Design & Development of 5G Antenna literature survey (2).pptx

5g antenna literature survey

1. Literature Survey on Design & Development of 5G Antennas Presented By:- Supervisor:- Deepak Agrawal Prof.(Dr.) Mithilesh Kumar

2. Antenna-Introduction The antennas are an essential part of any wireless system. According to the IEEE Standard Definition of terms for Antennas, an antenna is defined as “a means for radiating and receiving radio waves” An antenna is an electrical conductor or system of conductors Transmission - radiates electromagnetic energy into space Reception - collects electromagnetic energy from space In two-way communication, the same antenna can be used for transmission and reception

3. Schematic Diagram of Basic Antenna Parameters

4. Antenna Types Electrically small antennas R e s on a n t a nt e n nas B r oa d band a n t enn a s Ape r tu r e a n t e n nas A r r a y a n t enn a s Dipole Folded Dipole Monopole Loop Helical Turnstile Dish Y a g i - U da ( p a r a s i tic a r r a y s ) Pha s ed A r r a y s Microstrip Patch R F I D T ag A n t enn a s UWB Antennas W e a r able a n t enna S m a r t a n t enn a s

5. Mobile Telephony

6. What is 5G? Next Generation Mobile Network Current Generation: 4G LTE 1G 2G 3G 4G 5G Mid 1980s 1990s 2000s 2010s 2020s analog voice Digital voice + Simple data Mobile broadband Mobile Internet More & faster

7. Microstrip Patch Antenna Antenna made from patches of conducting material on a dielectric substrate above a ground plane.

8. Advantages & Disadvantages ADVANTAGES Small Size, low cost & weight. Ease of Installation. Does not give rise to Aerodynamic drag, when used in aircrafts. Low profile Antennas. Can be easily mounted to metallic conduc t or or o t h er s ur fa c e s . No space for feed line required. The feed line can be placed behind the ground plane. Compatible with MMIC designs They allow the use of additional tuning elements like pins or varactor diodes between the patch and the ground plane. DISADVANTAGES Low efficiency. Small Bandwidth. Typically a few Percent. Low g ain Low power handling capability

9. Frequency Bands of 5G below 6 GHz (FR1)) Frequency Bands of 5G above 6 GHz (FR2)

10. Specifications of 5G Technology

11. 5G Usage Scenarios as per 3GPP Enhanced Mobile Broadband ( eMBB ):- Provides ultra high speed indoor and outdoor connection Massive Machine Type Communications ( mMTC ) Supports Internet of Things Ultra-reliable and Low Latency Communications( uRLLC ) For Remote Medical Surgery, Safety in Transportation & Wireless control of manufacturing process

12. 5G Antenna Classification Based on Input Output Ports

13. 5G Antenna Classification Based on Input Output Ports Single Input Single Output (SISO): The SISO antenna is easy to design and implement. Also, it can be easily integrated into 5G communication devices. To achieve a high gain, the size of a single element antenna is large. At above 6 GHz frequency bands, the signals suffer from higher propagation losses and quality of service degrades.

14. 5G Antenna Classification Based on Input Output Ports Multiple I nput Multiple Output (MIM O) : The wireless communication is prone to interference, multipath fading, and radiation losses. It becomes severe at higher frequencies. To overcome these issues, the utilization of multiple input multiple output (MIMO) antennas becomes very important as it enhances the transmission range without increasing the signal power. MIMO design can be used in 5G to achieve low latency, maximum throughput, and large efficiency. In MIMO, more signals can be launched intelligently by using multiple antennas and thus enhancing channel capacity significantly. The method used to reduce the number of an antenna in MIMO is to use multiband antennas that provide coverage of different wireless app lications .

15. 5G Antenna Classification Based on Input Output Ports The MIMO antennas can be classified depending upon their frequency band as wideband and multiband antennas. Different types of enhancement techniques are used in various antenna structures to increase the gain, improve isolation (mutual coupling) among antennas, b a n dw i d t h, envelop correlation coefficient (ECC), and efficiency.

16. CLASSIFICATION BASED ON ANTENNA TYPES Another important method of classification can be based on antenna types as shown in Figure. Monopole Antenna: Dipole Antenna: Magneto-Electric (ME) Dipole Antenna: Loop Antenna: Antipodal Vivaldi Antenna (AVA): Fractal Antenna: Inverted F Antenna (IFA): Planar Inverted F Antenna (PIFA):

17. Advantages and Disadvantages of Antenna Types

18. 5G Antenna Performance Enhancement Techniques Substrate Selection Corrugation Multi-element Dielectric Lens Decoupling Techniques

19. Substrate Choice : The main requirement of an antenna implementation is the appropriate selection of a substrate. To increase gain and reduce power loss a substrate with less relative permittivity and low loss tangent must be selected. Corrugation: The corrugation means removal of a metal part (rectangular, sine, triangular, or square shape) from the edge of a radiator. It helps to improve bandwidth and front to back ratio. Multi-element: The gain of an antenna can be increased by the multi- element antenna. I t a ls o enhan c es the a n t enna b a ndwi d th a nd e ff ic ien c y .

20. Dielectric Lens: Electrostatic radiation is transmitted in one direction by the dielectric lens which leads to increase in gain and directivity of an antenna. Mutual Coupling Reduction Techniques: In multielement antenna design, the antenna elements effects the performance of each other. To reduce this, incorporate different mutual coupling techniques in the MIMO antenna which is also named as isolation or decoupling techniques in the literature.

21. Decoupling Techniques Neutralization Lines Decoupling Network Electromagnetic Band gap (EBG) Structure Dielectric Resonator Defected Ground Structure (DGS) Meta-Material Slot Elements Complementary Split Ring Resonators (CSRR) Frequency Reconfigurable

22. Neutralization Lines : Using metallic slit or lumped element, neutralization lines pass electromagnetic waves between antenna elements to reduce mutual coupling. It reduces the antenna area and improves bandwidth when connected between ground planes. D e c oupling N e t w o r k : In decoupling network, cross admittance gets transformed to purely imaginary value by adding discrete components or transmission lines. This technique employs a plane decoupling network which acts as a resonator to reduce mutual coupling. Electromagnetic Bandgap (EBG) Structure: EBG structure is made up of dielectric or metallic material and having a periodic arrangement. EBG structure provides low mutual coupling and high efficiency. Dielectric Resonator: An antenna that contains dielectric resonator is called as dielectric resonator antennas (DRA). DRA provides high gain, high radiation efficiency, and low loss. DRA can also provide high isolation with dual-band property. Defected Ground Structure (DGS): It is the structure where the slots or defects consolidated on the ground plane of the antenna. DGS can be used to provide maximum efficiency, low m utu a l c ouplin g , a nd w ide b a n d w idt h.

23. Metamaterial: It contains an electromagnetic characteristic. Different types of metamaterials are a single negative, electromagnetic, electromagnetic bandgap, double negative, anisotropic, isotropic, terahertz, chiral, tunable, photonic, frequency selective surface based, nonlinear, and tunable me t a ma t e r i a l . Metamaterials are designed manually by using two or more materials. Using metamaterial, it is possible to have an antenna with low mutual coupling, high gain, bandwidth, and compact size of an antenna. Slot Elements: It is used to enhance impedance bandwidth using the coupling method in the ground plane or the radiation patch. The slot antenna is used to provide wide bandwidth, high gain, high efficiency, and high mutual coupling value Complementary Split Ring Resonators (CSRR): CSRR is used for isolation improvement, to perform filtering function, and to provide lower mutual coupling. CSRRs are also used to provide high efficiency with miniaturizing the size of the antenna. CSRR is made up of two concentric ring structure with slots opposite to each other. Frequency Reconfigurable: It is based on switching techniques. In reconfigurable antenna to increase frequency range and to increase envelop correlation coefficient; varactor diodes, MEMS switches, and p- i -n are used. The reconfigurable antenna structure can provide lower mutual coupling, a high value of diversity gain, and efficiency.

24. SISO WIDEBAND ANTENNAS These antennas are either a single element or multi-element. So, the SISO antennas for 5G applications can be categorized into a single element and multi-element antennas. MULTI-ELEMENT ANTENNAS It provides the most important requirements of 5G antennas are high gain, stable radiation pattern, and wider frequency band. SISO MULTIBAND ANTENNA SISO multiband antennas can be also classified as a single and multi-element antenna. It provides less gain and bandwidth.

25. MIMO WIDEBAND ANTENNAS MIMO wideband antennas can also be categorized as multi element without metal rim and multi-element with a metal rim. MIMO MULTIBAND ANTENNAS Multi-element Antenna without Metal Rim Multiband multi-element antenna is the panacea of the rapid development of wireless communication which demands heterogeneous network simultaneous accessing two or more technologies like Wi-Fi, GSM, Bluetooth, 4G, and 5G. This antenna can cover GSM, LTE, and UMTS applications with good isolation and better efficiency for both lower and higher frequency bands.

26. MIMO MULTIBAND ANTENNAS MULTI-ELEMENT WITH METAL RIM ANTENNAS The demand for multiband metal rim antennas is rapidly increasing because of the advancement in modern devices like smartphones and smartwatches.

27. Ref. Findings Gaps [1] a multilayer wideband differentially fed dual polarized laminated resonator antenna is reported. For generating dual polarization, two differential pairs of L probes are inserted into the LRA. An IBW of 29% at centre frequency of 5 GHZ is achieved. Isolation of 35 dB and cross polarization of less than -25 dB is achieved between ports high profile because of multilayer design. [2] A two-port broadband full duplex antenna based on three port radiating disk and broadband balun for differential feeding . It operates from 2.3-7.2 GHz covering 5G NR and all Wi-Fi bands including Wi-Fi 7. More than 30 dB isolation is achieved in the mentioned frequency range. Peak realized gain is in the range of 2.92-8.26 dBi. complex Radiation pattern at higher frequencies, complex structure [3] two SRR based antenna designs for 5G microcell applications are proposed for wideband operations in 5G N78 band. First antenna design employs 3-D SRR and is dual polarized. Second antenna design employs crossed SRR and is circularly polarized. To excite orthogonal polarized radiation, two orthogonal coupling feed lines are designed. Additional resonant mode is generated by providing open stubs on the feeding lines which provides enhanced bandwidth. Measured peak gain of 4.7 dB and radiation efficiency better than 83% is achieved. Low Gain, High Profile

28. Ref. Findings Gaps [4] wideband beam switchable 5G antenna operating in the range of 4.25- 5.82 GHz. It consists of a SIW crossover and a dielectric slab. Surface waves of the dielectric slab image waveguide are excited by four centrosymmetric slots etched on SIW. Due to crossover configuration and four ports, four transmission directions of EM waves, four tilted beams are received. Antenna bandwidth of 31% (4.25- 5.82 GHz) and a gain of 6.2-9.1 dBi is reported. Poor port isolation [5] a reconfigurable antenna having dual polarization and beam steering capability operating in the range of 3.2-4.3 GHz is reported. By employing a pair of reconfigurable cross shaped parasitic strips, beam steering is achieved in the directions θ= {-25 ,0 ,25 }. Gain of 7 dB and IBW of 30% (3.2-4.3 GHz) is reported. Antenna has dual port aperture stacked patch structure with symmetrical orthogonal currents. High Profile [6] In band full duplex antenna operating in 3.4-3.8 GHz range . It employs a shared aperture cavity like structure with two orthogonal modes namely quarter wavelength slot mode and half mode cavity mode resulting in high isolation between Tx and Rx ports. To implement dual mode cavity, two quarter wavelength slots are etched on both sides of the cavity. This cavity is fed by a pair of even-odd mode feeding structures which provides orthogonal polarization modes. Isolation greater than 43 dB and radiation efficiency greater than 87% is reported. Low Gain

29. Ref. Findings Gaps [7] A dual Circularly Polarized (CP) magnetoelectric dipole antenna is fabricated using 3-D printing technology. Trade-off between high gain and wide beamwidth has been resolved by loading circular ring-shaped dipoles by twelve meta-columns placed evenly along the circumference on the ground. Considerable increase in beamwidth using this technique has been reported. This antenna operates in 5G (NR) n77, n78 and n79 bands. High Profile Complex Structure [8] A 4x4 metasurface based wideband array antenna has achieved wider impedance bandwidth (IBW) and improved boresight gain characteristics due to the excitation of closely spaced multiple TM resonance modes and large lateral size respectively. Antenna design consists of 4X4 unequal size MTS unit cells which is fed by parallel microstrip feed network in the form of a thin strip cross dipole. Author has reported IBW of 41.1% with centre frequency of 5.64 GHz and a peak boresight gain of 10.14dbi. High cross polarization in some antenna elements [9] a tripolarized metasurface based antenna operating in 5G N78 band is reported. By use of suitable feeding networks TM10, antiphase TM20 and TM00 are excited. To implement vertical polarization, metasurface is loaded by shorting vias which displays TM00 mode. Horizontal polarization is achieved in x-axis and y-axis. By combining and coupling TM10/TM20 dual modes wideband response is realized. The overall bandwidth achieved from all the three excitations is 3.26-3.84 GHz (16.3%) which is quite low. Port isolation reported is greater than 22 dB. Measured peak gain and radiation efficiency are 10.3 dBi and 90.8% respectively. Coupling effects due to shared aperture

30. Ref. Findings Gaps [10] a frequency selective triband dual polarized having shared aperture for 2G/3G/4G/5G base station applications is investigated. It consists of a dual polarized square loop antenna with two parasitic loops for 2G/3G/4G and a differentially fed dual polarized planar antenna for 5G. These two antennas are placed coaxially at different altitudes for saving installation space .LB antenna is designed as a FSS for the M/UB antenna to achieve good performance in the same aperture without interference or blocking. High Profile due to multilayer, coupling effects [11] A microstrip fed heaxaband quad-circular polarized slotted patch antenna operating in 5G (3.5 GHz), GPS L5, GPS L1, WLAN IEEE 802.11 b/g/n, LTE (0.7 GHz) and radio navigation (1.3 GHz) bands by exciting and optimizing TM modes .TM 100 , TM 110 , TM 210 & TM 220 modes are excited at 0.7, 1.7, 1.57 and 2.4 GHz respectively. Three additional hybrid modes EH 1 , EH 3 and EH4 are excited by tuning feeding microstrip line at 1.3 GHz and 2.7-3.6 GHz band respectively. To enable the antenna to radiate CP waves at 1.17, 1.57, 3.18 and 3.5 GHz, a rotated and inverted S-shaped slot is etched on the patch metal which splits surface currents of the modes TM 110 , TM 210 , EH 3 and EH 4 into two orthogonal and 90 phase shifted versions. Antenna gain ranges from 3 to 9 dBi/ dBic over operating bands Low gain [12] four-port annular ring patch antenna is reported for 5G MIMO Access points . It generates four decoupled waves in 3.3-5.0 GHz (41% at 4.15 GHz) having antenna efficiency of about 84% and ECC less than 0.05. Antenna design consists of four annular ring patches which are short circuited to the ground plane using gap coupled shorting strips (GCS). Each of the four ports is surrounded by ring gap. This design provides wide bandwidth and good isolation between ports. Further isolation is achieved by incorporating four shorting strips on the edge of inner patch. Antenna is fabricated on FR4 Substrate. Low Antenna Gain

31. Ref. Findings Gaps [13] antenna with square open cavity with an X shaped isolating blocks and four feeding monopoles having wideband operation for 5G indoor base station is reported. Characteristic mode analysis is used cleverly to identify the modes which are contributing to the coupling. It operates from 1.55 GHz to 6 GHz covering most of the sub-5GHz bands. It is reported that antenna provides four independent radiation patterns with good isolation of 16 dB between ports and efficiency around 84%. ECC of less than 0.5 is reported. High Profile , Complex Structure, S-parameters not in sync with Simulation Results [14] Dual polarized microstrip MIMO antenna for 5G mobile phone applications is investigated. It operates in N79 band and is of compact size. Radiator of antenna pair is constituted by four shorted radiation patches and four pairs of such antenna form a MIMO antenna. These microstrip elements are differentially fed. It exhibits efficiency of more than 40%, ECC (<0.068) and mutual coupling (< -22dB). Not suitable for mobile phones having metal back cover. User’s hands had a great influence on the proposed MIMO antenna. [15] an 18 element mMIMO using simple slot as the radiating element operating in LTE 42/43 bands for 5G smartphones is reported. Open ended slots are used as decoupling elements to improve the isolation among different radiators. This antenna is designed on FR4 substrate having dimensions 150mmX80mmX1.6mm which is suitable for 6-inch smartphones. It exhibits antenna gain of (>5.3dBi), ECC of (<0.01), total efficiency of (>87%), port isolation of (>20 dB) and impedance matching of (reflection coefficient >20dB). User’s hands had a great influence on the proposed MIMO antenna.

32. Ref. Findings Gaps [16] A wideband 4 element 4 port dual mode PIFA is investigated for MIMO applications. This antenna is coupled fed by an L-shaped microstrip line. It covers 5G N77 band and is having diameter of 30.6mm and height of 2mm. Each antenna element is a slotted quasi quarter circle with one inner edge shorted and other two edges left open. To improve isolation a crossline is connected across all the four elements. Author reports that ECC is less than 0.5 and isolation is better than 9.7dB. In this antenna considerable size reduction is achieved but efficiency is considerably reduced. Performance is affected severely when placed on large ground plane [17] A wideband integrated open slot antenna pair and an 8 X 8 MIMO consisting of four antenna pairs for 5G smartphones is reported. In the proposed design a connecting line is inserted between two closely spaced open slot antenna which constitutes a top slot structure with odd and even mode resonances in the lower and higher bands respectively which cancels out the strong mutual coupling. Moreover, the top slot structure also improves the bandwidth. It operates in the range of 3.3-5.0 GHz. ECC reported between all ports is less than 0.14 for MIMO configuration. [18] A wideband four element MIMO antenna operating in 5G N77, N78 and N79 bands for 5G smartphones is investigated . Face to face and back-to-back configurations of closely spaced open slot antenna is analysed for wideband decoupling. Combination of these complementary pairs form a quad element antenna. By combination of quad element pair 8X8 MIMO is designed. Isolation of more than 10 dB is achieved between any two ports. Further higher order MIMO systems can be designed using these complementary antenna pairs. Antenna efficiency is considerably reduced by impact of user’s hands.

33. Ref. Findings Gaps [19] a dual band antenna pair having low profile for 5G MIMO terminals is reported. It consists of intersecting T-shaped monopole and T-shaped slot as antenna pair. Symmetrical low pass high stop filter and high pass low stop filter is added to horizontal stub of the T-monopole and gap of T-slot respectively to achieve an extra resonance mode. It operates in partial N78 (3.4-3.6 GHz) and partial N79 (4.8-4.9 GHz) band. Low Gain, Low Bandwidth [20] a triband four port MIMO antenna exhibiting pattern diversity is reported. It is designed on RT Duroid having circular printed monopole antenna as common radiator and CPW fed. It operates in sub-1GHz, sub- 6GHz 5G NR and WI-FI 6 bands. It is designed using characteristic mode analysis. As per author ECC of less than 0.5 and good isolation is also achieved for sub-1GHz band. Enhancement of operating bandwidth in sub-1GHz band is obtained by using stubs in the design. High Cross Polarization, Low efficiency in sub 1GHz Band [21] A dual band dual polarized shared aperture antenna for base station applications is reported . Antenna working in low frequency band (1.8-2.7 GHz) is electromagnetically transparent to the antenna array working in high frequency band (3.3-3.8 GHz) and LB antenna is placed above the aperture of HB array. FSS is used for LB antenna. LB has effect on HB Performance, High Profile

34. Ref. Findings Gaps [22] A four element eight port MIMO antenna for 5G IoT and cellular handheld applications is reported. In this design four antenna elements are placed at four corners of antenna ground structure, each having two feeding ports placed perpendicularly to achieve cross polarization. Small strip is etched along the entire length of ground plane and rectangular slots cut in ground plane under every antenna element to reduce mutual coupling between different antenna elements. It covers most of the 5G sub 6GHz bands. It exhibits ECC of below 0.03 and measured peak gain is in the range of 3.2-5 dB. Low Antenna Gain [23] Author has proposed 10 element multiband MIMO antenna system for 5G smartphones . It operates in the LTE 42/43/46 bands. It consists of 10 identical and highly isolated T-shaped slot antennas fed with T-shaped microstrip lines. Antenna is fabricated on FR4 substrate. Author has reported return loss values (<-6dB) and total efficiency (>83%) for all the three bands. Peak value of ECC has been reported at 0.06. Effect of hand grip, presence of battery and as well as LCD screen is also reported. Reduced Efficiency due to user’s Hands. Human Head impact not analysed [24] A three ports Quasi-Yagi MIMO antenna, vertically polarized operating in 5G N78 band is reported in [1]. In this there are three driven elements integrated on the same patch and three Γ shaped vertical metal plates are used as directors. Due to strong coupling between driven element and director generating a directional beam, high gain and good pattern diversity performance. Isolation is achieved by metal posts between every two ports.

35. Ref. Findings Gaps [25] an annular array low profile centre fed via shorted circular patch antenna having omnidirectional vertically polarized radiation pattern operating in 5G sub 6 GHz band with high gain and wide bandwidth is proposed. But it suffers from tilted beam which leads to low gain in azimuth plane. Instead of increasing the profile, multiple passive magnetic dipoles consisting of an annular side coupling open cavity are used as directors to increase the gain in azimuth plane. Omnidirectional Gain can be further increased by adding more annular omnidirectional directors. Low Gain, Low impedance bandwidth [26] A wideband dual circularly polarized antenna is investigated . Size reduction is achieved by incorporating vertical SRR Metaresonator (made of metallic sheets and PCB substrate) and wideband dual circular polarization radiation is achieved by introducing composite right/left-handed transmission lines (CRLH-TLs) loaded 3dB branch-line coupler in the feeding network. It operates in 5G N78 band and is suitable for 5G indoor communications. Low Gain, Complex Designing [27] Another wideband CP antenna is reported . The design consists of two semi-circular patch antennas with a suspended metal rod on each patch. The antenna is fed by aperture coupled feed having microstrip feed line on the opposite side. The two semi-circular patches along with the slot form a CP resonance point at low frequencies band. The two metal rods combined with the slot form a loop type antenna creating another CP resonance point at high frequency band. The combination of these two resonance points provides the antenna with wideband operation. Large Size

36. Ref. Findings Gaps [28] A dual MIMO antenna system for 5G mobile is reported. Antenna is designed and fabricated on FR4 substrate. It has an 8 port MIMO antenna (working in 5G band) placed on the board while 4 port MIMO antenna (working in WLAN/WiMAX/5.8 GHz/6 GHz Wi-Fi 6E band) is placed on chassis. Proposed antenna is devoid of ohmic losses as it does not involve any active elements (diodes, switches etc.) to switch between different bands. Effect of user’s hands is not reported [29] Another 8 element MIMO antenna is discussed . Based on characteristic mode theory a wideband decoupled dual antenna pair is designed for 5G mobile terminal applications. By using this decoupled pair an 8 element MIMO antenna is constituted by placing four pairs at both side frames. To achieve broadband and high isolation, parasitic strip and defective ground structure (DGS) are used respectively. Slits are etched in system ground to reduce mutual coupling between antenna pairs. This antenna operates in n77/n78/n79 bands of 5G NR and WLAN 5 GHz band. Effect of users’ both hands has not been analysed [30] A wideband 4 port MIMO square patch antenna is reported in [7]. This antenna has low profile and operates in the 5G N77 band. To generate four uncorrelated waves over a wideband single square patch is used. Half Patch TM 11 and the quarter patch TM 1/2,1/2 mode are generated for each port to achieve wideband operation. Two diagonal linear slots are etched in square patch to create half patch TM 11 mode. Quarter patch TM 1/2,1/2 mode are generated by placing shorting pins along the patch’s two centrelines. Due to back ground plane, this antenna can be directly placed on metal objects for practical applications.

37. Research Gap Stable Radiation Pattern An Escalation in Bandwidth, Demand for High Linearity in RF Systems. Gain Vs Size Constraints Reduction in Mutual Coupling Beamwidth ECC Effects of User’s Hands on antenna efficiency Port Isolation Radiation Efficiency

38. Objectives of the Proposed Research To Design & Develop mm/microwave Antennas for 5G Applications Various Diversity of MIMO Antenna To Study the Effects of Variation in Antenna Parameters Using Proper Software of Industry/Academia Standards

39. Research Methodology Literature Survey Problem Identification or Research Gap Formulation of Objectives Design, Fabrication & Testing Analysis of the Results Conclusion

40. Semester Work I II III IV V VI VII VIII Course Work Literature Survey Simulation Fabrication

41. Y. Hou, Z. Shao, Y. Zhang and J. Mao, "A Wideband Differentially Fed Dual-Polarized Laminated Resonator Antenna," in  IEEE Transactions on Antennas and Propagation , vol. 69, no. 7, pp. 4148-4153, July 2021, doi : 10.1109/TAP.2020.3048537. L. Y. Erol, A. Uzun , M. Seyyedesfahlan and I. Tekin , "Broadband Full-Duplex Antenna for IEEE 802.11 Protocols," in  IEEE Antennas and Wireless Propagation Letters , vol. 20, no. 10, pp. 1978-1982, Oct. 2021, doi : 10.1109/LAWP.2021.3101423. S. Liu, Z. Wang and Y. Dong, "Compact Wideband SRR-Inspired Antennas for 5G Microcell Applications," in  IEEE Transactions on Antennas and Propagation , vol. 69, no. 9, pp. 5998-6003, Sept. 2021, doi : 10.1109/TAP.2021.3070001. Y. Cheng and Y. Dong, "Wideband Beam-Switchable Antenna Loaded With Dielectric Slab for 5G Applications," in  IEEE Antennas and Wireless Propagation Letters , vol. 20, no. 8, pp. 1557-1561, Aug. 2021, doi : 10.1109/LAWP.2021.3091330. G. A. Ramírez  et al ., "Reconfigurable Dual-Polarized Beam-Steering Broadband Antenna Using a Crossed-Strips Geometry," in  IEEE Antennas and Wireless Propagation Letters , vol. 20, no. 8, pp. 1379-1383, Aug. 2021, doi : 10.1109/LAWP.2021.3081065. Z. Wang, T. Liang and Y. Dong, "Compact In-Band Full Duplexing Antenna for Sub-6 GHz 5G Applications," in  IEEE Antennas and Wireless Propagation Letters , vol. 20, no. 5, pp. 683-687, May 2021, doi : 10.1109/LAWP.2021.3060086. B. Feng, L. Li, K. L. Chung and Y. Li, "Wideband Widebeam Dual Circularly Polarized Magnetoelectric Dipole Antenna/Array With Meta-Columns Loading for 5G and Beyond," in  IEEE Transactions on Antennas and Propagation , vol. 69, no. 1, pp. 219-228, Jan. 2021, doi : 10.1109/TAP.2020.3008632. J. d. D. Ntawangaheza , L. Sun, Z. Xie , Y. Pang, Z. Zheng and G. Rushingabigwi , "A Single-Layer Low-Profile Broadband Metasurface Antenna Array for Sub-6 GHz 5G Communication Systems," in  IEEE Transactions on Antennas and Propagation , vol. 69, no. 4, pp. 2061-2071, April 2021, doi : 10.1109/TAP.2020.3027042. Z. Wang, S. Liu and Y. Dong, "Low-Profile Metasurface-Based Antenna With Tripolarization for 5G Applications," in  IEEE Transactions on Antennas and Propagation , vol. 69, no. 9, pp. 5437-5445, Sept. 2021, doi : 10.1109/TAP.2021.3061013. G. -N. Zhou, B. -H. Sun, Q. -Y. Liang, S. -T. Wu, Y. -H. Yang and Y. -M. Cai, "Triband Dual-Polarized Shared-Aperture Antenna for 2G/3G/4G/5G Base Station Applications," in  IEEE Transactions on Antennas and Propagation , vol. 69, no. 1, pp. 97-108, Jan. 2021, doi : 10.1109/TAP.2020.3016406. A. Abdalrazik , A. Gomaa and A. A. Kishk , "A Hexaband Quad-Circular-Polarization Slotted Patch Antenna for 5G, GPS, WLAN, LTE, and Radio Navigation Applications," in  IEEE Antennas and Wireless Propagation Letters , vol. 20, no. 8, pp. 1438-1442, Aug. 2021, doi : 10.1109/LAWP.2021.3086152. K. -L. Wong, J. -Z. Chen and W. -Y. Li, "Four-Port Wideband Annular-Ring Patch Antenna Generating Four Decoupled Waves for 5G Multi-Input–Multi-Output Access Points," in  IEEE Transactions on Antennas and Propagation , vol. 69, no. 5, pp. 2946-2951, May 2021, doi : 10.1109/TAP.2020.3025237. J. Molins- Benlliure , E. Antonino- Daviu , M. Cabedo-Fabrés and M. Ferrando -Bataller, "Four-Port Wide-Band Cavity-Backed Antenna With Isolating X-Shaped Block for Sub-6 GHz 5G Indoor Base Stations," in  IEEE Access , vol. 9, pp. 80535-80545, 2021, doi : 10.1109/ACCESS.2021.3084852.

42. B. Cheng and Z. Du, "Dual Polarization MIMO Antenna for 5G Mobile Phone Applications," in  IEEE Transactions on Antennas and Propagation , vol. 69, no. 7, pp. 4160-4165, July 2021, doi : 10.1109/TAP.2020.3044649. N. Jaglan , S. D. Gupta and M. S. Sharawi , "18 Element Massive MIMO/Diversity 5G Smartphones Antenna Design for Sub-6 GHz LTE Bands 42/43 Applications," in  IEEE Open Journal of Antennas and Propagation , vol. 2, pp. 533-545, 2021, doi : 10.1109/OJAP.2021.3074290. L. Chang and H. Wang, "Miniaturized Wideband Four-Antenna Module Based on Dual-Mode PIFA for 5G 4 × 4 MIMO Applications," in  IEEE Transactions on Antennas and Propagation , vol. 69, no. 9, pp. 5297-5304, Sept. 2021, doi : 10.1109/TAP.2021.3069490. L. Sun, Y. Li and Z. Zhang, "Wideband Decoupling of Integrated Slot Antenna Pairs for 5G Smartphones," in  IEEE Transactions on Antennas and Propagation , vol. 69, no. 4, pp. 2386-2391, April 2021, doi : 10.1109/TAP.2020.3021785. L. Sun, Y. Li and Z. Zhang, "Wideband Integrated Quad-Element MIMO Antennas Based on Complementary Antenna Pairs for 5G Smartphones," in  IEEE Transactions on Antennas and Propagation , vol. 69, no. 8, pp. 4466-4474, Aug. 2021, doi : 10.1109/TAP.2021.3060020. L. Chang, G. Zhang and H. Wang, "Dual-Band Antenna Pair With Lumped Filters for 5G MIMO Terminals," in  IEEE Transactions on Antennas and Propagation , vol. 69, no. 9, pp. 5413-5423, Sept. 2021, doi : 10.1109/TAP.2021.3060827. K. R. Jha, Z. A. P. Jibran , C. Singh and S. K. Sharma, "4-Port MIMO Antenna Using Common Radiator on a Flexible Substrate for Sub-1GHz, Sub-6GHz 5G NR, and Wi-Fi 6 Applications," in  IEEE Open Journal of Antennas and Propagation , vol. 2, pp. 689-701, 2021, doi : 10.1109/OJAP.2021.3083932. D. He, Q. Yu, Y. Chen and S. Yang, "Dual-Band Shared-Aperture Base Station Antenna Array With Electromagnetic Transparent Antenna Elements," in  IEEE Transactions on Antennas and Propagation , vol. 69, no. 9, pp. 5596-5606, Sept. 2021, doi : 10.1109/TAP.2021.3061151. H. T. Chattha , M. K. Ishfaq , B. A. Khawaja, A. Sharif and N. Sheriff, "Compact Multiport MIMO Antenna System for 5G IoT and Cellular Handheld Applications," in  IEEE Antennas and Wireless Propagation Letters , vol. 20, no. 11, pp. 2136-2140, Nov. 2021, doi : 10.1109/LAWP.2021.3059419. N. Jaglan , S. D. Gupta, B. K. Kanaujia and M. S. Sharawi , "10 Element Sub-6-GHz Multi-Band Double-T Based MIMO Antenna System for 5G Smartphones," in  IEEE Access , vol. 9, pp. 118662-118672, 2021, doi : 10.1109/ACCESS.2021.3107625. Y. Xu, Y. Dong, S. Wen and H. Wang, "Vertically Polarized Quasi-Yagi MIMO Antenna for 5G N78 Band Application," in  IEEE Access , vol. 9, pp. 7836-7844, 2021, doi : 10.1109/ACCESS.2020.3049058. S. Lin, S. Liao, Y. Yang, W. Che and Q. Xue , "Gain Enhancement of Low-Profile Omnidirectional Antenna Using Annular Magnetic Dipole Directors," in  IEEE Antennas and Wireless Propagation Letters , vol. 20, no. 1, pp. 8-12, Jan. 2021, doi : 10.1109/LAWP.2020.3035819. Z. Wang, Y. Dong and T. Itoh, "Miniaturized Wideband CP Antenna Based on Metaresonator and CRLH-TLs for 5G New Radio Applications," in  IEEE Transactions on Antennas and Propagation , vol. 69, no. 1, pp. 74-83, Jan. 2021, doi : 10.1109/TAP.2020.3008626. Y. Cheng and Y. Dong, "Wideband Circularly Polarized Split Patch Antenna Loaded With Suspended Rods," in  IEEE Antennas and Wireless Propagation Letters , vol. 20, no. 2, pp. 229-233, Feb. 2021, doi : 10.1109/LAWP.2020.3045988. P. Mathur, R. Augustine, M. Gopikrishna and S. Raman, "Dual MIMO Antenna System for 5G Mobile Phones, 5.2 GHz WLAN, 5.5 GHz WiMAX and 5.8/6 GHz WiFi Applications," in  IEEE Access , vol. 9, pp. 106734-106742, 2021, doi : 10.1109/ACCESS.2021.3100995. Y. Q. Hei , J. G. He and W. T. Li, "Wideband Decoupled 8-Element MIMO Antenna for 5G Mobile Terminal Applications," in  IEEE Antennas and Wireless Propagation Letters , vol. 20, no. 8, pp. 1448-1452, Aug. 2021, doi : 10.1109/LAWP.2021.3086261. K. -L. Wong, M. -F. Jian and W. -Y. Li, "Low-Profile Wideband Four-Corner-Fed Square Patch Antenna for 5G MIMO Mobile Antenna Application," in  IEEE Antennas and Wireless Propagation Letters , vol. 20, no. 12, pp. 2554-2558, Dec. 2021, doi : 10.1109/LAWP.2021.3119753.