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In low earth orbit (LEO) satellite constellations, when earth-fixed footprint mode is used, the switching of beams between coverage regions affects the elevation angle of the coverage, which in turn affects the communication quality. A coverage region switching method was proposed to address the coverage region switching problem in earth-fixed footprint mode. Firstly, a coverage region division mechanism was designed to keep the coverage region topology regular. Then, a switching time selection mechanism and a target coverage region selection mechanism were designed with the objective of maximizing the minimum elevation angle of the beams. The proposed method takes the differences between polar and inclined orbit constellations into account and supports both constellations. The OneWeb and Telesat constellations are used as simulation scenarios to validate the proposed method. The simulation results show that the proposed method can effectively improve the minimum elevation angle of the beams, which helps to improve the link quality.

We propose and demonstrate an integrated optical switch that leverages an optical phased array (OPA) and an on-chip metalens, highlighting its potential for efficient and scalable beam switching across multiple ports within a compact footprint. The device consists of an input multimode interference (MMI) coupler, a phase modulator (PM) array, a beam-transformation region featuring an on-chip metalens layer, and a tapered waveguide array serving as the output ports. The PM array, engineered to effectively manipulate multiple phases for a waveguide array using a single voltage, utilizes metal strips of varying lengths to streamline operation. The on-chip metalens, characterized by varying slot lengths, facilitates the wavefront manipulation of the fast Fourier transform, resulting in beam deflection with a focusing length of 20 µm. The simulated validation of the proposed compact optical switch demonstrated efficient beam deflection, yielding a 1 × 8 beam switching at a wavelength of 1550 nm. Combinations of diverse OPAs and metalens configurations resulted in potential scalability, allowing for the realization of optical switches with pathway numbers ranging from 4 to 16. This development of a metalens-assisted optical switch on a compact chip presents significant practical implications for enhancing data transmission efficiency and scalability in photonic integrated circuits. [ABSTRACT FROM AUTHOR]

Fifth Generation (5G) Millimeter cellular networks are particularly interesting within the Industry 4.0 paradigm. mmWaves provide flexibility to the industrial use case, as well as enable specific application requirements, e.g. robots needing high data rates and low latency communication. Coverage at mmWaves, however, is challenged by additional attenuation and blocking effects, requiring the use of beamforming to overcome this by steering transmissions towards specific directions. Reliability is a key requirement as well, and requires, e.g, seamless beam switching during movement. Here, the resulting directivity of the antennas makes the beam switching procedures key to maintain the connectivity as the users move by. The present work aims to analyze the beam switching performance in a real-world indoor industrial scenario with high clutter to identify potential failures and propose optimization strategies. Firstly, this work has gathered insights into how beamforming operates under specific situations, identifying unused beams, relating the beam switching to the User Equipment (UE)’s movement, and collecting statistics from the beam switchings. Finally, a refined beam switching criteria is proposed based on radio metrics and location information, which outperforms the current criteria used by the network. This is evaluated based on the Reference Signal Received Power (RSRP) and the number of beam switchings under different criteria.

This paper proposes a design of a multilayer controlled beam horn antenna for the D-band. The multilayer design can achieve easy to control, low cost, and compact structure. The designed structure achieves the effect of a conventional horn antenna by stacking multiple layers and realizes the effect of beam switching by modifying the multi-layer plate structure. The widest bandwidth can be obtained when stacking 4 layers of boards, covering 24.7% (110-141GHz) of the bandwidth with a simulation gain of approximately 13.5dBi. By replacing the third plate structure, beam switching of ±30 degrees can be achieved, and the gain after beam switching can also reach 11.5 dBi.

The paper proposes a four-directional beamforming switched antenna system based on Butler matrix for 28 GHz mmWave. It is made up of a 90-degree coupler, a crossover, and a 45-degree phase shifter. A $4\times 4$ Butler matrix is combined with a 28 GHz patch antenna to form a Butler network antenna. Four directions of the radiation beam can be changed when the input position is changed. From the simulation and measurement results, the measured reflection coefficients cover 27.9-29.3 GHz at all four ports with a standard reflection coefficient of -10 dB and four different angles of 15°, -46°, +44° and -13° for switching beam direction. The antenna’s compact size of $39.1\times 45.6\,\,{\mathrm {mm}}^{2}$ ( $3.65\lambda _{0}\times 4.26\lambda _{0}$ ) makes it ideal for use in millimeter wave bands for 5G NR n258, and n261 applications, while also providing a high gain of 11.5 dBi.

Shared aperture antennas are versatile structures that can fulfill the demand for multi-band compact antennas in multi-standard emerging communication systems. However, the requirement of operation at widely separated frequency bands, such as sub-6-GHz band and mm-wave band in 5G, poses a challenge. This paper introduces a novel Encapsulated Dielectric Resonator Antennas (E-DRAs) designed for operation at sub-6-GHz and mm-wave bands for 5G and beyond applications. The DRA part of the antenna consists of an array of small cylindrical DRAs (cDRA) encapsulated in a larger cylinder. At mm-wave band, the small cDRAs are radiating elements while the larger cylinder acts as a lens to enhance the gain and provide beam switching at discrete angles by switching the feed between the small cDRAs. At sub-6-GHz band, the large cylinder is the main radiator. The antenna is realized with a 3D printing process using two distinct ABS materials with different infills. Measurements of the fabricated antenna show a maximum gain of 7.8 dBi at 3.35 GHz and 19.7 dBi at 27 GHz. The measured bandwidth is 20.2% centered at 3.45 GHz and 28.7% centered at 28.5 GHz. The array of small cDRAs with five elements enables beam switching within ±30°.

We propose and demonstrate an integrated optical switch that leverages an optical phased array (OPA) and an on-chip metalens, highlighting its potential for efficient and scalable beam switching across multiple ports within a compact footprint. The device consists of an input multimode interference (MMI) coupler, a phase modulator (PM) array, a beam-transformation region featuring an on-chip metalens layer, and a tapered waveguide array serving as the output ports. The PM array, engineered to effectively manipulate multiple phases for a waveguide array using a single voltage, utilizes metal strips of varying lengths to streamline operation. The on-chip metalens, characterized by varying slot lengths, facilitates the wavefront manipulation of the fast Fourier transform, resulting in beam deflection with a focusing length of 20 µm. The simulated validation of the proposed compact optical switch demonstrated efficient beam deflection, yielding a 1 × 8 beam switching at a wavelength of 1550 nm. Combinations of diverse OPAs and metalens configurations resulted in potential scalability, allowing for the realization of optical switches with pathway numbers ranging from 4 to 16. This development of a metalens-assisted optical switch on a compact chip presents significant practical implications for enhancing data transmission efficiency and scalability in photonic integrated circuits.

We present an electrically switchable, compact metasurface device based on the metallic polymer PEDOT:PSS in combination with a gel polymer electrolyte. Applying square-wave voltages, we can reversibly switch the PEDOT:PSS from dielectric to metallic. Using this concept, we demonstrate a compact, standalone, and CMOS compatible metadevice. It allows for electrically controlled ON and OFF switching of plasmonic resonances in the 2–3 µm wavelength range, as well as electrically controlled beam switching at angles up to 10°. Furthermore, switching frequencies of up to 10 Hz, with oxidation times as fast as 42 ms and reduction times of 57 ms, are demonstrated. Our work provides the basis towards solid state switchable metasurfaces, ultimately leading to submicrometer-pixel spatial light modulators and hence switchable holographic devices.

This article provides for the first time a detailed discussion of the optimal assignment of adjacent output phase differences in terms of matrix performance out of all possible combinations in generalized one-dimensional parallel switching matrices with four beams. In this specific case, the topology of the proposed matrix reduces to that of a single-layer Butler matrix, connecting hybrid couplers and crossovers with adequate phase shifters. The values of the phase shift required are dependent on the assignment of the output phase differences, which in turn is shown to have an impact on the radiation characteristics of the linear array fed by such networks when imposing constraints on the matrix layout for a more generic implementation. The configuration having the smallest phase difference with reference to the transmission phase of a straight waveguide with the same length as the coupled region of the crossover is chosen and compared with the conventional well-known Butler matrix. The two matrix configurations are implemented using post-wall waveguides designed to operate over the band 20 GHz – 24 GHz. The prototypes are manufactured and tested, using transitions to standard waveguide WR42. The measured results confirm the benefits of the identified optimal adjacent phase difference assignment in terms of transmission coefficients, reflection coefficients, phase differences between adjacent output ports, and frequency dependence of the array factor. These results will also benefit the design of larger generalized one-dimensional parallel switching matrices.

Ensuring a seamless connection with various types of mobile user equipment (UE) items is one of the more significant challenges facing different generations of wireless systems. However, enabling the high-band spectrum – such as the millimeter wave (mmWave) band – is also one of the important factors of 5G networks, as it enables them to deal with increasing demand and ensures high coverage. Therefore, the deployment of new (small) cells with a short range and operating within the mmWave band is required in order to assist the macro cells which are responsible for operating long-range radio connections. The deployment of small cells results in a new network structure, known as heterogeneous networks (HetNets). As a result, the number of passthrough cells using the handover (HO) process will be dramatically increased. Mobility management (MM) in such a massive network will become crucial, especially when it comes to mobile users traveling at very high speeds. Current MM solutions will be ineffective, as they will not be able to provide the required reliability, flexibility, and scalability. Thus, smart algorithms and techniques are required in future networks. Also, machine learning (ML) techniques are perfectly capable of supporting the latest 5G technologies that are expected to deliver high data rates to upcoming use cases and services, such as massive machine type communications (mMTC), enhanced mobile broadband (eMBB), and ultra-reliable low latency communications (uRLLC). This paper aims to review the MM approaches used in 5G HetNets and describes the deployment of AI mechanisms and techniques in ″connected mode″ MM schemes. Furthermore, this paper addresses the related challenges and suggests potential solutions for 5G networks and beyond.

Ensuring a seamless connection with various types of mobile user equipment (UE) items is one of the more significant challenges facing different generations of wireless systems. However, enabling the high-band spectrum -- such as the millimeter wave (mmWave) band -- is also one of the important factors of 5G networks, as it enables them to deal with increasing demand and ensures high coverage. Therefore, the deployment of new (small) cells with a short range and operating within the mmWave band is required in order to assist the macro cells which are responsible for operating long-range radio connections. The deployment of small cells results in a new network structure, known as heterogeneous networks (HetNets). As a result, the number of passthrough cells using the handover (HO) process will be dramatically increased. Mobility management (MM) in such a massive network will become crucial, especially when it comes to mobile users traveling at very high speeds. Current MM solutions will be ineffective, as they will not be able to provide the required reliability, flexibility, and scalability. Thus, smart algorithms and techniques are required in future networks. Also, machine learning (ML) techniques are perfectly capable of supporting the latest 5G technologies that are expected to deliver high data rates to upcoming use cases and services, such as massive machine type communications (mMTC), enhanced mobile broadband (eMBB), and ultra-reliable low latency communications (uRLLC). This paper aims to review the MM approaches used in 5G HetNets and describes the deployment of AI mechanisms and techniques in "connected mode" MM schemes. Furthermore, this paper addresses the related challenges and suggests potential solutions for 5G networks and beyond. [ABSTRACT FROM AUTHOR]

In this paper, an antenna array for the X-band aerial landing system has been proposed. The proposed antenna is an ellipse-shaped leaky-wave array radiating in slow mode wave and has a scanning range of 75° for different inter-element spacing. Four antenna arrays were designed: two with 60 elements and two with 30 elements each, all operating from 9.3 GHz to 12.3 GHz providing a gain of 30 dBi and 20 dBi, respectively. To verify the performance, a 15-element sub-array having an overall size of 210 mm × 30 mm and achieving a total gain of 17 dBi was fabricated and tested. The proposed sub-array was fabricated using Rogers Duroid5880 (ɛr = 2.2 and h = 1.575 mm). It has been shown through comparison of radiation patterns that measured and simulation results are in good agreement.

A novel array antenna with reconfigurable polarizations and radiation pattern agility is presented in this paper. The digital-controllable array antenna has the functional capabilities of reconfigurable polarization and switching beam, which consists of cavity-backed antenna element based on substrate integrated waveguide (SIW) technique, parasitic patch array, power dividers and phase shifters. Polarization modes and radiation patterns can be dynamically controlled by means of Microcontroller Unit (MCU) with the different feeding ports and phase difference. To validate this proposal, the performance of the fabricated device was measured at the operating frequency of 5.4 GHz. Measured results indicate that the 10 dB impedance bandwidths and 3 dB axial ratio (AR) bandwidths cover from 5.25 to 5.6 GHz, and the measured gains range from 7.9 to 10.1 dBic. The experimentation and simulation verify that the proposed antenna can achieve two polarization states and five radiation beams of each polarization state, which indicate a good performance of the polarization reconfigurable and beam switching antenna array.

In this work, a novel leaky-wave antenna (LWA) with Archimedean spiral slots is proposed for realizing high radiation efficiency and stable gain performance in both frequency-controlled and fixed-frequency beam-scanning applications. The structural feature of the proposed Archimedean spiral slot privileges LWA with properties of easy impedance matching and high leakage rate, because it avoids the strong reflection from large-size slots that commonly used in LWA design for high leakage rate. The bandwidths of the final designed Ka-band LWA defined by radiation efficiency larger than 90% and 80% are 13% and 25%, respectively, while the bandwidth defined by return loss less than −10 dB is 29%. And the gain fluctuations between different scanned beams are less than 2.4 dBi in the whole broadband. The LWA is further applied in designing a new-type antenna with double-layer substrate-integrated waveguide (SIW) structures, which has four feeding ports at the ends and a coupling plane in the middle interface and can realize the fixed-frequency beam switching between directions of −46°, −36°, 34°, and 45° at 28 GHz through changing the excitation port. The proposed LWAs are potential candidates for applying in future millimeter wave communication systems where multifunction integrated and multifrequency adaptive antennas are required. [ABSTRACT FROM AUTHOR]

In this paper, an antenna array for the X-band aerial landing system has been proposed. The proposed antenna is an ellipse-shaped leakywave array radiating in slow mode wave and has a scanning range of 75° for different inter-element spacing. Four antenna arrays were designed: two with 60 elements and two with 30 elements each, all operating from 9.3 GHz to 12.3 GHz providing a gain of 30 dBi and 20 dBi, respectively. To verify the performance, a 15-element sub-array having an overall size of 210 mm × 30 mm and achieving a total gain of 17 dBi was fabricated and tested. The proposed sub-array was fabricated using Rogers Duroid5880 (εr=2.2 and h =1.575 mm). It has been shown through comparison of radiation patterns that measured and simulation results are in good agreement. [ABSTRACT FROM AUTHOR]

A 2-D beam switching dipole antenna working at 60 GHz is proposed. To realize this, a folded electric-field coupled (ELC) resonator is designed to achieve a high-refractive-index medium in the band of 57–64 GHz. By integrating an array of ELC resonators in the off-center of a printed dipole antenna in the E- and H-planes forming high-refractive-index medium lenses (metalenses) in each plane, the main beam direction is manipulated to generate 2-D beam switching at 60 GHz. In the final configuration, six slabs each containing three folded ELC inclusions are incorporated vertically in front of the dipole antenna in the azimuth plane to tilt the radiation beam by 25° in the H-plane. In addition, a $2\times5$ array of folded ELC resonators is added into the elevation plane of the antenna substrate to deflect the radiated beam in the E-plane by 20°. The measurement results confirm that the radiated beam is tilted by 25° and 20° in the H- and E-planes, respectively, over a frequency band of 57–64 GHz. The measured antenna gain is 10.7 dBi at 61 GHz, the measured reflection coefficient is below −10 dB over 57–64 GHz, and the measured radiation efficiency of the antenna is 82% at 60 GHz. [ABSTRACT FROM AUTHOR]

Integrated lens antennas are widely used in high gain and beam steering applications at millimeter-wave frequencies. The ILA has often large height and suffers from significant scan loss. In this article, we demonstrate a low-profile, efficient, and scanloss-reduced integrated metal-lens antenna (IMLA). An IMLA is a combination of a dielectric lens and metal–plate lens. A 16- $\lambda _{0}$ diameter IMLA is designed using the HDPE and 58 stainless steel plates to achieve the $f/d$ of 0.69. The simulated aperture and radiation efficiency of the IMLA are 73% and 92%, respectively. At 76 GHz, the simulated and measured realized gains of the fabricated IMLA are 31.24 and 31 dBi, respectively. The IMLA is designed to steer the main beam to ±30°. The scan loss is reduced by tilting the radiation pattern of the feeds at offset positions along the focal plane. The radiation pattern of the square waveguide feed is tilted using asymmetrical dielectric pins. The asymmetrical dielectric pins reduce the simulated gain scan loss of the IMLA by more than 1.5 dB at 30° steering angle. The simulation results show that the inclination of the feed radiation pattern helps limit the scan loss of the IMLA to 4.1 and 4.3 dB in the H- and E-planes for 30° steering angle, respectively. The measured scan loss of the manufactured IMLA is 3.8 and 6.2 dB in the H- and E-plane, respectively. [ABSTRACT FROM AUTHOR]

This paper presents designs and prototypes of low cost multiple input multiple output (MIMO) antennas for 5G and millimetre-wave (mm-wave) applications. The proposed MIMOs are fabricated using 3D printing and are able deliver beams in multiple directions that provide continuous and real time coverage in the elevation of up to F300 without using phase shifters. This equips the proposed MIMO with a superior advantage of being an attractive low cost technology for 5G and mm-wave applications. The proposed MIMO antennas operate at the 28 GHz 5G band, with wide bandwidth performance exceeds 4 GHz and with beam switching ability of up to F300 in the elevation plane. The direction of the main beam of the single element antenna in the MIMO is steered over the entire bandwidth through introducing 3D printed walls with different heights on the side of the 3D printed radiating antenna. Unlike all other available beam steering techniques; the proposed wall is not only able to change the direction of the beam of the antenna, but also it is able to increase the overall directivity and gain of the proposed antenna and MIMO at the same time over the entire bandwidth.

Millimeter wave antennas have applications in several sensing and communication systems. Such antennas, designed for modern miniaturized devices and systems, must be low profile, flexible, and low cost. Some applications also require beam steering for detection purposes. Combining all these features into an antenna system and delivering decent antenna performance is challenging. In this study, we combined a partially reflective surface with a parasitic patch array to create a simple beam-switching, low-profile, and flexible wearable detection system. To ensure lower costs as well as compatibility with wearable systems, screen printing was utilized on a flexible substrate. The antenna array was optimized for the 77 GHz band and had a high gain of 11.2 dBi. The designed system has three independent beams, which can be oriented from bore-sight to ±32° through a simple switching mechanism. The antenna array maintains its performance in both flat and flexed conditions. Finally, the antenna array was tested in the field to successfully detect objects moving in three different directions.

A novel fixed-frequency beam switchable dual-beam antenna array is presented, which consists five dual-beam leaky-wave antenna (LWA) elements designed on substrate integrated waveguide (SIW) and integrated together on a common substrate. The LWAs work on fundamental wave and -1th spatial harmonic wave simultaneously and excite two symmetrical radiation beams in forward and backward direction respectively. In order to realize beam switching, three voltage-driven radio frequency chip switches (CSW-RFs) are used and integrated behind the antenna aperture. Since the periodic slot in LWA causes open stopband at the operating frequency, so the staggered radius amplification of local vias in the via walls of SIW is performed to suppress the open stopband. In addition, electromagnetic band-gap (EBG) structures, capable of reducing coupling between neighboring antenna elements, are embedded in between LWAs. The proposed dual-beam antenna array with beam switching capability between ±35, ±45, ±55, ±65 and ±75 degrees at 28 GHz are simulated, fabricated and measured. Both analysis and measurement results show that the proposed antenna array exhibits an excellent performance, which can be used in fixed-frequency beam-switching millimeter wave communication.

This study proposes a cylindrical conformal array antenna (CCAA) for fifth-generation (5G) micro base station applications. The CCAA is composed of five Chebyshev flexible linear array antennas (LAAs) with a circumferentially uniform arrangement on the cylindrical surface. The LAA with a logarithmic periodic arrangement is constructed by synthesizing the current amplitude distribution coefficients in elements with the Chebyshev method. The LAA with a half-power bandwidth (HPBW) wider than 76° (-8.41° to 38.58°) and a peak gain greater than 10 dBi is fabricated via the micro-electromechanical system process. Cost-performance analysis shows that five is the best number of linear arrays. To achieve omnidirectional switching scanning of the circumferential section, five LAAs wrapped on the cylindrical surface are individually excited by connecting a radio frequency semiconductor switch to the exciting ports of an eight-way power divider. Moreover, beam-switch scanning of the CCAA is measured with the aid of a standard anechoic chamber. The irradiated performance with low mutual coupling and high realized gain is verified to be irrelevant to the structural variation of various flexible experiments of LAAs wrapped around a cylindrical surface. The CCAA with beam-switch scanning operates at 26 GHz and belongs to the 5G millimeter-wave band. Results show the proposed antenna achieves omnidirectional scanning property in the H plane and has a HPBW of only 9.08° in the E plane. The performances of the CCAA present potential advantage in flexible terminal equipment wireless communication.

Collaborative beamforming (CB) enables uplink transmission in a wireless sensor network (WSN) composed of sensors (nodes) and far-away access points (APs). It can also be applied to the case where the sensors are equipped with beam-switching structures (BSSs). However, as the antenna arrays of the BSSs are randomly headed due to the irregular mounting surface, some sensors form beams that do not illuminate a desired AP and waste their limited energy. Therefore, to resolve this problem, it is required to switch the beams toward the desired AP. While an exhaustive search can provide the globally optimal combination, a greedy search (GS) is utilized to solve this optimization problem efficiently. Simulation and experimental results verify that under certain conditions the proposed algorithm can drive the sensors to switch their beams properly and increase the received signal-to-noise ratio (SNR) significantly with low computational complexity and energy consumption. [ABSTRACT FROM AUTHOR]

Collaborative beamforming (CB) enables uplink transmission in a wireless sensor network (WSN) composed of sensors (nodes) and far-away access points (APs). It can also be applied to the case where the sensors are equipped with beam-switching structures (BSSs). However, as the antenna arrays of the BSSs are randomly headed due to the irregular mounting surface, some sensors form beams that do not illuminate a desired AP and waste their limited energy. Therefore, to resolve this problem, it is required to switch the beams toward the desired AP. While an exhaustive search can provide the globally optimal combination, a greedy search (GS) is utilized to solve this optimization problem efficiently. Simulation and experimental results verify that under certain conditions the proposed algorithm can drive the sensors to switch their beams properly and increase the received signal-to-noise ratio (SNR) significantly with low computational complexity and energy consumption.

A waveguide short-slot two-plane coupler is proposed as a component of 2-D beam-switching Butler matrix. The hybrid and cross coupler operations are designed by including the 2-D polarity symmetry, the propagation constant, and the coupling with the ports of the modes in the coupled region. Their designs are confirmed by experiments. The achieved bandwidth is approximately 2%, restricted by the frequency characteristic of the modes in the coupled region. Since the short-slot two-plane hybrid coupler itself acts as the 2\times2-way 2-D beam-switching Butler matrix, the beam switching is also verified by measurements. The general configuration of the 2-D beam-switching Butler matrix is also proposed by using the short-slot two-plane couplers. [ABSTRACT FROM PUBLISHER]

One- (1-D) and two-dimensional (2-D) beamforming is presented for a planar dipole antenna operating at millimeter-wave bands. 1-D beamforming was achieved by using mu $\left({{\mu }} \right)-near-zero (MNZ) metamaterial slabs that were integrated in the dipole antenna, where each slab was loaded with an array of low refractive-index unit-cells. The resulting radiated beam can be scanned by 35° due to the phase shift in the beam introduced by its interaction with the metamaterial slabs. In addition, the proposed antenna configuration provides gain improvement of 8 dB as the slabs effectively increase the aperture size of the antenna. An array of MNZ inclusions in the E-plane of a double dipole antenna is shown to provide scanning from - 35^\circ to + {35}^\circ with respect to the end-fire direction over 57–64 GHz. 2-D beam-scanning was realized by increasing the number of MNZ unit-cells in the elevation plane of double dipole antenna. Loading the slabs in front of the double dipole antenna with {10} \times {7}$ array of MNZ unit-cells is shown to provide a beam deflection of 35° in both the azimuth and elevation planes. [ABSTRACT FROM PUBLISHER]

This paper presents a compact-size, low-cost smart antenna with electronically switchable radiation patterns, and reconfigurable polarizations. This antenna can be dynamically switched to realize three different polarizations including two orthogonal linear polarizations and one diagonally linear polarization. By closely placing several electronically reconfigurable parasitic elements around the driven antenna, the beam switching can be achieved in any of the three polarization states. In this design, a polarization reconfigurable square patch antenna with a simple feeding network is used as the driven element. The parasitic element is composed of a printed dipole with a PIN diode. Using different combinations of PIN diode on/off states, the radiation pattern can be switched toward different directions to cover an angle range of 0° to 360° in the azimuth plane. The concept is confirmed by a series of measurements. This smart antenna has the advantages of compact size, low cost, low power consumption, reconfigurable polarizations, and beams. [ABSTRACT FROM PUBLISHER]

The alternative solution is presented for single- and multi-ring arrays with a high-gain and wide elevation coverage conical beam. Effects of ring radii, number of elements, beam switching and multi-ring operation are analyzed using array theory. Gain enhancement at the large flare angle is obtained by using grating lobes of the array factor with conical pattern elements. The switching technology is employed to improve pattern ripple in azimuthal plane and to exploit the grating lobes for achieving high gain. Excitations of all the elements are in phase. A prototype of a single-ring array with 13 elements has been fabricated and measured. Three sub-arrays each composed of four elements are arranged on the ring and the other single element is located at the center. Measured results show that elevation beam coverage is from 20^\circ to 55^\circ and the maximum radiation gain is 9 dBi at 48^\circ elevation at 12.5 GHz. [ABSTRACT FROM PUBLISHER]

With the aid of tri-operational mode synthesized transmission lines, an innovative heterogeneous integrated phased array having the functions of beam-switching and retrodirection in three individual bands is proposed and demonstrated. The key innovation is the array feeding network, capable of automatically reconfiguring its topology into three states without applying any active switch. In the low band, the feeding circuit, and hence, the entire system function as a beam-switching array using the Butler matrix for communication and positioning. In the mid and high bands, the integrated array rearranges its feeding network into pairs of isolated delay lines and becomes a Van Atta array and a phase-conjugating array, respectively, to re-radiate the signals to the direction of arrival. The core building blocks are the three-channel selector, tri-mode coupler, and diplexer, all realized by synthesized transmission lines with rigorous design formulae. The operational principle is first introduced, followed by the design and implementation of the key components. A phase compensation scheme is discussed to complete the tri-mode array design. This unique concept is experimentally verified using the radiation characteristics of the integrated array at the end of this paper. [ABSTRACT FROM AUTHOR]

A high gain beam switching pattern reconfigurable quasi-Yagi dipole antenna is presented for wireless local area network (WLAN) systems at 5.2 GHz. The antenna consists of a microstrip-to-coplanar stripline (CPS) balun, the length of which can be controlled by using PIN diodes. The change of the length of the balun allows the currents on the two arms of the dipole to have different phase differences, thereby making the antenna operate at three states with the E-plane maximum beam direction towards 20^\circ, -20^\circ, and 0^\circ, respectively. In order to validate the design method, a prototype of the proposed antenna with a practical biasing network was fabricated and measured. Measured results on the reflection coefficients, radiation patterns, and realized gains for three operating states are provided, which agree well with the numerical simulations. [ABSTRACT FROM AUTHOR]

By utilizing synthesized transmission lines, in this paper a four-element heterogeneous integrated beam-switching/ retrodirective phased array is proposed and demonstrated. Without using active devices, the innovative array can switch its feeding network in two operational modes, making it identical to a beam-switching Butler matrix array in one frequency band, but become a reflection-type retrodirective array in the other band. The key building blocks of the unique feeding network are the dual-mode crossover and dual-mode delay lines, realized by synthesized transmission lines consisting of quasi-lumped meander-line inductors and series LC tanks in microstrip form. The operational principles, including the architecture and phase compensation scheme, are first discussed, followed by the design considerations and experimental results of the core components. The circuit responses of the feeding network and the radiation characteristics of the heterogeneous integrated array are validated through experiments. Discussion is given at the end of this paper. [ABSTRACT FROM PUBLISHER]

A compact broadband 8-way Butler matrix integrated with tunable phase shifters is proposed to provide full beam switching/steering capability. The newly designed multilayer stripline Butler matrix exhibits an average insertion loss of 1.1 dB with amplitude variation less than ±2.2 dB and an average phase imbalance of less than 20.7° from 1.6 GHz to 2.8 GHz. The circuit size is only 160 × 100 mm², which corresponds to an 85% size reduction compared with a comparable conventional microstrip 8-way Butler matrix. The stripline tunable phase shifter is designed based on the asymmetric reflection-type configuration, where a Chebyshev matching network is utilized to convert the port impedance from 50 Ω to 25 Ω so that a phase tuning range in excess of 120 can be obtained from 1.6 GHz to 2.8 GHz. To demonstrate the beam switching/steering functionality, the proposed tunable Butler matrix is applied to a 1 × 8 antenna array system. The measured radiation patterns show that the beam can be fully steered within a spatial range of 108°. [ABSTRACT FROM AUTHOR]

We present the analysis and experimental results of a beam-steering and -switching antenna array using coupled oscillators and phase-locked loops. With the use of a type-II coupled phase-locked loop array and an external reference signal, the antenna array can steer its beam by a single control voltage, reduce the beam-pointing error arising from the phase errors of the oscillator array, and hold its output frequency stably at the reference signal frequency in operation. Using a double-pole double-throw switch and a difference amplifier at the center element of the antenna array, one can switch the array radiation pattern between the sum pattern and the difference pattern. Moreover, the beam- scanning range is extended to ±90° by properly using frequency prescalers in the phase-locked loops. The radiation characteristics of a three-element antenna array are measured to verify the array performance. [ABSTRACT FROM AUTHOR]

A new type of substrate integrated waveguide (SIW) multibeam antenna is proposed for mobile satellite communications using beam switching and diversity techniques. It employs an SIW Rotman lens as the beamforming network. The prototype of a single multibeam antenna is implemented at 28.5 GHz with seven input ports and an antenna array constructed by nine SIW linear slot arrays, which can generate a corresponding number of beams along one dimension. Several such antennas are grouped in two different ways to cover a 2-D solid angle with multiple beams. Experiment results show that the 2-D solid angle around (-40deg, 40deg) X (-35deg, 35deg) or (-25deg, 25deg) x (-35deg, 35deg) are covered with 20 or 25 beams with 5 -dB beamwidth, respectively. It is demonstrated that this type of printed multibeam antenna is a good choice for communication applications where mobility and high gain are simultaneously required. [ABSTRACT FROM PUBLISHER]