Reconfigurable Multiple-input Multiple-output Antenna Research Articles

Reconfigurable MIMO antenna: previous advancements and the potential for future wireless communication

Abstract Future smart reconfigurable antennas (RAs) (Haupt R-L and Lanagan M (2013) Reconfigurable antennas. IEEE Antennas and Propagation Magazine 55, 49–61) will likely be fully multipurpose and controlled by software and equipped with machine learning skills that can discern and respond to alterations in the radio frequency environment. Cognitive radio utilizations will be accomplished using a new generation of antenna technology and communication protocols. The effective use of frequencies and the use of polarization diversity and radiation pattern reconfigurability to send data over existing congested frequencies will be major advantages for such applications. The usage of antennas that can be reconfigured in multiple-input multiple-output (MIMO) channels will enhance channel capacity while simultaneously improving channel efficiency and lowering costs (Christodoulou C-G, Tawk Y, Lane S-A and Erwin S-R (2012) Reconfigurable antennas for wireless and space applications. Proceedings of the IEEE 100, 2250–2261). There are a lot of antennas used both at the transmitter and at the receiver front end in a MIMO system. The benefit of employing such arrangements is that different types of information can be conveyed at a similar time, boosting the spectral efficiency of communication in a multipath situation. The coding rate, modulation level, and transmission signaling method of a MIMO system can all be changed in response to changing channel circumstances and user needs. In a MIMO context, polarization reconfigurable/frequency-reconfigurable/radiation pattern RA increase the degree of freedom and enhancing the system’s performance. The usage of such antennas greatly enhances capacity by enabling a choice of various polarization configurations and pattern diversity. Antenna arrays that can be reconfigured are also an appealing MIMO system solution that needs to retain robust communication channels, particularly in portable gadgets where the area is limited.

Frequency reconfigurable two-element MIMO antenna for cognitive radio and 5G new radio sub-6 GHz applications

Abstract In this paper, a compact two-element reconfigurable multiple-input multiple-output (MIMO) antenna for 5G new radio sub-6 GHz is presented and discussed. The proposed MIMO antenna has four frequency operating modes: a wideband operating mode (2.41–6 GHz), a wideband operating mode with a notching band at 3.5 GHz (3.2–3.66 GHz), a low-pass filter mode that filters the higher frequencies with a wide operating band from 2.41 GHz to 4.7 GHz, and a dual-band mode with two operating narrow bands (2.41–3.16 GHz and 3.64–4.7 GHz). To improve the isolation over the entire operating band, a strip line connecting the two ground planes of the two antenna elements has been used. To validate the proposed approach, different prototypes have been fabricated and measured. The simulation results are in good agreement with the measurement results. The proposed antenna has good MIMO diversity performance with a maximum gain of 4.64 dBi. The minimum isolation is 18 dB for the four operating modes, while a measured envelope correlation coefficient of less than 0.008 is achieved. The diversity gain is near 10 dB for various operating modes. The antenna is suitable for cognitive radio and 5G sub-6 GHz applications.

A compact 4 × 4 reconfigurable MIMO antenna design with adjustable suppression of certain frequency bands within the UWB frequency range

This paper introduces a novel 4 × 4 multiple-input multiple-output (MIMO) antenna design with a reconfigurable operating band within the Ultra-Wideband (UWB) range. The antenna consists of four rectangular radiating elements arranged symmetrically and orthogonally on a defected ground plane. The design incorporates switching elements that allow adjustable and reversible suppression of specific bands within the UWB range, enabling the antenna to operate in three different modes: UWB, X-band, and dual-band with sub-6GHz and X-band. Thus, a single UWB antenna can serve as three different antennas, suppressing certain frequencies as required. To mitigate mutual coupling between adjacent antenna elements, four thin stubs are strategically placed at the center of the ground plane, forming a square with open corners. When one of the antenna elements is excited, this structure acts as an insulator, ensuring that the surface current is confined solely to that element and not induced in others. Experimental verification of the proposed design was performed by fabricating and testing the antenna. The results indicated good agreement between simulation and measurement data for various parameters, including S-parameters, radiation patterns, gains, and MIMO parameters such as envelope correlation coefficients (ECC), diversity gain (DG), mean effective gain (MEG), and total active reflection coefficient (TARC).

Design of Dual-Port Pattern-Reconfigurable MIMO Antenna With Four Operating States Using the TCM

Based on the theory of characteristic modes (TCM), this letter presents a novel pattern-reconfigurable dual-port multiple-input–multiple-output (MIMO) antenna with four operating states at the 2.4 GHz ISM band. The proposed antenna consists of the rectangular platform (RP), excitation units, and reconfigurable feeding network. Four elaborated characteristic modes (CMs) of the RP can be stimulated effectively by six groups of balanced inductive exciters. By using a reconfigurable feeding network controlled by four switches, two orthogonal CMs associated with the two ports are switched, and four possible operating states for the reconfigurable MIMO antenna are generated. In order to demonstrate the proposed TCM-based conceptual design, a prototype is fabricated and the measured results agree well with the simulated ones. Furthermore, the port isolations of the proposed MIMO antenna are higher than 36 dB.

A novel four port reconfigurable filtering MIMO antenna

AbstractThis paper presents the design and implementation of a novel four‐port multiple input multiple output (MIMO) antenna with reconfigurable filtering characteristics. The proposed filtering MIMO antenna is constructed using a super wideband (SWB) monopole. The feedline of the monopole radiator is integrated with a microstrip filter network. Reconfigurable filtering characteristics are realized using a feed selection network making the antenna work at two modes viz. SWB mode (2.2 to over 20 GHz) and dual narrow‐band (d‐NB) mode (2.45 and 5.8 GHz). The feed selection is accomplished using a PIN diode. An interlocked four‐port MIMO antenna is then constructed using the proposed reconfigurable filtering monopole antenna. The proposed antenna exhibits an average gain greater than 5.2 dBi in both operating modes and has total efficiency greater than 80%. The MIMO parameters such as envelope correlation coefficient (ECC), diversity gain (DG), and mean effective gain (MEG) are evaluated and presented. The prototype MIMO antenna is fabricated and the experimental results are validated in real‐time. The proposed reconfigurable MIMO antenna is suitable for wireless local area network (WLAN), Internet of things (IoT), dedicated short‐range communication (DSRC), ultra‐wideband (UWB), and SWB applications in the automotive scenario.

Bandstop Filter Decoupling Technique for Miniaturized Reconfigurable MIMO Antenna

In this work, a switchable bandstop filter is used as a decoupling structure for developing a miniaturized reconfigurable multiple input multiple output (MIMO) antenna. Initially, a dual band ((2.43-2.60 GHz and 3.51-3.79 GHz)) single monopole antenna structure is developed on FR4 substrate. Then the single monopole antenna and its replica are accommodated in a small space with an edge to edge separation distance of 11 mm to form a 2 port MIMO antenna. Now, a switchable bandstop filter is used as a decoupling network between two closely spaced monopole antenna elements to prevent mutual coupling and reconfigure the antenna characteristics. The dual pole switchable bandstop filter is configured in such a way that one of its poles lies at 2.5 GHz in one state (Mode 1) and at 3.68 GHz in another state (Mode 2) under the switching action of two PIN diodes. Controlling the ON/OFF states of the PIN diodes in the bandstop filter, high isolation is achieved alternately in lower (2.43-2.60 GHz) and upper (3.51-3.79 GHz) frequency bands of the MIMO antenna. Also, stub network is used to improve impedance matching in the upper frequency band. The proposed isolation technique helps the antenna to yield high isolation (>30 dB), fair gain (>2.97 dBi), reasonable radiation efficiency (>86.8 %), low envelope correlation coefficient (< 0.16), high diversity gain (DG >9.88 dB), low Mean effective gain ratio (MEG 1/MEG 2 < 0.05 dB) and low channel capacity loss (CCL < 0.06 bits/s/Hz) for both the operating frequency bands. The overall dimension of the antenna is restricted to 44mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 22mm ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.36\lambda _{o}\,\,\times \,\,0.18\lambda _{o}$ </tex-math></inline-formula> ) for its easy integration in compact wireless devices. This type of reconfigurable MIMO antenna is best suited for cognitive radio communication, which promotes efficient spectrum utilization.

Frequency reconfigurable Yagi‐like MIMO antenna system with a wideband reflector

A compact single layer frequency reconfigurable Yagi-like multiple-input multiple-output (MIMO) antenna system is presented based on a half-ring closed loop slot excitation. The traditional omnidirectional pattern of a slot antenna is made directional by using a single slot-based complementary wideband reflector (CWBR) element. The proposed CWBR is compact in size, simple in construction, and is based on a single-layer geometry unlike complex multi-layer reflectors used in the literature. It improves the front-to-back ratio between 5 and 17 dB in the entire frequency range covering 2.5–4.5 GHz. The proposed reconfigurable MIMO antenna system covers the LTE and WiMAX bands with a minimum measured bandwidth of 200 MHz per covered bands. The frequency reconfigurability is achieved by reactively loading the slot loop with varactor diodes. The overall size of the proposed antenna system is 40 × 100 × 0.76 mm 3 , making it suitable for tablet handheld devices and access points. It has a maximum measured peak gain of 5 dBi and total measured radiation efficiency of 78%. The proposed MIMO antenna system has port isolation of > 10 dB within the entire band of operation. The radiation patterns are isolated in space from each other and ensure very low envelope correlation coefficient.

Frequency reconfigurable dual-band MIMO antenna using pentagon slot resonator with improved bandwidth

In this paper, multiple-input–multiple output (MIMO) antenna with dual-band frequency reconfiguration is presented. The proposed antenna consists of two symmetrical pentagon radiating elements. These radiating elements support bands of 1.5 GHz (GPS) and 2.4 GHz (Wi-Fi) frequency. The two PIN diodes are appropriately located on slot line in order to control the current flowing through the radiator. All simulated results are compared and confirmed with measured results. The antenna has VSWR ⩽1.8 and isolation of −28 dB. The advantage of this antenna is that bandwidth is increased by switching of PIN diode in the range from 80 MHz up to maximum 300 MHz. These characteristics demonstrate that proposed antenna is an attractive solution for a multimode application such as GPS, Wi-Fi routers, vehicular communication, etc. where wideband is required.

Design of compact frequency reconfigurable planar invert‐F antenna for green wireless communications

This study proposes a single frequency reconfigurable planar invert-F antenna (FRPIFA) using PIN diodes based on the changes of shorting pin positions. The single FRPIFA operates in four configurations which cover the bands of GSM 900/GSM 850, GPS 1575, GSM 1800/GSM 1900 and UMTS (Universal Mobile Telecommunication System) with peak gains of −7.24, 2.30, 2.98 and 3.53 dBi, respectively. Furthermore, a frequency reconfigurable multiple-input multiple-output (MIMO) antenna consisting of two single reconfigurable ones with a distance of half-wavelength is presented. By switching the PIN diodes, the reconfigurable MIMO antenna obtains four different configurations. For MIMO antenna, results of the operating bands, gains, radiation patterns are similar to those of the reconfigurable single one. The MIMO antenna achieves a high isolation with |S21| less than −20 dB in all operating bands. The simulated results of S-parameters of the antennas are in good agreement with measurements. The proposed compact single and MIMO antennas are suitable for green smart wireless communication systems.

A Pattern Reconfigurable Chassis-Mode MIMO Antenna

Reconfigurable multiple-input multiple-output (MIMO) antennas have the potential to improve the performance of a MIMO antenna system operating in a dynamic environment. This paper presents a reconfigurable MIMO antenna that utilizes two tunable parasitic elements that manipulate the characteristic modes of the structure to provide pattern diversity. Simulation studies and calculation of envelope correlation coefficients from this two-port antenna confirm that the radiation patterns are orthogonal to each other in each of the two states of the antenna, as well as between the two states. Measured two-port S-parameters of a prototype employing switched PIN diode loading correspond well with simulations. Radiation pattern measurements in the two principal planes indicate overall correlation with simulations.