A low‐profile dual port UWB‐MIMO/diversity antenna with band rejection ability

A band notched ultra‐wideband (UWB) antenna is presented in this article as a good prospect for multiple‐input multiple‐output (MIMO)/diversity application. The proposed MIMO antenna is constituted of two modified rectangle‐shaped patch antenna elements. A stepped stub is extended from the modified ground plane as a decoupling element between the radiators to realize a good isolation level between them. A band rejection response is obtained by connecting an open resonant stub to each of the radiators. The simulated prototype is fabricated and tested for verification. Results reveal that the proposed prototype provides a 10 dB return loss bandwidth from 3.08 to 10.98 GHz with band notch characteristics from 4.98 to 5.96 GHz, and a good port isolation level (S₂₁ ≤ 20). Diversity performances are ensured in terms of total active reflection coefficient, envelope correlation coefficient (<0.013 except notch band), diversity gain (≈9.51 dB), mean effective gain ratio (≈1), and channel capacity loss (≤0.35 bps/HZ except notch band). It evidences that the presented band notched UWB antenna can be a good prospective for MIMO/diversity applications.     

High isolation two‐port compact MIMO fractal antenna with Wi‐Max and X‐band suppression characteristics

This article features about an ultra‐wideband (UWB)‐multiple‐input multiple‐output (MIMO) antenna that exhibits the potentials of good port isolation and dual‐band suppression. The proposed antenna model consists of a unique fractal‐shaped radiating patch, a common ground interface leading to the incorporation of an intuitive approach; parasitic inverted neutralization stubs, which is located at the central co‐ordinate axis system, protruded vertically, where its extension is twisted with a motive of enhancing the port isolation. In addition to that, contiguous notches are implemented to achieve band‐notching at WiMAX (3.35‐4.45 GHz) and X‐band (9‐10 GHz). The total electrical area of UWB MIMO antenna is 0.179(λ₀)² at 2.25 GHz. To rationalize the counterparts of MIMO and band‐notching, diversity performance is studied through the electromagnetic (EM) solver and the corresponding circuit analysis is pursued through a electronic design automation (EDA) solver. The prototype has been fabricated, measured, and agreed well with the simulated results. The feasibility of proposed antenna model is considered to be quite optimum, with due consideration of its outcomes from applications point‐of‐view.     

Compact four‐port MIMO antenna on slotted‐edge substrate with dual‐band rejection characteristics

A compact ultra‐wideband (UWB) multiple‐input‐multiple‐output (MIMO) antenna with dual band elimination characteristics is presented. The proposed MIMO antenna is comprised of four identical elliptical shaped monopole radiators located orthogonally to each other. A second order Koch fractal geometry is applied on the edges of the ground planes of the radiating elements; to reduce the overall size of the MIMO antenna, without compromising the lower frequency response. Further, in order to eliminate the undesired resonant bands (3.5 and 5.5 GHz) from UWB, an elliptical complementary split ring resonator is introduced in the monopole radiator. For reducing inter‐element coupling in the proposed MIMO antenna, a different approach (of slotted edge substrate) is used, as a substitute of traditional decoupling stub/elements. In the entire operating band of 3 to 13.5 GHz, inter‐element isolation more than 22 dB and envelope correlation coefficient less than 0.008 are obtained. The measured parameters of the fabricated prototype antenna are found in good agreement with the simulated results.     

Compact eight‐port MIMO/diversity antenna with band rejection characteristics

A new compact three‐dimensional multiple‐input‐multiple‐output (MIMO) antenna comprised of eight antenna elements is presented. The unit cell of the proposed MIMO/diversity antenna consists of three elliptical rings connected together in the region close to the feed line and a rectangular‐shaped modified ground plane. To achieve polarization diversity with the proposed eight‐port MIMO configuration, four antenna elements are horizontally arranged and the remaining four are vertically oriented. The proposed antenna has an impedance bandwidth (S₁₁ < ?10 dB) of 25.68 GHz (3.1‐28.78 GHz) with a wireless local area network notch‐band at 5.8 GHz (5.2‐6.5 GHz). In addition to polarization diversity, the proposed antenna provides a reliable link with wireless devices. The prototype antenna design is fabricated and measured for diversity performance. Also, the proposed MIMO antenna provides good performance metrics such as apparent diversity gain, channel capacity loss, envelope correlation coefficient, isolation, mean effective gain, multiplexing efficiency, and total active reflection coefficient.     

A low‐profile quad‐port UWB MIMO antenna using defected ground structure with dual notch‐band behavior

A compact (45 × 45 × 1.6 mm³) ultrawide‐band (UWB), multiple‐input multiple‐output (MIMO) design using microstrip line feeding is presented. The proposed design comprises four elliptical monopoles placed orthogonally on a cost‐effective FR‐4 substrate. In order to improve the impedance bandwidth and lessen the return loss of the MIMO antenna, defects in ground plane are created by etching symmetrical square slots and half‐rings. Moreover, a different method (of unsymmetrical H‐shaped slot with C‐shaped slot) was proposed into the patch to introduce dual‐band rejection performance from UWB at center frequency 5.5 GHz (covering lower WLAN as well as upper WLAN) and 7.5 GHz (X band). In addition, a stub is introduced at the edge of each defected ground structure to obtain isolation >–22 dB covering entire performing band from 2 to 16.8 GHz (where, S₁₁ < –10 dB). The proposed design has miniaturized size, very low envelop correlation coefficient less than 0.1, stable gain (2‐4 dBi except for notch bands). Furthermore, various MIMO performance parameters are within their specifications, such as diversity gain (= 10 dB), total active reflection coefficient (<–5 dB, and channel capacity loss (<0.35 bits/s/Hz). The presented design is optimized using the HFSS software, and fabricated design is tested using vector network analyzer. The experimental results are in good agreement with the simulation results.     

Dual‐band CPW fed MIMO antenna with polarization diversity and improved gain

A dual‐band MIMO slot antenna with polarization diversity and improved gain is proposed in this article. The antenna is composed of two C‐type back‐to‐back connected slot resonators and offers resonances at 3.5 and 5.2 GHz. This antenna element is further used to design a MIMO antenna. By introducing one U‐shaped slot between two antenna elements, isolation between the ports of this MIMO antenna is improved further. Finally, an artificial magnetic conductor (AMC) is placed below the MIMO antenna to enhance its gain. Gain enhancement of 1.5 and 2.2 dB is achieved at lower and upper band, respectively. S‐parameters, radiation patterns, gain, envelope correlation coefficient, and channel capacity loss are investigated to conclude about its performances in MIMO applications. Dual band dual polarization (circular and linear), improved isolation, polarization diversity (right‐hand circular polarization and left‐hand circular polarization), gain enhancement all are presented in a simple design represents the novelty of the proposed MIMO antenna.     

A compact six port antenna for better spectrum utilization efficiency in cognitive radio applications

In this article, a novel six port antenna for better spectrum utilization efficiency in cognitive radio (CR) applications is presented. In this six port antenna system, an ultra‐wideband (UWB) sensing antenna and five wideband/narrowband (NB) antennas are integrated on the same substrate in a compact area of 1134 mm² . Antenna associated with port 1, which is meant for sensing, has ?10 dB reflection coefficient bandwidth of 3 to 11 GHz and the antennas associated with ports 2, 3, 4, 5, and 6 have ?10 dB reflection coefficient bandwidths of 3.6 to 5.8 GHz (single band), 2.9 to 3.6 GHz and 5.4 to 7.98 GHz (dual band), 7.95 to 8.38 GHz and 9 to 9.85 GHz (dual band), 8.38 to 9 GHz (single band) and 9.7 to 10.7 GHz (single band), respectively. Minimum isolation of 20 dB is attained between UWB sensing antenna and any narrowband/wideband antenna except between the antennas associated with ports 1 and 2 where minimum isolation of 12 dB is achieved over the operating bandwidth of UWB sensing antenna. Moreover, among all wideband/narrowband antennas, isolation of less than 15 dB is achieved. More importantly, the narrowband and wideband antennas meant for communication cover all frequency bands in UWB and a good match between the simulated and measured results is noticed.     

Design of a dual‐band MIMO dielectric resonator antenna with high port isolation for WiMAX and WLAN applications

A novel dual‐band MIMO dielectric resonator antenna with high port isolation for WiMAX and WLAN applications is designed and investigated. The proposed antenna operates at 3.5 and 5.25 GHz bands. High port isolation is achieved using hybrid feeding mechanism that excites two orthogonal modes at each frequency bands. The measured impedance bandwidth of the proposed antenna covers the entire WiMAX (3.4–3.7) GHz and WLAN (5.15–5.35) GHz bands. The scalable behavior along with the frequency ratio of the antenna has also been investigated in this work. The measured isolation between antenna ports is ?52 dB at the lower band and ?46 dB at the upper band, respectively. Envelope correlation coefficient, diversity gain and mean effective gain have also been investigated. Moreover, measured results are in good agreement with the simulated ones.     

A WLAN band‐notched compact four element UWB MIMO antenna

A compact four‐element multiple‐input‐multiple‐output (MIMO) antenna for ultra‐wideband (UWB) applications with WLAN band‐notched characteristics is proposed here. The proposed antenna has been designed to operate from 2 to 12 GHz while reject the frequencies between 4.9 to 6.4 GHz. The four antenna elements are placed orthogonal to attain the polarization diversity and high isolation. A thin stub connected to the ground plane is deployed as a LC notch filter to accomplish the rejected WLAN band in each antenna element. The mutual coupling between the adjacent elements is at least 17 dB while it has low indoor and outdoor envelop correlation (<0.45) and high gain with compact size of two boards, each measuring 50 × 25 mm². To validate the concept, the prototype antenna is manufactured and measured. The comparison of the simulation results showed good agreement with the measured results. The low‐profile design and compact size of the proposed MIMO antenna make it a good candidate for diversity applications desired in portable devices operating in the UWB region.     

Design of wideband antenna with band notch characteristics based on single notching element

In this article, a coplanar waveguide (CPW) fed planner monopole antenna with a compact size of 0.32λ × 0.30λ × 0.0056λ mm³ is presented. The radiator is fed with 50 Ω CPW feed line that provides impedance matching from 1.7 to 30 GHz for VSWR ≤2. In addition, three narrow bands are filtered out in the ultra‐wideband (UWB) range. The narrow notched bands are filtered for WiMAX (3.52‐4.2 GHz), WLAN (5.04‐5.40 GHz), and X band (8.22‐9.10 GHz) application. The rejecting bands are achieved by loading a single tri‐square ring resonator (SRR) on the backside of the feed line. The dimensions of SRR control the notch resonance frequencies. A single‐, dual‐, and tri‐notch frequencies have been achieved by using single‐, dual‐, and tri‐SRR, respectively. The measured results of antenna structures in the absence and presence of the SRR are compared with the simulations. The measured results validate the proposed design.     

Modified ground with 50 Ω step fed WLAN notch 2 × 2 MIMO UWB antenna

In this research paper, an optimized 2 × 2 MIMO UWB antenna (antenna‐E) with half circled radiators as well as 50 Ω step fed has been introduced. The proposed UWB MIMO antenna has been evolved from recent peer published papers that provide WLAN notch (5.15‐5.85GHz), ultra wide band width (3.1‐10.6 GHz) and again a very good isolation (?20 dB) also maintained. In this paper the evolutions have been derived from antenna‐A to antenna‐E. The Ultra wide band is achieved by using step feed line, cutting a metal strip on a partial ground plane, a rectangular slot underneath the feed line of each radiator in antenna‐E. A high isolation (?20 dB) is obtained by introducing two inverted Г shaped stubs in the ground plane. Both antenna‐D and antenna‐E maintain high isolation (?20 dB). But antenna‐E performs better isolation compared to antenna‐D. The notch at WLAN band (5.15‐5.85GHz) is achieved by etching rectangular C‐shaped slot on the both the radiators. In antenna‐E two radiators are placed horizontally where as in antenna‐D two radiators placed orthogonally. It has been observed that the dimension of final outcome (antenna‐E) is reduced by 33% compared to antenna‐D without compromising the overall performance of the antenna.     

A dual‐feed MIMO antenna pair with one shared radiator and two isolated ports for fifth generation mobile communication band

In this article, a pair of unsymmetrical dual‐feed antennas with one shared radiator and two isolated ports is proposed for multiple‐input‐multiple‐output (MIMO) systems. The proposed antenna pair achieves high isolation between the two ports by properly adjusting the distance between the two feeding ports and the position and length of shorting strips on the radiator. The antenna has simple structure and covers the 3.3‐3.7 GHz band, which could meet the demand of future 5G applications. The measured results show that antenna has good impedance matching (better than 10 dB return loss) and high port isolation (better than 20 dB isolation) from 3.35 to 3.65 GHz. The total efficiencies are above 55% and the envelope correlation coefficient is <0.1, which is sufficient for MIMO applications.     

Complementary meander‐line‐inspired dielectric resonator multiple‐input‐multiple‐output antenna for dual‐band applications

The communication presents a simple dielectric resonator (DR) multiple‐input‐multiple‐output (MIMO) dual‐band antenna. It utilizes two “I”‐shaped DR elements to construct an “I”‐shaped DR array antenna (IDRAA) for MIMO applications. The ground plane of the antenna is defected by two spiral complementary meander lines and two circular ground slots. In the configuration, two “I”‐shaped DR elements are placed with a separation of 0.098λ. The antenna covers dual‐band frequency spectra from 3.46 to 5.37 GHz (43.26%) and from 5.89 to 6.49 GHz (9.7%). It ensures the C‐band downlink (3.7‐4.2 GHz), uplink (5.925‐6.425 GHz), and WiMAX (5.15‐5.35 GHz) frequency bands. Each DR element is excited with a 50‐Ω microstrip line feed with aperture‐coupling mechanism. The antenna offers very high port isolation of around 18.5 and 20 dB in the lower band and upper band, respectively. The proposed structure is suitable to operate in the MIMO system because of its very nominal envelope correlation coefficient (<0.015) and high diversity gain (>9.8). The MIMO antenna provides very good mean effective gain value (±0.35 dB) and low channel capacity loss (<0.35 bit/s/Hz) throughout the entire operating bands. Simulated and measured results are in good agreement and they approve the suitability of the proposed IDRAA for C‐band uplink and downlink applications and WiMAX band applications.     

A compact printed ultra‐wideband multiple‐input multiple‐output prototype with band‐notch ability for WiMAX,LTEband43, and WLAN systems

A compact ultra‐wideband multiple‐input multiple‐output (UWB‐MIMO) antenna with good isolation and multiple band‐notch abilities is developed in this work. It consists of two quadrant shaped monopole antennas backed by ground stubs. A good isolation is achieved due to the two proposed extended curved ground stubs. The frequency rejection for the WLAN system is realized by loading a capacitive loaded loop resonator adjacent to the feed line. The band rejection for the WiMAX and LTE band43 system is achieved by embedding a quadrant shaped CSRR on each radiator's surface. The measured bandwidth of the antenna is 3.06 GHz‐11 GHz (|S₁₁| < ?10 dB and |S₂₁| < ?18 dB) with a band rejection from 3.5 GHz‐4 GHz to 5.1 GHz‐5.85 GHz, respectively. Time domain performances are investigated in terms of group and phase delay characteristics. Diversity characteristics are evaluated in terms of the envelope correlation coefficient, mean effective gain, and channel capacity loss.     

A UWB MIMO slot antenna using defected ground structures for high isolation

In this article, a multiple‐input‐multiple‐output (MIMO) antenna with high isolation is proposed for ultrawideband (UWB) applications. The proposed MIMO antenna consists of two symmetric slot antenna elements with quasi F‐shaped radiators and L‐shaped open‐slots to increase impedance bandwidth. To improve isolation at the lower band, a decoupling network, composed of a narrow slot and a fork‐shaped slot, is introduced in the common ground. The measured results show that the proposed antenna provides high isolation of better than 20 dB over the operating band from 3 to 10.9 GHz. The performances of the UWB MIMO antenna in terms of radiation patterns, peak gain, envelope correlation coefficient, mean effective gain, and diversity gain are also studied.     

Dual‐band and enhanced‐isolation MIMO antenna with L‐shaped meta‐rim extended ground stubs for 5G mobile handsets

A novel compact planar dual‐band multiple input multiple output (MIMO) antenna with four radiating elements for 5G mobile communication is proposed. Each radiating element has a planar folded monopole, which is surrounded by L‐shaped meta‐rim extended ground stubs. The compact folded arms act as the main radiating elements, while combined with the L‐shaped meta‐rim stubs, the proposed antenna forms multiple resonances so as to achieve dual‐band coverage. The simulated and measured results show that the proposed antenna has two wide bands of ?6 dB return loss, consisting of 1.6 to 3.6 and 4.1 to 6.1 GHz, respectively. Without any additional isolation structure between the elements, the isolation for the proposed 2 × 2 MIMO antenna in both desired bands can be achieved better than 12 dB. The measured results show that the proposed MIMO antenna with good performance, that is, stable radiation patterns, high efficiencies, low specific absorption ratio (SAR) to human tissues, is suitable for WLAN/LTE, 4G and future 5G mobile phone applications.     

Compact planar frequency reconfigurable multiple‐input‐multiple‐output antenna with pattern and polarization diversity characteristics for WiFi and WiMAX standards

A compact planar frequency reconfigurable dual‐band multiple‐input‐multiple‐output (MIMO) antenna with high isolation and pattern/polarization diversity characteristics is presented in this article for WiFi and WiMAX standards. The MIMO configuration incorporates two symmetrically placed identical antenna elements and covers overall size of 24 mm × 24 mm × 0.762 mm. Reconfiguration of each antenna element is achieved by using a PIN diode which allows antennas to switch from state‐1 (2.3‐2.4 GHz and 4.6‐5.5 GHz) to state‐2 (3.3‐3.5 GHz and 4.6‐5.5 GHz). In state‐1, the configuration offers isolation ≥18 dB and 20 dB in lower band (LB) and upper band (UB) respectively; whereas, in state‐2, isolation ≥21 dB and 20 dB in LB and UB respectively is achieved. The same decoupling circuit provides high isolation in dual‐band of two states, which makes overall size of the proposed design further compact. The antennas are characterized in terms of envelope correlation coefficient, radiation pattern, gain, and efficiency. From measured and simulated results, it is verified that the proposed frequency reconfigurable dual‐band multi‐standard MIMO antenna design shows desirable performance in both operating bands of each state and compact size of the design makes it suitable for small form factor devices used in future wireless communication systems.     

A compact dual‐band 2 × 1 metamaterial inspired mimo antenna system with high port isolation for LTE and WiMax applications

This article proposes a compact (43 × 26 × 0.8 mm³) dual‐band two‐element metamaterial‐inspired MIMO antenna system with high port isolation for LTE and WiMAX applications. In this structure, each antenna element consists of a square–ring slot radiator encircling a complementary split ring resonator. A tapered impedance transformer line feeds these radiating apertures and shows good impedance matching. A 2 × 3 array of two‐turn Complementary Spiral Resonator structure between the two antenna elements provides high dual‐band isolation between them. The fabricated prototype system shows two bands 2.34 – 2.47 GHz (suitable for LTE 2300) and 3.35 – 3.64 GHz (suitable for WiMAX). For spacing between two antennas of 10 mm only, the measured isolation between the two antenna elements in the lower band is around ?32 dB while that in the upper band is nearly 18 dB. The system shows a doughnut‐shaped radiation patterns. The peak measured antenna gains for the proposed MIMO system in the lower and higher bands are 3.9 and 4.2 dBi, respectively. The MIMO system figure of merits such as the envelope correlation coefficient, total efficiency are also calculated and shown to provide good diversity performance.     

Dielectric resonator based two‐port dual band antenna for MIMO applications

This article investigates a dual band multiple input multiple output (MIMO) cylindrical dielectric resonator antenna (cDRA) for WLAN and WiMAX applications. It consists of two symmetrical orthogonally placed radiators. Each radiator is excited through a narrow rectangular aperture with the help of a microstrip line. For higher mode excitation, the proposed structure uses dual segment DRA which apparently looks like stacked geometry. The aperture fed dielectric resonator works as a feed for upper cDRA to generate higher order mode. The presented radiator covers the band between 3.3‐3.8 GHz and 5‐5.7 GHz. The measured isolation is better than 20 dB in the desired band. The average gain and radiation efficiency achieved for the proposed antenna is 6.0 dBi and 85%, respectively at the operating frequency band. In the proposed geometry, broadside radiation patterns are achieved by exciting HEM_11δ and HEM_12δ modes in a stacked geometry. Different MIMO performance parameters (ECC, DG, MEG, and CCL) are also estimated and analyzed. The prototype of proposed antenna is fabricated and tested. The measured outcomes are in good accord with the simulated one.