Reconfigurable MIMO Research Articles

A pattern reconfigurable hybrid graphene-metal terahertz MIMO antenna with improved isolation by metasurface absorber for 6G communication

This paper introduces an innovative 2 × 2 MIMO, Multi-Input Multi-Output, antenna working in the sub-Terahertz (THz) band for 6G, 6-Generation, communications (0.1–1.2 THz). This antenna was designed with main metal octagonal patches and parasitic graphene elements, providing pattern reconfigurable antenna for Single-Input Single-Output (SISO) and MIMO applications. In the YZ-plane, aforementioned antenna illustrates a tunable pattern (0°, +70°, −70°) for SISO in three distinct states. In the XZ-plane, it obtains a versatile MIMO function with a controllable pattern (0°, ±20°, ±45°, ±75°) across four states, simultaneously. The adaptability of the radiation pattern is originated from changing graphene conductivity through biasing. In addition, a graphene metasurface was applied as an absorber, moderately improving isolation between 2 antenna elements, minimizing interference, and enhancing the overall system capability. The proposed schematization achieves a significant isolation up to −35 dB within the MIMO antenna’s operational frequency band. Moreover, the MIMO antenna touches a maximum gain of 9.5 dBi, maximum impedance bandwidth of approximately 91% during different states, 10 dBi Diversity Gain, and 2.62×10−7 ECC in the resonance frequency, which demonstrates novelty designing, remarkable pros, and broad applications in the landscape evolution of 6G communication networks.

Partially Reflecting Surface Loaded Graphene-Silicon Ceramic based Frequency Reconfigurable MIMO Antenna with Pattern Diversity for THz Applications

Partially Reflecting Surface Loaded Graphene-Silicon Ceramic based Frequency Reconfigurable MIMO Antenna with Pattern Diversity for THz Applications

Dual Polarized Reconfigurable MIMO Antenna for Multi-Band Functioning

This work presents the development, fabrication, and measurements of a new Ultra-wideband sensing multi-band frequency reconfigurable MIMO Active Integrated Antenna (AIA). The proposed antenna has two frequency reconfigured (switching element PIN diodes) planar inverted F-shape antennas (PIFA) using meandered line (ML) structures and a Mirror-shape UWB sensing antenna. The Mirror-shape UWB sensing antenna is integrated with 2x2 MIMO Meandered line PIFA elements for spectrum sensing. PIN diodes (BAR 6402V) are used to provide all digital switching on/off combination modes to attain frequency reconfigurability. Varactor diodes are used for tuning over the wide band. The proposed antenna senses a wide frequency band from 0.5GHz-3GHz and provides frequency reconfigurability over the five bands based on BARP6402V switching modes (0.78GHz-1.01GHz, 1.34GHz-1.62GHz, 1.85GHz-2.18GHz, 2.44GHz-2.67GHz, and 2.76GHz-2.80GHz). All the measured resultant performance parameters are compared with simulation software results. The antenna system is fabricated on an FR4 substrate of size 120mmX65mmX1.6mm. The proposed method used to achieve frequency reconfigurable ultra-wideband MIMO provides a high gain 6.15dBi at a frequency of 1.75GHz. The research also analyzed and investigated all 2x2 MIMO resultant parameters like Total Active Reflection Coefficient (TARC), Isolation coefficient, Envelope correlation Coefficients (ECC), Diversity Gain (DG), Multiplexing efficiency, etc. The proposed antenna is applicable for sensing, communication, & UWB sensing, and cognitive radio (CR) applications since it exhibits stable excellent gain and Omni-directional radiation pattern over the desired bands. Because of its reconfigurable nature, the same antenna also supports use in multiple general-purpose applications like GPS tracing, LTE, UMTS, GSM1800, rescue operation, Wi-Fi/Bluetooth/ISM/WLAN, CDMA, etc applications.

L-shaped reconfigurable band decoupling assisted dual band four port MIMO antenna for 5G and IoT application

Reconfigurable MIMO antennas adapt dynamically to changing communication needs and environmental conditions by changing their emission patterns, polarization, and frequency characteristics. By adjusting the antenna configuration, reconfigurable MIMO systems can prevent interference and improve spectral efficiency, resulting in increased data rates and optimal utilization of available frequency ranges. Furthermore, the antenna parameters are optimized to obtain better results and help to enhance the overall efficiency of the model. In this study, an L-shaped reconfigurable band decoupling assisted dual band four port MIMO antenna is designed. The antenna reconfigurability has been obtained from a band stop filter with a pin diode in the proposed design, with four PIN diodes in each individual antenna for improved isolation. The mutual coupling between the antenna elements has been reduced by inserting a DGS to the antenna elements. The presented reconfigurable four-port L-shaped MIMO antenna is applied over 5G and IoT applications. The overall dimensions of the antenna is 40×40×0.508mm3, which resonates over a dual frequency range between 2.344 GHz for 5G applications and 1.433 GHz for IoT applications. Rogers RT Duroid 5880 substrate with a thickness of 0.508 mm, a dielectric constant of 2.2, a relative permeability of 1, and loss tangents of 0.009 in the proposed design and coplanar waveguide feed line are employed, and an I-shaped stub is used to increase isolation. Defected ground structure (DGS) is used in this work to minimize the antenna mutual coupling issue.

Reconfigurable MIMO Antenna for IoT Wireless Applications Controlled by Embedded System

Reconfigurable MIMO Antenna for IoT Wireless Applications Controlled by Embedded System

Frequency and Pattern Reconfigurable CPW-Fed MIMO Antenna with Multiband and Wideband Characteristics

Frequency and Pattern Reconfigurable CPW-Fed MIMO Antenna with Multiband and Wideband Characteristics

Compound reconfigurable symmetric slotted mimo antenna with abs enclosure for indoor wireless applications

This research work reports the Compound Reconfigurable MIMO Antenna (CRMA) utilizing RF PIN diodes for indoor wireless communication applications. The proposed CRMA comprises a quad-symmetric Slotted Radiator (SSR) with a common ground structure. It can perform frequency, polarization and pattern switching at frequency standards such as IEEE 802.11a/b/g/n (2.4/5.5 GHz), IEEE 802.11ax (6 GHz) and 5G/n78 (3.5 GHz). A parasitic element of a modified U-shaped stub is utilized to achieve polarization reconfiguration. Further, to achieve pattern reconfiguration two crossed-shaped slots are implemented. The proposed antenna achieves a bandwidth of 320 MHz at 2.4 GHz, 950 MHz at 3.5 GHz and 1870 MHz at 5.5 GHz. At these resonant frequencies, the antenna is capable of producing both circular and linear polarization with a pattern tilt towards different angular directions such as 30°, 120°, 210°, 300°, 330°, 240°, 150°, 60°. The designed CRMA follows orthogonal orientation and exhibits better diversity performance with ECC < 0.1, DG > 9 dB, TARC < -13 dB and CCL < 0.27 bps/Hz. Also, an Acrylonitrile Butadiene Styrene (ABS) enclosure is designed and fabricated to validate the performance of the antenna with casing, further to analyze the suitability of the antenna for indoor wireless applications

Compact Reconfigurable MIMO Antenna for 5G and Wi-Fi Applications

Compact Reconfigurable MIMO Antenna for 5G and Wi-Fi Applications

A reconfigurable wideband MIMO antenna combines RF energy harvesting

SummaryThis article introduces a novel and groundbreaking approach combining multiple‐input‐multiple‐output (MIMO) technology with radio frequency (RF) energy harvesting. The proposed antenna consists of two semi‐circular monopole antenna components, optimized with dimensions of 89 × 51.02 × 1.6 mm3, that share a common ground plane to achieve MIMO characteristics. A series of split‐ring resonators on the ground plane significantly enhances the isolation between the two radiating components. Band‐notched features are performed in the 3.5 GHz WiMAX and 5.5 GHz WLAN bands through modified C‐shaped slots in the radiating patch and two rectangular split‐ring resonators serving as parasitic devices near the feed line. The reconfiguration of band‐notching is made possible by controlling the modes of the embedded PIN diodes. The two antenna elements maintain mutual coupling below −18 dB from 1.5–13 GHz, achieving an impressive 158.62% impedance bandwidth. The antenna's efficiency and gain experience significant drop, indicating effective interference suppression at the center frequencies of the notch bands, and its performance in MIMO systems is assessed through parameters including envelope correlation coefficient, port isolation, radiation patterns, efficiency, gain, and diversity gain. The simulated properties of the designed antenna closely align with the measured outcomes, demonstrating its reliability and consistency. Moreover, the article evaluates the antenna's potential for RF energy harvesting, achieving a maximum harvested energy of 4.88 V. This proposed antenna can be used in multiple applications, like wideband, band‐notching MIMO, and RF energy harvesting. This proposed antenna is an efficient, reconfigurable wideband MIMO antenna with novel RF energy harvesting capability.

Achievable Rate Maximization Pattern Design for Reconfigurable MIMO Antenna Array

Reconfigurable multiple-input multiple-output can provide performance gains over traditional MIMO by reshaping the channels, i.e., introducing more channel realizations. In this paper, we focus on the achievable rate maximization pattern design for reconfigurable MIMO systems. Firstly, we introduce the matrix representation of pattern reconfigurable MIMO (PR-MIMO), based on which a pattern design problem is formulated. To further reveal the effect of the radiation pattern on the wireless channel, we consider pattern design for both the single-pattern case where the optimized radiation pattern is the same for all the antenna elements, and the multi-pattern case where different antenna elements can adopt different radiation patterns. For the single-pattern case, we show that the pattern design is equivalent to a redistribution of gains among all scattering paths, and an eigenvalue optimization based solution is obtained. For the multi-pattern case, we propose a sequential optimization framework with manifold optimization and eigenvalue decomposition to obtain near-optimal solutions. Numerical results validate the superiority of PR-MIMO systems over traditional MIMO in terms of achievable rate, and also show the effectiveness of the proposed solutions.

Reconfigurable grounds MIMO antenna with PIN diodes for 5G NR n3/n1/n40/n41/n77/n79 to X-bands

ABSTRACT The paper addresses the investigations of four elements MIMO antenna with reconfigurable grounds for 5 G NR n3/n1/n40/n41/n77/n79 to X-bands using PIN diodes. Initially, a single unit ultra wideband antenna is implemented, and then it is extended to 2 × 2 MIMO with reconfigurable grounds using one PIN diode. Later, the 4 × 4 MIMO antenna with reconfigurable grounds using six PIN diodes is developed. This study has the novelty that it gives the analysis and design of MIMO antennas switching between unconnected and connected grounds by the method of reconfiguration. The proposed 4 × 4 MIMO is fabricated on FR4 substrate with a volume of 0.485λ0 × 0.326λ0 × 0.0075λ0 mm3, where λ0 is calculated at a lowest resonating frequency. It has operating frequency bands of 1.4–1.6 GHz, 1.75–2.5 GHz and 2.7–13 GHz with connected grounds. The port isolation in the majority of the band is ≤ −15 dB. The inference is included on all the performance metrics. The fabricated MIMO performance is in line with simulated results and hence validates the observations of this research work. So, the proposed MIMO designs are compatible with 5 G wireless applications.

Bandwidth and frequency agile MIMO antenna for cognitive vehicular communications

SummaryA reconfigurable MIMO antenna for heterogeneous vehicular networks is reported in this paper. The frequency and bandwidth characteristics of the MIMO antenna can be reconfigured to meet multi‐standard and multi‐frequency requirements in automobiles. The antenna element evolved from an edge‐chamfered ultra‐wideband (UWB) antenna operating from 2.1 to &gt;15 GHz. The bandwidth reconfiguration is achieved through the selection of excitation paths connecting the feed and radiator. The feedline selection is performed using PIN diodes, making the antenna operate in three distinct modes, namely, UWB mode (Mode 1: 2.1–&gt;15 GHz), industrial, scientific and medical/Internet of Things (ISM/IoT) mode (Mode 2: 2.45 GHz), and wireless local area network (WLAN) mode (Mode 3: 5–6 GHz). The feed path corresponding to Mode 2 and Mode 3 is incorporated with a suitable filtering network to shape the frequency response of the antenna based on the user's requirements. Owing to the requirement of cognitive selection of frequency bands, the frequency tunability in Mode 2 is realized using varactor diodes. The varactor‐incorporated feed path reconfigures the center frequency between 2.45 and 3.5 GHz. The proposed MIMO antenna offers gain and total efficiency greater than 2.94 dBi and 76%, respectively. The prototype of the 4‐port MIMO antenna is being fabricated to test its functionality in real time.

Spectral efficiency enhancement by hybrid pre-coding technique for reconfigurable intelligent surfaces-based massive MIMO systems under variable CSI

Spectral efficiency enhancement by hybrid pre-coding technique for reconfigurable intelligent surfaces-based massive MIMO systems under variable CSI

On demand reconfigurable notch-based UWB MIMO antenna for wireless application

In this paper, on demand reconfigurable notch based UWB-MIMO antenna for wireless applications has been proposed. The proposed antenna consists of two square patch monopole radiators with inverted Z and extended U slots cut through them. Antenna offers good impedance matching (S11 < -10 dB) over the entire Ultra-Wide Band (2.9–13.4 GHz) spectrum. The connected ground structure is used to improve the isolation (S21 < -15 dB) over the entire operating band. Reconfigurability has been achieved using switching elements S1 and S2 which are inserted in the extended U slot and inverted Z slot in each radiator. When both the switches are OFF, notch mechanism is obtained on both the notches C band uplink (5.7 to 6.5 GHz) and C band downlink (3.6 to 4.2 GHz) simultaneously. When the Switch 1 is ON the notch is obtained at C band uplink (5.7 to 6.5 GHz) whereas when the Switch 2 is ON the notch is obtained at C band downlink (3.6 to 4.2 GHz). The proposed antenna offers a simulated bandwidth of 10.5 GHz along with a compact size of 34 × 20 × 1.6 mm 3 with efficient port isolation of more than −15 dB throughout the operating band. ECC and directive gain are less than 0.02 and more than 9.9 dBi respectively.

Compact Dual-polarized Reconfigurable MIMO Antenna Based on a Varactor Diode for 5G Mobile Terminal Applications

Compact Dual-polarized Reconfigurable MIMO Antenna Based on a Varactor Diode for 5G Mobile Terminal Applications

High-isolated, low correlation and wide frequency reconfigurable (2.1–4.2 GHz) MIMO antenna for cognitive radio applications

ABSTRACT This paper proposes a unique and small (2508 mm2) penta-band frequency agile MIMO antenna based on RF switches for cognitive radio mobile, WLAN, WiMAX, and wireless sensing applications. Three RF switches generate five resonant bands at 2.1, 3, 3.5, 4, and 4.2 GHz in four usable states-100, 011, 111, 100, and 000, respectively. The proposed antenna's fractional bandwidth was 4.95 % (simulated) and 5.5 % (measured) in state-000, 3.09 % (simulated) and 2.8 % (measured) at a lower frequency (2.1 GHz), 2.12 % (simulated) and 2 % (measured) at higher frequency (4.2 GHz) in state-100, 12.5 % (simulated) and 12 % (measured) in state-011, and 4.6 % (simulated) and 4.7 % (measured) in state-111. A large peak gain of 3.6 dB at 4 GHz, maximum isolation of 32.2 dB at 3.5 GHz, significant radiation efficiency of 93.7% at 4GHz is obtained. At 4 GHz, a strong peak gain of 3.6 dB, maximum isolation of 32.2 dB at 3.5 GHz, and considerable radiation efficiency of 93.7 % are realised. For this work, MIMO parameters such as ECC (approx. 0), DG (approx.10dB), TARC (<0.5), MEG (−12 dB < MEG (dB) < −3 dB) and CCL (< 0.5 bit/s/Hz) were achieved. The suggested antenna was simulated, constructed, and tested, and the simulated results were found to be very close to the experimental findings.

Optically Remote Control of Miniaturized 3D Reconfigurable CRLH Printed Self-Powered MIMO Antenna Array for 5G Applications.

A novel design of a reconfigurable MIMO antenna array of a 3D geometry-based solar cell integration that is operating at sub-6 GHz for self-power applications in a 5G modern wireless communication network. The proposed antenna array provides three main frequency bands around 3.6 GHz, 3.9 GHz, and 4.9 GHz, with excellent matching impedance of S11 ≤ -10 dB. The proposed MIMO array is constructed from four antenna elements arranged on a cubical structure to provide a low mutual coupling, below -20 dB, over all frequency bands of interest. Each antenna element is excited with a coplanar waveguide (CPW). The proposed radiation patterns are controlled with two optical switches of Light Dependent Resistors (LDRs). The proposed antenna array is fabricated and tested experimentally in terms of S-parameters, gain and radiation patterns. The maximum gain is found to be 3.6 dBi, 6.9 dBi, and 3.5 dBi at 3.6 GHz, 3.9 GHz, and 4.9 GHz, respectively. It is realized that the proposed array realizes a significant beam forming by splitting the antenna beam and changing the main lobe direction at 3.9 GHz after changing LDR switching statuses. Such an antenna array is found to be very applicable for femtocell wireless communication networks in the 5G systems.

Reconfigurable Intelligent Surface-Aided Cell-Free Massive MIMO with Low-Resolution ADCs: Secrecy Performance Analysis and Optimization

The secure communication in reconfigurable intelligent surface-aided cell-free massive MIMO system is investigated with low-resolution ADCs and with the existence of an active eavesdropper. Specifically, an aggregated channel estimation approach is applied to decrease the overhead required to estimate the channels. Using the available imperfect channel state information (CSI), the conjugate beamforming and random beamforming are applied at the APs and the RIS for downlink data transmission, respectively. The closed-form expression of the achievable secrecy rate is acquired to appraise the achievable secrecy performance using only the channel statistics. With the achievable analytical results, the impacts of the quantization bit of ADCs, channel estimation error, the number of RIS elements, and the number of the APs can be unveiled. Aiming to maximize the minimum achievable rate of all legitimate users subject to security constraints, the power control optimization scheme is first formulated. To tackle this nonconvex property of the proposed optimization problem, a path-following algorithm is then utilized to solve the initial problem with continuous approximations and iterative optimization. Numerical results are presented to verify the achieved results along with availability of the presented power allocation approach.

Optically remote‐controlled miniaturized 3D reconfigurable CRLH‐printed MIMO antenna array for 5G applications

AbstractA reconfigurable MIMO antenna array of a three‐dimensional geometry that is operating at sub‐6 GHz for 5G applications. The proposed antenna array provides a wideband with excellent matching impedance, S11 ≤ −10 dB, from 3.1 to 5.75 GHz. The proposed MIMO array is constructed from four antenna elements arranged on a cubical structure to provide a low mutual coupling, below −20 dB, over all frequency bands of interest. Each antenna element is excited with a coplanar waveguide. The proposed radiation patterns are controlled with two optical switches of light‐dependent resistors (LDRs). The antenna array is tested in terms of S‐parameters and radiation patterns. The maximum gain is found to be 3.6, 6.9, and 3.5 dBi at 3.6, 3.9, and 4.9 GHz, respectively. It is realized that the proposed array realizes a significant beam forming by splitting the antenna beam and changing the main lobe direction at 3.9 GHz after changing LDR switching statuses.

A Frequency Reconfigurable MIMO Antenna with Bandstop Filter Decoupling Network for Cognitive Communication.

A compact reconfigurable MIMO antenna was developed for cognitive radio applications in this research work. A bandstop filter-based decoupling network was employed in this MIMO antenna to keep mutual coupling at a minimum. A single PIN diode was connected in the filter configuration for the purpose of reconfiguration. Controlling the ON/OFF conditions of the PIN diode, it became possible to achieve a MIMO operating frequency of 4.75 GHz in mode 1 and 1.77 GHz in mode 2, respectively. At 4.75 GHz, isolation was 42.68 dB, while at 1.77 GHz, isolation was 26.52 dB. The proposed reconfigurable MIMO antenna achieved a peak gain and radiation efficiency of 6.63 dBi and 92.04 percent in mode 1 and 4.41 dBi and 89.64 percent in mode 2. MIMO characteristics such as an envelope correlation coefficient (ECC) less than 0.253, diversity gain (DG) greater than 9.675 dB, a mean effective gain (MEG) measurement ratio of less than 0.00388 dB, and channel capacity loss (CCL) of less than 0.06528 bits/s/Hz were measured for both operational frequency bands. To make it simple to integrate into small wireless devices, the overall size of the antenna is limited to .