This communication presents a reconfigurable antenna capable of independently reconfiguring the operating frequency, radiation pattern and polarization. A switched grid of small metallic patches, ...known as pixel surface, is used as a parasitic layer to provide reconfiguration capabilities to existing antennas acting as driven element. The parasitic pixel layer presents advantages such as low profile, integrability and cost-effective fabrication. A fully operational prototype has been designed, fabricated and its compound reconfiguration capabilities have been characterized. The prototype combines a patch antenna and a parasitic pixel surface consisting of 6 × 6 pixels, with an overall size of 0.6 λ×0.6 λ and 60 PIN-diode switches. The antenna simultaneously tunes its operation frequency over a 25% frequency range, steers the radiation beam over ±30° in E and H-planes, and switches between four different polarizations (x̂, ŷ, LHCP, RHCP). The average antenna gain among the different parameter combinations is 4 dB, reaching 6-7 dB for the most advantageous combinations. The distance between the driven and the parasitic layers determines the tradeoff between frequency tuning range (12% to 25%) and radiation efficiency (45% to 55%).
A multifunctional reconfigurable antenna (MRA) capable of operating in nine modes corresponding to nine steerable beam directions in the semisphere space {-30°,0°, 30°}; φ ∈ {0°, 45°, 90°, 135°}) is ...presented. The MRA consists of an aperture-coupled driven patch antenna with a parasitic layer placed above it. The surface of the parasitic layer has a grid of 3 × 3 electrically-small square-shaped metallic pixels. The adjacent pixels are connected by PIN diode switches with ON/OFF status to change the geometry of the parasitic surface, which in turn changes the current distribution on the antenna, thus provides reconfigurability in beam steering direction. The MRA operates in the IEEE 802.11 frequency band (2.4-2.5 GHz) in each mode of operation. The antenna has been fabricated and measured. The measured and simulated impedance and radiation pattern results agree well indicating an average of ~ 6.5 dB realized gain in all modes of operation. System level experimental performance evaluations have also been performed, where an MRA equipped WLAN platform was tested and characterized in typical indoor environments. The results confirm that the MRA equipped WLAN systems could achieve an average of 6 dB Signal to Noise Ratio (SNR) gain compared to legacy omni-directional antenna equipped systems with minimal training overhead.
The design, prototyping, and characterization of a radiation pattern reconfigurable antenna (RA) targeting 5G communications are presented. The RA is based on a reconfigurable parasitic layer ...technique in which a driven dipole antenna is located along the central axis of a 3-D parasitic layer structure enclosing it. The reconfigurable parasitic structure is similar to a hexagonal prism, where the top/bottom bases are formed by a hexagonal domed structure. The surfaces of the parasitic structure house electrically small metallic pixels with various geometries. The adjacent pixels are connected by PIN diode switches to change the geometry of the parasitic surface, thus providing reconfigurability in the radiation pattern. This RA is designed to operate over a 4.8-5.2 GHz frequency band, producing various radiation patterns with a beam-steering capability in both the azimuth (0° <; φ <; 360°) and elevation planes (-18° <; θ <; 18°). Small-cell access points equipped with RAs are used to investigate the system level performances for 5G heterogeneous networks. The results show that using distributed mode optimization, RA equipped small-cell systems could provide up to 29% capacity gains and 13% coverage improvements as compared to legacy omnidirectional antenna equipped systems.
A reconfigurable antenna (RA) capable of steering its beam into the hemisphere corresponding to <inline-formula> <tex-math notation="LaTeX">\theta \in </tex-math></inline-formula> {−40°, 0°, 40°}, ...<inline-formula> <tex-math notation="LaTeX">\phi \in </tex-math></inline-formula> {0°, 45°, 90°, −45°}, and of changing 3 dB beamwidth, where <inline-formula> <tex-math notation="LaTeX">\theta _{3\,\text {dB}} \in </tex-math></inline-formula>(40°, 100°), <inline-formula> <tex-math notation="LaTeX">\phi \in </tex-math></inline-formula> {45°, 90°, −45°} for broadside direction is presented. The RA operating in 5 GHz band consists of a driven patch antenna with a parasitic layer placed above it. The upper surface of the parasitic layer has two pixelated metallic strips, where each strip has four pixels. The pixels connected via p-i-n diode switches enable to change the current distribution on the antenna providing the desired modes of operation. A prototype RA was characterized indicating an average gain of 8 dB. Measured and simulated impedance and radiation patterns agreed well. The proposed RA offers an efficient solution by using less number of switches compared to other RAs. The system level simulations for a 5G orthogonal frequency division multiple access system show that the RA improves capacity/coverage tradeoff significantly, where the RA modes and users are jointly determined to create proper beamwidth and directivity at the access point antennas. For a hotspot scenario, the presented RA provided 29% coverage and 16% capacity gain concurrently.
A novel antenna reconfiguration mechanism based on the displacement of liquid metal sections is presented. The liquid nature of the moving parts of the antenna helps avoid the main disadvantage of ...mechanically-actuated reconfigurable antennas which is the mechanical failure of their solid parts due to material fatigue, creep or wear. Furthermore, the displacement of liquid elements can be more effectively performed than in the case of solid materials by applying precise microfluidic techniques such as continuous-flow pumping or electrowetting. The reconfiguration mechanism is demonstrated through the design, fabrication and measurement of a radiation pattern reconfigurable antenna. This antenna operates at 1800 MHz with 4.0% bandwidth and is capable of performing beam-steering over a 360° range with fine tuning. The antenna is a novel circular Yagi-Uda array, where the movable parasitic director and reflector elements are implemented by liquid metal mercury (Hg). The parasitics are placed and rotated in a circular microfluidic channel around the driven element by means of a flow generated and controlled by a piezoelectric micropump. The measured results demonstrate good performance and the applicability of the microfluidic system.
The ability to use resources to meet the need of growing diversity of communication services and user behavior marks the future of cognitive wireless communication systems. Cognitive wireless ...technologies for vehicular communications in combination with orbital angular momentum (OAM) modes aim at extending non-line-of-sight (NLOS) short-distance communications for smart mobility. In this regard, OAM antenna frameworks need to be developed to support these technologies. In this work, we describe a magnetoelectric dipole antenna framework supporting OAM modes. The framework is derived from moment tensors of specific vector spherical harmonic (VSH) functions synthesized from dipoles. The antenna framework is discussed in terms of OAM generation, and it is validated numerically and experimentally for <inline-formula> <tex-math notation="LaTeX">l=1 </tex-math></inline-formula> OAM mode, achieving more than 500-MHz operation bandwidth at the frequency of operation of 3.5 GHz. In addition, for <inline-formula> <tex-math notation="LaTeX">l=1 </tex-math></inline-formula> OAM mode, the null aligns precisely with the anticipated dimensions numerically computed.
MU-MIMO transmission relies on exploiting multi-user diversity among a multitude of users. In this paper, to enhance MU-MIMO transmission, techniques for designing and exploiting reconfigurable ...antennas (RAs) are developed. A single-element RA is capable of generating modes with different radiation pattern and polarization states resulting in multiple different channel states for each user. This capability expands the search space for user-pairing optimization. To reduce complexity, an iterative user and antenna mode selection algorithm is proposed. Based on parasitic tuning, an RA optimized for MU-MIMO transmission and capable of creating four pattern types is designed using a genetic algorithm and full-wave electromagnetic analyses. Pattern- and channel-aware mode-set generation methods are developed, where mode groups are determined to reduce channel estimation overhead and mode selection complexity while achieving superior performance. Simulation results indicate that the proposed schemes need a lower number of users and/or relax user selection requirements to benefit from MU-MIMO transmissions. It is also seen that more legacy antennas are needed to achieve similar MU-MIMO performance provided by the RA system. Simulations show up to 16-dB signal-to-noise ratio gains for a single cell with 12 users, where the base station has four RAs and four single-antenna users are simultaneously served via MU-MIMO transmission.
A new kind of double- and single-arm cantilever type DC-contact RF MEMS actuators has been monolithically integrated with an antenna architecture to develop a frequency reconfigurable antenna. The ...design, microfabrication, and characterization of this ¿reconfigurable antenna (RA) annular slot¿ which was built on a microwave laminate TMM10i ( ¿ r = 9.8, tan ¿ = 0.002), are presented in this paper. By activating/deactivating the RF MEMS actuators, which are strategically located within the antenna geometry and microstrip feed line, the operating frequency band is changed. The RA annular slot has two reconfigurable frequencies of operation with center frequencies f low = 2.4 GHz and f high = 5.2 GHz, compatible with IEEE 802.11 WLAN standards. The radiation and impedance characteristics of the antenna along with the RF performance of individual actuators are presented and discussed.
A parasitic layer-based multifunctional reconfigurable antenna (MRA) design based on multi-objective genetic algorithm optimization used in conjunction with full-wave EM analysis is presented. The ...MRA is capable of steering its beam into three different directions (θ i = -30°, 0°, 30°) simultaneously with polarization reconfigurability (P j = Linear, Circular) having six different modes of operation. The MRA consists of a driven microstrip-fed patch element and a reconfigurable parasitic layer, and is designed to be compatible with IEEE-802.11 WLAN standards (5-6 GHz range). The parasitic layer is placed on top of the driven patch. The upper surface of the parasitic layer has a grid of 5 5 electrically small rectangular-shaped metallic pixels, i.e., reconfigurable parasitic pixel surface. The EM energy from the driven patch element couples to the reconfigurable parasitic pixel surface by mutual coupling. The adjacent pixels are connected/disconnected by means of switching, thereby changing the geometry of pixel surface, which in turn changes the current distribution over the parasitic layer, results in the desired mode of operation in beam direction and polarization. A prototype of the designed MRA has been fabricated on quartz substrate. The results from simulations and measurements agree well indicating ~8 dB gain in all modes of operation.
We present a novel antenna reconfiguration mechanism relying on electrowetting based digital microfluidics to implement a frequency reconfigurable antenna operating in the X-band. The antenna built ...on a quartz substrate (εr = 3.9, tan δ = 0.0002) is a coplanar waveguide fed annular slot antenna, which is monolithically integrated with a microfluidic chip. This chip establishes an electrowetting on dielectric platform with a mercury droplet placed in it. The base contact area of the mercury droplet can be spread out by electrostatic actuation resulting in a change of loading capacitance. This in turn changes the resonant frequency of the antenna enabling a reversible reconfigurable impedance property. This reconfigurable antenna has been designed, fabricated and measured. The frequency of operation is tuned from around 11 GHz to 13 GHz as demonstrated by simulations and measurements. The design methodology, fabrication processes and the experimental results are given and discussed.
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