Switched-beam Antenna Research Articles

A Wide-Angle Scanning Switched-Beam Antenna System in LTCC Technology With High Beam Crossing Levels for V-Band Communications

Wide-angle coverage, fine angular resolution, and low-power consumption are the key characteristics of millimeter-wave short-range wireless systems, such as access points in fifth-generation cellular networks and automotive radars. In this paper, we present a 60 GHz switched-beam antenna system addressing all these requirements. It consists of two identical parallel-fed arrays of eight slots, each fed by a passive pillbox beamformer. A switch network comprising four single-pole-multiple-throw switches excites one of the two arrays at a time and selects the radiated beam. The whole system is fully integrated into a multilayer low-temperature cofired ceramic module. The antenna covers a scan range of about ±39° in one plane using 11 beams between 57 and 66 GHz. The proposed architecture enables the simultaneous achievement of continuous coverage (beam crossover levels of about −3 dB) and of low sidelobe levels. Dedicated numerical tools are used for a preliminary design of the antenna. The design procedure, the technological development, and the experimental results are discussed in detail.

Design and Performance Analysis of Segmented Wireless Sensor Networks

This article presents the design and a theoretical performance analysis of a segmented wireless sensor network whose sink node is equipped with a switched-beam smart antenna. We compare the performance of the proposed segmented system against that of a conventional wireless sensor network (WSN) where all the nodes contend to access the medium in order to identify the system's conditions where the use of a smart antenna is justified. Our results show that the segmented network outperforms the WSN by reducing the cluster formation time in up to 25 with similar energy savings.

A Cost-Effective Wideband Switched Beam Antenna System for a Small Cell Base Station

A wideband switched beam antenna array system operating from 2 to 5 GHz is presented. It is comprised of a $4\times 1$ Vivaldi antenna elements and a $4\times 4$ Butler matrix beamformer driven by a digitally controlled double-pole four-throw RF switch. The Butler matrix is implemented on a multilayer structure, using 90° hybrid couplers and 45° phase shifters. For the design of the coupler and phase shifter, we propose a unified methodology applied, but not limited, to elliptically shaped geometries. The multilayer realization enables us to avoid microstrip crossing and supports wideband operation of the beamforming network. To realize the Butler matrix, we introduce a step-by-step and stage-by-stage design methodology that enables accurate balance of the output weights at the antenna ports to achieve a stable beamforming performance. In this paper, we use a Vivaldi antenna element in a linear four-element array, since such element supports wideband and wide-scan angle operation. A soft condition in the form of corrugations is implemented around the periphery of the array, in order to reduce the edge effects. This technique improved the gain, the sidelobes, and helped to obtain back radiation suppression. Finally, impedance loading was also utilized in the two edge elements of the array to improve the active impedance. The proposed system of the Butler matrix in conjunction with the constructed array can be utilized as a common RF front end in a wideband air interface for a small cell 5G application and beyond as it is capable to simultaneously cover all the commercial bands from 2 to 5 GHz.

A Compact, Low-Cost, Ultrawideband Direction-Finding System: Techniques Suitable for Small-Aperture Designs

A review of different direction-finding (DF) systems and the design of a compact, very low-cost ultrawideband (UWB) DF system are presented. The proposed system uses a compact, reconfigurable switched-beam antenna with a height of 0.089 l0 and a diameter of 0.25 l0. The antenna can generate 11 figure-eight-shaped radiation patterns in the 460- to 1,550-MHz band, which can be electronically rotated in the azimuth plane. This allows for using a single-channel, amplitude-only receiver to perform DF. Commercially available single-pole, six-throw switches and a two-way 180d-power splitter are used to feed the antenna and perform the beam selection. The DF system is controlled using a low-cost, microcontroller unit (MCU) connected to a computer, which is also used for data collection and processing. The angle of arrival (AoA) of the signal is determined using the maximum likelihood estimation (MLE) method. The UWB DF system was fabricated and characterized in an outdoor field. For a signal-to-noise ratio (SNR) of 36 dB, the AoA bias is l1.5d with a l0.8d-error of estimation over all of the azimuth angles across the whole operation band. For SNRs g 5 dB, a better than 5d-AoA estimation accuracy is obtained over all of the azimuth angles and the entire band of operation.

Beam‐switching antenna implemented by reconfigurable slots on cylindrical cavity

A design for beam-switching antennas is proposed in this study. A cylindrical cavity with a reconfigurable conformal slot array distributed evenly along the middle of its side wall is presented. The reconfigurable feature of the slots is achieved by placing a diode switch across each slot. An integrated bias scheme is introduced for the diode switches to activate and disable the slots. By properly selecting the dimensions for the cavity and the number of activated slots, the optimum values for the gain and front-to-back ratio (FBR) of the antenna can be obtained. The gain value is further increased by adding a skirt-like structure to both the top and bottom of the cavity. A design example is presented with the operating frequency set at 5.8 GHz. The conformal array comprises 24 slots to provide a 15° resolution for main beam switching. The simulation results indicate that the design can offer an antenna gain up to 8.62 dBi and a FBR above 10 dB. These results and the corresponding radiation patterns have gone through experimental verification, from which good agreement is observed.

Consistently High MIMO Rates via Switched-Beam Antennas

The demand for wireless bandwidth is rising to unprecedented levels. The industry has responded with the inclusion of advanced PHY techniques, most notably multi-user (MU) MIMO, in the most recent Wi-Fi and LTE standards. However, despite the theoretical promise for large multiplexing gains, in practice the rate gains are modest due to a combination of large overhead to collect channel state information and not-so-well-conditioned channel matrices. In this paper, we propose to replace omni-directional antennas with inexpensive switched-beam antennas to produce well-conditioned channel matrices for MU-MIMO purposes with very low overhead. Remarkably, the experimental results with both software-defined radios and commercial Wi-Fi chipsets show that, when appropriate antenna modes are used, this leads to a $3.5\times-5\times $ average throughput improvement in indoor environments. What is more, our backward compatible protocol extension coupled with an efficient algorithm to select appropriate antenna modes, achieve the aforementioned gains with almost zero overhead.

Design of a switched beam antenna with 360° multibeam steering and omnidirectional capabilities for S‐X band datalink communications

Design of a switched beam antenna with 360° multibeam steering and omnidirectional capabilities for S‐X band datalink communications

Beam‐switching millimetre‐wave antenna using cantilever‐based FSSs

A beam-switching antenna for millimetre-wave applications at 30 GHz is presented in this study. The radiation reconfigurability for a cylindrical dielectric resonator antenna (DRA) is obtained by using a cantilever-enabled frequency selective surface (FSS). The proposed cantilever-enabled FSS provides reconfigurable bandpass and band-stop performance with good isolation between them. The investigation of designed FSS is performed using electromagnetic simulation and an array of the proposed FSS unit cell is fabricated and measured using the free-space measurement method, which shows a good agreement with the simulation results. Finally, six panels of the 1 × 5 array of the proposed reconfigurable FSS are arranged in a hexagonal configuration around a cylindrical DRA to obtain a reconfigurable radiation pattern in the azimuth plane. A prototype of the proposed radiation reconfigurable DRA is fabricated and the switching radiation patterns are measured at 30 GHz.

Miniaturisation of switched beam array antenna using phase delay properties of CSRR‐loaded transmission line

The application of phase delay property of complementary split-ring resonator (CSRR)-loaded transmission line in the miniaturisation of Butler matrix beam forming network is proposed. The design of left-handed transmission line and the influence of the capacitive stubs in the phase delay properties of the CSRR-loaded transmission line with a gap are presented. The CSRR-loaded transmission line with a 7 mm capacitive stub provides 93° more phase delay than the CSRR-loaded transmission line without the stubs. CSRR-loaded transmission line with capacitive stubs is applied to the phase compensating lines of 4 × 4 Butler matrix configurations, without disturbing the 90° hybrids and crossovers. The CSRR-loaded configuration exhibits a size reduction of 48% of the footprint of the conventional Butler matrix. The output of the miniaturised Butler matrix is connected to a linear microstrip antenna array of four radiating elements and its radiation parameters (beam pointing direction, beamwidth and sidelobe levels) are compared with that of an unloaded conventional 4 × 4 Butler matrix. The miniaturised switched beam-steering antenna exhibits similar radiation characteristics as that of a conventional switched beam antenna.

Circularly Polarized Beam-Switching Antenna Array Design for Directional Networks

For modern directional communication networks, there is a significant and growing need for advanced antenna array designs that combine the high gain and broadband performance together with the low-cost and lightweight characteristics. In this letter, the beam-switching characteristics of a new 4 × 8 right-hand circularly polarized long slot antenna (LSA) array were analyzed when fed by an 8 × 8 Butler matrix. The radiation characteristics were analyzed in terms of bandwidth, beamwidth, gain, cross polarization (x-pol), and axial ratio. Stable radiation patterns were obtained when the main beam directions were within the ±30° angle. The beam-switching LSA array has measured gain of 13.5 dBic and beamwidth of 15° with x-pol greater than 10 dB and axial ratio less than 6 dB. Comparative results with a 4 × 8 stacked patch antenna array are also included for reference.

Beam Switching Antenna Based on a Reconfigurable Cascaded Feeding Network

In this paper, a beam switching antenna (BSA) based on a reconfigurable cascaded feeding network (RCFN) is presented. The RCFN is engineered by cascading several varactor-loaded quasi-lumped couplers (QLCs). As the output port of the RCFN, the coupled port of every QLC is connected to an endfire radiator. BSAs based on two types of RCFN, the open-loop RCFN and closed-loop RCFN, are designed, simulated, and measured. The open-loop design features flexible beam switching strategies with the dynamic control of operation modes allocating the input power to the intended radiator(s), and single-/multibeam switching is achieved. In the case of the closed-loop RCFN, a power-recycling circuit is introduced to improve the efficiency of the single-beam switching mode of the BSA. Measured results show that the BSA operating in single-beam mode is able to radiate six switched beams each with a 3 dB beamwidth of 60°, covering 360° in the azimuth plane. The return losses and gain fluctuation of both prototypes are better than 15 dB and less than 1 dB, respectively. The corresponding experiments agree well with both the theoretical analysis and the simulation results.

28 GHz Switched-Beam Antenna Based on S-PIN Diodes for 5G Mobile Communications

This letter presents a 28 GHz switched five-beam antenna system based on a rectangular waveguide and a reconfigurable semiconductor circuit (RSC) with slots. Surface p-i-n diodes are used to close or open slots in order to achieve required configuration of an aperture. The RSC with a modified WR28 waveguide composes a reconfigurable radiating structure (RRS), which provides three beams directed toward 0°, 30°, and 45°. Beam switching is achieved by reconfigurable arrangement of a set of slots. Complementary RRSs connected to the electromechanical RF switch is used to generate remaining −30° and −45° beams. The gain of each generated beam is similar because different numbers of slots are opened, i.e., three, five, and nine slots for beams directed toward 0°, 30°, and 45°, respectively. Aperture of the antenna is controlled by a unit composed of high-current operational amplifiers. Measured results validate the performance of designed millimeter-wave reconfigurable antenna.

A Gain Enhancement and Flexible Control of Beam Numbers Antenna Based on Frequency Selective Surfaces

This paper describes a beam-switching antenna with high gain and flexible control of beam numbers based on frequency selective surfaces (FSSs). The proposed antenna is composed of an omnidirectional monopole antenna, a hexagon FSS screen, and six metallic sheets that surround the monopole antenna. The hexagon FSS screen contains six columns, each is made up of two FSS unit-cells. The beam-switching antenna is divided into six equal portions by six metallic sheets, which are employed here to improve the gain of the antenna. The proposed FSS unit-cell consists of the two metallic crosses connected by a pin-diode. The transmission characteristics of the FSS unit-cell are investigated for different pin-diode states. Therefore, by changing the states of the pin-diodes in the hexagon FSS screen, the proposed antenna can sweep six directions with gain enhancement in the azimuth plane. Moreover, it can also flexibly operate at multiple beams modes, including two-beam mode and three-beam mode with low power. This proposed antenna is fabricated and measured, showing good performances at 5.2 GHz. The maximum enhancement of the antenna gain is up to 7 dB, which is achieved by using the metallic sheets and verified with simulated and measured results, which show good agreement.

Assessment of LTCC-Based Dielectric Flat Lens Antennas and Switched-Beam Arrays for Future 5G Millimeter-Wave Communication Systems

This paper presents the design, low-temperature co-fired ceramics (LTCC) fabrication, and full experimental verification of novel dielectric flat lens antennas for future high data rate 5G wireless communication systems in the 60 GHz band. We introduce and practically completely evaluate and compare the performance of three different inhomogeneous gradient-index dielectric lenses with the effective parameters circularly and cylindrically distributed. These lenses, despite their planar profile antenna configuration, allow full 2-D beam scanning of high-gain radiation beams. A time-domain spectroscopy system is used to practically evaluate the permittivity profile achieved with the LTCC manufacturing process, obtaining very good results to confirm the viability of fabricating inhomogeneous flat lenses in a mass production technology. Then, the lenses performance is evaluated in terms of radiation pattern parameters, maximum gain, beam scanning, bandwidth performance, efficiencies, and impedance matching in the whole frequency band of interest. Finally, the performance of the three lenses is also experimentally evaluated and compared to a single omni-directional antenna and to a ten-element uniform linear array of omni-directional antennas in real 60 GHz wireless personal area network indoor line-of-sight (LOS) and obstructed-LOS environments, obtaining interesting and promising remarkable results in terms of measured received power and root-mean-square delay spread. At the end of this paper, an innovative switched-beam antenna array concept based on the presented cylindrically distributed effective parameters lens is also introduced and completely evaluated, confirming the potential applicability of the proposed antenna solution for future 5G wireless millimeter-wave communication system.

A Dual-Band Single-Feed Switched Beam Antenna for WLAN

Abstract This article presents the dual-band of a single patch antenna that can operate at a frequency of 2.47 to 5.04 GHz, which is available in WLANs (IEEE 802.11). The beam pattern of the antenna can be switched by changing the position of shorted-circuit points at each edge of the antenna. The advantage of the proposed antenna is that it is a simple structure which is small in size, weighs little and has an easily adjustable beam. In addition, the antenna is tested under real circumstances using the existing WLAN infrastructure. The results confirm that the signal strength can be improved when the proposed switched beam antenna is utilized.

Cavity‐backed high‐gain switch beam antenna array for 60‐GHz applications

This study presents a cavity-backed aperture-coupled switch beam antenna array for 60-GHz applications. A 1 × 4-element cavity-backed aperture-coupled patch antenna array is adopted as the radiating part, which is fed by the Butler matrix feed network that consists of couplers, crossovers, and phase shifters. By using the cavity that can help suppress the surface wave propagation along the substrate, the array not only achieves a high-aperture efficiency and gain but also maintains a wide beam steering angle in the H -plane. The feed network is designed by using substrate integrated waveguide (SIW) technology with a low profile, low radiation loss, and low cost. Measured results show the array exhibits wide -10-dB impedance bandwidths of 12.6% (56.6-64.2 GHz) for port 1 and port 4 and 11.6% (56.8-63.8 GHz) for port 2 and port 3. The beam angle coverage is from -38° to 38° with good steerable radiation patterns.

Frequency-Agile Beam-Switchable Antenna

A novel antenna with both frequency and pattern reconfigurability is presented. The reconfigurability is achieved by integrating an active frequency selective surface (AFSS) with feed antenna. The smart FSS comprises a printed slot array loaded by varactors. A novel dc biasing arrangement is proposed to feed the slots vertically so that the unwanted effects caused by bias lines are minimized. A monopole antenna is designed to illuminate the AFSS. The resulting structure can operate in a frequency tuning range of 30%. By reconfiguring the different sections of active FSS cylinder into a transparent or reflector mode, the omnidirectional pattern of the source antenna can be converted to a directive beam. As an illustration, half of the AFSS cylinder is successively biased, enabling the beam switching to cover the entire horizontal plane over a range of frequencies. An antenna prototype was fabricated and measured. Experimental results demonstrate the capability of providing useful gain levels and good impedance matching from 1.7 to 2.3 GHz. The antenna offers a low-cost, low-power solution for wireless systems that require frequency and beam reconfigurable antennas. The proposed design consumes about 1000 times less dc power than the equivalent narrowband beam-switching antenna design using p-i-n diode-loaded AFSS.

Microstrip patch based switched beam antenna at 2.45 GHz for wireless sensor network applications

The design and development of a switched beam antenna at 2.45 GHz industrial, scientific and medical band for wireless sensor network applications is presented in this paper. The antenna is capable of switching the beam pattern in directions such as in the boresight direction 0°, ±63° and as a bidirectional endfire radiator (±85°). The directive gain of the antenna is 3.9, 5.8 and 5.8 dBi in respect to those angles. The shift in the resonance frequency is found to be negligible irrespective of the direction of the switched beam. The realized gain of the proposed antenna in the steering direction is found to be better than a standard microstrip patch antenna on the same size of the substrate and ground plane. The antenna was designed and optimized through simulations using CST microwave studio and the prototype was experimentally tested using R&S ZVB8 network analyser.

Beam Switching Dual Polarized Antenna Array With Reconfigurable Radial Waveguide Power Dividers

In this paper, we propose a new method for designing dual polarized beam switching antennas by using reconfigurable radial waveguides excited by central probes and feeding multiple radiating elements. The power distribution of the radiating elements is controlled by cylindrical electromagnetic bandgap structures made of metallic wires loaded with PIN diodes. The proposed technique allows azimuth beam switching and multiple beams, with arbitrary and well controlled polarizations, using low dc voltage. First, a new rectangular periodic structure is used as a model for analyzing the transmission and reflection coefficients for different diode states. Then, numerical and experimental results are presented for a reconfigurable radial waveguide power divider and for the radiating elements. Finally, numerical and experimental results are presented and discussed for a complete dual polarized antenna operating at wireless local area network (WLAN) 5 GHz band (5.18–5.825 GHz).

Dual-Band Electronically Beam-Switched Antenna Using Slot Active Frequency Selective Surface

This communication presents an a cylindrical active frequency selective surface (AFSS)-based electronically beam-switching antenna, which can operate at two different frequency bands. The antenna consists of a slot AFSS and an omnidirectional dual-band feed antenna. The p-i-n diodes of the AFSS can be switched on or off to reconfigure the AFSS as transparent or opaque to the incident electromagnetic waves, respectively. Thus, by controlling the dc bias voltages to different columns of p-i-n diodes, the directive beams of the antenna can be swept to cover the whole azimuth plane. To validate the design concept, the transmission coefficients of the active FSS sheet are experimentally examined. An antenna prototype operating at 2.5 and 5.3 GHz frequency bands is also fabricated and measured. Simulation and measurement results of the antenna are presented to verify the design principle. A comparison between this communication and other recent designs is provided. The antenna has advantages of low power, low cost, easy fabrication, and electronic beam switching covering a full 360° angular range.