Compact Ultrawideband Multiple-input Multiple-output Antenna Research Articles

A Novel Densely Packed 4 × 4 MIMO Antenna Design for UWB Wireless Applications.

In this article, a compact 4-port UWB (Ultra-Wide Band) MIMO (Multiple Input Multiple Output) antenna is proposed. A low profile FR-4 substrate is used as a dielectric material with the dimensions of 58 × 58 mm2 (0.52λ × 0.52λ) at 2.8 GHz and a standard thickness of 1.6 mm. The proposed design characterizes an impedance bandwidth starting from 2.8 to 12.1 GHz (124.1%). Each of the four elements of the proposed MIMO antenna configuration consists of a monopole antenna with PG (partial ground) that has a slot at its center. The corner of each patch (radiator) and ground slot are rounded for impedance matching. Each unit cell is in an orthogonal orientation, forming a quad-port MIMO antenna system. For reference, the partial ground of each unit cell is connected meticulously with the others. The simulated results of the proposed quad-port MIMO antenna design were configured and validated by fabrication and testing. The proposed Quad-port MIMO design has a 6.57 dBi peak gain and 97% radiation efficiency. The proposed design has good isolation below 15 dB in the lower frequency range and below 20 dB in the higher frequency range. The design has a measured ECC (Envelop Correlation Co-efficient) of 0.03 and DG (Diversity Gain) of 10 dB. The value of TARC (Total Active Reflection Coefficient) over the entire operating band is less than 10 dB. Moreover, the design maintained CCL (Channel Capacity Loss) < 0.4 bits/sec/Hz and MEG (Mean Effective Gain) < 3 dB. Based on the obtained results, the proposed design is suitable for the intended high data rate UWB wireless communication portable devices.

Mutual coupling reduction in a textile ultra-wide band MIMO antenna

This paper presents a mutual coupling reduction technique in a textile ultra-wideband (UWB) multiple-input–multiple-output (MIMO) antenna system implemented on a textile substrate. The compact textile UWB MIMO antenna consists of two patch antennas implemented on a felt textile substrate. The compact size and close placement of the antennas in a MIMO system cause higher mutual coupling which deteriorates the performance of the communication systems. To minimize the mutual coupling, Parasitic Elements and Defected Ground Structures are used in the designed textile UWB MIMO antenna. The MIMO antenna performed very well over almost the whole UWB frequencies ranging from 3.29 GHz to 13.3 GHz. The simulated and the measured parameters showed a good impedance matching with an impedance bandwidth of 133.4%. The results showed an improvement of 20 dB isolation at certain frequencies without impacting the reflection coefficient S11 and the antenna impedance bandwidth. The MIMO antenna has good diversity performance parameters in terms of Envelope Correlation Coefficient (ECC), Diversity Gain, Mean Effective Gain (MEG) and radiation pattern and the results indicate that the textile antenna is suitable for UWB MIMO applications. The overall size of the antenna is 30x60 mm2. Fully embroidered structure provides freedom of movement and comfort, so it is a good fit for Wireless Body Area Network applications.

Accelerated current-driven multi-objective topology optimization for compact ultrawide-band MIMO antenna design

In this work, an accelerated current-driven multi-objective topology optimization method is proposed for compact high-isolation ultrawide-band (UWB) multiple input multiple output (MIMO) antenna design. The proposed method takes the current Pareto solutions as the centers to perform fuzzy clustering (FC) and then drives the evolution of individuals in each cluster according to the current distribution characteristics of the clustering centers. Individuals in each cluster purposefully generate antennas with expected performance, thereby accelerating the process of optimization design. The proposed method uses about half the computational cost of traditional algorithms to design a compact (20 × 18 mm2) and high-isolation (>20 dB) UWB MIMO antenna. The proposed method provides a new way for accelerating multi-objective topology optimization with a high design degree of freedom. Also, the optimized antenna is a competitive candidate solution for UWB applications.

A compact dual-port UWB-MIMO antenna with quadruple band-notched characteristics

A compact dual-port ultra-wideband multiple-input multiple-output (UWB-MIMO) antenna with quadruple rejection bands is presented. The oversize of the proposed antenna is 39mm×30mm×0.8mm, which consists of two identical antenna elements with microstrip-fed and a common ground plane. A rectangular strip with the size of 10mm×22mm and two concave grooves are introduced in common ground plane to broaden the impedance bandwidth and enhance the isolation. The band-notched at 5.2–5.51 GHz and 6.1–6.53 GHz can be obtained by etching two various U-shaped slots on radiating patches. Moreover, by adding two different sizes of U-shaped parasitic strips on both sides of each feed lines, band suppression characteristics at 7.37–7.8 GHz and 9.15–9.7 GHz are achieved. Simulated results indicate that each center frequency of band-notched can be tuned by changing the size of its structure without affecting other notches. Besides, the equivalent circuit model of the designed antenna is analyzed. The proposed antenna is fabricated and measured. The measured results show that the designed antenna has a wide bandwidth ranging from 3.0–11.0 GHz with four rejection bands, low mutual coupling is less than −20 dB, stable radiation patterns, and envelope correlation coefficient (ECC) is less than 0.02.

Design and analysis of a compact UWB MIMO antenna incorporating fractal inspired isolation improvement and band rejection structures

This paper numerically proposes and experimentally investigates a compact coplanar waveguide fed two element ultra-wideband (UWB), multiple-input–multiple-output (MIMO) antenna array accompanying peak isolation and triple band notch mechanism. The proposed antenna consists of two identical printed monopole elements along with the incorporation of multiple 2nd order Hilbert defects in the ground structure and proposes to incorporate three different mechanisms to reduce the electromagnetic interference of the UWB antenna with existing narrowband systems. The measured impedance bandwidth for the intended antenna ranges from 2.7 GHz to 11.22 GHz. The incorporation of notch mechanisms provides interference suppression at the C-band (3.7–4.2 GHz), WLAN (5.15–5.825 GHz), and X-band communication (7.9–8.4 GHz). The overall size of the intended UWB MIMO antenna is 30.75 mm × 37.80 mm. Moreover, the diversity parameters of the proposed UWB MIMO antenna are numerically calculated and empirically investigated, these calculations and investigations depicts high diversity performance. It is noteworthy to observe that the spacing between the elements is staggeringly reduced to 2 mm. The concurrence among the diverse numerical and experimental outcomes supports the candidature of the suggested layout for portable UWB as well as UWB MIMO systems.

Novel double-side EBG based mutual coupling reduction for compact quad port UWB MIMO antenna

In this article, novel compact quad-port double-side Multiple-input-multiple- output (MIMO) antenna designed with Electromagnetic Band Gap (EBG) structure to improve isolation for Ultra Wide Band (UWB) applications. The presented MIMO configuration comprises four polygon shape radiating elements and partial slotted EBG stub ground structure. Both sides of the FR4 substrate are symmetrical, each side consisting of two radiators, and one partial ground plane is related with the other two components attached on the opposite side. The EBG decoupling structures are used on both the front and the back side of the board to diminish the correlation coupling among the radiators. The proposed MIMO antenna performance has also been studied regarding impedance bandwidth, current distribution, radiation model, envelope correlation coefficient (ECC), peak gain and TARC. The proposed MIMO antenna system has an impedance bandwidth of 3.1–11 GHz, peak gain of 2.5–6.8 dBi and less than 0.004 ECC. Furthermore, the proposed MIMO antenna shows UWB bandwidth, an almost omnidirectional radiation pattern, high isolation, uniform gain, and multi-polarization. The proposed double-sided MIMO antenna was tested in an indoor environment using NI USRP to verify performance in real time.

Compact CPW-fed UWB MIMO antenna with a novel modified Minkowski fractal defected ground structure (DGS) for high isolation and triple band-notch characteristic

A compact printed ultra-wideband (UWB) multiple input multiple output (MIMO) antenna with coplanar waveguide feed for portable UWB applications is presented. The radiator and ground plane of the antenna are etched with an overall size of 26.75 mm × 41.5 mm. The UWB MIMO antenna consists of two planar identical monopole antenna elements and a novel modified Minkowski fractal defect is introduced in the ground plane for enhancing the isolation of the MIMO system. The proposed antenna has an impedance bandwidth (for │S11│ < −10 dB) ranging from 3.1 to 11.5 GHz (VSWR ≤ 2) and an isolation of more than 15 dB is achieved between the adjacent planar monopoles. The band rejection phenomenon in wireless local area network band is achieved by etching rotated C-shaped slots from the respective patches. Also, two identical rectangular slots are etched on the respective ground planes which enhances the lower UWB bandwidth and cause interference suppression at Wi-Max and C-band (3.3–3.7 and 3.7–4.2 GHz), respectively. A further improvement in isolation from 14.71 to 21.81 dB is achieved by the addition of parallel rectangular strips at the back side of the antenna. Acceptable agreement is obtained between the simulated and measured antenna performance parameters.

COMPACT UWB MIMO ANTENNA WITH ACS-FED STRUCTURE

A compact UWB (Ultrawideband) MIMO (Multiple-input multiple-output) antenna with asymmetric coplanar strip (ACS)-fed structure is proposed in this paper. The antenna consists of two modifled ACS feeding staircase-shaped radiation elements which are orthogonally placed, and the wideband isolation is achieved through a fence-like stub between them. The efiectiveness of the fence- like stub is analyzed. Measured results show that the presented antenna can achieve a broad impedance bandwidth (jS11j 6 i10dB) of 3.1{11GHz with good performance in terms of isolation > 15dB. Radiation patterns and correlation coe-cient (ECC) denote the consistent diversity performance across the entire UWB bandwidth. By introducing the ACS-fed structure, the antenna size can be considerably reduced to 43:5mm £ 43:5mm £ 1:6mm compared to the recently published UWB MIMO antennas, which makes the antenna suitable for portable UWB MIMO applications.

Compact Dual Band-Notched UWB MIMO Antenna With High Isolation

A compact dual band-notched ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna with high isolation is designed on a FR4 substrate (27 × 30 × 0.8 mm3). To improve the input impedance matching and increase the isolation for the frequencies ≥ 4.0 GHz, the two antenna elements with compact size of 5.5 × 11 mm2 are connected to the two protruded ground parts, respectively. A 1/3 λ rectangular metal strip producing a 1.0 λ loop path with the corresponding antenna element is used to obtain the notched frequency from 5.15 to 5.85 GHz. For the rejected band of 3.30-3.70 GHz, a 1/4 λ open slot is etched into the radiator. Moreover, the two protruded ground parts are connected by a compact metal strip to reduce the mutual coupling for the band of 3.0-4.0 GHz. The simulated and measured results show a bandwidth with |S11| ≤ -10 dB, |S21| ≤ -20 dB and frequency ranged from 3.0 to 11.0 GHz excluding the two rejected bands, is achieved, and all the measured and calculated results show the proposed UWB MIMO antenna is a good candidate for UWB MIMO systems.