A compact planar UWB-MIMO antenna array with WLAN band rejection is presented. The array consists of four monopole radiators and a common ground plane. These monopoles are placed in such a way that the polarisation diversity of nearly placed radiators is exploited, resulting in high isolation. The proposed MIMO antenna array is electrically small (50 × 39.8 mm 2), printed on a low loss 1.524 mm thick Rogers TMM4 laminate with a dielectric constant of 4.5 and a loss tangent of 0.002. A band-stop design was inserted on the ground plane to behave similar to a LC band-stop filter and reject the WLAN band. Simulation and measurement results satisfy the return loss requirement of better than 10 dB and isolation better than 17 dB over the entire 2.7-5.1 and 5.9-12 GHz bandwidths.

An eight element, compact Ultra Wideband− Multiple Input Multiple Output (UWB-MIMO) antenna capable of providing high data rates for future Fifth Generation (5G) terminal equipments along with the provision of necessary bandwidth for Third Generation (3G) and Fourth Generation (4G) communications that accomplishes band rejection from 4.85 to 6.35 GHz by deploying a Inductor Capacitor (LC) stub on the ground plane is presented. The incorporated stub also provides flexibility to reject any selected band as well as bandwidth control. The orthogonal placement of the printed monopoles permits polarization diversity and provides high isolation. In the proposed eight element UWB-MIMO/diversity antenna, monopole pair 3−4 are 180 • mirrored transform of monopole pair 1−2 which lie on the opposite corners of a planar 50 × 50 mm 2 substrate. Four additional monopoles are then placed perpendicularly to the same board leading to a total size of 50 × 50 × 25 mm 3 only. The simulated results are validated by comparing the measurements of a fabricated prototype. It was concluded that the design meets the target specifications over the entire bandwidth of 2 to 12 GHz with a reflection coefficient better than −10 dB (except the rejected band), isolation more than 17 dB, low envelope correlation, low gain variation, stable radiation pattern, and strong rejection of the signals in the Wireless Local Area Network (WLAN) band. Overall, compact and reduced complexity of the proposed eight element architecture, strengthens its practical viability for the diversity applications in future 5G terminal equipments amongst other MIMO antennas designs present in the literature. INDEX TERMS Band rejected, compact, diversity, envelope correlation coefficient , multiple input multiple output, ultrawide band, 5G communication, 5G terminal devices. I. INTRODUCTION W IRELESS broadband communication system such as Worldwide Interoperability for Microwave Access (WiMAX (3.4 to 3.6 GHz)), large capacity Microwave Relay Trunk Network (4.4 to 4.99 GHz), and Wireless Local Area Network (WLAN signals in 5.15 to 5.35 and 5.75 to 5.8225 GHz bands), impose a limited power spectral density of the low power and a high data rate

An ultra‐compact dual‐polarised ultra‐wideband multi‐input multi‐output antenna made with a single‐shared‐radiating element and two meandered feeding lines are proposed. Miniaturisation is achieved by using a combination of techniques, including a resonant stub connected to the ground through which shorts the excessive coupled energy before it reaches the other port and minimises coupling, slots etched in the radiator that also help minimise mutual coupling, while the meandered lines allow to bring the antenna closer to the greatly reduce the overall size of the antenna. Slots etched in the radiator and the use of a stub connected to the ground through, help to minimise the mutual coupling. The formation of orthogonal surface currents provides the necessary dual polarisation. Simulated and measured results demonstrate the wideband impedance matching, low mutual coupling and low envelope correlation coefficient. This antenna has an extremely compact size (22 × 24.3 mm2, including the ground plane) that makes it an excellent candidate for portable and handheld devices.

In this article, a novel design of a compact planar Ultra Wideband (UWB) monopole antenna with dual band notched characteristics has been presented. The antenna has a unique structure meeting UWB standards. The proposed antenna is fed through a 50 normalΩ micro strip feed line, whereas a better impedance is achieved by truncating the ground plane. The dual notches are achieved by incorporating a meandered slot on the radiator patch and U‐slot in the feed line. The antenna is fabricated on FR‐ 4 substrate having a compact size of  33 × 32 × 1.5 normalmnormalm3. A good agreement is observed between measured and simulated results. The radiation pattern is omnidirectional in H‐plane, whereas dipole like radiation pattern is observed in the E‐plane. The gain of antenna is stable across the whole UWB except at notched bands. It is shown that any UWB can be notched at any desired frequency band by incorporating appropriate slot length.

This article presents a four elements frequency reconfigurable ultrawideband (UWB) multiple-input-multiple-output (MIMO) design, capable of rejecting on-demand WLAN band ranging from 4.8 to 6.2 GHz. The proposed design consists of two U-shaped monopole UWB radiators and two circular slotted-monopole radiators. These monopole radiators are placed orthogonally with respect to each other to exploit polarization diversity, whereas the PIN diodes are used to connect the band-stop design with the ground plane to introduce the on-demand band rejection feature. An isolation of better than 17 dB between the four UWB-MIMO elements is achieved in the 2.7-12 GHz frequency range for the both PIN diodes biased and unbiased states. The simulations and measurements results showed good agreement over the band of interest

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This paper presents a compact frequency reconfigurable antenna for flexible devices and conformal surfaces. The antenna consists of a simple easy to fabricate structure consisting of a stub loaded circular radiator, designed on commercially available RT5880 flexible substrate (εr = 2.2) with a thickness of 0.254 mm. The combination of stub loading and slot etching techniques are utilized to achieve the advantages of compactness, frequency reconfigurability, wide impedance bandwidth, and stable radiation pattern with structural conformability. The frequency reconfigurability is achieved by employing two p-in diodes. Simulated and experimental results showed that the antenna operates in various important commercial bands, such as S-band (2 GHz-4 GHz), Wi-Max (3.5 GHz and 5.8 GHz), Wi-Fi (3.6 GHz, 5 GHz, and 5.9 GHz), 5G sub-6-GHz (3.5 GHz and 4.4 GHz-5 GHz), and ITU-band (7.725 GHz-8.5 GHz) with the additional advantages of structural conformability. Furthermore, the performance comparison of the proposed flexible antenna with the state-of-the-art flexible antennas in terms of compactness, frequency reconfigurability, and number of operating bands demonstrates the novelty of the proposed antenna and its potential application in heterogeneous applications.

In this article, an antenna with two patch elements is pattern and frequency reconfigured. One feed line is used to excite the two patch elements placed at any angle with respect to each other. The maximum rotation of each patch antenna element incorporated is 458. For the impedance matching with 50 X, both elements are fed from the corner. The radiating elements are fed simultaneously using one feed line with the help of PIN diodes. When patch 1 is excited by biasing PIN diode 1, a broad side radiation pattern in the yz plane of the patch 1 is observed. Therefore, for the rotation angle by 7.58 the pattern rotation is about 58 Similarly, biasing PIN diode 2, resulted excitation of Patch 2. It is observed that pattern reconfiguration of 308 can be achieved by biasing PIN diode 1, whereas, up to 2308 pattern reconfiguration can be achieved by exciting PIN diode 2, without compromising on the gain of the radiating elements. On the other hand, to achieve the frequency reconfiguration, two small radiating patches are added at 0.7 mm gap with the large radiating elements. PIN diodes are used between the small and large radiating elements. When diodes on the antenna elements are