Open Slot Antenna Research Articles

Wideband Terminal Antenna System Based on Babinet's Principle for Sub-6 GHz and Wi-Fi 6E/7 Applications.

In this paper, a novel input impedance analysis methodology based on Babinet's principle to broaden bandwidth is proposed, and a broadband multiple-input and multiple-output (MIMO) antenna system is designed, fabricated, and measured for fifth-generation (5G) and Wireless Fidelity (Wi-Fi) 6E/7 mobile applications. By analyzing the input impedance of open-slot antennas and planar monopole antennas using numerical calculations, the characteristics of the input impedance can be obtained. We find that combining the two antenna types in parallel can significantly enhance the bandwidth. Then, the four-dimensional image calculated by MATLAB based on the parallel impedance formula is processed to validate the methodology. Thus, a broad antenna element based on the impedance property analysis methodology is achieved, which operates ranging from 2.6 GHz to 7.46 GHz. Moreover, the equivalent circuit of the antenna element is established to further verify the validity of the methodology. Finally, a broadband MIMO antenna system consisting of eight antenna elements is designed, fabricated, and measured, and the isolation performance is better than 12 dB. Acceptable total efficiency higher than 45% is also obtained with envelope correlation coefficients (ECCs) lower than 0.05. The proposed impedance property analysis methodology innovatively proposes a new way to increase bandwidth, which can be widely applied in various antenna designs. Also, reasonable results show that the proposed MIMO antenna system is a good candidate for 5G and Wi-Fi 6E/7 mobile applications.

A decoupling structure without sacrificing antenna‐element performance for 5G smartphone designs

Operating frequencies and isolation are two critical parameters for 5G smartphone antennas. However, most of the existing decoupling methods will cause the unexpected variations on the performance of antenna element, such that the designers have to spend a lot of time to adjust the configuration of antenna element again and again for the purpose of maintaining the desired performance. To address this issue, a decoupling structure, which introduces another path for canceling the coupling, is proposed in this work. Such method is helpful in achieving the high isolation between two coupled antenna elements without sacrificing the radiating-mode performance and geometrical configuration of each individual antenna element. Under this method, an open-slot antenna pair operating at the sub-6 GHz band of 3.3–3.6 GHz is designed and an isolation higher than 11 dB is obtained. This decoupling method is capable of not only maintaining the original self-performance of each antenna element but also attaining good isolation between two elements. Owing to this attractive feature, the proposed method is promising for supporting the design of antenna element and decoupling structure in two separate steps, which might save a lot of time in the future design of a large array or massive MIMO.

Design and Development of MIMO Antenna for Wireless Communications

A high-isolation eight-antenna multi-input multi- output (MIMO) array running in the 3.5 – 3.6 GHz band for future smartphones is proposed. Here, a novel balanced open-slot antenna is designed as an array antenna element, in which this antenna diagram can yield a balanced slot mode (with decreased ground effects) that can enhance the isolation between two adjoining enter ports. Furthermore, by means of meticulously arranging the positions of the eight antenna elements, proper polarization variety can additionally be correctly achieved, which similarly mitigates the coupling between antenna elements. A prototype used to be manufactured to validate the simulation. A excellent impedance matching (return loss >10 dB), excessive isolation(>17.5 dB), high complete effectivity (>63%), and low envelope correlation coefficient (ECC, <0.05) had been measured throughout the preferred operation bandwidth.

Wideband and High-Gain Substrate Integrated Folded Horn Fed Open Slot Antenna

This article presents a novel substrate-integrated folded horn-fed open slot antenna with wide bandwidth and high gain for millimeter-wave (mmW) applications. The antenna has a three-layer planar structure, including a pair of open slot radiators and two substrate-integrated H-plane horns (SIHs) that are incorporated as the feed to generate quasi-TEM wave excitations. A folded SIH structure is introduced, which reduces the antenna size by 37%. To improve the gain and radiation patterns, the proposed antenna is designed with differentially fed excitations. The measured results validate that the antenna achieves a wide impedance bandwidth of 54.4% from 52.3 to 91.4 GHz and a peak gain of 16.3 dBi. Meanwhile, the radiation patterns are stable throughout the operating bandwidth with low cross-polarization, sidelobe, and back lobe levels. The proposed wideband, high-gain, planar, and low-cost antenna is an attractive candidate for mmW applications.

Eighteen-Element Antenna for Metal-Rimmed Smartphone Sub-6 GHz LTE42 Band Applications

Due to the limited space and large mutual coupling levels, the design of sub-6 GHz massive Multi-Input Multi-Output (m-MIMO) smartphone antenna system attracts antennas’ designers and engineers worldwide. Therefore, this paper presents 18-element m-MIMO antenna system that covers the long-term evolution 42 (LTE42) frequency band (3.4–3.6 GHz) for the fifth generation (5G) applications in metallic frame smartphones. The proposed array system is etched on the long sides of a metal rim of the mobile chassis symmetrically, which is electrically connected to the system ground plane with zero ground clearance. A low-profile frame of height 7 mm (λ/12.3) is symmetrically placed below & above the ground system level. The two frame parts (above/ below the ground level) are utilized separately for the implantation of the antenna elements to achieve good space exploitation and perfect pattern diversity between elements. Orthogonal feeds are used to further increase the level of the isolation where each antenna element above the ground level is fed by a 50-ohm microstrip line, and each antenna element below the ground level is fed by a 50-ohm coplanar waveguide (CPW). The proposed antenna structure is a capacitive coupled-fed open-slot antenna with a small footprint area of 12 × 3.5 mm2 (λ/7.2 × λ/24.5, where λ represents the free space wavelength at 3.5 GHz). A small coupling L-shaped strip provides a capacitive coupling for the proposed 5G antenna structure. To establish the contribution of the proposed 18-element m-MIMO, the prototype of the proposed system was manufactured and successfully measured. Both measured and simulated results are shown to be in good agreement. This proves that the proposed antenna provides coverage for the LTE42 band (3.4–3.6 GHz) with acceptable isolation and efficiency. Moreover, the performance of the proposed m-MIMO were further verified via channel capacity calculation and the envelope correlation coefficient (ECC) measurement. Based on that, the proposed m-MIMO is shown to provide a desirable performance for all m-MIMO parameters while it owns the largest MIMO order in mobile terminals in the open literature.

A side-edge frame dual-band eight-element MIMO antenna array for 5G handset

Abstract In this paper, a dual-band 8 × 8 multi-input multi-output (MIMO) array antenna operating in 3.5 GHz band (3400–3600 MHz) and 5.5 GHz band (5150–5925 MHz) for 5G mobile handset is presented. The proposed hybrid antenna includes a comb-shaped monopole and an L-shaped open slot antenna which are symmetrically located on the inner surface of the side-edge frame of smartphone. Pattern diversity is achieved that can mitigate envelope correlation coefficients (ECCs) and improve the MIMO system performances. The prototype of proposed dual-band eight-element MIMO antenna is fabricated and experimentally measured. The results show that isolation <−10 and <−15 dB, respectively in the lower band and high band without any additional decoupling element are achieved and the desired bands are satisfied under the condition of −6 dB impedance matching. Moreover, the essential parameters for evaluation of the MIMO system performance such as the ECC, mean effective gain (MEG), and ergodic channel capacity are calculated. Furthermore, the influence of user's hand on the radiation characteristics of proposed MIMO antenna are also investigated and discussed. Based on the result, the proposed MIMO antenna is a good candidate for use in future 5G applications.

A New L-Shaped Open-Slot Antenna for Diversity Applications of Operated Frequency and Circular Polarization

ABSTRACT This paper presents a novel small differentially-fed open-slot antenna for diversity of the operated frequency and circular polarization. The proposed antenna structure, which consists of an L-shaped open slot and two bent feeding lines, provides two separate effective bandwidths. The proposed antenna achieves the operation bandwidths of a global positioning system (GPS) and satellite digital audio radio (SDAR) service system. To excite the even and odd modes for bandwidth enhancement, a rectangular patch was embedded in the vertical segment of the L-shaped open slot, thereby forming a coplanar-waveguide topology. An additional rectangular patch was placed above the open slot to increase the interport isolation performance between the two feeding ports. After optimization, the measurement results indicated that the final open-slot antenna provided −10-dB reflection coefficient (S11) bands from 1.29 to 1.70 GHz for the GPS operation and from 2.09 to 2.56 GHz for the SDAR application. Measured 3 dB axial-ratio bandwidths of the proposed structure were 410 MHz (28.5%) from 1.23 to 1.64 GHz and 430 MHz (18.4%) from 2.12 to 2.55 GHz for right- and left-hand circular polarization, respectively.

Reconfigurable narrow open-slot LTE MIMO antennas for metal-rimmed smartphone applications

This paper presents a ‘reconfigurable narrow open-slot LTE MIMO antennas for metal-rimmed smartphone applications,’ which consist of two structurally identical L-shaped slot antennas combined with a metal rim with a 1 mm wide opening. The slots are 3 mm wide and 90 mm long, and are placed diagonally on the upper left and lower right corners of the mobile phone in a mirror-symmetrical manner to achieve good isolation. The 1 mm wide opening divides the L-slot structure into a longer open-slot and a shorter open-slot, and two different feed monopoles are designed to couple and excite the resonance modes of the slot by switching between the two different feed monopoles to cover LTE700/GSM850/900 and GSM1800/1900/UMTS/LTE2300/2500, respectively. The measured isolation is better than 11 dB, the measured antenna efficiency is better than 40%, and the calculated ECCs from measured radiation patterns are lower than 0.3.

Investigation on the Radiation Efficiency Local Minimum in Open-Slot and T-Shaped Antennas

The mechanism for the radiation efficiency local minimum in antennas, especially for open-slot antennas and T-shaped antennas, has been investigated. It is found that the local minimum in those antennas always corresponds to an ideal differential mode. Furthermore, the frequency position of the ideal differential mode is decided by the parasitic parts of the antennas. Simple methods for estimating the local minimum position are proposed based on the mechanism we have found. In addition, the duality relation between those two types of antennas is also discussed. Our findings provide a guideline for designing mobile phone antennas with improved efficiency.

Wideband Integrated Quad-Element MIMO Antennas Based on Complementary Antenna Pairs for 5G Smartphones

In this article, a wideband and highly-integrated quad-element multiple-input multiple-output (MIMO) antenna is proposed for the first time, to adapt to the size-limited environment in fifth-generation (5G) smartphones. First, the wideband decoupling between two extremely closely-spaced open-slot antennas with face-to-face and back-to-back configurations are investigated. Then, based on the complementary antenna pairs, wideband integrated quad-element MIMO antennas are implemented by the ingenious combination of these antenna pairs. For validation, an 8 ×8 MIMO system, constituted by two sets of integrated quad-antenna configurations, is simulated, fabricated, and measured. Both the simulated and measured results show that the 8×8 MIMO system can provide isolation of better than 10 dB between any two ports and a total antenna efficiency of 52.8%-70.8%/40.5%-75.0% across 3.3-5.0 GHz. Compared with the existing integrated quad-antenna design schemes, the proposed solution can expand the bandwidth from less than 200 to 1700 MHz, covering the entire 5G N77, N78, and N79 bands. In addition to the integrated quad-antenna design, further extension to integrated multiantenna configurations is also discussed by the flexible combination of complementary antenna pairs, which paves the way for future higher-order MIMO system in smartphones.

Wideband Decoupling of Integrated Slot Antenna Pairs for 5G Smartphones

This communication proposes a wideband decoupling technique to suppress the strong coupling between two extremely closely spaced open-slot antennas and implements a wideband integrated slot antenna pair for fifth-generation (5G) metal-rimmed smartphones. By simply inserting a connecting line between two closely spaced open-slot antennas, a top slot structure can be constituted with odd- and even-mode resonances in the lower and higher bands, respectively, to cancel the original strong mutual coupling. In addition to the decoupling effect, the top slot can also expand the effective radiation aperture of the antenna pair for the bandwidth improvement. The proposed slot antenna pair, with a compact footprint of 28 ×7 ×1.8 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , shows good impedance matching, isolated and diversity performance across 3.3-5.0 GHz. Then, an 8 ×8 multiple-input multiple-output (MIMO) system, constituted by four sets of slot antenna pairs, is simulated, fabricated, and measured. Both the simulated and experimental results show that the 8 ×8 MIMO system can offer isolations of better than 10.8 dB and envelope correlation coefficients (ECCs) of less than 0.14 between all eight ports across 3.3-5.0 GHz. Also, a total efficiency of 55.0%-83.1% and 52.5%-83.1% is achieved for Ant1 and Ant2, respectively. Featuring wide bandwidth, compact size, high integration level, and metal rim compatibility, we forecast the proposed solution has great potential for future 5G smartphones.

Low-Profile Wideband Conjoined Open-Slot Antennas Fed by Grounded Coplanar Waveguides for $4\times4\,\,5$ G MIMO Operation

Four grounded coplanar waveguide (GCPW)-fed open-slot antennas conjoined into a cross shape with a central circular slot are presented for $4\times4$ fifth-generation (5G) multi-input multi-output (MIMO) operation in 3.3–4.2 GHz. The four conjoined slot antennas have a 1 mm low profile (about $0.01\lambda $ at 3.3 GHz) and a compact size of 42 mm $\times42$ mm (about $0.46\lambda \times 0.46\lambda $ at 3.3 GHz) to provide four wide operating bands (about 24% centered at 3.75 GHz) with antenna efficiency better than 40%. The conjoined circular slot leads to enhanced operating bandwidth of the four slot antennas and good decoupling thereof. Owing to the 1 mm low profile, the conjoined slot antennas are promising to be integrated within the dielectric back cover of the 5G terminal device, thereby decreasing the antennas’ volume inside the device. Details of the GCPW-fed conjoined slot antennas for 5G-MIMO operation are presented.

Wideband Substrate Integrated Waveguide Fed Open Slot Antenna Array

This work investigates the use of substrate integrated waveguide fed open slot antenna (WOSA) in an array for the first time to provide a new SIW slot antenna array with wide bandwidth and single-layer structure. The antenna array consists of 4×2 substrate integrated WOSA elements as a radiating part and two 1-to-4 SIW power dividers as the feeding network. The whole array is differentially fed and built on a single-layered laminate. To demonstrate the wideband performance of the substrate integrated WOSA elements, two sets of feeding networks designed at different frequencies are used to feed the same radiating part. In this way, a V-band and a W-band array were built. Both the antenna arrays were fabricated and measured. Benefiting from the excellent performance of the substrate integrated WOSA elements, the antenna array achieves a wide bandwidth of 32.3% (54.0 to 74.8 GHz) with a peak gain varies from 11.3 to 15.6 dBi. It has been demonstrated that the substrate integrated WOSA array can achieve a wide bandwidth with a single-layer structure, which is attractive for millimeter-wave applications.

A Wideband Substrate Integrated Waveguide-Fed Open Slot Antenna

In this article, we introduce a new structure of an open slot antenna excited by a substrate-integrated-waveguide (SIW) feed to obtain a wide bandwidth of about 60%. Different from conventional slot antennas, two short sides of the slot are open which do not connect to any metal. To excite the open slot, an SIW section is used as the feed. In this way, the antenna is constructed on a single laminate which includes the feeding structure and the radiator. The open slot structure serves as a single-mode resonator with a low Q-factor and, thus, contributes a much wider bandwidth than that of conventional slot antennas and simultaneously maintains stable radiation performance. Intensive parametric studies were implemented to provide a design guideline. To verify our design, antenna prototypes were fabricated and measured. The measured results validate that the antenna achieves a wide impedance bandwidth of 59.3% from 50.8 to 93.6 GHz. Meanwhile, the radiation patterns keep stable over the entire operating frequency band. This new type of slot antenna with wide bandwidth and planar structure is a good candidate for mmW applications.

High-Isolation 3.5 GHz Eight-Antenna MIMO Array Using Balanced Open-Slot Antenna Element for 5G Smartphones

A high-isolation eight-antenna multi-input multi-output (MIMO) array operating in the 3.5 GHz band (3.4–3.6 GHz) for future smartphones is proposed. Here, a novel balanced open-slot antenna is designed as an array antenna element, in which this antenna design can yield a balanced slot mode (with reduced ground effects) that can enhance the isolation between two adjacent input ports. Furthermore, by meticulously arranging the positions of the eight antenna elements, desirable polarization diversity can also be successfully achieved, which further mitigates the coupling between antenna elements. A prototype was manufactured to validate the simulation. A good impedance matching (return loss > 10 dB), high isolation (>17.5 dB), high total efficiency (>62%), and low envelope correlation coefficient (ECC, <0.05) were measured across the desired operation bandwidth. To verify the MIMO performance, ergodic channel capacity using the Kronecker channel model was calculated. The effects of hand phantom were also studied.

Design of a symmetric open slot antenna for UWB applications

Design of a symmetric open slot antenna for UWB applications

Design of L-Shaped Open-Slot Antenna Used in UAV Airborne Communication System

According to the communication demands of communication system used in the UAV (Unmanned Aerial Vehicle) communication system, a ladder-shaped open-slotted antenna design is presented. The impedance effects and directional radiation performance of designed antenna are improved with adopting a pair of L-shaped narrow slot and a passive resonator among the antenna structures. The measured results show that the impedance bandwidth of the antenna is about 90%, the frequency range can cover from 3 GHz to 12 GHz, and the antenna has a relative small size just as 22 mm × 24 mm. The antenna is realized through adopting improved ground structure, and its electrical length is increased simultaneously. To improve its impedance matching effect, the ladder structure is adopted in the antenna. The measured results show that the proposed design scheme is useful and effective, the antenna size can be controlled within the size of 22 mm × 24 mm and the good impedance bandwidth can also be obtained, its frequency bandwidth is from 3 GHz to 13.2 GHz, and the designed antenna has good group delay characteristics at the same time.

Dual open-slot antennas integrated in metal frame and metal case of tablet computer for long-term evolution applications

Dual open-slot antennas were integrated in the metal back case and metal frame of a tablet computer for long-term evolution applications. The single feed dual excitation source antennas were sufficiently narrow (2 mm) for installation between the metal frame and metal back case of the tablet computer. Each antenna had two open-slot radiators (slot 1 and slot 2) with embedded filter circuits to enable wideband (699-906 and 1710-2690 MHz) operation required for LTE applications. The filter circuit values were adjusted to make the impedance more smooth and excite the desired modes. The proposed multiple-input-multiple-output antennas were installed lengthwise on the long sides of the tablet and facing in operate directions. In this configuration, the user hand grip did not interfere with antenna performance, and isolation was improved (> 20 dB). The operating mechanism of the proposed antenna with matching circuits is described in detail. The effects of the user hand grip and the embedded display panel are also discussed.

A novel single L‐shaped open slot antenna for octa‐band metal‐framed smartphones

AbstractA novel single L‐shaped open‐end slot antenna for octa‐band metallic frame smartphones is presented. The antenna mainly comprises an L‐shaped open slot and a simple LC circuit. The slot is placed at the top of the ground plane which is excited by the 50‐Ω feedline with a band‐stop match circuit. According to the proposed feeding arrangement, the antenna can cover all dual‐wideband LTE/WWAN operations at 698‐960 MHz and 1710‐2690 MHz. A prototype antenna is manufactured and tested. Experimental results such as return loss, radiation patterns, and radiation efficiencies are also presented.

Integrated Inverted-F and Open-Slot Antennas in the Metal-Framed Smartphone for &lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$2\times2$ &lt;/tex-math&gt; &lt;/inline-formula&gt; LTE LB and &lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$4\times4$ &lt;/tex-math&gt; &lt;/inline-formula&gt; LTE M/HB MIMO Operations

Six antennas placed on the short edges of the metal-framed smartphone for the long-term evolution (LTE) multi-input multi-output (MIMO) operation are presented. The six-antenna structure comprises three antennas placed on the top edge of the smartphone and three antennas placed on the bottom edge thereof. The three antennas on the bottom edge are identical to those on the top edge. Each three-antenna structure consists of one inverted-F antenna (IFA) that covers the LTE low band (LB) in 698–960 MHz and two open-slot antennas (OSAs) that cover the LTE middle/high bands (M/HB) in 1710–2690 MHz. The three-antenna structure is compactly integrated, with the IFA placed between two OSAs, to fit in one short edge of the smartphone. In addition, the presence of the IFA is able to decrease the mutual coupling between two OSAs in the LTE M/HB. Furthermore, two IFAs at opposite short edges can also show good decoupling to have decreased envelope correlation coefficients in the LTE LB. The six antennas at two short edges can, therefore, achieve good performances for $2\times 2$ LTE LB MIMO and $4\times 4$ LTE M/HB MIMO operations.