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Single split-ring resonator loaded self-decoupled dual-polarized MIMO antenna for mid-band 5G and C-band applications

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Abstract

This paper presents the design and development of a dual-band and dual-polarized two-port multiple-input-multiple-output (MIMO) antenna for mid-band 5G (3.4–3.6 GHz), and C-band (4–8 GHz) applications. The antenna design is very simple and it mainly consists of a circular-shaped single split-ring resonator on the top side of the substrate which is coupled with the microstrip line feed line. The bottom side is comprised of a rectangular-shaped defected ground structure. Due to this dual-band response is obtained and the first band shows linear polarization and the second band provides circular polarization. The entire dimensions of the intended two-port MIMO antenna are 46 mm × 21 mm × 1.6 mm. The antenna measured results offer a wider impedance bandwidth (IBW) of 20.22% and 44.07% for the two bands centered at 3.54 GHz and 6.33 GHz respectively. Also, the proposed MIMO antenna shows minimum isolation of 15 dB for the two frequency bands with a smaller edge-to-edge spacing of 4 mm (0.04λ0) between the two antenna elements. Moreover, the second band provides an axial ratio bandwidth of 3.97% centered at 6.78 GHz. The antenna shows excellent IBW, good isolation between the single antenna elements without the use of any decoupling mechanism, better antenna gain, and improved envelope correlation coefficient by maintaining smaller antenna size compared to similar types of existing two-port MIMO antennas in literature.

Introduction

In the modern world of arising technologies and their associated applications, effective antennas with greater capacity are needed. The Multiple-Input-Multiple-Output (MIMO) antenna is the best candidate for higher transmission speed, wide-coverage, and higher signal security. The MIMO antennas have the higher potential to work in mid-band 5G (3.4–3.6 GHz) [1] as well as C-band (4.0–8.0 GHz) small satellite applications [2], are some of the prominent applications. Recently, more number researches are ongoing in the area compact MIMO antennas with improved isolation and better radiation performance. The most significant parameter governing the accomplishment of the MIMO antenna is the isolation between multiple antenna elements. Several techniques such as enabling reflectors in between the antenna elements [1], multilayer configuration [2], defected ground structure (DGS) [3], [4], neutralization lines [5], parasitic element loadings [6], [7], [8], [9], [10], substrate integrated waveguide (SIW) based structures [11], annular slot loadings [12], and meander loops [13], [14], electromagnetic bandgap (EBG) unit cell [15] structures are incorporated in the antennas to obtain higher isolation between the antenna elements in a MIMO antenna system.

Currently, the multiband MIMO antennas are gaining more interest in modern applications. A large number of MIMO antenna geometries are existing in various literature such as a two-element diversity antenna with metasurface acquires a higher volume of 83.8 mm × 83.8 mm × 15 mm [2], symmetrical single-feed patch elements and decoupling structure consists of H-shaped DGS [3], dual-band MIMO antenna is realized by the loading of λ/4 and λ/2 slot with a back-to-back slot arrangement for isolation enhancement [4], band-notched antenna with high inter-element isolation is implemented using parasitic elements using two monopole antenna comprises of radiating patch with slots and stepped ground plane [7], two truncated corner square patches and parasitic patches are implemented in [8], compact and closely spaced circular shaped ultra-wideband MIMO antenna using T-shaped stub and strips [9], two identical modified P-shaped semi-circular monopole radiators with a spacing 0.075λo utilizing rectangular strips for isolation improvement [10], textile MIMO antenna using SIW technology [11], inverted F-shape antenna combined with frequency-agile annular slots for isolation improvement [12], planar inverted-F antenna and cross-coupled semi-loop structure for isolation improvement [13], inverted-F antenna utilizes meandering and T-shaped slot is implemented for isolation enhancement [14], two rectangular patch antenna positioned opposite to each other with a separation of 10 mm with an EBG unit cell is introduced for isolation enhancement is explained in [15], two-port optically transparent MIMO antenna with slotted interconnected ring resonator [16], self-decoupled dual-band antenna pairs [17], orthogonally arranged monopole antenna elements with metal strips and shorting vias [18], and so on. Out of these antenna designs mentioned above, several antenna designs are implemented by using complex isolation schemes and also it suffers from higher antenna size (ref. [11], [12], [13], [14], [16], [17]), lower impedance bandwidth (IBW) (ref. [3], [4], [11], [14], [17], [18]), higher antenna profile (ref. [3], [17]), lower radiation efficiency (ref. [4], [11], [12], [17], [18]), and higher edge-to-edge antenna spacing (ref. [12], [14], [15], [16], [17]). Hence these antennas are not suitable for the current and future MIMO antenna systems.

In this work, a miniaturized dual-band and dual-polarized two-port MIMO antenna is designed and analyzed with ka = 1.88. The antenna compactness is accomplished due to the loading of the single split-ring resonator (S-SRR) combined with microstrip feed line on the top-side and DGS implementation in the backside ground. Due to this, wider IBW for the two bands and circular polarization (CP) radiation is obtained at the second band useful for mid-band 5G and C-band small satellite applications. Also, the edge-to-edge spacing between the two antenna elements is only 4 mm (0.04 λ0) with isolation better than 15 dB is obtained for the two frequency bands. The intended two-port MIMO antenna provides a compact size of 46 × 21 × 1.6 mm3 which is smaller in size compared with existing [3], [4], [11], [12], [13], [14], [16], [17], [18] two-port MIMO antenna configurations. Hence the intended MIMO antenna can work in mid-band 5G (3.4–3.6 GHz) and C-band (4.0–8.0 GHz) applications.

Section snippets

Design of the proposed two-element MIMO antenna

The three-dimensional top and bottom surface of the proposed two-port MIMO antenna arranged in parallel configuration is depicted in Fig. 1(a) and (b) respectively. Also, the schematic representation of the intended MIMO antenna top and the bottom view with dimensions are marked as shown in Fig. 2(a) and (b) respectively. The intended MIMO antenna primarily consists of port-1 and port-2 arranged in a parallel configuration. The antenna is designed on low-cost FR-4 substrate with a height of

Measurement results and discussions

The intended two-port MIMO antenna is fabricated using the photolithographic process and measurements are done using N9925A vector network analyzer. The measured and simulated scattering parameters (S-parameters) are depicted in Fig. 18(a). It shows a measured S11 and S22 bandwidths of 20.22% (3.18–3.90 GHz) and 44.07% (4.94–7.73 GHz) at the center frequencies of 3.54 GHz and 6.33 GHz respectively. Also, the measured isolation is better than 15 dB and 16 dB for two frequency bands. The antenna

MIMO antenna performance characteristics

For analyzing the diversity performance of the proposed MIMO antenna, the envelope correlation coefficient (ECC), diversity gain (DG), total active reflection coefficient (TARC) and channel capacity loss (CCL) are plotted in Fig. 21(a) and (b). The envelope correlation coefficient (ECC) is used to find the correlation between the different antennas in a multiple antenna system (i.e., in the proposed design, ECC is the correlation between antenna-1 and antenna-2). The typical value of ECC will

Conclusion

A compact (ka = 1.88) dual-polarized MIMO antenna is designed and experimentally verified. The antenna compactness and wider IBW are achieved by the loading of S-SRR and implementation of DGS. The antenna provides a compact size of 0.54 λ0 × 0.24 λ0 × 0.019 λ0 at the first resonating frequency of 3.54 GHz with overall physical dimensions of 46 mm × 21 mm × 1.6 mm. The intended MIMO antenna provides a wider IBW of 20.22% and 44.07% for the two bands with isolation more than 15 dB for the two

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors would like to acknowledge the Science and Engineering Research Board (SERB), Department of Science and Technology (DST), Government of India for financial support under grant number EEQ/2016/000023.

Mohammad Ameen was born in Kerala, India on October 07, 1990. He received B.Tech and M.Tech degree in Electronics and Communication Engineering from Mahatma Gandhi University, Kottayam, Kerala in 2012 and 2014 respectively. Currently he is working as a Project Associate-II in Defence Research and Development Organisation (DRDO), Govt. of India sponsored project and pursuing Ph.D. from Department of Electronics Engineering, Indian Institute of Technology (Indian School of Mines). Dhanbad, India.

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  • Cited by (0)

    Mohammad Ameen was born in Kerala, India on October 07, 1990. He received B.Tech and M.Tech degree in Electronics and Communication Engineering from Mahatma Gandhi University, Kottayam, Kerala in 2012 and 2014 respectively. Currently he is working as a Project Associate-II in Defence Research and Development Organisation (DRDO), Govt. of India sponsored project and pursuing Ph.D. from Department of Electronics Engineering, Indian Institute of Technology (Indian School of Mines). Dhanbad, India. He is currently serving as a student Coordinator of Intellectual Property Rights (IPR) at Centre for Innovation, Innovation and Entrepreneurship (CIIE), Indian Institute of Technology (ISM), Dhanbad. He is selected for the Young Scientist Award in the Union Radio Science General Assembly and Scientific Symposium (URSI GASS-2020), Rome, Italy, from August 29 to September 5, 2020. He is a potential reviewer of many journals and conferences such as IEEE Access, IET Microwaves Antennas and Propagation, IET Electronics Letters, IET Communications, Microwave and Optical Technology Letters, International Journal of RF & Microwave Computer Aided Engineering, AEU-International Journal of Electronics and Communication, IETE Journal of Research, etc. His current research interests involve Metamaterials, Electromagnetic Bandgap Structures, Artificial Magnetic Conductors, Frequency Selective Surfaces, Massive MIMO, Conformal dielectric resonator antennas, Circularly polarized antennas, Electrically small antennas, Metamaterial based sensors and its applications. He is reachable at [email protected].

    Ozair Ahmad was born in Patna, Bihar, India. He has got his Bachelor of Technology degree from Biju Patnaik University of Technology, Odisha. He received M. Tech in RF and Microwave Engineering from Indian institute of Technology (Indian School of Mines), Dhanbad during 2018. He has received fellowship from MHRD, Govt. of India during his M.Tech tenure. His current research includes design of multiband antennas, high gain multiple-input-multiple-output antennas, Artificial magnetic conductors, frequency selective surfaces. He is reachable at [email protected].

    Raghvendra Kumar Chaudhary is an Assistant Professor of the Department of Electronics Engineering, Indian Institute of Technology (ISM) Dhanbad, India. He received the B.Tech. from UIET Kanpur, India, in 2007, the M.Tech. from IIT(BHU) Varanasi, India, in 2009, and the PhD from IIT Kanpur, India in 2014. He has researched in developing the metamaterial antenna and dielectric resonator antenna (DRA). Development of the circularly polarized compact antenna is one of his major areas of contribution. He has published over 95 papers in top SCI Journals. Dr. Chaudhary has guided 04 PhD students and currently, 12 PhD students are working under him. He was a recipient of the Young Engineers Award (2019-20) of IEI (Institution of Engineers, India) and many Best Paper awards in different categories in national and international conferences, such as IEEE APACE Malaysia, PIERS Singapore, and ATMS India. He has served as the Chair for the IEEE Student Branch of Uttar Pradesh Section, in 2012–2013 and currently serving as a counsellor of the IEEE Student Branch of IIT(ISM) Dhanbad. Dr. Chaudhary is serving as an Associate Editor of IET Microwave Antennas & Propagation (UK), IEEE Access (USA), and Microwave and Optical Technology Letters, Wiley (USA). He is a Senior Member of IEEE and URSI, and potential reviewer of international journals such as the IEEE Transactions on Antennas and propagation, the IEEE Antennas and Wireless Propagation Letters, etc. He has also been featured interviewed by IET Electronics Letters, UK. His current research interests include MIMO and Cognitive Radio, reconfigurable metamaterial/metasurface for antenna and absorber design, circularly polarized DRA, and frequency reconfigurable active array antenna with beam steering.

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