Switched-beam Antenna Array Research Articles

A Miniaturized Metamaterial-Loaded Switched-Beam Antenna Array System With Enhanced Bandwidth for 5G Applications

A Miniaturized Metamaterial-Loaded Switched-Beam Antenna Array System With Enhanced Bandwidth for 5G Applications

Switched Beam Array Antenna Optimized for Microwave Powering of 3-D Distributed Nodes in Clustered Wireless Sensor Network

The IoT applications like smart warehouse, smart industry, and smart vertical farming will require microwave power transmission (MPT) to the densely deployed low-power sensor nodes in 3-D space. To address this issue, a switched beam array antenna (SBA) is synthesized as an MPT system to power the proposed 3-D clustered wireless sensor network (WSN). The 3-D space is divided into nine clusters; each illuminated individually with RF power using a dedicated patch antenna subarray. The subarrays can be switched ON or OFF based on the energy requirement of the WSN cluster nodes resulting in efficient power transmission. Moreover, the low complexity of switched beam design reduces the cost and processing overhead as compared to the exiting adaptive beamforming systems in a dense WSN scenario. The subarray size and excitation coefficients are optimized with a constraint over the harvested dc power ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{dc}$ </tex-math></inline-formula> ) to enhance the 3-D coverage. In addition, the optimal location of the cluster head (CH) is evaluated to minimize the average power consumption of WSN cluster. The subarrays are designed and fabricated with the evaluated excitation coefficients, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{dc}$ </tex-math></inline-formula> measurements are carried out validating analytical results.

An ultra‐wideband 3 × 3 Butler matrix with unique Vivaldi array structure for high‐range resolution radars

Steerable antenna beam capability is an outstanding expectation for the development of automatic tracking systems and target detection. A switched beam array antenna, which can generate multiple fixed beams with enhanced sensitivity, emerges as a solution for beamforming tracking. On the other hand, it is known that the target can be detected with high-range resolution thanks to ultra-wideband (UWB) systems. In this work, a compact switched beam Vivaldi array antenna based on a Butler matrix for a UWB application capable of target detection with accurate target tracking is presented to meet the high gain and low side lobe level requirements. Based on a three-element antenna array, two methods have been applied to obtain small grating lobes and it has been shown that significant improvements can be achieved. Designed with a 3 × 3 UWB Butler matrix, the UWB array antenna can direct its beams in three directions in a direction range from −42 to 42°. The measured result showed that the group delay was less than about 4.5 ns with variation of less than ±0.7 ns over the entire operating frequency band.

A Wideband Switched-Beam Antenna Array Fed by Compact Single-Layer Butler Matrix

This communication describes a wideband switched-beam antenna fed by a compact single-layer beamforming network. First, a novel hybrid coupler structure that can provide an arbitrary phase difference over a bandwidth larger than 58% is proposed with the theoretical analysis. Based on this compact coupler configuration, a wideband 4 ×4 Butler matrix is devised with the need for standalone phase shifters and crossovers eliminated. The proposed Butler matrix achieves the widest bandwidth among the single-layer structures up to present. Consequently, a wideband switched-beam antenna array is realized by utilizing the log-periodic endfire antenna elements with bowtie dipoles on the Butler matrix. For validation, a broadband switched-beam antenna array is designed, fabricated, and measured. A stable beamforming performance is ascertained with a gain variation smaller than ±1.66 dB over a bandwidth from 1.98 to 3.14 GHz.

A Compact Switched Beam Antenna Array for ISM Band

This paper proposes the switched beam antenna array at the center frequency of 2.45GHz with a bandwidth of 187 MHz, from 2.32 GHz to 2.51 GHz. The phase shifter of antenna utilizes a 4×4 planar Butler matrix with phase differences between its outputs of ±135° and ±45° to obtain four the different main beam directions. The proposed design is fully described including the patch antenna element, the antenna array, the phase shifter that forms the completed antenna array. The antenna array achieves a gain max up to 7 dBi, and the angles of the main beam directions of -41°, -12°, +15°, +48° in a horizontal plane. The beamwidth of the four main beams is from 26° to 31.8° in E-plane and from 38.5° to 55.4° in H-plane. The advantage of the antenna is the planar structure and compact dimension of 200×230mm2. The proposed antenna is suitable for ISM band.

Switched Beam SIW Horn Arrays at 60 GHz for 360° Reconfigurable Chip-to-Chip Communications With Interference Considerations

Traditional wired interconnects in multicore multichip (MCMC) systems can be replaced with chip-integrated switched beam antenna arrays to provide reconfigurable chip-to-chip communications. By simply switching the directive beams of the arrays, the chips can be made to dynamically communicate with their surrounding neighbors. Radiation from the arrays in the unintended direction, however, causes interference when multiple pairs of chips are simultaneously communicating. In this paper, the noise and interference limitations of such concurrent chip-to-chip communication systems are analyzed at 60 GHz for the channels defined in the IEEE 802.11ay standard. Each array consists of eight substrate integrated waveguide (SIW) horn elements printed on a thin dielectric substrate. The elements can be individually excited to produce eight directive endfire beams, providing full 360° coverage, in the horizontal plane. The substrate acts as a hybrid space-surface wave interconnect (HSSW-I) that allows near-field, space and surface wave coupling to occur between the arrays, and thus, increases interchip transmission. The antenna and link parameters that dictate the signal-to-noise-plus-interference ratio (SNIR) of such systems are established by considering all the major components. The maximum achievable data rates are then determined based on the SNIR, calculated from the measured and simulated transmission coefficients between the arrays.

An efficient WBAN aggregator switched-beam technique for isolated and quarantined patients

In this paper, an efficient beamforming technique at the aggregator node in the patient wireless body area network (WBAN) is proposed to improve the communication performance with the gateway node using C-shaped switched-beam antenna arrays. This proposed technique provides high gain beams towards the gateway node which may be located indoor or outdoor based on the medical quarantine or isolation topology and help medical staff monitor patients with less contact and infection probability. Also, a semi-blind switched-beam algorithm is developed to both reduce the processing time required for beam selection and reduce the power loss due to the off-mainlobe orientation of the selected beam with the signal direction. The proposed technique is analyzed at different wearing scenarios and simulation results show that the received power levels are improved with as less as 0.3 dBm standard deviation which helps in extending the communication range between the WBAN aggregator and gateway nodes in the health monitoring system and also extend the battery lifetime at the patient WBAN.

A 28-GHz Reconfigurable SP4T Switch Network for a Switched Beam System in 65-nm CMOS

A 28-GHz SP4T absorptive switch (SAS) and reconfigurable switch network (RSN) in the 65-nm CMOS process are presented for a switched beam antenna array. The proposed SAS has the smallest electrical size among the previous millimeter-wave SASs. The length of the $t$ -line used in the proposed SAS is only 1/3 of that of the conventional quarter-wave $t$ -line-based absorptive switch. The proposed RSN is the first CMOS millimeter-wave switch-based RSN for a $4\times 4$ Butler matrix-based switched beam transceiver. The RSN is designed based on the SAS in order to operate in both the switch and divider modes. In the switch mode for single-port excitation, the RSN acts as an SAS. In the divider mode for dual-port excitation, the RSN operates as a Wilkinson power divider. Furthermore, the proposed RSN is realized in 2/3 the size of the conventional SAS. The measured insertion loss and isolation of the SAS are 3.8 and 22 dB, respectively. All return losses of the SAS input, output, and absorptive ports are better than 10 dB from 26 to 31 GHz. The silicon area and electrical size of the SAS is 0.9 mm2 ( $0.0078\lambda _{0}^{2}$ ), including pads. The measured insertion losses of the RSN in the switch and divider modes are 4.1 and 4.3 dB, respectively. The isolation of the switch and divider modes is 24 and 25 dB, respectively. All return losses of the RSN are better than 10 dB from 21 to 31.2 GHz. The silicon area of the RSN is 0.78 mm2 ( $0.0068\lambda _{0}^{2}$ ).

Compact Switched-Beam Array Antenna with a Butler Matrix and a Folded Ground Structure

A compact switched-beam array antenna, based on a switched Butler matrix with four folded ground antennas, is presented for unmanned aerial vehicle (UAV) applications. The folded ground structure, including a slotted patch radiator surrounded by multiple air-gapped ground layers, is adopted to maximize compactness. The extra ground layers provide extra capacitive coupling around the patch antenna, resulting in a down-shift of resonant frequency and a reduction in the antenna size. Also, to optimize aerial operation with a wider beam coverage, the 1 × 4 array is integrated with a switched Butler matrix controlled by a microcontroller unit (MCU). The choice of the Butler matrix reduces the complexity of beamforming circuitry and avoids the use of high-cost phase shifters requiring extra control-bit signals. Further, the array antenna is optimized for high isolation among the antenna ports and a minimal UAV body effect. Then, the proposed structure was verified at 1.96 GHz for test purposes only, and the array size, excluding the antenna case, was 2.16λo × 0.54λo × 0.07λo. The measured 10 dB impedance bandwidth for all antenna elements in the array was always better than 3.4%, and the isolation among the antenna ports was also better than 19 dB. The measured peak gain, excluding the loss of the switched Butler module, was about 9.98 dBi, on average. Lastly, the measured peak scan angles were observed at −39°, −17°, 9° and 31° according to switching modes.

Two dimensional switched beam antenna based on cascaded butler matrix beamforming network

This paper presents a low cost, two dimensional (2-D) millimetre wave switched-beam array antenna attained by feeding a planar array antenna with a cascaded 4 x 4 Butler matrix (BM) beam forming network (BFN). To minimise the surface current, ensure low cost and ease fabrication, a single layer has been implemented. The prototype is fabricated and measured results presented. According to the results, the maximum beam scanning of from -41ᵒ to +42ᵒ, and a maximum antenna gain of 13.8 dBi are obtained in the x-z plane. While the maximum beam scanning of from -43ᵒ to +41ᵒ and the maximum antenna gain of 13.7 dBi are realized in the y-z plane. With a single pole multiple throw switches, switching the various matrix terminals on the BM in the horizontal plane gives the beams in the x-z plane, while switching the BM in the vertical plane gives the beams in the y-z plane. All experimental and numerical results are in good agreement which can be practically used for fifth generation (5G) wireless systems. Keywords: Cascaded Butler matrix, Beamforming Network, switched-beam antenna, 5G

An Overlapped Switched-Beam Antenna Array With Omnidirectional Coverage for 2.4/5.8 GHz Three-Channel MIMO WLAN Applications

In the design of smart antenna, switched-beam technology is widely used to increase the communication capacity and to reduce electromagnetic interference. This letter presents a switched-beam antenna array for the three-channel multiple-input–multiple-output (MIMO) wireless local area network operating in 2.4/5.8 GHz. In the proposed array, there are 12 directional beams, and every four partially overlapped beams form a channel. Thus, the proposed array provides three channels. For each channel, the four antenna elements used to radiate directional beams are rotationally symmetrical. Therefore, for all channels, good omnidirectional coverage is obtained by dynamically switching directional beams. To demonstrate the effectiveness and advantages of the proposed array, a prototype is fabricated and measured. In it, the peak gain of directional radiation reaches 9.5 dB, and the values of the horizontal plane fluctuation for three channels are smaller than 5 dB.

Dual‐band switched‐beam antenna array for MIMO systems

This work reports the development of a dual-band switched-beam antenna array for multiple-input multiple-output (MIMO) fifth-generation systems, operating in millimetre waves. The proposed antenna array consists of applying four slotted-waveguide antenna arrays (SWAAs), rotated by $ 30^\circ $30°, as the final array element. The SWAA elements were designed to simultaneously operate in the 28 and 38 GHz bands, by using two groups of slots with different electrical lengths on the opposite faces of the waveguide. The measured array fractional bandwidth was ~25.6 and 10% at 28 and 38 GHz, respectively. Its applicability for MIMO systems was evaluated as a function of mutual coupling, active reflection coefficient, total active reflection coefficient and envelope correlation coefficient. Experimental results demonstrate low mutual coupling as low as -36 dB within the 28 and 38 GHz frequency bands.

Switched-beam array antenna at 28 GHz for 5G wireless system based on butler matrix beamforming network

This work presents a compact, switched-beam array antenna on 4 × 4 Butler Matrix (BM) beamforming network (BFN) at 28 GHz for fifth generation (5G) wireless system. A single layer has been chosen to ensure low cost and ease fabrication. The four input ports of the designed antenna have the capability of producing four independent directional beam patterns at 13.8°, -43.5°, 44° and -14°, when P1, P2, P3 and P4, respectively are excited. The radiation efficiency obtained from each of the four ports is well above 80% at the designated frequency. The peak antenna gain of 15.9 dBi is obtained at port 1 and 4. The design is verified by measurement and all results have a good correlation with simulation. Keywords: Array antenna, Butler matrix, millimetre wave, switched-beam antenna, 5G

Design and fabrication of two‐port three‐beam switched beam antenna array for 60 GHz communication

This article presents a novel, low-cost, beam-switchable $2 \times 10$2x10 antenna array system operating at 60 GHz. This antenna system is constructed of two rows of Chebyshev-tapered microstrip antenna arrays. Each row is a 10 element series-fed array which are fed by a $90 \circ $90 circle coupler. The designed antenna array has only two input ports, but it is capable of generating three switchable beams. This antenna system can spatially scan $90 \circ $90 circle with at least -5 dB normalised gain using only one SPDT switch and a single transceiver. The maximum gain realised by the system was measured as 16.4 dBi and the bandwidth (BW) was >1 GHz. The features of the proposed antenna system make it applicable to do mmWave research such as beamforming algorithms and channel sounding, and to use in handsets for 5G communication.

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.

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.

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.

Wideband Circularly Polarized 2 × 2 Antenna Array With Multibeam Steerable Capability

A circularly polarized (CP) switched-beam antenna array with the capability of generating nine steerable beams in the hemispherical space is presented in this letter. A single radiator is first constructed with two triangular-shaped dipoles crossing through printed rings, and four parasitic elements are introduced to enhance the CP operation bandwidth. For the beam steering operation, its array antennas are implemented in a $2 \times 2$ arrangement and fed by a four-input port feeding network composed of four double-box branch-line couplers. With a suitable feed excitation mechanism, the proposed antenna can generate CP axial beams in nine directions. The antenna is fabricated with an overall size of $2{{\rm{\lambda }}_{\rm{o}}} \times 2{{\rm{\lambda }}_{\rm{o}}} \times 0.2{{\rm{\lambda }}_{\rm{o}}}$ (at 6 GHz), and the measured results demonstrate that the proposed design provided very wide −10-dB impedance and 3-dB axial-ratio bandwidths of 48.6% and 46.2%, respectively. Additionally, stable radiation patterns with a gain of approximately 11.5 dBic and radiation efficiency of greater than 90% were observed for every beam direction.

A Simple Cross Correlation Switched Beam System (XSBS) for Angle of Arrival Estimation

We propose a practical, simple and hardware friendly, yet novel and efficient, angle of arrival (AoA) estimation system. Our intuitive, two-phases cross-correlation-based system requires a switched beam antenna array with a single radio frequency circuitry, which is used to collect an omni-directional reference signal using a single element of the antenna array in the first phase. Our system applies energy detection on the collected reference signal to decide on the presence or absence of a transmitted signal. In the second phase, the system steers the main beam to scan the angular region of interest. The collected signal from each beam angle is cross correlated with the omni-directional reference signal to determine the angle of arrival of the received signal. The combined practicality and high efficiency of our system is demonstrated through performance and complexity comparisons with one of the literature’s best performing multiple signal classification (MUSIC) algorithm. Our proposed AoA estimation system has a negligible root mean square error at signal to noise ratio level greater than −16 dB, which is very comparable to MUSIC.

A 60‐GHz multi‐beam antenna array design by using MHMICs technology

ABSTRACTThe integration feasibility of two technologies including Miniaturized Hybrid Microwave Integrated Circuit (MHMIC) and Printed Circuit Board (PCB) are experimentally demonstrated at millimeter wave frequencies through the design of a switched beam antenna array. A 1 × 4 array of aperture coupled patch antennas etched on a RO5880 substrate is fed by a 4 × 4 butler matrix etched on a piece of high permittivity ceramic substrate. By using the proposed combined fabrication technologies, the feeding part on the ceramic substrate can be easily integrated with MMIC active component, while the radiation part is individually improved. Comparison of simulated and measured results show that the proposed switched beam antenna offers a −10 dB matching bandwidth of 6 GHz ranging from 58 GHz to 64 GHz and a multi beam radiation pattern which is focused in 45°, 15°, −15°, −45° directions. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1844–1847, 2016