Multiple input multiple output (MIMO) antenna is at core of the presently available wireless technologies. The design of MIMO antennas over a limited space requires various approaches of mutual coupling reduction, otherwise gain, efficiency, diversity gain, and radiation patterns will be severely affected. Various techniques have been reported in literature to control this degrading factor and to improve the performance of the MIMO antennas. In this review paper, we have carried out an extensive thorough investigation of diversity and mutual coupling (correlation) reduction techniques in compact MIMO antennas.

MIMO antennas with diversity and mutual coupling reduction techniques: a review

© 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:495-501, 2015. © 2014 Wiley Periodicals, Inc.A dual-port reduced size multiple input multiple output (MIMO) Dielectric Resonator Antenna (DRA) has been studied and proposed. The MIMO antenna consists of a Rectangular Dielectric Resonator antenna, which is fed by two symmetrical feed lines for orthogonal mode excitation. The proposed antenna is suitable for operation over various long term evolution (LTE) bands. A measured bandwidth of 264 MHz for |S 11 | <-10dB and isolation of 18 dB at 1.8 GHz has been obtained. Besides, the Envelope Correlation Coefficient, Mean Effect Gain and Diversity Gain have been studied for the presented MIMO DRA using the S-parameters. Based on these results, it can be concluded that the proposed antenna can be a suitable candidate for MIMO applications.

A reduced size dual port MIMO DRA with high isolation for 4G applications

In this study, a novel dual-band multiple-input multiple-output (MIMO) rectangular dielectric resonator antenna (DRA) for Worldwide interoperability for microwave access (WiMAX) (3.4–3.7) GHz and wireless local area network (WLAN) (5.15–5.35) GHz applications is proposed and investigated. The design operates at fundamental TEδ11 x, TE1δ1 y and higher order TEδ21 x, TE2δ1 y modes, excited through two coaxial probes, symmetrically placed adjacent to the DRA. A compact design is achieved by stacking a high permittivity material. The obtained impedance bandwidth at 3.6 GHz is 9.97% and at 5.2 GHz is 8.88%. Measured antenna gain through both ports at 3.6 GHz is 5.7 dBi and at 5.2 GHz is 6.61 dBi, respectively. Isolation achieved at 3.6 GHz is −13 dB and at 5.2 GHz is −16 dB, respectively. Co- and cross-polarisation, radiation efficiency, diversity gain, envelope correlation and mean effective gain of the proposed design are measured. Results show that the proposed design is suitable for use in MIMO WiMAX/WLAN applications.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-map.2015.0745

Dual-band MIMO dielectric resonator antenna for WiMAX/WLAN applications

A novel compact single-substrate planar multiband five-element multiple-input multiple-output (MIMO) antenna system is presented in this paper. The tunable two-element folded meandered MIMO antenna covers the long-term evolution frequency bands below 1 GHz (687–813 MHz) and radio frequency identification bands centered around 2.4 and 5.8 GHz. The other two-element compact MIMO antennas operate over 754–971 MHz, 1.65–1.83 GHz, 2–3.66 GHz, and 5.1–5.6 GHz frequency bands. Furthermore, the proposed antenna elements are integrated with a wideband sensing antenna for the spectrum sensing in 0.668–1.94 and 3–4.6 GHz, which also acts as the ground plane for the MIMO elements in the cognitive radio application environment. The antenna is fabricated on a 65 mm $\times \,\, 120$ mm $\times \,\, 1.56$ mm low-cost FR-4 substrate. The antenna’s radiation characteristics are experimentally verified, and the results are in agreement with the full-wave simulation. The 3-D radiation pattern-based envelope correlation coefficient of the MIMO antennas is also experimentally verified which is below the desired value of 0.5. Finally, to show its utility at the Internet-of-Things platform, the antenna is tested in the realistic application environment.

Compact Planar Multistandard MIMO Antenna for IoT Applications

An improved particle swarm optimization (PSO) algorithm with a neighborhood-redispatch (NR) technique is presented to design an ultrawideband (UWB) antenna in this letter. Based on the conventional version of PSO algorithm, some new parameters are introduced in the NR-PSO algorithm to improve optimization performance. In order to illustrate the effectiveness of the algorithm in representative topology problems, several benchmark functions are used to test the performance of the improved PSO algorithm. The results show that it is better than the conventional PSO algorithm for multimodal and unimodal functions. Combined with the HFSS solver, one UWB antenna with a respective notched band is designed by using the proposed NR-PSO algorithm. It not only covers the UWB band (3.1-10.6 GHz) and Bluetooth passband (2.40-2.484 GHz), but also realizes a stopband (5.15-5.825 GHz) to avoid potential interferences.

An Improved PSO Algorithm and Its Application to UWB Antenna Design

This paper presents a compact dual-band multiple input multiple output (MIMO) antenna with low mutual coupling, operating in the 2.4GHz band (2.4{2.485GHz) and 5.5GHz band (5.15{ 5.85GHz). The proposed antenna system consists of two antenna elements located at the top two corners of FR4 substrate (PCB). Each element dimension is reduced substantially by employing a folded structure and slots on the top patch plate, so that it takes up a small volume of 12 £ 9 £ 6mm 3 . To enhance port-to-port isolation and e-ciency of each antenna, an additional non-radiating folded shorting strip is connected between each antenna element and ground plane of PCB. The measured isolation values are lower than i28dB over the lower WLAN band (2.4{2.485GHz) and better than i26dB (i30dB in most of the band) across the higher WLAN band (5.15{5.85GHz). The improvement in antenna's e-ciency caused to raise up 1dB of efiective diversity gain of MIMO system. Furthermore, S-parameters, radiation patterns and diversity performance characteristics are provided.

/pdf/low-mutual-coupling-between-mimo-antennas-by-using-two-49eq2r2lo8.pdf

Low Mutual Coupling Between MIMO Antennas by Using Two Folded Shorting Strips

A metamaterial-based novel compact microstrip antenna is presented for ultra-wideband (UWB) applications. The antenna consists of two layers of metamaterials made by etching a π-shaped slot and crossed-shaped slots, on the radiating patch and the ground plane, respectively. The series capacitance and shunt inductance developed due to the patterned radiating patch and ground plane lead to the left-handed behaviour of the metamaterial. The proposed antenna has a compact size of 30.8 × 27.6 × 0.8 mm3 and is fed by a 50 Ω microstrip line. The impedance bandwidth (−10 dB) is from 3 GHz to more than 14 GHz with maximum radiation in the horizontal plane and tends towards a directional pattern as the frequency increases.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/el.2014.2366

Metamaterial-based UWB antenna

Recent methods for optimization of plastic injection molding process-a retrospective and literature review

A WLAN band notched compact ultra-wideband (UWB) microstrip monopole antenna with stepped geometry is proposed. A L-slot loaded modifled mushroom type Electromagnetic Band Gap (EBG) is designed, analyzed and used to realize notched band characteristics for wireless local area network (WLAN) in the UWB frequency range. The proposed antenna having partial ground plane is fabricated on a low cost FR4 substrate having dimensions 40(Lsub) £ 30(Wsub) £ 1:6(h)mm 3 and is fed by a 50-› microstrip line. The results show that the proposed antenna achieves impedance bandwidth (VSWR 2) from 4.9GHz to 6GHz. Fidelity factor for proposed antenna is also analyzed to characterize time domain behavior. Simulation and measurement results of VSWR are found in good agreement.

/pdf/design-of-wlan-band-notched-uwb-monopole-antenna-with-2i45421y94.pdf

Design of WLAN Band Notched UWB Monopole Antenna with Stepped Geometry Using Modified EBG Structure

To mitigate the interference with coexisting wireless systems operating over 3.3-3.6 GHz, 5.15-5.825 GHz, and 7.725-8.5 GHz bands, a novel triple band notched coplanar waveguide fed pitcher-shaped planar monopole antenna is presented for ultrawideband applications. Bands notched characteristics are achieved using a novel mushroom type electromagnetic band gap structure like resonator and a split ring slot. A conceptual equivalent RLC Resistor-Inductor-Capacitor-resonant circuit is presented for the band notched characteristics. Furthermore, the input impedance and VSWR voltage standing wave ratio obtained from the equivalent circuit are validated with simulated and measured results. Performances of the antennas in both, the frequency domain and the time domain are investigated. The simulated and measured results demonstrate that the proposed antennas have wide impedance bandwidth, nearly stable radiation patterns, and suppression of gain and total radiation efficiency at notched bands. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:795-806, 2015.

Pradutt Kumar Bharti

Papers

Low Mutual Coupling Between MIMO Antennas by Using Two Folded Shorting Strips

Metamaterial-based UWB antenna

Recent methods for optimization of plastic injection molding process-a retrospective and literature review

Design of WLAN Band Notched UWB Monopole Antenna with Stepped Geometry Using Modified EBG Structure

Design and analysis of multiband notched pitcher-shaped UWB antenna