Compact Multi-input Multi-output Research Articles

COMPACT MIMO ANTENNA WITH MULTIBAND DISPENSATION

Multi input multi output (MIMO) technology is used to enhance data speed. In this technique, multiple antennas are used at the source and destination ends. The current work mainly focuses on MIMO antenna with dimensions 50.8 × 37 mm<sup>2</sup>, designed using low dielectric constant material with thickness 1.57 mm. In this MIMO design, two monopole antenna elements are fed with coplanar waveguide feeding. To achieve good isolation characteristics, both the antennas are kept transverse to each other. In between the two patches a stub is placed to enhance the isolation and also to increase the bandwidth. To evade the interference of ultra-wide band (UWB) with the existing wireless bands U slots are placed on the patch and in the feed line to notch worldwide interoperability for microwave access, wireless local area network, and X band satellite communication applications. The designed antenna units were simulated for optimized performance using computer simulation technology microwave studio and antenna parameters like radiation pattern, group delay, envelope correlation coefficient (ECC), and return losses are measured and reported. Results emphasize that the proposed MIMO antenna operates from 3 GHz-11 GHz with a peak gain of 6 dB at 7 GHz and isolation is less than -21 dB in the entire band. An exception at notches the ECC is less than 0.001 and diversity gain (DG) is approximately 9.995 dBi. These characteristics show that the antenna can be used for UWB applications.

Compact Wideband Four-Port MIMO Antenna for Sub-6 GHz and Internet of Things Applications.

A compact four-port multi-input, multi-output (MIMO) antenna with good isolation is proposed for sub-6 GHz and Internet of Things (IoT) applications. Four similar L-shaped antennae are placed orthogonally at 7.6 mm distance from the corner of the FR4 substrate. The wideband characteristics and the required frequency band are achieved through the L-shaped structure and with proper placement of the slots on the substrate. To obtain good isolation between the ports, rectangular slots are etched in the bottom layer and are interconnected. The proposed antenna has total dimensions of 40 mm × 40 mm × 1.6 mm. The interconnected ground plane provides good isolation of less than -17 dB between the ports, and the impedance bandwidth obtained by the proposed four-port antenna is about 54% between the frequency range of 3.2 GHz to 5.6 GHz, thus providing a wideband antenna characteristic covering sub-6 GHz 5G bands (from 3.4 to 3.6 GHz and 4.8 to 5 GHz) and the WLAN band (5.2 GHz). The proposed design antenna is fabricated and tested. Good experimental results are achieved when compared with the simulation results. As the proposed design is compact and low profile, this antenna could be a suitable candidate for 5G and IoT devices.

Dielectric Decoupler for Compact MIMO Antenna Systems

A novel decoupling method based on the superposition principle is proposed for compact multi-input–multi-output (MIMO) antenna systems in this work. A dielectric block is introduced to encompass all radiators in a compact MIMO system and works as a decoupler when the block is appropriately designed. Owing to the presence of dielectric–air boundary (DAB) introduced by the dielectric block, scattered paths show up for electromagnetic (EM) waves inside the block. For any two encompassed primary radiators, mutual couplings via the direct and scattered paths are superposed one on another. Because the scatted wave paths can be controlled by changing the shape and dimension of the DAB, mutual coupling between two encompassed primary radiators can be minimized with a properly designed DAB. To illustrate this decoupling principle, the electric field distribution of a basic Hertzian dipole wrapped in a dielectric decoupler is first studied. Results show that this method can generate several field valleys inside the dielectric block and can lead to good isolation when a second radiator is placed at a valley. A dual-port antenna wrapped in a dielectric decoupler is then proposed for demonstration. By optimizing the DAB shape, this antenna can realize a measured 20 dB isolation bandwidth of 12.6%, covering the whole 3.3–3.7 GHz 5G frequency range 1 (FR1) band. Furthermore, a quad-port decoupled antenna is studied to show the generality of the proposed decoupling method. Using a hollow rectangular dielectric block, isolations among four ports of more than 21.5 dB can be obtained in the 3.3–3.7 GHz band with a 20-dB isolation bandwidth of 18%. The envelope correlation coefficients (ECCs) and calculated ergodic channel capacity (CC) results show that the proposed compact dual-port and quad-port antennas are competitive for MIMO applications.

Mutual Coupling Compensation for Compact MIMO Radar

A calibration method to compensate for the mutual coupling and channel imbalance in a compact multi-input multi-output (MIMO) radar array based on turn table measurements is proposed. Two mutual coupling matrices, one for the transmit array and the other for the receive array, are used to model the relationship between the ideal manifold and the measured manifold. The practical factors such as the nonisotropic element pattern and the displacement of the array phase center are also taken into account. All the unknowns are determined by solving the nonlinear least-squares fitting problem iteratively. Using two coupling matrices consists of the mutual coupling mechanism in an MIMO array and has better calibration performance than using one matrix for the virtual array. It also reduces the dimension of the matrix and hence the computation load of calibration. Measurements by a microstrip array with two transmitters and four receivers are used to verify its effectiveness in angle estimation, beamforming, and superresolution of close targets.

A Compact Self-Isolated MIMO Antenna System for 5G Mobile Terminals

A compact self-isolated Multi Input Multi Output (MIMO) antenna array is presented for 5G mobile phone devices. The proposed antenna system is operating at the 3.5 GHz band (3400–3600 MHz) and consists of eight antenna elements placed along two side edges of a mobile device, which meets the current trend requirements of full-screen smartphone devices. Each antenna element is divided into two parts, a front part and back part. The front part consists of an I-shaped feeding line and a modified Hilbert fractal monopole antenna, whereas the back part is an L-shaped element shorted to the system ground by a 0.5 mm short stub. A desirable compactness can be obtained by utilizing the Hilbert space-filling property where the antenna element’s overall planar size printed on the side-edge frame is just (9.57 mm × 5.99 mm). The proposed MIMO antenna system has been simulated, analyzed, fabricated and tested. Based on the self-isolated property, good isolation (better than 15 dB) is attained without employing additional decoupling elements and/or isolation techniques, which increases system complexity and reduces the antenna efficiency. The scattering parameters, antenna efficiencies, antenna gains, and antenna radiation characteristics are investigated to assess the proposed antenna performance. For evaluating the proposed antenna array system performance, the Envelope Correlation Coefficients (ECCs), Mean Effective Gains (MEGs) and channel capacity are calculated. Desirable antenna and MIMO performances are evaluated to confirm the suitability of the proposed MIMO antenna system for 5G mobile terminals.

MIMO Antenna Design and Optimization with Enhanced Bandwidth for Wireless Applications

This paper demonstrates a compact MIMO (Multi Input Multi Output) fractal type antenna for ultra-wide band applications. The proposed antenna is manufactured on a lowcost substrate material and the design is analyzed for various iterations in terms of reflection coefficient, gain, and bandwidth. The 50 Ω transmission line feed is used for both fractal patches and a metamaterial structure is used as the ground plane. The proposed design achieved a wide-band frequency response between 5.8 and 15 GHz, with the reflection coefficient of less than –10 dB. Reduced mutual coupling, positive gain and stable radiation patterns were observed throughout the operating band as well. The bandwidth of 9.2 GHz is achieved with the use of a metamaterial structure on the ground plane. The ECC and diversity gain obtained prove the excellent diversity performance of the antenna. The design was simulated using HFSS software and was tested in a lab.

Compact MIMO Slots Antenna Design with Different Bands and High Isolation for 5G Smartphone Applications

In this paper, two elements of the multi-input multi-output (MIMO) antenna had been used to study the five (3.1-3.55GHz and 3.7-4.2GHz), (3.4-4.7 GHz), (3.4-3.8GHz) and (3.6-4.2GHz) 5G bands of smartphone applications that is to be introduced to the respective US, Korea, (Europe and China) and Japan markets. With a proposed dimension of 26 × 46 × 0.8 mm3, the medium-structured and small-sized MIMO antenna was not only found to have demonstrated a high degree of isolation and efficiency, it had also exhibited a lower level of envelope correlation coefficient and return loss, which are well-suited for the 5G bands application. From the fabrication of an inexpensive FR4 substrate with a 0.8 mm thickness level, a loss tangent of 0.035 and a dielectric constant of 4.3, the proposed MIMO antennas that had been simulated under the five different band coverage were discovered to have demonstrated a respective isolation level of about 14dB, 12dB, 21.5dB, 19dB and 20dB under a -10dB impendence bandwidth. In the measurement and fabrication outcomes that were derived from the use of the prototype MIMO in the (3.4-3.8) band of the Europe and Chinese markets, the proposed MIMO was thus found to have produced a better performance in terms of efficiency, isolation, and envelope correlation coefficient (ECC).

Compact planar ultrawideband MIMO antenna for wireless applications

<p>A compact microstrip fed printed monopole MIMO antenna with ultrawideband (UWB) frequency response (S11< -10 dB for 3.1-10.6 GHz) is proposed in this paper. The proposed antenna is miniaturized and has a high isolation of > 23 dB between the ports compared to the existing UWB multiinput multi output (MIMO) antennas in the literature. The proposed antenna is built on FR4 substrate with thickness of 1.6 mm using all-digital single chip architecture and it is planar in geometry to be easily integrated with the other electronic components in the printed circuit board (PCB). The UWBMIMO antenna is analyzed using simulation and measurements and its performance is investigated. The antenna is extremely useful for low power short range communications and it provides high multipath immunity due to diversity.</p>

Extensible compact 8‐port MIMO antenna with pattern gain

ABSTRACTA novel and compact 8‐port multi‐input multioutput (MIMO) antenna is presented, which uses pattern gain to achieve more than an ideal 6‐port polarimetric antenna gain. Antenna elements types, geometry on the common ground and antenna elements rotation are optimized for the pattern gain. The antenna consists of four pairs of inverted‐F antennas, quarter wavelength slot antennas, parasitic elements, and ground plane. For the orthogonality, the inverted‐F antenna for electric dipole and slot antenna for magnetic dipole are selected as elements of radiator. Four pairs of the inverted‐F antenna and slot antenna symmetrically stand on the ground and the antenna direction, location and the parasitic elements are studied for low mutual coupling and correlation. The proposed MIMO antenna shows isolation of better than −10 dB with an overall size of 0.5λ × 0.5λ × 0.13λ. The ergodic capacity of proposed antenna is presented to verify the MIMO antenna performance. The proposed 8‐port MIMO antenna is extensible to 40‐port antenna cube and its prototype is presented. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:236–240, 2017

Design of a Compact MIMO Antenna Using Coupled Feed for LTE Mobile Applications

A compact multi-input multi-output (MIMO) antenna with a coupled feed structure for 4th generation (4G) handsets is proposed for operation in long-term evolution (LTE) band 13 (0.746 GHz–0.787 GHz). The MIMO antenna consists of two symmetrically distributed identical antenna elements. The size of each element is limited to 20 mm × 10 mm × 5 mm (λ0=392 mm at 0.765 GHz), and the separation between different elements is minimized to 15 mm. Each antenna element contains a Z-shaped coupled feed strip and a simple folded monopole-type radiating element. The simple folded radiating element supports two monopole modes (first order) excited at adjacent frequencies to achieve broadband performance. The coupled feed strip effectively modifies impedance matching and maintains good isolation. The proposed antenna has a 6 dB return loss bandwidth of 55 MHz (0.735 GHz–0.79 GHz) and isolation above 12 dB without the use of an additional isolation enhancement element. Moreover, the envelope correlation coefficient (ECC) is maintained below 0.5 over the designed frequency band.

The MIMO cube - a compact MIMO antenna

In this paper, we suggest a multi-input multi-output (MIMO) cube antenna to be used in a wide angular spread environment like an indoor channel. Both space and polarization diversity has been used to constitute the MIMO cube where all the 12 edges consist of electrical dipole antennas. There exist 12 parallel orthogonal transmission links, also called eigenmodes. For a half-wavelength dipole, nine of the eigenmodes have a mean gain higher than the conventional single-input single-output (SISO) system; the highest mean gain is about 8.5 dB/cube, and the theoretical capacity is about 62.5 b/s/Hz for a signal-to-noise ratio (SNR) of 20 dB. The number of essentially active eigenmodes, which is about 11 for a side length of /spl lambda//2, reduces to six for a very compact cube with a side length of /spl lambda//20. With the latter side length, the theoretical capacity is about 34 b/s/Hz. The compact MIMO system promises to give high capacity in a rich scattering environment and may be used for high data rate communications like wireless local area network systems.