Metamaterial inspired multi-split square shaped printed antenna for WLAN applications

This paper describes the design of a compact dual band microstrip antenna based on metamaterial inspired split ring radiating element and a complementary spilt ring resonator (CSRR). The antenna has a very compact dimension of 20×20×0.8 mm3. It covers the 2.5/5.2/5.8 GHz frequencies, pertaining to IEEE 802.11 b/g/a standards suitable for WLAN applications with a -10dB impedance bandwidth of 250 MHz and 860 MHz. The CSRR creates a negative permittivity region, thus providing miniaturization of the antenna and the introduction of additional split gaps in the radiating element creates a positive permeability within the desirable frequency range, yielding better impedance matching. The negative properties of those structures are verified using S-parameter retrieval method. A prototype of the proposed antenna is fabricated and the measured results are fairly in good agreement with the simulation results. Dipole like radiation patterns are observed at both the operating frequencies. The measured peak gains are 0.58 dBi, 1.27 dBi and 2.10 dBi at 2.5, 5.2 and 5.8 GHz respectively.

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.

Design of Low-Cost Miniaturized Metamaterial-Based Circular Split-Ring Monopole Radiating System for LTE Applications

A compact low-cost metamaterial circular monopole antenna for LTE applications is presented here. This paper addresses an asymmetric circular split-ring radiator for 2.6[Formula: see text]GHz (LTE-7 band), 3.5[Formula: see text]GHz (LTE-22 band). The design here employs split rings with varying split gaps in the consecutive ring layers of the radiating element which helped in achieving better impedance matching for obtaining multiband operation. The work presented here demonstrates the feasibility of achieving double negative material property, without loading the SRR’s separately in the system. The antenna was modeled using a 1.6[Formula: see text]mm thick FR-4 lossy material. The simulated results were compared with measured results and found to be in good agreement with each other. Employing asymmetric split ring as radiator helped in achieving 29% of size reduction in the patch layer. The modified split-ring radiator achieved directional radiation pattern and minimum side-lobe levels with a peak gain of 1.29 and 0.204[Formula: see text]dB at the lower band and upper band, respectively. The compact dimension [Formula: see text] of the radiating system makes it suitable for LTE-WLAN/Wi-Max applications.

MTM- and SIW-Inspired Bowtie Antenna Loaded with AMC for 5G mm-Wave Applications

This paper investigates a feasible configuration of slotted bowtie antenna based on MTM and SIW properties for 5G millimeter-wave applications. To realize the proposed slotted bowtie antenna in a compact dimension with high performances, the MTM and SIW concepts are implemented by applying the trapezoidal slots on the top surface of the antenna and metallic via holes through the substrate layer connecting the top surface to the ground plane. The antenna has been fed with a simple microstip-line which is connected to a waveguide-port. It is shown that the slotted bowtie antenna with a small dimension of 30 × 16 × 0.8 mm3 operates over a measured wideband of 32–34.6 GHz with the fractional bandwidth, average gain, and radiation efficiency of 7.8%, 3.2 dBi, and 50%, respectively. To improve the antenna's performance, the artificial magnetic conductor (AMC) properties have been employed on the ground plane by loading vertical and linear slots with various lengths. The AMC slots are aligned under the trapezoidal slots on the top surface to transfer the maximum electromagnetic signals to them for optimum radiation. The proposed method enlarges the antenna’s effective aperture area, keeping constant its physical dimensions. The proposed AMC-loaded antenna covers wider frequency range of 30–37 GHz in measurement, which corresponds to 21% fractional bandwidth. The average experimental gain and radiation efficiency have been increased to 5.5 dBi and 66.5%, respectively, which illustrate the effectiveness of the proposed AMC-loaded antenna. The results confirm that the proposed slotted bowtie antenna with advantages of compact dimension, wide bandwidth, high gain and efficiency, low profile, being cost-effective, simple design, and easy fabrication process, which makes it applicable for mass production, can be a good candidate for 5G millimeter-wave applications.

Induced Currents and Aharonov–Bohm Effect in Effective Fermion Models and in Spaces with a Compact Dimension

We consider fermion models in 3D- and 5D-space-time with an Aharonov–Bohm potential and a domain wall. Induced current is calculated, which is due to vacuum effects in the topologically nontrivial space-time. Violation of chiral symmetry and appearance of induced current is demonstrated in a simple example of quantum mechanical violation of symmetry in a model of a massless Dirac fermion moving in a background vector field and domain walls as barriers for the electron propagation. The effective Dirac equation for massless electrons modeling monolayer graphene is used. One of the solutions to the problem of describing domain walls in planar systems is reduced to finding exact analytic solutions. In this paper, we consider appearance of induced current in two-fermion model with a compact dimension as a result of vacuum polarization in the field of the external gauge field in the 4 + 1 and the 2 + 1 dimensional models with one type of fermions and with two types of fermions living in the brane and in the bulk. Two different approaches (Kaluza–Klein and Aharonov–Bohm) to the problem of induced current are used. Production of an induced current in a planar model with a thin solenoid is also studied.

Nothing is certain in string compactifications

A bubble of nothing is a spacetime instability where a compact dimension collapses. After nucleation, it expands at the speed of light, leaving “nothing” behind. We argue that the topological and dynamical mechanisms which could protect a compactification against decay to nothing seem to be absent in string compactifications once supersymmetry is broken. The topological obstruction lies in a bordism group and, surprisingly, it can disappear even for a SUSY-compatible spin structure. As a proof of principle, we construct an explicit bubble of nothing for a T3 with completely periodic (SUSY-compatible) spin structure in an Einstein dilaton Gauss-Bonnet theory, which arises in the low-energy limit of certain heterotic and type II flux compactifications. Without the topological protection, supersymmetric compactifications are purely stabilized by a Coleman-deLuccia mechanism, which relies on a certain local energy condition. This is violated in our example by the nonsupersymmetric GB term. In the presence of fluxes this energy condition gets modified and its violation might be related to the Weak Gravity Conjecture.We expect that our techniques can be used to construct a plethora of new bubbles of nothing in any setup where the low-energy bordism group vanishes, including type II compactifications on CY3, AdS flux compactifications on 5-manifolds, and M-theory on 7-manifolds. This lends further evidence to the conjecture that any non-supersymmetric vacuum of quantum gravity is ultimately unstable.

Vacuum bosonic currents induced by a compactified cosmic string in dS background

In this paper, we study the vacuum bosonic currents in the geometry of a compactified cosmic string in the background of the de Sitter spacetime. The currents are induced by magnetic fluxes, one running along the cosmic string and another one enclosed by the compact dimension. To develop the analysis, we obtain the complete set of normalized bosonic wave functions obeying a quasiperiodicity condition. In this context, we calculate the azimuthal and axial current densities and we show that these quantities are explicitly decomposed into two contributions: one originating from the geometry of a straight uncompactified cosmic string and the other induced by the compactification. We also compare the results with the literature in the case of a massive fermionic field in the same geometry.

A Miniaturized CPW-Fed Reconfigurable Antenna with a Single-Dual Band and an Asymmetric Ground Plane for Switchable Band Wireless Applications

A miniaturized reconfigurable antenna with a hexagonal slot is presented. The motivation of this study is to overcome the problem of switching band antenna with minimum electronic components while designing a miniaturized antenna. The reconfigurable band property has been obtained using only two PIN diodes. The suggested structure has successfully permitted the reconfigurable ability up to three bands of 2.36-2.81 GHz, 3.20-4.23 GHz, and 3.13-5.92 GHz, which well suitable for the standard of the WLAN and WiMAX bands of 5.8/2.4/5.2 GHz and 5.5/2.5/3.5 GHz respectively. The peck gain and efficiency of the reconfigurable antenna at resonant frequencies 2.58, 3.56, 3.58, and 5.63 GHz are 1.48, 1.69, 1.89, 3.44 dBi and 89.60, 87.14, 90.48, 81.57%. The suggested antenna has a compact dimension of 31 × 14.5 mm2. This antenna has a better performance which makes it a good candidate to use in a variety of multimode wireless devices.

Induced fermionic current in AdS spacetime in the presence of a cosmic string and a compactified dimension

In this paper, we consider a massive charged fermionic quantum field and investigate the current densities induced by a magnetic flux running along the core of an idealized cosmic string in the background geometry of a 5-dimensional anti-de Sitter spacetime, assuming that an extra dimension is compactified. Along the compact dimension quasi-periodicity condition is imposed on the field with a general phase. Moreover, we admit the presence of a magnetic flux enclosed by the compactified axis. The latter gives rise to Ahanorov–Bohm-like effect on the vacuum expectation value of the currents. In this setup, only azimuthal and axial current densities take place. The former presents two contributions, with the first one due to the cosmic string in a 5-dimensional AdS spacetime without compact dimension, and the second one being induced by the compactification itself. The latter is an odd function of the magnetic flux along the cosmic string and an even function of the magnetic flux enclosed by the compactified axis with period equal to the quantum flux. As to the induced axial current, it is an even function of the magnetic flux along the string’s core and an odd function of the magnetic flux enclosed by the compactification perimeter. For untwisted and twisted field along compact dimension, the axial current vanishes. The massless field case is presented as well some asymptotic limits for the parameters of the model.

Back-iron design-based electromagnetic regenerative tuned mass damper

Implementation of tuned mass dampers is the commonly used approach to avoid excessive vibrations in civil engineering. However, due to the absence of the compact dimension, there are still no practical applications of the tuned mass dampers in automotive industry. Meanwhile, recent investigations showed the benefit of utilizing a tuned mass damper in a vehicle suspension in terms of driving comfort and road holding. Thus, the current investigation aimed to explore a novel compact dimension tuned mass damper, which can provide both sufficient vibration mitigation and energy harvesting. This paper presents a prototype of a back-iron-based design of an electromagnetic regenerative tuned mass damper. The mathematical model of the tuned mass damper system was developed and has been validated by the experimental results of the tuned mass damper prototype implemented in a protected mass test-bench. The indicated results concluded that the attenuation performance dramatically deteriorated under random excitations and a reduction in the root-mean-square acceleration of 18% is concluded compared to the case with undamped tuned mass damper. Under harmonic excitations, the designed tuned mass damper prototype is able to reduce the peak acceleration value of the protected structure by 79%. According to the experimental results, the designed tuned mass damper prototype revealed a peak regenerative power of 0.76 W under a harmonic excitation of 8.1 Hz frequency [Formula: see text]m amplitude. Given the simulated random road profiles from C to E, the back-iron electromagnetic tuned mass damper indicated that root-mean-square harvested power from 0.6 to 6.4 W, respectively.