Microsoft Word - ETASR_V13_N1_pp9893-9898 Engineering, Technology & Applied Science Research Vol. 13, No. 1, 2023, 9893-9898 9893 www.etasr.com Sarade & Ruikar: Development of a UWB Multiband MIMO Antenna with Enhanced Isolation and … Development of Two UWB Multiband MIMO Antennas with Enhanced Isolation and Cross- Correlation Shrenik Sarade Electronics Engineering Department, Walchand College of Engineering, India shreniks2k7@rediffmail.com (corresponding author) Sachin Ruikar Electronics Engineering Department, Walchand College of Engineering, India sachin.ruikar@walchandsangli.ac.in Received: 17 October 2022 | Revised: 4 November 2022 and 17 November 2022 | Accepted: 19 November 2022 ABSTRACT An Ultra-Wide Band (UWB) MIMO antenna working at millimeter-wave is proposed in this research. It is composed of eight radiating elements with various shapes. It is designed with a rectangular structure and various carved slots. The carved slots are used to increase the antenna's bandwidth. The antenna's radiating elements are placed near one another, and thus, isolation is widespread. In order to improve the isolation of the MIMO antenna, parasitic elements and a defective ground structure are used. Antenna parameters such as Correlation Coefficient (CC), Envelope Correlation Coefficient (ECC), Diversity Gain (DG), and Total Active Reflection Coefficient (TARC) depend on the isolation. Parasitic elements with a rectangular form are positioned between the radiating patches. Rectangular-shaped ground structures with defects comprise the ground plane. An FR-4 substrate is used to fabricate the antenna. The analysis of the antenna shows that there is less than -14dB return loss, less than -40dB isolation, less than 0.0010 cross- correlation, less than 0.10 TARC, and higher than 500MHz bandwidth. The antenna uses a fractional bandwidth higher than 35% (UWB) for the 6GHz frequency and operates on a variety of bands. This antenna is suitable for many different wireless system applications. Keywords-MIMO; UWB;DGS; TARC; CC; ECC; DG I. INTRODUCTION Modern antenna technology relies heavily on Multiple Input-Multiple Output (MIMO) antennas with several antennas in both transmitter and receiver. MIMO antenna systems increase the poor data rate of the Single Input-Single Output (SISO) system. Depending on the number of patches in the antenna, the data rate of the MIMO antenna increases linearly. Return loss, isolation, Correlation Coefficient (CC), and Total Active Reflection Coefficient (TARC) represent a MIMO antenna's performance. Multiple radiating patches are arranged on the same substrate in a MIMO antenna [1]. The radiating elements are positioned near one another. The isolation and the CC are influenced by the close proximity of the rectangular radiating patches. The data rate is reduced by the isolation. The isolation, CC, and data rate of the antennas all need to be improved. Various techniques, such as Defective Ground Structure (DGS), Parasitic Elements (PEs), metamaterials, Decoupling Structures (DSs), and Electromagnetic Band Gap (EBG) are used to increase isolation and CC. In the ground plane, carved holes of different shapes are employed in DGS methods [2-7]. In order to promote isolation, a decoupling structure is built that isolates the input of the radiating patches from the corresponding network arrangement in [8-12]. To increase the isolation between the patches, parasitic components are utilized in [13–18]. Using the literature mentioned above, it is necessary to create a MIMO antenna that operates on a multiband application with an ultra-wide bandwidth, improved TARC, and better cross correlation. In previous works, the same shaped radiating elements were used to design an MIMO antenna, whereas the cross correlation (CC and ECC) between the radiating elements was high. In this study, a 2-MIMO antenna with a variety of shapes is proposed. The antenna is developed using radiating elements of different shapes. The designed antenna operates on a multiband and its bandwidth is UWB. For bandwidth improvement, a rectangular shaped cut slot is introduced between the radiating elements of the antenna. The isolation between the radiating elements is improved using DGS and PEs. Antenna parameters such as isolation, cross correlation (CC and ECC), and TARC depend on isolation. Engineering, Technology & Applied Science Research Vol. 13, No. 1, 2023, 9893-9898 9894 www.etasr.com Sarade & Ruikar: Development of a UWB Multiband MIMO Antenna with Enhanced Isolation and … The novelty of the current work is that the radiating elements are developed in different shapes, the rectangular shaped DGS cut slot and PEs are designed for the improvement of isolation, CC, ECC, TARC, and DG. For the improvement of the bandwidth, different rectangular cut slots are designed and introduced in the radiating elements. II. DESIGN OF A MASSIVE MIMO ANTENNA USING DEFECTIVE GROUND STRUCTURE (DGS) In this section, the design of the massive MIMO antenna is explained in detail. The designed antenna comprises 8 rectangular radiating patches with distinct cut slots for the 6GHz frequency with the antenna dimensions, as shown in Figure 1. The antenna is analyzed and fabricated using an FR-4 substrate with 1.6mm height (h) and 4.4 dielectric constant. The radiating element's geometrical features, such as length (Lp) and width (Wp) have been created using the rectangular radiating patch transmission line model [21-23] (Table I). Table I shows the measurements of the 8 radiating elements with varying cut slots. A rectangular cut slot [21-22] is placed in the radiating elements P1 to P8. Patch 1 has rectangular cut slots-1 and 2 (CS-1 and 2). Patches 2, 3, and 7 have the rectangular cut slot-2. Cut slot-3 is placed in patches 6 and 8. In patch 4, rectangular cut slot-1 is introduced. Patch 5 introduces rectangular cut slots-1 and 3 (CS-1 and 3). The radiating elements of the antenna are excited using an Inset Feed Line (IFL) [21-22]. The fabricated antenna structure is shown in Figure 3. The antenna is fabricated on the FR-4 substrate. The radiating elements of the antenna are placed close to each other. Therefore, the isolation between the radiating elements is high. Isolation of the antenna affects the performance parameters of the antenna [21-22]. Fig. 1. The dimensions of a developed massive MIMO antenna (top side). Fig. 2. The dimensions of a ground plane (back side) of the antenna. Engineering, Technology & Applied Science Research Vol. 13, No. 1, 2023, 9893-9898 9895 www.etasr.com Sarade & Ruikar: Development of a UWB Multiband MIMO Antenna with Enhanced Isolation and … Fig. 3. Fabricated top side of a massive MIMO antenna. TABLE I. MIMO ANTENNA DIMENSIONS Parameter Dimensions (mm) Patch length (LP) 11.38 Patch width (WP) 15.21 Width of IFL N = 6.41 Length of IFL M= 2.942 Width of cut slot-1 N = 6.41 Length of cut slot-1 M= 2.942 Width of cut slot-2 M= 2.942 Length of cut slot-2 N = 6.41 Width of cut slot-3 K = 12.69 Length of cut slot-3 M= 2.942 Length of a substrate LG= 32.58 Width of a substrate WG = 74 Length of a DGS cut slot A = 5.884 Width of a DGS cut slot B = 6.38 Fig. 4. Fabricated back side (ground plane) of a massive MIMO antenna. Hence, there is a requirement to improve the isolation between the radiating elements. For isolation improvement, the DGS cut slots G1 to G8 [2-7] are introduced in the ground plane as shown in Figure 2, whereas the fabrication of the ground plane is shown in Figure 4. The dimensions of the ground plane with DGS are shown in Table I. The result analysis of the antenna (for radiating elements-1 and 4) is shown in Figures 5 and 6. The antenna parameters are tested in the Vector Network Analyser (VNA). The analysis shows -14.40dB return loss and -42.72dB isolation have been measured in the -6dB line of return loss. At the -6dB line of return loss, the antenna operates on the frequency band of 0.33GHz-7.5GHz. This antenna is operated on UWB. The Voltage Standing Wave Ratio (VSWR) is illustrated in Figure 7. The VSWR for the antenna is less than 3.65dB. Fig. 5. Result of return loss S11 and isolation. Fig. 6. Result of return loss S44 and isolation. Fig. 7. VSWR of radiating elements of the antenna. Fig. 8. Radiation pattern of the antenna. Engineering, Technology & Applied Science Research Vol. 13, No. 1, 2023, 9893-9898 9896 www.etasr.com Sarade & Ruikar: Development of a UWB Multiband MIMO Antenna with Enhanced Isolation and … Figure 8 shows the radiation pattern for the gain of the antenna. The gains G1, G2 and G3 of the antenna are measured at ɸ=0 0 , ɸ=90 0 and ɸ=180 0 , respectively. The obtained gain of the antenna is 1.54dB. The antenna parameters, such as TARC, CC, ECC, and DG depend on the return loss and isolation [21- 22]. The analysis of the antenna shows CC less than 0.153, ECC less than 0.0237, TARC less than 0.137 (-8.63dB), and 9.99 DG. III. DESIGN OF THE MASSIVE MIMO ANTENNA USING PARASITIC ELEMENTS In this section, the massive MIMO antenna is designed using PEs for the frequency of 6GHz as shown in Figure 10. It consists of 8 radiating elements (Patch 1 to 8), which are designed using a rectangular shaped transmission line model [21-23]. Radiating elements 2, 4, 7, and 8 have rectangular cut slots. The radiating elements are placed close to each other and the isolation between them is high. For the isolation enhancement between the radiating elements, rectangular shaped PEs (P1 to P14) are placed among them [21-23]. The dimensions of the antenna are shown in Figure 9 and Table II. The PEs are used to negate parts of the coupled field between the radiating elements because they create the opposite coupling field, which lessens the original field and hence reduces the total coupling on the antenna. The PE structure and the radiating patch are not physically related [22]. Figure 9 exhibits the fabricated antenna (top side). This antenna is fabricated on the FR-4 substrate which has a 4.4 dielectric constant and 1.6mm height. The fabricated ground plane (back side) of the antenna is shown in Figure 11. The ground plane has 36.522mm length (LSUB) and 90mm width (WSUB). The result analysis of the antenna (for radiating elements-2 and 6) is shown in Figures 12 and 13. The antenna parameters are tested in the VNA. The measured return loss and isolation in the -6dB line of return loss are -13.96dB and -46.46dB, respectively. At the -6dB line of return loss, the antenna operates on two frequency bands, namely, 0.82-1.76GHz and 3.03-7.5GHz. This antenna operates on UWB. Figure 14 shows the radiation pattern of the gains of the antenna. The gains G1, G2 and G3 of the antenna are measured at ɸ=0 0 , ɸ=90 0 , and ɸ=180 0 , respectively. The obtained gain of the antenna is 2.73dB. The ECC is less than 0.001, CC is less than 0.01, DG is close to 10, and TARC is less than 0.015 (-8.23dB) [21-23]. TABLE II. DIMENSIONS OF A MASSIVE MIMO ANTENNA USING PES Parameter Dimensions (mm) Patch length (Lrrp) 11.34 Patch width (Wrrp) 15.234 Width of IFL B = 6.41 Length of IFL A= 2.942 Width of cut slot B = 6.41 Length of cut slot A= 2.942 PE width (P1 to P10) D= 2.942 PE length (P1 to P10) C= 11.34 PE width (P11 to P14) E= 15.234 PE length (P11 to P14) D= 2.942 Length of substrate LSUB= 36.522 Width of substrate WSUB = 90 Fig. 9. The fabricated MIMO antenna (top side). Fig. 10. Dimensions of the massive MIMO antenna using PEs. Engineering, Technology & Applied Science Research Vol. 13, No. 1, 2023, 9893-9898 9897 www.etasr.com Sarade & Ruikar: Development of a UWB Multiband MIMO Antenna with Enhanced Isolation and … Fig. 11. The fabricated MIMO antenna (back side-ground plane). Fig. 12. Result analysis of return loss S22 and isolation. Fig. 13. Return loss S66 and isolation. Fig. 14. Radiation pattern of the antenna. IV. ANTENNA PERFORMANCE COMPARISON The major contribution of the designed antenna is the different-shaped radiating elements. The antenna parameters are enhanced using two different techniques, namely, DGS and PEs. The designed antenna can operate on various UWB applications. The analysis shows that the cross correlation and TARC are better than the ones reported in previous research works. The comparison of the proposed antenna parameters with the other research works is shown in Table III. The proposed antenna is developed with 8 differently shaped radiating elements. It operates on a multiband frequency with a wide bandwidth. TABLE III. COMPARISON OF THE PROPOSED WORK WITH OTHER WORKS Ref Method Parameter values Frequency band and bandwidth Radiating patches [2] DGS -10 dB RL, -12dB isolation Single band and narrow band 8 same shaped radiating patches [8] DS -20 dB RL, -15dB isolation Dual band and narrow band 8 same shaped radiating patches [13] PE -10 dB RL, -10dB isolation Dual band and wide band 8 same shaped radiating patches Proposed (section II) DGS -14.40 dB RL, -42.72dB isolation 0.33-7.5GHz and UWB with better cross correlation 8 radiating patches of different shapes Proposed (section III) PE -13.96 dB RL, -46.46dB isolation 0.82-1.76GHz and 3.03-7.5GHz and UWB with better cross correlation 8 radiating patches of different shapes V. CONCLUSION In this paper, two MIMO antennas were designed. First, an antenna was developed using the DGS technique. The isolation, CC, ECC, TARC, DG, and channel capacity of the antenna were enhanced with the use of DGS. The DGS cut slots were introduced in the ground plane of the antenna. The analysis shows -14.40dB return loss and -42.72dB isolation measured in the -6dB line of return loss. At that line, the antenna operates on the frequency band of 0.33-7.5GHz. This antenna is operated on multiband applications with ultra-wide bandwidth. Another antenna was developed using PEs. The antenna parameters CC, isolation, ECC, TARC, DG, and channel capacity were enhanced. The PEs were placed between the radiating elements. The analysis shows -13.96 dB return loss and -46.46dB isolation measured in the -6dB line of return loss, in which the antenna operates on two frequency bands, namely 0.82-1.76GHz and 3.03-7.5GHz. REFERENCES [1] Z. A. 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Ruikar, "Development of a Wide Bandwidth Massive Eight Dissimilar Radiating Element Multiband MIMO Antenna for mm-Wave Application," Engineering, Technology & Applied Science Research, vol. 12, no. 5, pp. 9166–9171, Oct. 2022, https://doi.org/10.48084/etasr.5133. [23] C. A. Balanis, Antenna Theory: Analysis and Design, 3rd ed. Hoboken, NJ, USA: Wiley, 2005. AUTHORS PROFILE Shrenik Sarade has received the degree in Electronics Engineering from PVPIT, Budhagaon, Sangli, under the aegis of Shivaji University, Kolhapur, in 2007. He has received the postgraduate degree in Electronics Engineering from TKIET, Warananagar, Shivaji University, and Kolhapur, India in 2014. He is pursuing his PhD in Electronics Engineering under WCE, Sangli, affiliated to Shivaji University, Kolhapur. Sachin Ruikar has received the degree in Electronics and Telecommunication from GCE, Aurangabad, in 1998. He has received a postgraduate degree in Electronics and Telecommunication Engineering from COEP, Pune University, India in 2002. He has completed his PhD in Electronics in the Shri Guru Gobind Singh Institute of Engineering Technology, SRTMU Nanded, in 2013. Presently, he is working as an Associate Professor in Electronics Engineering at WCE, Sangli, India. His research interests include image denoising with wavelet transforms, image fusion, image painting, and image superresolution