Open-ended Slot Research Articles

Miniaturized and Flexible Dual-Band Antenna Based on Open-Ended Slots for Wi-Fi/ISM and Wearable/Portable Application

Miniaturized and Flexible Dual-Band Antenna Based on Open-Ended Slots for Wi-Fi/ISM and Wearable/Portable Application

COMPACT TWO-PORT ANTENNA WITH PARASITIC NOTCH AND DEFECTive GROUND FOR WIRELESS COMMUNICATION

This paper presents a compact multiple input multiple output antenna (MIMO) with a wireless local area network (WLAN) notch characteristic for ultra-wideband (UWB) applications. The two modified rectangular radiators share a common ground that provides UWB response. The design is modeled over FR4 material and has an overall compact size of 0.34 λ0 × 0.24 λ0 × 0.015 λ0 mm3 at the frequency of 2.9 GHz. A tree-shaped decoupling structure with multiple slots in the ground is introduced between the ports to establish good isolation. The open-ended slots in the ground perturb diminish the surface current between two ports and ensure the isolation larger than 20 dB in the entire UWB from 2.9 GHz to 10.2 GHz. An S-shaped parasitic stub is utilized at the backside of the radiating element to implement a band notch characteristic from 5.03 GHz to 5.90 GHz. The proposed antenna is also investigated for wearable applications with a human tissue model showing a small SAR value (less than 1.6 W/kg). The simulated and measured result shows that the designed antenna suits MIMO performance and wearable devices.

Compact two-port antenna with high isolation based on the defected ground for THz communication

The two-port antenna is designed for THz communication where isolation is achieved with the defective ground. The radiator of the two-port antenna is inspired by the half-cutting technology which reduces the size and makes it a compact antenna. The T-shaped stub and open-ended slot are used to modify the capacitive and inductive reactance which diminish and discontinued the surface current to improve the port isolation. The T-shaped stub improves the electric length of the ground and enhances the port isolation by up to 3.4 dB and open-ended slot in the ground is used to weaken the mutual current and create the non-uniform current which intensifications the port isolation up to 7.7 dB at 2.2 THz. The dimensions of the design is 100 µm × 105 µm and the edge distance of the antennas is only 0.20λ with maximum isolation is 30 dB at 2.2 THz. The bandwidth of the two-port antenna is 1.74 THz to 2.52 THz that can be applicable in wireless communication applications.

An Omnidirectional CPW Leaky-Wave Antenna With Steering Conical Beam

This paper proposes a planar omnidirectional leaky-wave antenna with steering conical beam and stable radiation through the broadside on the periodically modulated coplanar waveguide (CPW). The radiation characteristics of the leaky CPW cells are investigated according to different-shaped open-end slots and various widths of the substrate layer. Then, the omnidirectional conical radiation beam is obtained by etching exponentially tapered open-end slots on the CPW ground parts and modifying the width of the substrate layer properly. Under the frequency balanced condition, a pair of additional series inductive slots are etched on the modulated CPW to balance the Bloch impedance and suppress the open-stop band effect. An antenna demonstration is designed as verification. The measured results validate the simulated results experimentally, confirming the conical beams in the H-plane and the wide-angle beam scanning of −60° to 17° in the E-plane.

Two-Port Antenna Based on Shorting Pins and Open-Ended Slots with T-Shaped Stub for Isolation Enhancement

In this paper, a compact two-port antenna consisting of an open-ended slot loaded with shorting pins and a T-shaped stub is presented. The beak-shaped two-port antenna radiators enhance the antenna bandwidth and electrical length. The two inverted L-shaped open-ended slots form an effective capacitance and an inductance, resulting in a dual-operating band. The T-shaped stub improves electrical height and impedance matching to ground, while the combination of the T-shape and open-ended slots provides a dual-band response and improves isolation by up to 8 dB. Shorting pins connected to the ground show inductive behavior that improves isolation by up to 6 and 4 dB for the low- and high-frequency bands. The two-port antenna exhibits more than 20 dB of isolation with only 2 mm of edge-to-edge distance of the antenna element. The two-port antenna operates in dual frequencies from 4.1 GHz to 4.6 GHz and from 5.55 GHz to 6 GHz, and the 32 mm × 26.5 mm size makes it suitable for 5G and WLAN/ISM applications.

Two-port miniaturized textile antenna for 5G and WLAN applications

AbstractA compact, two-element textile MIMO antenna is designed with enhanced isolation by using modification in the ground, open-ended slots along with shorting pins. Maximum 27.8 dB isolation is achieved in two-element antennae, where the edge-to-edge distance is kept at 0.19 λ0 which is less than the conventional half wavelength. The Y-shaped decoupling and shorting pins improve the isolation up to 14 dB and can mitigate the current moment between the two ports effectively. The open slots in the ground are enhancing the mutual impedance and shift the operating band of the antenna toward the lower frequency band and thus size miniaturization is also achieved. The textile antenna achieves a 10 dB impedance bandwidth from 4.24 to 5.38 GHz with more than 21.1 dB isolation in the entire band. The phantom wrist model and bending analysis are carried out with the textile antenna to validate the on-body effects of the antenna in wearable and 5G applications.

Dual-Band Antenna With Omni/Unidirectional Radiation Realized by Single Metal Plate

This letter proposes a novel dual-band antenna realized by single metal plate. The basic antenna structure is a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> /2 dipole with omnidirectional radiation pattern, operating at 1.4 GHz. To obtain a second working band with directional radiation, this dipole is folded, therefore forming an open-end slot in-between its two arms, serving as a magnetic dipole. Then, by properly exciting these two dipoles with 90° phase difference in time domain, the inherent 90° phase difference formed between the slot and the electric dipole is cancelled. As a result, cardioid radiation pattern is obtained at 3.7 GHz. The measured results show that an impedance bandwidth of 10.3% and 18.1% is achieved at these two bands, respectively, with omnidirectional radiation pattern at 1.4 GHz band, and unidirectional radiation with at 3.7 GHz with wide beamwidth.

Application of PSO and Curve Fitting for the Optimization of Compact L-Shaped Open Ended Slot Loaded Rectangular Patch Antenna

Application of PSO and Curve Fitting for the Optimization of Compact L-Shaped Open Ended Slot Loaded Rectangular Patch Antenna

A Periodic Coplanar Strips Leaky-Wave Antenna With Horizontal Wide-Angle Beam Scanning and Stable Radiation

A periodic leaky-wave antenna (LWA) with unidirectional horizontal radiation and wide-angle beam-scanning capacity through broadside is presented. The proposed antenna is made of a slow wave coplanar strips line with open-ended slots and short-ended slots etched on the two strips, respectively. The energy leaks mainly from the open-ended slots, contributing to the horizontal radiation of the antenna. Consequently, the constraint of the ground plane on the radiation patterns is reduced, suggesting the potential of the proposed structure to break the scanning range limitation of the traditional LWAs. The scanning range of LWAs is determined theoretically by the normalized phase constant. Therefore, the slow wave structure is utilized to ensure the normalized phase constant of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n = -1$ </tex-math></inline-formula> harmonic varying from −1 to 1. Subsequently, a pair of extended slots are introduced to the slow wave LWA unit cell to eliminate the open-stopband (OSB) effect. As a validation of the proposed antenna, a prototype with broadside frequency of 10 GHz is designed, fabricated, and measured. The measured results are in good agreement with the simulated results. It is shown that the fabricated antenna scans from −75° to 83° in the horizontal plane with eliminated OSB and measured gain variation of 2.65 dB.

A Compact Ultra-Thin 4 × 4 Multiple-Input Multiple-Output Antenna.

This article reported a compact ultra-thin tightly arranged 4 × 4 multiple-input multiple-output (MIMO) antenna pair (AP) functioning in the fifth-generation (5G) n78 band (3.4–3.6 GHz) for the ultra-thin 5G mobile handset. Two APs were printed on the center of two sideboards. A T-shaped open-ended slot was utilized in the grounding plane to improve the port impedance matching and attenuate the reciprocal magnetic coupling. A minimized total volume of 145 × 75 × 5 mm3 was obtained, and the area of each radiating unit was only 8.5 × 4.2 mm2 (0.1λ0 × 0.05λ0, λ0 is the free-space wavelength at the frequency of 3.5 GHz). By placing two radiating elements in an exceeding closed (1 mm or 0.01167λ0) distance, the designed AP precisely resonated at 3.5 GHz, and an acceptable measured isolation performance superior to 17 dB was attained. A prototype of this presented APs system was printed and tested, and remarkable consistency was observed between the simulated and measured curves. Numerous indicators were computed to assess its MIMO performance, such as Envelope Correlation Efficiency (ECC), Diversity Gain (DG), Total Active Reflection Coefficient (TARC), and Multiplexing Efficiency (ME).

A Multiband Multibeam Antenna for Sub-6 GHz and mm-Wave 5G Applications

This letter first presents a concept of a dual-band antenna with a very large frequency ratio, which can be suitable for integrated 4G/millimeter (mm)-wave fifth-generation (5G) and beyond 5G applications for Internet of Things devices. The antenna is based on a tapered slot, which simultaneously works as a resonant open-ended slot at low frequency and a high-gain Vivaldi antenna at high frequency. The impedance bandwidth is improved by modifying the slot shape, i.e., creating multisections within the slot. Based on this approach, a multibeam antenna (gain of 10 dBi) at an mm-wave frequency which also covers multibands at lower frequency extending from 2.5 to 6 GHz is designed. The design is validated numerically and experimentally in terms of return loss, radiation efficiency, gain, total scan pattern, and coverage efficiency.

A Novel Wideband and Multi-band Implantable Antenna Design for Biomedical Telemetry

In this work, a novel multi-tracks wideband and multi-band miniaturized antenna design for implanted medical devices biomedical telemetry is proposed. This antenna entirely covers seven frequency bands which are the bands (401−406) MHz of the Medical Device Radiocommunications Service (MedRadio), the three bands (433.1−434.8), (868.0−868.6), and (902.8−928.0) MHz of the Industrial, Scientific, and Medical (ISM), and the three bands (608−614) MHz, and (1.395−1.400) and (1.427−1.432) GHz of the Wireless Medical Telemetry Service (WMTS). The antenna possesses a compact full size of (19.5 × 12.9 × 0.456) mm3. The antenna miniaturization and impedance bandwidth enhancement are achieved using two techniques: the patch slotting and insertion of open-end slots in the ground plane, respectively. Prototype of proposed antenna with multi-tracks has been fabricated and tested in free space. The comparison between the simulated and measured reflection coefficient has been done and found in good agreement with each other. Furthermore, simulations of the proposed antenna implanted in the underneath the scalp in a realistic human model shows a wideband operation from 0.19 to 0.94 GHz, and from 1.38 to 1.54 GHz corresponding to return loss (S11 ≤ −10 dB). Link budget calculation is performed to specify the range of telemetry considering both Specific Absorption Rate (SAR) restrictions and effective isotropic radiated power (EIRP) limitations. The designed implantable antenna with full ground plane presents an appropriate reflection coefficient for muscle implantation. Furthermore, the designed implanted muscle antenna may be also suitable for skin implantation.

Miniaturized Antenna for High Data Rate Implantable Brain-Machine Interfaces

Technological advancements in medical care have necessitated the development of efficient and miniaturized implantable medical devices. This paper presents an ultra-wide-band implantable antenna for use in scalp-based biomedical applications covering the industrial, scientific, and medical (ISM) (2.4&#x2013;2.48 GHz) band. The proposed antenna is mounted on a 0.1&#x2013;mm thick liquid crystalline polymer (LCP) Roger ULTRALAM (tan&#x03B4; = 0.0025 and &#x03B5;_r = 2.9), serving as a dielectric material for both the superstrate and substrate layers. LCP materials are widely used in manufacturing electronic devices owing to their desirable properties, including flexibility, conformable structure, and biocompatibility. To preserve the capability of an electrically small radiator and achieve optimum performance, the proposed antenna is designed to have a volume of 9.8 mm³ (7 mm &#x00D7;7 mm &#x00D7; 0.2 mm). The addition of a shorting pin and open-ended slots in the radiating patch, and close-ended slots in the ground plane facilitates antenna miniaturization, impedance matching, and bandwidth expansion. Notably, the antenna exhibits a peak gain of &#x2013;20.71 dBi and impedance-matched bandwidth of 1038.7 MHz in the ISM band. Moreover, the antenna is safe to use according to the IEEE C905.1-2005 safety guidelines based on low specific absorption rates. To evaluate the performance of the implantable antenna, finite-element simulation was performed in homogeneous and heterogeneous environments. For validation, measurements were performed in a minced pork-filled container. The simulation results are consistent with the measurements. In addition, a link budget analysis is performed to confirm the robustness and reliability of the wireless telemetric link and determine the range of the implantable antenna.

Dual-Polarized Millimeter-Wave Endfire Array Based on Substrate Integrated Mode-Composite Transmission Line

A dual-polarized endfire array is presented in this article for millimeter application. The substrate integrated mode-composite transmission line is introduced to exciting the dual-polarized radiation. Specially, the horizontal polarization is excited by the transverse electromagnetic (TEM) mode, whereas the vertical polarization is based on the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode. Two metal blocks sandwich the substrates to form a sandwich structure, and an open-ended slot is designed on the block edge to construed complementary sources radiation. Benefiting from the wideband feature of complementary sources, the proposed dual-polarized endfire array achieved a considerable bandwidth performance of 26.9% (24.8–32.5 GHz) based on the standard that both the voltage standing wave ratios of the two ports are less than 2. In terms of the key factor of dual-polarized antenna and isolation, measured results show a high port isolation of over 36 dB and a cross-polarization discrimination rate of over 30 dB. The excellent dual-polarized performance gives the proposed endfire array the potential of application in millimeter-wave mobile communications.

Compact Super Wideband Frequency Diversity Hexagonal Shaped Monopole Antenna With Switchable Rejection Band

To reduce interference from other wireless communications, a compact super wideband frequency diversity hexagonal shaped monopole antenna with switchable rejection band capabilities is proposed. The patch consists of hexagonal structure with an open-ended horizontal slot that divides the patch into upper and lower parts. The overall size of the proposed antenna is 36 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times\,\,36$ </tex-math></inline-formula> mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times\,\,1.6$ </tex-math></inline-formula> mm on an FR-4 substrate material with a loss tangent of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$tan\delta$ </tex-math></inline-formula> = 0.02. The notch switchable features and the frequency diversity are controlled by changing the length of the resonator through alternating the state of two inserted parallel PIN diodes inside the horizontal open-ended slot. The upper part of the hexagonal patch is connected to the negative terminal of the diodes and the biasing circuit in the back layer through a conducting via. The lower part is connected to the positive terminal of the diode. When both diodes are OFF, the proposed antenna behaves as a super wideband covering a bandwidth from 3.37 GHz to 27.71 GHz. When both diodes are ON, there is a band notch and a frequency a frequency band (3.81 – 6.62 GHz) is filtered. The antenna’s radiation pattern is broadsided directional, and the efficiency is observed 92.9% and 96% for the ON and OFF cases, respectively. The reflection coefficient ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{11}$ </tex-math></inline-formula> ) at the rejection band is −3.06 dB at 5.38 GHz. Hence, the proposed super wideband antenna is well-suited for applications in wireless communications.

CPW-Fed Penta Band Monopole Antenna for Multiservice Wireless Applications

A compact triple T-shaped stub with meander loaded strip antenna for penta band applications is proposed. The rectangular patch antenna with meandered and open-ended slot cuts is utilized to realize four operating bands at 2.45 GHz, 3.1 GHz, 5.3 GHz, and 6.5 GHz with an impedance bandwidth of 400 MHz (2.15-2.550 GHz), 1000 MHz (2.7-3.7 GHz), 200 MHz (5.4-5.6 GHz), and 200 MHz (6.4-6.6 GHz), respectively. For an additional resonance frequency, the length of the central T-shaped stub is slightly modified which causes the variation in the current distribution. As a result, the resonance frequency of 5.5 GHz is divided into two resonance frequency bands which are operating at 5.25 GHz and 5.85 GHz with an impedance bandwidth of 100 MHz (5.25-5.35 GHz) and 200 MHz (5.75-5.95 GHz), respectively. Furthermore, a parametric reflection coefficient and surface current distribution analysis is carried out to understand the strip and slot behavior at resonance frequency bands. Finally, a prototype is fabricated and its reflection coefficient, gain, and radiation pattern are measured. The experimental result shows that the proposed antenna is reliable for penta band applications.

Half cutting dual-band circularly polarized monopole antenna for wireless communications

In this work, a novel half-cutting technique has been implemented on the CP antenna to enhance the axial ratio bandwidth. The projected antenna is designed on 26mm×14.5mm×1.6mm FR4 substrate with relative permittivity 4.4 and loss tangent 0.02. The proposed patch is developed by loading an L – shaped open-ended slot on the monopole element. The half-cutting technique is incorporated on the ground plane flowed by loading circular-shaped slots and stubs. Results have been improved intensely. The achieved two impedance bandwidth (IBW) are 1.80 GHz (3.6 – 5.4 GHz) and 5.3 GHz (5.7 – 11 GHz) at the −10 dB reflection coefficient. Two 3 dB, ARBW of 0.29 GHz (4.38 – 4.67 GHz) and 4.91 GHz (5.79 – 10.70 GHz) are confirmed. The peak gain of 4.77 dBi at 8.46 GHz is achieved. The RHCP and LHCP waves are radiated along the broadside direction under the lower and higher CP modes. It is strongly applied for military and mobile communication (4.4 – 4.5 GHz), 802.11p WLAN (5.850 – 5.925 GHz), WiFi (5.925 – 7.125 GHz) in the united state, in satellite, DL (7.25 – 7.75 GHz) and UL (7.9 – 8.4 GHz) and X – band applications.

Size Miniaturization and Isolation Enhancement of Two-Element Antenna for Sub-6 GHz Applications

In this paper, a two-port dual-band antenna is designed with high isolation. The beak-shaped radiator and open stubs are used to achieve miniaturization of the antenna. A T-shaped stub is used to isolate the antenna at higher frequencies whereas open-ended slots effectively miniaturized the antenna size thereby increasing the impedance and isolation by more than 20 dB. The isolation is enhanced due to the suppression of current between radiators without increasing the size of the MIMO antenna for lower frequencies. The proposed antenna parameter CCL, DG, TARC and ECC reflects better diversity performance. The two-port antenna covers 2570, 2300, 2496, 3400, 3600 MHz (LTE 38, 40, 41, 42, 43) 2500, 3500, 3700 MHz (5G n7, n48, n77) 5.15/5.85 GHz (WLAN), 2.4/5.0 GHz (Wi-Fi) and 2.45/5.8 GHz (ISM) sub-6 GHz bands and can be a good choice for wireless communication.

Efficient Six-Port MIMO Antenna System for 5G Mobile Handsets

A six-port MIMO antenna system for forthcoming mobile applications (Sub 6 GHz) is presented in this paper. Four F-shaped antenna elements are placed at four extreme corners and two at the middle side edges of 0.8 mm thick FR4 substrate. An open-ended slot is carved into the ground plane to improve the impedance matching. The proposed antenna operates in the frequency range of 3.4–3.6 GHz (LTE Band 42), with a-10 dB (2:1 voltage standing wave ratio) impedance bandwidth of 200 MHz. The proposed antenna operates in the frequency range of 3.4–3.6 GHz (LTE Band 42), with a-10 dB (2:1 voltage standing wave ratio) impedance bandwidth of 200–MHz. The fabricated MIMO antenna is practically measured and compared with simulated results. The obtained isolation is lower than 20 dB without employing isolation enhancing procedures, making the antenna highly appropriate for 5G smartphone applications. High isolation results in lower values of Envelope Correlation Coefficient (ECC) below 0.01. The antenna’s diversity performance is validated by calculating Total Active Reflection Co-efficient (TARC) which is better than 40 dB. The calculated channel capacity of the six-port antenna array is 32.5 bps/Hz at 20 dB Signal to Noise Ratio (SNR). The six-antenna array’s reliability is evaluated by examining the influence of hand effects and Specific Absorption Rate (SAR). The measured results are consistent with simulated results which exhibit the antenna presented in this article is highly capable of mobile phone applications for future cellular communication.

Ultra-Wideband Microstrip Bandpass Filter and Its Equivalent Circuit

Microstrip filters can be designed with various methods to obtain good performances, such as defected ground structure, open-ended slot, planar edge coupled, and split ring resonator with groundplane windowing. In this paper, the design of an ultra-wideband microstrip bandpass filter used the defected ground structure (DGS) method by adding a circular slot to the groundplane. The addition of the circular slot was carried out to improve the value of S parameter (return loss and insertion loss) from the initial filter design without a circular slot. In the simulation process, optimization was carried out by changing the value of filter component parameters such as patch length and thickness and circular slot width. The simulation results showed that the microstrip bandpass filter could pass frequencies in the range of 1.4 GHz to 5.7 GHz with the bandwidth response of 4.3 GHz. In addition, filter analysis could also be done with an equivalent circuit represented by lumped element components in the form of capacitors and inductors connected in series or parallel. The simulation results of the equivalent circuit had a wider bandwidth, which was able to pass frequencies in the range of 1.2 GHz to 6.1 GHz with a bandwidth response of 4.9 GHz.