In this paper, a compact design of multiple-input multiple-output (MIMO) Antenna with dual sharply rejected notch bands for portable wireless ultrawideband (UWB) applications is presented and experimentally investigated. The proposed UWB MIMO Antenna has a compact size of 18 mm $\times$ 34 mm. The tapered microstrip fed slot Antenna acts as a single radiating element with inverted L-shaped slits to introduce notches at wireless local area network and the IEEE INSAT/Super-Extended C-bands. The mutual coupling of less than −22 dB is achieved over the entire operating band (2.93–20 GHz). At the center of notched band, the efficiency of the Antenna drops that indicates a good interference suppression performance. The performance of the MIMO Antenna in terms of isolation among the ports, radiation pattern, efficiency, realized gain, envelope correlation coefficient, mean effective gain, and total active reflection coefficient is studied.

Tapered Fed Compact UWB MIMO-Diversity Antenna With Dual Band-Notched Characteristics

Triple band-rejection MIMO/Diversity UWB antenna characteristics are described in this paper. Proposed antenna discards worldwide interoperability for microwave access WiMAX band from 3.3 to 3.6 GHz, wireless local area network WLAN band from 5 to 6 GHz and X-Band satellite downlink communication band from 7.1 to 7.9 GHz. Mushroom Electromagnetic Band Gap (EBG) structures helps to attain band notches in WiMAX and WLAN bands. Uniplanar plus shaped EBG structure is used for notch in X-band downlink satellite communication band. Decoupling strips and slotted ground plane are employed to develop the isolation among two closely spaced UWB monopoles. The individual monopoles are 90° angularly separated with stepped structure which helps to reduce mutual coupling and also contributes towards impedance matching by increasing current path length. Mutual coupling magnitude of more than 15 dB is found over whole UWB frequency range. The Envelope Correlation Coefficient is less than 0.02 over whole UWB frequency range.The variations in the notched frequency with the variations in mushroom EBG structure parameters are investigated.The antenna has been designed using FR-4 substrate and overall dimensions is (64 × 45 × 1.6) mm3.

Triple band notched mushroom and uniplanar EBG structures based UWB MIMO/Diversity antenna with enhanced wide band isolation

This study describes the design of a very compact dual-band-notched ultrawide band (UWB) multiple-input multiple-output (MIMO) antenna. The main features of the proposed antenna are its compact dimensions and high isolation between the two antenna elements. The UWB performance of the antenna is attained by designing two identical triangular-shaped patch elements, which are designed opposite to each other and connected to a tapered microstrip feedline. The ground plane of the proposed antenna consists of a funnel-shaped patch connected with two triangles at the lower end. In addition, two J-shaped slits are etched in the radiator to get the band rejection characteristics at wireless local area network band from 5.1 to 5.8 GHz and IEEE INSAT/Super-Extended C-band from 6.7 to 7.1 GHz. The designed antenna has the smallest dimension of 
. Results show that the MIMO antenna has a large impedance bandwidth of 31.9 GHz from 3.1 to 35 GHz. The diversity performance of the proposed antenna is also analysed using different parameters such as envelope correlation coefficient (ECC), diversity gain, total active reflection coefficient and so on. Due to the low mutual coupling of <−24 dB and ECC of <0.2 across the frequency band this antenna is a good candidate for portable UWB applications.

Design of ultra-compact UWB antenna with band-notched characteristics for MIMO applications

A compact printed differential multiple-input–multiple-output (MIMO) antenna is presented for ultrawideband system applications with band-notched characteristic. The proposed MIMO antenna element consists of a differential U-shaped microstrip feedline and a stepped-shaped slot, printed on the bottom and top of the substrate, respectively. A half-wavelength resonant stub embedded in the stepped-shaped slot is exploited to obtain notched band, whose center frequency can be adjusted by the length of the stub. The staged slots among antenna elements are introduced to enhance the differential isolation. The final antenna has a compact size of $44 \times 44\; \text{mm}^{2}$ . Measured results show that the proposed MIMO antenna achieves −10-dB impedance bandwidth from 2.95 to 10.8 GHz, isolation better than 15.5 dB over the whole operating band, and a notched band from 5.10 to 5.95 GHz.

Compact Differential Band-Notched Stepped-Slot UWB-MIMO Antenna With Common-Mode Suppression

Low-profile band-notched G-shaped ultra-wideband (UWB) multiple input multiple output (MIMO) antenna design for mobile terminals has been presented. In this context, two UWB MIMO antenna systems have been designed: The first is with square elements and the second is with G-shaped elements. An MIMO antenna with two symmetrical square elements each of 8 × 8 mm
 2
 operating between 2.2 and 13.3 GHz was firstly designed for the UWB applications. Each square element was fed through a 50-Ω microstrip transmission line (MTL). A thin strip line was designed at the end of MTL to provide impedance matching. Although the isolation level between the elements was satisfactory for efficient MIMO implementation, a T-shaped strip on the ground was employed to further improve the isolation for low frequency. The frequency range of 4.4-6.2 GHz which is an important band of wireless local area network (WLAN) standard was then notched by forming a G-shaped structure on the square element. The performance of G-shaped antenna system was studied in terms of important antenna characteristics and MIMO parameters. The results demonstrate that the G-shaped MIMO antenna has nearly omnidirectional patterns, stable gain and good diversity performance besides having low-profile elements.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-map.2016.0820

G-shaped band-notched ultra-wideband MIMO antenna system for mobile terminals

A compact multiple-input–multiple-output (MIMO) antenna is presented for ultrawideband (UWB) applications with band-notched function. The proposed antenna is composed of two offset microstrip-fed antenna elements with UWB performance. To achieve high isolation and polarization diversity, the antenna elements are placed perpendicular to each other. A parasitic T-shaped strip between the radiating elements is employed as a decoupling structure to further suppress the mutual coupling. In addition, the notched band at 5.5 GHz is realized by etching a pair of L-shaped slits on the ground. The antenna prototype with a compact size of $38.5 \times38.5~\hbox{mm}^{2}$ has been fabricated and measured. Experimental results show that the antenna has an impedance bandwidth of 3.08-11.8 GHz with reflection coefficient less than $-10~\hbox{dB}$ , except the rejection band of 5.03-5.97 GHz. Besides, port isolation, envelope correlation coefficient and radiation characteristics are also investigated. The results indicate that the MIMO antenna is suitable for band-notched UWB applications.

Compact Offset Microstrip-Fed MIMO Antenna for Band-Notched UWB Applications

A dual-polarized dual-mode orbital angular momentum (OAM) microstrip antenna array is presented. The OAM radio beams are generated by employing a four-element antenna array with specific excitation. Each antenna element is an aperture-coupled microstrip patch antenna with a low profile of $0.1\lambda _{{\rm{0}}}$ . The quasi-cross-shaped aperture is excited by a U-shaped and an M-shaped microstrip feedline, which leads to two orthogonal polarizations. By adopting two types of phase-shifting schemes, the antenna array can be used to produce dual-mode OAM waves ( ${\rm{l}} = \pm 1$ ). The measured results show that the proposed antenna array has achieved good impedance matching over the band of 5.4–5.6 GHz, and a port-to-port isolation better than 25 dB. Moreover, the rotational phase fronts indicate waves properly bearing OAM with different states.

A Low-Profile Dual-Polarized Microstrip Antenna Array for Dual-Mode OAM Applications

In this communication, an orbital angular momentum (OAM) mode-reconfigurable antenna based on a uniform circular array (UCA) is presented. To realize multiple switchable operating states while maintaining a relatively simple structure, a simplified feeding scheme is developed. By introducing a set of optimal reference phases for different OAM modes, the tunable phase states for the entire array are degenerated, which leads to a reduction in the total number of required phase states. Then, the excitation phases are decomposed into two parts and generated by the reconfigurable radiators and reconfigurable feed network, respectively. In addition, p-i-n diodes are selected as switches to control the operating states of the radiators and feed network. Therefore, OAM-mode switching capability can be obtained by altering the direct current (dc) bias configurations of the diodes. The antenna design is validated by both simulation and measurement. Results indicate that the proposed eight-element array antenna produces six operating states corresponding to OAM modes l = ±1, ±2, and ±3. The measured overlapped band among the states with $\vert \text{S}_{\mathbf {11}}\vert dB covers 2.33–2.73 GHz. Moreover, the proposed antenna also features the advantages of easy fabrication and low cost.

A Mode-Reconfigurable Orbital Angular Momentum Antenna With Simplified Feeding Scheme

This article presents a trust-region parallel Bayesian optimization (TRPBO) method for simulation-driven antenna design problems. In this method, a multipoints acquisition function and trust region (TR)-based design space were developed to accelerate the solution efficiency of antenna design optimizations. For each optimization cycle in TRPBO, the acquisition function is applied to choose multiple updating points in a dynamic sampling space managed by a gradient-free TR, and then the responses at the updating points are calculated using parallel electromagnetic simulations. The proposed TRPBO was illustrated and tested on several benchmark problems, and then the TRPBO was applied to perform the design optimizations of a circularly polarized antenna, two wideband antennas, and an array antenna. Compared with the state-of-the-art methods, the proposed TRPBO achieves better optimization results with significantly less calculation time. The measured results of three fabricated antenna prototypes further show great potential of the TRPBO for solving simulation-driven antenna design problems.

A Trust-Region Parallel Bayesian Optimization Method for Simulation-Driven Antenna Design

A compact multiple-input multiple-output (MIMO) antenna is presented for band-notched ultra-wideband (UWB) applications. Miniaturization of the proposed antenna is realized by employing the asymmetric coplanar strip (ACS)-fed structures. To obtain the band-notched function, open stubs are introduced on the radiators. In addition, an H-shaped slot is etched on the ground to reduce the mutual coupling between the antenna elements. The designed antenna with an overall size of 28 × 22 × 0.8 mm3 was fabricated and tested. Measured results show the antenna operates over a frequency band of 2.9–11.8 GHz with reflection coefficient less than −10 dB, except at the rejection band of 4.9–6 GHz. Within the operating band, measured port isolation is better than 20 dB. Radiation characteristics and diversity performance of the antenna are also investigated through measurement. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:878–881, 2016

Le Kang

Papers

Compact Offset Microstrip-Fed MIMO Antenna for Band-Notched UWB Applications

A Low-Profile Dual-Polarized Microstrip Antenna Array for Dual-Mode OAM Applications

A Mode-Reconfigurable Orbital Angular Momentum Antenna With Simplified Feeding Scheme

A Trust-Region Parallel Bayesian Optimization Method for Simulation-Driven Antenna Design

Miniaturized band‐notched UWB MIMO antenna with high isolation