controlled phase shifters and attenuators is designed along with four individual printed microstrip patch antennas attached to a conformal surface. Each antenna is connected to the corresponding receiver port with a flexible SMA cable. It is shown that with appropriate phase compensation, the distorted radiation pattern of the array can be recovered as the surface of the conformal array changes shape. This pattern recovery information is then used to develop a new self-adapting flexible 1 t 4 microstrip antenna array with an embedded flexible sensor system. In particular, a flexible resistive sensor is used to measure the deformation of the substrate of a conformal antenna array, while a sensor circuit is used to measure the changing resistance. The circuit then uses this information to control the individual voltage of the phase shifters of each radiating element in the array. It is shown that with appropriate phase compensation, the radiation properties of the array can be autonomously recovered as the surface of the flexible array changes shape during normal operation. Throughout this work, measurements are shown to agree with analytical solutions and simulations.

UWB Low-Profile Tightly Coupled Dipole Array With Integrated Balun and Edge Terminations

Abstract: Tightly coupled phased arrays (TCPAs) provide UWB performance due to their strong inter-element coupling. However, in finite tightly coupled phased array realizations, mutual coupling is reduced near the array edges, causing the edge elements to become narrowband. To address this issue, a nonuniform array excitation scheme, referred to as “characteristic mode (CM) excitation,” was recently proposed. A more practical alternative for designing UWB tightly coupled phased arrays is proposed here. In this paper, we present a strategy that employs uniform excitation of the central array elements and short-circuits the periphery elements. We report that at least for medium size arrays, this approach provides up to 3 dB more gain and 50% higher efficiency than typical resistive termination. This concept is demonstrated using a 7 × 7 linearly polarized dipole array, 60.96 cm × 60.96 cm (2' × 2') in size, for operation from 200 MHz-600 MHz. Feeding of the active elements is challenging due to several constraints on the feed design, including balanced to unbalanced transitions, impedance transformations, common mode suppression, compact size, low cost, etc. To address these issues we propose a novel array feed using a compact, ultrawideband balun (with 10:1 bandwidth for VSWR ). Simulated and measured data are provided for broadside and 30 scan in the H-plane.

Frequency Reconfigurable Microstrip Loop Antenna Covering LTE Bands With MIMO Implementation and Wideband Microstrip Slot Antenna all for Portable Wireless DTV Media Player

Abstract: A microstrip slot antenna covering Digital TV (DTV) and frequency reconfigurable microstrip printed loop antenna operating at LTE bands 3 (1.8 GHz) and 7 (2.6 GHz) with multiple-input-multiple-output (MIMO) implementation are designed which can find applications in portable wireless DTV media players. The DTV antenna is matched from 496-862 MHz and LTE bands 3 and 7 from 1710-1880 MHz and 2500-2700 MHz, respectively, all considering S11 = -6 dB matching criterion. Further, the LTE bands antennas are frequency reconfigurable antennas and its MIMO implementation shows an envelope correlation (EC) below 0.22 for both the LTE bands. Prototype antennas were fabricated and experimental verification was performed.

Generation of orbital angular momentum (OAM) radio beams with phased patch array

Abstract: This paper describes the design of an 8-element circular phased patch array antenna which can generate radio beams carrying orbital angular momentum at 10 GHz. Realistic antenna design issues are discussed, including mutual coupling and the array performance when operating in different OAM states.

A New Low Cost Leaky Wave Coplanar Waveguide Continuous Transverse Stub Antenna Array Using Metamaterial-Based Phase Shifters for Beam Steering

Abstract: In this paper, we have proposed a new leaky-wave coplanar waveguide (CPW) continuous transverse stub (CTS) antenna array with metamaterial-based phase shifters for beam steering applications. The array integrates three CTS elements and two 6-stage negative reflective index (NRI) phase shifters, and is fed by CPW transmission line. Beam steering capabilities are achieved by tuning the values of the NRI phase shifters. The proposed CPW-CTS array is fabricated for 2.4-GHz wireless local area network (WLAN). The measured data, including parameters, radiation patterns and gain, agree well with the simulation results. A scan-angle range from 58 to 124 of unidirectional radiation pattern is measured in the -plane with good impedance matching (-1 dB ). Designs incorporating continuous beam steering using tunable NRI metamaterial phase shifters are also discussed.

Integrated 60-GHz Antenna on Multilayer Organic Package With Broadside and End-Fire Radiation

Abstract: Existing antenna and array systems for 60-GHz wireless personal area network communications suffer from inherent poor radiation at grazing angles. This limitation is overcome in this work with a highly integrated antenna module that combines both broadside and end-fire radiators in a single multilayer organic package. Liquid crystal polymer and Rogers RO3003 are used to implement a small form factor (12.5 mm × 10 mm × 1.3 mm) antenna architecture. The co-designed broadside and end-fire antennas are characterized and measured for operation in the 57-66-GHz frequency range. Measured boresight gains of 8.7 and 10.9 dBi are achieved for the broadside and end-fire antennas while maintaining 35-45-dB isolation between both antennas. The numerically estimated radiation efficiency is found to be 92.5% and 78.5% for the broadside and end-fire elements. These antennas are orthogonally polarized and suitable for frequency reuse. Integrated circuits are mounted inside recessed cavities to realize a fully active antenna module with beam switching or simultaneous radiation. To the best of our knowledge, this is the first publication of a single package multilayer integration of millimeter-wave active antennas with both azimuth and elevation coverage.

A Dual-Layer Broadband Compact UHF RFID Tag Antenna for Platform Tolerant Application

Abstract: In this paper, we present a compact tag antenna for radio frequency identification (RFID) application By embedding four parasitic planar inverted-F antennas under the top patch, four adjacent resonant modes are excited simultaneously and the impedance bandwidth is broadened to 140 MHz or more, which fully covers the entire worldwide ultra high frequency (UHF) band (860-960 MHz) The proposed antenna is printed on two FR4 substrates with a total volume of 56 mm×26 mm×32 mm The measured read range was 4 m in a copper plate sized of 500 mm × 500 mm Experimental studies demonstrate that the proposed antenna could work properly on general tagged objects

True-Time-Delay-Based Multi-Beam Arrays

Abstract: A broadband true-time-delay-based multi-beam array architecture is presented in this paper that is applicable to 1-D and 2-D linear antenna arrays. A 1-D millimeter-wave multi-beam array receiver and a 2-D ultra-wide band multi-beam array receiver have been implemented in 0.13- μm SiGe and a 0.13- μm CMOS technology, respectively. The 1-D millimeter-wave multi-beam array receiver with six antennas and seven beams covers the entire 30-40-GHz instantaneous bandwidth, and achieves 18° spatial resolution and ±54° spatial coverage with 4-mm antenna spacing. The 2-D ultra-wideband multi-beam array receiver with 2 × 2 antennas and 7 × 7 beams covers the 3-15-GHz instantaneous bandwidth, and achieves 10° spatial resolution and ±30° spatial coverage in each dimension with 3-cm antenna spacing.

Enhancing the security of communication via directly modulated antenna arrays

Abstract: A new approach to enhance the security of data transmission using direction dependent antenna modulation based on an array with wide element spacing combined with directional array elements is presented. For illustrative purposes, the system investigated, and reported here, consists of an array of only two elements but the approach is general and can be extended to multi-element array systems. It is shown that by increasing the element spacing of an array the directional error rate characteristics of the system, in a given direction, can be significantly improved. Furthermore, the directly modulated system shows superior error rate performance to that of an equivalent, conventionally modulated, system in the grating lobe directions. The error rate characteristics of the proposed system are analysed for two scenarios: firstly when the angular separation between an eavesdropper and the intended recipient is small and secondly for the case when a potential eavesdropper is located much closer to the transmit antenna than the intended recipient.

Front-to-Back Ratio Enhancement of Planar Printed Antennas by Means of Artificial Dielectric Layers

Abstract: In this paper, we investigate the use of artificial dielectric layers (ADLs) as a mean to enhance front-to-back radiation ratio in printed, planar antennas. These artificially engineered substrates can be designed to be anisotropic and present high dielectric constants for the waves propagating orthogonal to metallic layers. However, the dielectric constants is as low as that of the host material for the waves that propagates towards grazing direction, and thus surface waves due to multiple reflections at the dielectric air interface are not enhanced. A simple qualitative description of this concept is followed by the presentation of a experimentally verified prototype which clearly highlights the potential advantages of the proposed ADL for antenna applications.

3D beamforming designs for Single User MISO systems

Abstract: In this paper, we study a transmit beamforming technique for multiple input single output downlink single-user systems with three dimensional antennas where a transmit antenna gain is determined in three dimensional coordinates. In general, the transmit antenna gain is controlled by adjusting the boresight of antennas in directional antennas. To derive the optimal tilting angles for the directional antenna systems, we provide the probability density functions (PDF) of the three dimensional user distribution. Furthermore, based on the PDF, the analysis for the average rates of passive and active antenna systems is presented. Simulation results verify the accuracy of the performance analysis.

A Resonant Printed Monopole Antenna With an Embedded Non-Foster Matching Network

Abstract: Non-Foster reactive elements are embedded inside compact resonant antennas, rather than being employed in matching networks located at the antenna terminals. These embedded non-Foster elements interact with the inherent Foster reactances of the antenna, resulting in a broadband antenna with a high radiation resistance. The class of suitable antennas for this application is discussed, a design procedure is presented and a sensitivity and a stability analysis are performed. Finally, experimental results for a representative non-Foster antenna are presented and discussed.

Compact 2 x 2 Coupled Double Loop GPS Antenna Array Loaded With Broadside Coupled Split Ring Resonators

Abstract: The design and nulling capability of a compact 2 × 2 dual-band coupled double loop (CDL) GPS antenna array loaded with broadside coupled split ring resonators (BC-SRR) are presented. The high level of L2 band mutual coupling is reduced by utilizing -negative (MNG) BC-SRR metamaterial within the array volume. This metamaterial loading is possible due to the small L2 band electrical size (λo / 8.5 × λo / 8.5) of the CDL antenna elements. Different than the existing work on coupling reduction of linearly polarized antenna arrays, mutual coupling mechanism within the circularly polarized GPS array is considered and MNG metamaterials are shown to reduce the mutual coupling if they are placed between the antennas in a particular alignment. Specifically, a 2 × 2 array with inter-element spacing is designed to be loaded with BC-SRRs and experimentally verified to exhibit a 10 dB L2 band mutual coupling reduction. Through simulations and experiments, it is also demonstrated that the reduction in L2 band mutual coupling improves the L2 band array nulling capability in terms of accuracy and null depth without affecting the already well-behaved L1 band performance. The presented array has an overall footprint size 4.3" × 4.3" of and can be potentially miniaturized further for different inter-element spacing.

Measurement-Based Analysis: The Effect of Complementary Antennas and Diversity on Vehicle-to-Vehicle Communication

Abstract: In vehicle-to-vehicle (V2V) communication systems, the antennas are prone to shadowing, and the antenna gain is dissimilar even for same antenna elements if mounted at different positions on the car. This letter investigates the impact of antenna placement based on channel measurements performed with four omnidirectional antennas mounted on the roof, bumper, windscreen, and left-side mirror of the transmitter and receiver cars. Results suggest to use antennas with complementary characteristics, e.g., antennas on each side, mounted on the roof and bumper, to exploit diversity and decrease the effect of shadowing.

An Integrated 122-GHz Antenna Array With Wire Bond Compensation for SMT Radar Sensors

Abstract: This paper shows the antenna design of an integrated 122-GHz radar sensor. The sensor consists of a SiGe IC with a complete radar circuit and two antennas for transmitting and receiving the 122-GHz signal. The IC and the antennas are integrated into a low-cost plastic package that is assembled using wire bond technology. The antenna design was specifically optimized regarding the integration into the package and the compensation of the parasitic effects of the wire bond interconnect. First, the antenna design and its novel feeding technique based on a GCPW transmission line are explained. Then, measurement results including the wire bond interconnect are presented. Finally, details of the complete radar sensor are given.

Array Antenna Limitations

Abstract: This letter defines a physical-bound-based array figure of merit for both single and multiband array antennas. It provides a measure to compare their performance with respect to return loss, bandwidth(s), thickness of the array over the ground plane, and scan range. The result is based on a sum-rule result of Rozanov-type for linear polarization. For single-band antennas, it extends an existing limit for a given fixed scan-angle to include the whole scan range of the array, as well as the unit-cell structure in the bound. The letter ends with an investigation of the array figure of merit for some wideband and/or wide-scan antennas with linear polarization. We find arrays with a figure of merit >0.6 that empirically defines high-performance antennas with respect to this measure.

A 900 MHz Beam Steering Parasitic Antenna Array for Wearable Wireless Applications

Abstract: A 900 MHz wearable beam steering antenna array is proposed. A wideband driven dipole when assisted by several varactor diode controlled parasitic dipoles allows the array beam to be steered in the azimuth. Antenna array prototypes fabricated using copper, conductive fabrics and conductive threads show good bandwidth and radiation performance. The array when placed against an anatomically correct human body model shows that the array beam can be steered along 3 distinct angles, 0, 45, and 315 degrees with 5.9 dBi peak gain.

Dual-Frequency Folded Reflectarray Antenna

Abstract: Design and experimental results of a dual-frequency folded reflector antenna are presented. With an effective diameter of 180 mm and a depth of 60 mm, gain values of 25 and 30 dB at 20 and 30 GHz, respectively, have been achieved. Beamwidths are 6.2° at 20 GHz and 3.7°/4° at 30 GHz.

Crumpling of Microstrip Antenna Array

Abstract: The performance of a 2 × 2 microstrip patch array under crumpling conditions is presented. The antenna array was manufactured on textile material, and three cases of crumpling resembling real applications are discussed. The performance of the individual patch elements correlate with the overall performance of the array. Frequency shifts of up to 6% are measured for the array when crumpled, the boresight gain is reduced by up to 6 dB with significant changes in directivity and efficiency, up to 20%. The overall efficiency for the textile array increases for crumpling in one plane but falls in the other.

Decade Bandwidth Circularly Polarized Antenna Array

Abstract: A circularly polarized antenna array design comprising of a feed network that splits an input signal into four orthogonal (0°, 90°, 180°, and 270°) phased signals with equal magnitudes and connected to four anti-podal Vivaldi antennas sequentially rotated by 90° is presented. The proposed antenna array yields 10-dB return loss and 3-dB axial ratio bandwidths from 1-10 GHz. The symmetrical structure gives the antenna array almost identical azimuth and elevation radiation patterns. Pulse reception from various angles show equi-amplitude outputs and very little distortion. The proposed design is suited for high-resolution microwave imaging systems.

Smart antenna array configuration for multiple-input multiple-output communications

Abstract: An access point can include an array of antennas and a smart antenna selector. The smart antenna selector is configured to select a subset of antennas from the antenna array for use in multi-user multiple-input multiple-output (MU MIMO) data transmissions. Stations that are communicatively coupled to the access point can be selected for inclusion in a multi-user group based, at least in part, on performance measurements of the stations. Performance measurements are determined directly and indirectly from data transmissions sent in response to sounding packets. Antennas for use in MU MIMO data transmissions are selected for the antenna array based, at least in part, on previous antenna selections used for single user data transmissions.

High‐isolation 2.4/5.2/5.8 GHz WLAN MIMO antenna array for laptop computer application

Abstract: An isolation technique for two small-size triband wireless wide area network (WLAN) multiple-input multiple-output (MIMO) laptop computer antennas covering the 2.4/5.2/5.8 GHz bands is presented. The proposed WLAN MIMO antennas have measured isolation of better than −21 dB in the 2.4 GHz band and −32 dB in the 5.2/5.8 GHz bands in this study. In addition to enhanced isolation achieved, good antenna efficiencies of better than about 70 and 90%, respectively, in the 2.4 GHz and 5.2/5.8 GHz bands are obtained for the two antennas. The WLAN MIMO antenna array having a planar structure of size 9 × 55 mm2 is to be mounted at the top edge of the supporting metal plate of the laptop display. The two antennas can be fabricated at low cost on a thin FR4 substrate and are of a simple structure comprising a driven strip and a shorted strip, which provides two wide operating bands to cover the 2.4 and 5.2/5.8 GHz bands. Between the two antennas, there is an isolation element formed by a protruded ground plane and a spiral open slot embedded therein. The isolation element leads to enhanced isolation between the antennas in the 2.4/5.2/5.8 GHz WLAN bands and good antenna efficiencies for the antennas as well. Details of the isolation technique for the WLAN MIMO antennas are described, and the obtained results are presented and discussed. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:382–387, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27279

High-Frequency Radars: Beamforming Calibrations Using Ships as Reflectors*

Abstract: Linear array antennas and beamforming techniques offer some advantages compared to direction finding using squared arrays. The azimuthal resolution depends on the number of antenna elements and their spacing. Assuming an ideal beam pattern and no amplitude taper across the aperture, 16 antennas in a linear array spaced at half the electromagnetic wavelength theoretically provide a beam resolution of 3.5° normal to the array, and up to twice that when the beam is steered within an azimuthal range of 60° from the direction normal to the array. However, miscalibrated phases among antenna elements, cables, and receivers (e.g., caused by service activities without recalibration) can cause errors in the beam-steering direction and distortions of the beam pattern, resulting in unreliable ocean surface current and wave estimations. The present work uses opportunistic ship echoes randomly received by oceanographic high-frequency radars to correct an unusual case of severe phase differences between receiver...

Resonant-Type Antennas Loaded With CRLH Unit Cell

Abstract: The concept of loading monopole antennas with composite right/left-handed (CRLH) unit cell is extended to cover other types of resonant antennas, namely loop antennas and printed inverted-F antennas (printed IFAs). By adding one unit cell, these antennas achieve three operating bands while having their sizes unmodified. The new frequencies are lower than the unloaded antenna's nominal frequency. The printed IFA is fabricated, and measurements are consistent with theoretical predictions.

Efficient Robust Broadband Antenna Array Processor in the Presence of Look Direction Errors

Abstract: The performance of adaptive antenna array processors is known to decline severely in the presence of array imperfections and uncertainties. Hence the robustness of an array processor against uncertainties is an important issue. Diagonal loading of the correlation matrix is a popular technique applied to the standard Frost processor to increase robustness of the array system. This paper presents a number of robust beamforming algorithms using efficient realization techniques. The techniques do not use a presteered array and allow an array designer to specify the frequency response of the processor in the look direction and steer the main beam of specified frequency response in an arbitrary direction. The proposed techniques are computationally efficient and applicable in environments with strong mutual coupling. Simulation results show the effectiveness of the proposed beamforming algorithms and compare the performance of the beamformer using the proposed techniques with that of existing methods.

Optimizing Power Transfer Efficiency and Bandwidth for Near Field Communication Systems

Abstract: Near-field communication (NFC) is a specification for short-range wireless links operating at 13.56 MHz in the high-frequency (HF) band. The achievable bandwidth, efficiency, and range of lightweight, size-constrained, low-power NFC systems are limited by fundamental theorems of small antenna theory. We develop a relationship between near field power transfer and radiation efficiency for dipole-type antennas, which is applicable to both communications and wireless power transfer applications, and present modeled and experimentally measured results for the bandwidth efficiency product of two ferrite loop antenna designs. The model is used to determine the optimal geometrical parameters that maximize this figure of merit for a given antenna size. Modeled and measured results show that ferrite loops can approach theoretical limits on performance for the bandwidth efficiency product of an antenna with a given size.