High Mutual Coupling Research Articles

Design of Miniaturized and Enhanced Gain Antipodal Vivaldi Antenna for 5G Applications

In this project, method of designing of high gain and mutual coupling reduction is proposed, which can be done by antipodal Vivaldi antenna (AVA) for 5G applications. For the reduction of isolation between the antenna elements, the antennas are not placed adjacent to each other because they have a chance of absorbing the energy which is to be transmitted. The proposed AVA comprises of 2 x 1 multiple input multiple output (MIMO) antenna elements. The antenna parameter enhancement techniques used in this design are corrugation and circular slots. The antenna dimensions are 50mm x 48mm x 0.8mm. Here, we use corrugation and circular slots method, as to increase the gain than previously designed antenna. The maximum isolation of antenna is achieved is 37dB and gain is improved in the desired range. The simulated gain is in the range of 7.1-14.4 dB in the frequency band of 20-30GHz.

Polarization and Frequency-Selective Surface for Vehicular Beamforming Communications Requiring Near-Zero Profile

A polarization-selective and reconfigurable Fresnel zone plate consisting of frequency selective surfaces (FSS) loaded with varactor diodes is devised for compact vehicular wireless communication devices. The unit cell constituting the impedance zone exhibits rapid impedance transitions from 0 ohm (electrically-opaque) to 377 ohm (electrically-transparent). An I-shape configuration is employed for the resonant unit cell structure, featuring high compatibility with DC bias voltage network. In addition, double-sided FSS is employed on the top and bottom faces for polarization-selective beamforming. The FSS comprise of a dielectric with near zero thickness ( λ /250 of 2.40 GHz) resulting in intentionally high mutual coupling between the layers. The devised unit cell is designed using an equivalent circuit model analysis and optimized using finite element solver, achieving over 30 dB impedance switching. The proposed unit cell is experimentally confirmed in both vertical and horizontal polarizations. By configuring the DC voltage bias lines, the unit cells of the FSS are transformed into electrically-driven impedance zones formulating alternating and repetitive gratings. The width and the interval of the grating manipulate the constructive and destructive interference resulting in beam scanning range of 30° in both vertical and horizontal polarizations. The proposed approach can provide concise and compact beamforming solutions for future vehicular communications.

Multiple Beam Synthesis of Passively Cooled 5G Planar Arrays Using Convex Optimization

An extended-feature, system-driven convex algorithm for the synthesis of uniform-amplitude, irregular planar phased arrays with simultaneous multi-beam optimization for mm-wave 5G base station applications in multi-user scenarios is presented. The inter-user interferences are suppressed by minimizing the maximum sidelobe level (SLL) for a beam scanned freely inside a given sector. The aperture size is restricted to the size of the heatsink baseplate dimensions. A minimum guaranteed inter-element spacing in the final layout is pre-defined, which prevents element overlapping, eases the thermal problem and helps reduce the effects of high mutual coupling (MC). The algorithm performance is tested via the synthesis of a 64-element integrated array with at least half a wavelength inter-element spacing. The optimized array results show that, compared to their regular counterparts, significant reduction in the SLLs is achieved for a beam scanned inside the defined sector, while keeping the maximum temperature of the array at a reliable level. The effect of MC on the results is also investigated via full-wave simulations and it is explained how embedded element patterns can potentially be included in the optimization. Superior capabilities of the proposed method are illustrated by comparing the algorithm output to those reported in the state-of-the-art literature.

Recent techniques for enhancement of isolation in MIMO antenna system: a review

Nowadays the utilisation of wireless communication technologies is becoming more popular and there is a need of such ever evolving technologies. But these technologies have to provide minimum bit error rate, less fading effect, and good quality of service in order to qualify as the competent systems. Such requirements can be fulfilled with the use of multiple-input multiple-output (MIMO) antenna technology. In the MIMO antenna system, multiple antennas are used at the base station and also at the mobile terminals for the exchange of the information. For better results with the MIMO antenna system, the mutual coupling between the antenna components should be as low as possible. Due to the high mutual coupling in the antenna system, the characteristic performance of the antenna gets degraded. In this review, some recent isolation enhancement methods are discussed qualitatively. These methods have different design structures and are used in different wireless applications.

Recent techniques for enhancement of isolation in MIMO antenna system: a review

Nowadays the utilisation of wireless communication technologies is becoming more popular and there is a need of such ever evolving technologies. But these technologies have to provide minimum bit error rate, less fading effect, and good quality of service in order to qualify as the competent systems. Such requirements can be fulfilled with the use of multiple-input multiple-output (MIMO) antenna technology. In the MIMO antenna system, multiple antennas are used at the base station and also at the mobile terminals for the exchange of the information. For better results with the MIMO antenna system, the mutual coupling between the antenna components should be as low as possible. Due to the high mutual coupling in the antenna system, the characteristic performance of the antenna gets degraded. In this review, some recent isolation enhancement methods are discussed qualitatively. These methods have different design structures and are used in different wireless applications.

Design and Implementation of MIMO Antenna Using Swastika Slot for Wireless Applications

MIMO (Multiple-Input Multiple-Output) antenna has gained a lot of attention for research today due to various advantages such as increase in capacity, low signal loss, and less multipath fading. The main objective of this work is to design and implement a compact antenna using MIMO systems to reduce the mutual coupling between the antenna elements and to provide high isolation for Wi-Fi (2.4 GHz to 5 GHz) & Bluetooth (2.4 GHz to 2.57 GHz) and WLAN 802.11(2.4-2.485 GHz) applications. Different shapes of MIMO antennas are implemented but they have some interference with high mutual coupling and low gain. In order to avoid this, “Dumbell” shaped patch is introduced with a ‘Swastika’ slot between the patches. The antenna is designed over a frequency of 2.51GHz using FR-4 epoxy as a substrate material. The proposed antenna shows better performance than many existing systems with an overall size of 93.02 × 54.72 mm2 having isolation better than -16 dB, obtained gain of 8.29 dB and envelope correlation coefficient (ECC) is investigated about 0.0092. The proposed MIMO antenna is simulated using HFSS 18.0 (High Frequency Structural Simulator) software and fabricated to validate the results. It is clearly observed that simulated results are close to practical measured results.

A comparative study on slim 3-D receiver coil structures for omnidirectional wireless power transfer applications

AbstractThis paper presents a comparative study on three types of slim coil structures used as a three-dimensional (3-D) receiver in a wireless power transfer system with a planar transmitter coil. The mutual coupling values and their variations between the receiver structures and the transmitter coil are compared under different distances and angular orientations with respect to the transmitter coil. The merits of performance are related to the consistency of the mutual coupling values under different orientations in a range of distances from the transmitter coil. The practical results show that slim 3-D receiver coil structures can be compatible with a planar transmitter coil with reasonably high-mutual coupling.

A Dual-Wideband Dual-Polarized Magneto-Electric Dipole Antenna With Dual Wide Beamwidths for 5G MIMO Microcell Applications

A dual polarized magneto-electric dipole antenna with dual wide beamwidths is proposed and investigated. Dual-layer U-shaped electric dipoles are cooperated with orthogonal η-shaped feeding line to obtain dual polarized and dual wideband features for 5G microcell applications. In addition, modified tetrahedral ground together with dual-layer three-element dipoles that are arranged as a triangle array is used to provide dual wide H-plane radiation characteristics. By doing so, a large coverage area and a reduced number of antennas can be achieved at the same time. In order to satisfy the stringent needs of high capacity and low mutual coupling, a three-dimensional (3D) MIMO system that consists of three proposed antenna elements is also designed. The antenna prototypes were fabricated and measured. Measured results show that an overlapped impedance bandwidth of 22.6% (VSWR <; 2) with the stable gain of 6.9 ± 0.3 dBi were measured across the lower operating band. As for its corresponding upper operating band, it has exhibited overlapped impedance bandwidth of 19.6% (VSWR <; 2) with the gain of 5.4 ± 0.7 dBi. The half-power beamwidths in the H-plane for both ports varies from 83° to 162°, and from 90° to 133°, respectively. Moreover, a low ECC of 2 × 10 -4 and the nearly identical MEG can be achieved by the MIMO system due to the 3D design. Hence, the proposed antenna is a desirable candidate for the future 5G microcell applications.

Compact wideband MIMO antenna for 4G WI-MAX, WLAN and UWB applications

This article proposes a compact wideband MIMO antenna. The antenna comprises of two identical modified P shaped monopole radiators, spatially oriented at 180° to each other with side to side spacing of 0.075λo, where λo is the wavelength corresponding to the lowest operating frequency. To design a compact antenna, a semicircular monopole with a rectangular strip is designed instead of a circular monopole. This P shaped monopole antenna offers same impedance bandwidth with 50% size reduction. To enhance the impedance bandwidth of the antenna, the effective current path length is increased by introducing two semi-circular slots in P shaped monopole antenna. To achieve the desired impedance bandwidth of 2.5–12 GHz, the rectangular strip is corrugated on both sides in the slotted P shaped monopole. Triangular slots and meshed metal strip are introduced in the ground plane to achieve high mutual coupling over wideband. The triangular slots act as variable length capacitance and exhibits wide band notch characteristics. A meshed metal strip acts as decoupling structure for the surface current emerging from the surface waves and also act as reflector for space waves. Those bands which are not rejected by triangular slots, are notched by meshed metal strips. Thus by employing both triangular slots and meshed metal strip, isolation >20 dB is achieved over 2.5–12 GHz. The proposed antenna is a novel design which has smaller dimensions and still offers isolation >20 dB over a wider impedance bandwidth of 2.5 GHz to 12 GHz as compared to state of art antenna structures reported in literature. The band stop characteristics of proposed isolation techniques are analyzed by suspended stripline method. Mutual coupling reduction is also analyzed with the help of vector surface current density and magnetic field distribution. The proposed structure has compact dimensions of 0.25 λ0 × 0.241 λ0. The fabricated prototype antenna exhibits envelope correlation coefficient (ECC) >0.02, diversity gain >9.5 dB and stable radiation patterns. The antenna is suitable for 4G WI-MAX, WLAN and UWB applications.

An inversion of transient electromagnetic data from a conical source

Multiturn coils is an effective transmitter for transient electromagnetic method (TEM) used in narrow space and complex terrain at presently. However, its high mutual inductance coupling and long turn-off time affect the quality of later data processing and interpretation. Compared with multiturn coils, the new conical source has low mutual inductance and short turn-off time. Based on the superposition principle, we use Hankel transform and numerical filtering method for forward modelling of the conical source field in the layered-media and explore TEM characteristics excited by this source. We apply improved damped least square inversion to integrated transient electromagnetic (TEM) data. We first invert the induced voltage into similar resistivity and apparent depth, and then use the inverted results as input parameters in the initial model and transform the apparent resistivity data into the frequency domain. Then, damped least square inversion is performed in the frequency domain using the initial model. Subsequently, we use automated model building to search for the extremes and inflection points in the resistivity–depth data that are treated as critical layer parameters. The inversion of theoretical and observed data suggests that the method modifies the resistivity and depth and yields a model of the underground layers.

High mutual coupling reduction between microstrip patch antennas using novel structure

In this paper, a novel parasitic configuration to reduce the mutual coupling between two adjacent microstrip patch antennas is presented. It is shown that mutual coupling between the antenna elements can be reduced significantly by two simple slots structure on the ground plane and several shorted simple conducting strips between patch antennas. The structure has been constructed and tested. Both simulated and measured results are presented. The results are shown that more than 7dB reduction within operational frequency bandwidth with the maximum 41dB mutual coupling at center frequency can be achieved. The measurement results prove the high efficiency of this configuration in multi antenna systems.

Characteristics Analysis of PM Type Offshore Wind Power Generator with Dual Inverters according to Number of Per Pole Per Phase

This paper presents several characteristics of performance in dual 3-phase machine for offshore wind power generator according to number of per pole per phase, ‘q’. With the same rotor structure, the number of turn per coil is adjusted to the aim of same electrical loading. By using FEA, self-, mutual- and synchronous inductance are calculated. In addition, magnetic flux density, flux linkage, torque ripple, cogging torque, and demagnetization withstand are investigated. In case of q=1, the model can have large inductance, low mutual coupling between two phase coils, and good demagnetization withstand but it has large torque ripple and cogging. On the contrary, the generator with q=2 can have low torque ripple, cogging and relatively high average torque because of low MMF harmonics but it has high mutual coupling due to low inductance and bad demagnetization withstand.

CRLH MIMO antenna with reversal configuration

A design of CRLH MIMO metamaterial with reversal CRLH configuration antenna is presented. The two antenna elements are designed to operate at 5.8GHz for wireless applications. The two antenna elements are designed using reversed one left handed unit cell for high mutual coupling isolation in close separation. The two elements of MIMO antenna are put together with very small separation between them where the distance between the edges of two antenna elements is only 0.034 λ0. The MIMO antenna has compact size (its size is only 2.93×2.6cm2). The designed antenna elements have better than 35dB coupling isolation between the two inputs without using extra structures. The performance of MIMO antennas is evaluated by studying the correlation coefficient, diversity gain and total active reflection coefficient. A good agreement is achieved between simulation and measured results.

Optimization of planar strongly coupled wireless power transfer system for biomedical applications

ABSTRACTStrongly coupled four‐coil wireless power transfer (WPT) system is presented in this letter. Conformal architecture is used for both transmitter (TX) and receiver (RX) coils. Thus, a high mutual coupling coefficient is achieved between the coplanar coils. Furthermore, the quality factors of primary and secondary coils are improved. The proposed WPT system features a compact structure for biomedical applications and provides a measured efficiency greater than 79% when the distance between the TX and RX is 10 mm at a resonance frequency of 13.56 MHz. The designed system is also simulated for 10 mm human tissue medium using HFSS, which generates a power transfer efficiency of 55.1%. The simulated results are also verified by experimentation. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1861–1866, 2016

Design of a Planar MIMO Antenna for LTE-Advanced

This paper presents the design of a wideband microstrip patch antenna for LTE-A. The bandwidth of the conventional patch is enlarged by using etched slots at the antenna patch. The designed antenna has been fabricated by using thin film and photolithographic technique and has been measured by using the Vector Network Analyzer. The simulated and measured results were found to have good match with each other. Then, by using the designed single element antenna, a four-element MIMO antenna system has been built employing orthogonal polarization diversity. Isolation between the microstrip elements is increased by placing metal structure between antenna elements. For more isolation between antenna elements, Slotted Ground Plane SGP is utilized. It is found, by using commercial software CST Microwave Studio and measurement, that the designed planar MIMO antenna system has sufficiently high return loss and low mutual coupling at the required bandwidth of 70 MHz. It is found also that the developed antenna system meets the requirements for LTEAdvanced (2500 – 2570 MHz) band “CA-B7” as of today‟s standard based on 36.101 Table 5.5-1 (March 2012) .

Design of time modulated concentric circular and concentric hexagonal antenna array using hybrid enhanced particle swarm optimisation and differential evolution algorithm

Design of circular arrays (CAs) and hexagonal arrays (HAs) with low sidelobe level (SLL) and high directivity is usually achieved by increasing the number of array elements, which leads to a high undesired mutual coupling. Therefore this study presents an efficient optimisation method and a framework to show how to design multi-ring concentric CAs (CCA) and concentric HAs (CHAs) configurations using a hybrid enhanced particle swarm optimisation and differential evolution (hybrid EPSO/DE) optimisation technique. The presented optimum CCA and CHA have perfect invariant SLL and high directivity with low mutual coupling by keeping the inter-element spacing not less than half a wavelength which is not possible to be achieved in CA and HA arrangements. Different configurations with two-rings, three-rings and four-rings are presented. The rotation angle of outer rings and the complex excitations of array elements are first optimised. Then, this design is further optimised using a time modulation technique by controlling the switch-on times and the phases of elements excitations of the best CCA and CHA array designs. The presented time modulated (TM) concentric CA and TM concentric HA designs attain ultra-low SLL, reduced sideband level and maximised directivity besides reducing the dynamic range of the array excitations.

High quality factor integrated gigahertz magnetic transformers with FeGaB/Al2O3 multilayer films for radio frequency integrated circuits applications

This work report new integrated high quality factor (Q) GHz magnetic transformers based on solenoid structures with FeGaB/Al2O3 multilayer films. These transformers show excellent high-frequency performance with a wide operation frequency range of 0.5–5 GHz, in which primary, secondary, and mutual inductances are flat, and the peak quality factor can reach around 14 at frequency of 1.2 GHz. High mutual coupling and low insertion loss are also demonstrated. These novel GHz transformers with high Q and mutual coupling show great promise for applications in radio frequency integrated circuits.

Actual Diversity Performance of a Multiband Diversity Antenna With Hand and Head Effects

Using the metric actual diversity gain (ADG), diversity performance is investigated for a compact mobile terminal prototype with two internal, triple frequency band antennas in four different cases of user interaction. ADG is presented as a preferred alternative to apparent diversity gain and effective diversity gain. Absorption due to user proximity causes degradation and imbalance in mean effective gain of the antennas over the frequency bands, contributing to a degradation in diversity performance. However, user-induced changes in the antenna patterns cause a decrease in correlation in the low frequency band, which facilitates increased diversity gain. The study reveals that a significant net diversity gain, i.e., ADG of 5-8 dB compared to a single antenna prototype, can be achieved using multiband antennas in the proximity of a user, even at low frequencies for antennas with high mutual coupling.

Extended reciprocity‐based computation of mutual admittance between CPW‐fed slots on conductor‐backed two‐layer substrates

AbstractAn extended reciprocity‐based formulation for finding mutual admittance between coplanar waveguide fed slots on conductor‐backed two‐layer substrates was presented. The formulation updates the field distribution in both slots iteratively to account for coupling interaction between slots. This is especially relevant for cases of high mutual coupling. The results agree well with moment method‐based calculations. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 91–94, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24012

Power splitter design for two-element antenna array with high mutual coupling

Design principles for a power splitter driving a strongly coupled two-element handset array antenna have been derived and studied. Splitter circuits using lumped elements and distributed microstrip elements were designed and tested. The results show reasonable agreement between measured and theoretical results.