Impedance Bandwidth Of Antenna Research Articles

Triple band Compact Fractal Antenna with Defected Ground Plane for Bluetooth, WiMAX, and WLAN Applications

This paper presents a novel compact coplanar waveguide (CPW) monopole fractal-shaped antenna using fractal patch composed of hexagons with defected ground plane. Inclusion of a pair of S-shaped slots on the ground plane is used to extend the antenna impedance bandwidth and to provide multiband operation. The antenna has a compact size of 35×35×1.27 mm3 which is compact. The antenna is designed, fabricated and measured. Good performances in terms of return loss, gain and radiation pattern are obtained in the operating bands, which makes the proposed antenna a good candidate for multiband wireless systems. The obtained results show that the antenna operates at Bluetooth,Worldwide Interoperability for Microwave Access (WiMAX), and Wireless Local Area Network (WLAN).

Mutual Coupling Reduction Using a Protruded Ground Branch Structure in a Compact UWB Owl-Shaped MIMO Antenna

A compact ultra-wideband (UWB) multiple input-multiple output (MIMO) antenna with high isolation is designed for UWB applications. The proposed MIMO antenna consists of two identical monopole antenna elements. To enhance the impedance matching, three slots are formed on the ground plane. The arc structure as well as the semicircle with an open-end slot is employed on the radiating elements the fact which helps to extend the impedance bandwidth of the monopole antenna from 3.1 up to 10.6 GHz, which corresponds to the UWB band. A ground branch decoupling structure is introduced between the two elements to reduce the mutual coupling. Simulation and measurement results show a bandwidth range from 3.1 to 11.12 GHz with |S11_|<−15 dB, |S21_|<−20 dB, and ECC < 0.002.

Broadband Slotted Blade Dipole Antenna for Airborne UAV Applications

This paper presents a novel broadband dipole blade antenna for airborne unmanned aerial vehicle applications. Wideband performance and stable radiation pattern are achieved by the use of two perpendicular slots and two vertical tails. The vertical tails increase the excited surface current path and consequently increase the radiation efficiency of the antenna at lower frequencies. The feed line utilizes a matching circuit to achieve a wide impedance bandwidth, particularly at lower frequencies. The overall size of the antenna is $71\,\,\text {cm} \times 25\,\,\text {cm} \times 5$ cm. A prototype of the proposed antenna has been fabricated and tested. Measurements agree well with simulation results. Based on measurement results, the antenna impedance bandwidth for VSWR < 2.5 is 193.5% from 20 to 1200 MHz.

A Coplanar Waveguide Fed UWB Antenna using Embedded E-shaped Structure with WLAN Band-rejection

Abstract A compact coplanar waveguide (CPW)-fed ultra-wideband (UWB) monopole antenna using embedded E-shaped structure with wireless local area network (WLAN) band-rejection is presented. The introduction of this E-shaped structure working as the radiator can enhance the impedance bandwidth of the UWB antenna without increasing the overall size. For preventing the interference from WLAN system, a pair of L-shaped stubs are connected to the ground of UWB antenna to create the rejected band. The center frequency of this rejected band is about 5.5 GHz with the rejection range of 5.2~5.8 GHz. Good agreement can be observed between the simulated and measured results.

Improvement of ground radiation antenna performance using compact EBG in presence of battery effects

In Internet-of-things devices, to alleviate the performance degradation of the ground radiation antenna due to the large battery, two compact electromagnetic bandgap (EBG) unit cells are introduced between the ground radiation antenna and the battery. The ground radiation antenna is comprised a small loop-type circuit that is designed within a 5-mm × 5-mm ground clearance for 2.4-GHz WLAN applications. The compact EBG unit cell is a modified square split-ring resonator that is designed by meandering-line technology. The measurement results showed that the 3:1 VSWR impedance bandwidth of the ground radiation antenna increased from 30 to 90 MHz, and the average total efficiency increased from 19% to over 54% with and without the introduction of the EBG structure, respectively.

A-shaped wideband dielectric resonator antenna for wireless communication systems and its MIMO implementation

In this article, a new A-shaped dielectric resonator antenna (DRA) excited by a conformal strip is proposed for wideband applications. The wide bandwidth is achieved by combining two adjacent modes that is, TM101 and TM103. The experimental results demonstrate that the proposed DRA offers an impedance bandwidth (for S11−10 dB) of 59.7% (3.24-6.0 GHz), covering IEEE 802.11 and U-NII bands. The antenna provides a fairly stable radiation pattern with the gain ranging from 5.29 to 7 dBi across the operating bandwidth. A dual-element multiple-input multiple-output (MIMO) system is also realized using the proposed wideband DRA. The impedance bandwidth of the dual-element MIMO antenna is 59.2% and 60.9% for Port1 and Port2, respectively and the isolation between the ports is better than 20 dB across the bandwidth. For Port1, the gain of the MIMO antenna ranging from 6.03 to 7.45 dBi is obtained across the bandwidth. Furthermore, the diversity performance of the MIMO antenna is found to be good with envelope correlation coefficient below 0.003 over the operating band. The proposed antenna could be the potential candidate for worldwide interoperability for microwave access (WiMAX), wireless local area network (WLAN) and lower European UWB frequency band (3.4-5.0 GHz) applications.

Effect of the Aperture Ratio on the Impedance Bandwidth of an Aperture Coupled Microstrip Antenna

Effect of the Aperture Ratio on the Impedance Bandwidth of an Aperture Coupled Microstrip Antenna

Design and Experiments of Bandwidth-Controllable Broadband Monopole Antennas With Conformal Anisotropic Impedance Surface Coatings

In this paper, we report an ultrathin and lightweight coating approach for enhancing the impedance bandwidth of a conventional monopole antenna by using a single-layer dispersive anisotropic impedance surface (AIS). The design is facilitated by a rigorous and efficient modal-expansion analysis of a monopole coated by a homogeneous AIS, which is developed by approximating the AIS as a slab of anisotropic medium with a deep subwavelength thickness and introducing an auxiliary perfectly matched boundary above the AIS-coated monopole. This method is further utilized to efficiently optimize the dispersive properties of the AIS, which has a deep subwavelength radius, for tuning the impedance bandwidth of a monopole, thereby achieving a greatly broadened yet controllable bandwidth. Three AIS-coated antenna examples with different ratio bandwidths are illustrated, with their corresponding discrete realistic structures designed, fabricated, and characterized. The measured results agree strongly with simulation predictions, experimentally exhibiting a VSWR < 2 ratio bandwidth of 1.91:1, 2.79:1, and 3.81:1, respectively. The proposed antennas possess a stable omnidirectional pattern with a low cross-polarization level of less than −20 dB. The demonstrated AISs can serve as redeployable conformal coatings for obtaining broadband and ultrawideband antennas with a controllable bandwidth, which will be useful for various wireless systems, including the vehicle-to-X network.

Broadband Planar Aperture‐Coupled Antenna Array for WLAN and ITS Beam‐Steering Applications

AbstractA broadband multilayer beam‐steering antenna array with a modified mushroom‐like radiating element is introduced. The two‐layer aperture‐coupled array consists of four equal sets of mushroom‐like elements, each of which is made of 16 unit cells in a 4 × 4 configuration. The feeding network is a modified quasi‐Butler matrix, which benefits from improved double‐box branch line couplers. The network has an isolation bandwidth between 4 and 7.9 GHz (65%) and a transmission bandwidth from 4.8 to 7.1 GHz (39%), which operates acceptably in most of the C‐band, especially at wireless local area network and Intelligent Transport Systems (ITS). A broadband Butler matrix uses broadband 3 dB couplers and a middle network. The geometry of the element and feeding network is utilized in array form to enhance the impedance bandwidth and radiation efficiency of the antenna. The results show that the antenna impedance bandwidth covers 3.82 to 8.2 GHz (port 1) and 3.8 to 8.28 GHz (port 2) for Snn ≤ −10 dB, which covers the C‐band fully (4–8 GHz). Moreover, it has a 3 dB gain‐bandwidth of 2.25 GHz that extends from 4.65 to 6.9 GHz with a peak value of 13.65 dBi. The antenna array has a 3 dB axial ratio bandwidth of 1.65 GHz that extends from 4.9 to 6.55 GHz and involves wireless local area network (5.15–5.825 GHz) and ITS (5.795–6.400 GHz). The radiation efficiency of the array for both port excitations is in excess of 75% when circular polarization is achieved. Two firing beams at elevation angles of 20° and −35° are obtained for ports 1 and 2 upon excitation, respectively.

A Wideband Single-Fed, Circularly-Polarized Patch Antenna With Enhanced Axial Ratio Bandwidth for UHF RFID Reader Applications

A wideband single-fed, circularly-polarized patch antenna with enhanced axial ratio bandwidth for RFID reader application is proposed. The antenna consists of a modified half E-shaped patch, a near-field resonant parasitic (NFRP) patch, and four rotated vertical metallic plates on the ground plane. The metallic plates surrounding the main radiator of the modified half E-shaped patch antenna are fabricated vertically on the ground plane. The operating frequency of the antenna decreases substantially with the vertical metallic plates, which is important for miniaturization of RFID applications. With an elliptical slot and a cut on the modified half E-shaped patch, antenna impedance bandwidth and CP performance both improve. A truncated corner patch as an NFRP element can generate an additional CP radiation mode and further enhances the axial ratio and impedance bandwidth. The measured results show that the antenna has an impedance bandwidth of 14.2% (833–960 MHz), a 3-dB AR bandwidth of 9.0% (846–926 MHz), and an average gain of 7.3 dBic over a 3-dB AR bandwidth. The proposed antenna has a compact size and a low profile ( $0.45\lambda _{0}\times 0.45\lambda _{0}\times 0.074\lambda _{0}$ ).

High Gain and Wideband High Dense Dielectric Patch Antenna Using FSS Superstrate for Millimeter-Wave Applications

Gain and bandwidth enhancement of low profile, linearly polarized square dense dielectric patch antennas using a frequency selective surface (FSS) superstrate layer is proposed. A high dense dielectric patch antenna is utilized as a radiating element instead of a metallic patch in order to gain several significant advantages, including low profile, wide bandwidth, and high radiation efficiency. The implemented antenna is excited by an aperture-coupled feeding technique. The antenna gain is enhanced by using a highly reflective FSS superstrate layer, realizing an antenna gain enhancement of 11 dBi. The implemented antenna acquired a measured gain of about 17.78 dBi at 28 GHz with a 9% bandwidth and radiation efficiency of 90%. The bandwidth of the proposed antenna is improved by using a unit cell printed on two sides, as it provides a positive phase gradient over the desired frequency range. The antenna impedance bandwidth is broadened and the measured impedance matching $S{11}$ exhibited a 15.54% instead of 9% bandwidth while maintaining a high-gain characteristic of about 15.4 dBi. The implemented antenna presents a solid radiation performance with good agreement between the measured and simulation results. For some attractive advantages such as low profile, low cost, lightweight, small size, and ease of implementation, the proposed antenna is a very good candidate for millimeter-wave wireless communications.

Design of a Compact UWB MIMO Antenna without Decoupling Structure

A compact high isolation ultrawideband (UWB) multiple-input-multiple-output (MIMO) antenna is designed. The proposed MIMO antenna consists of a rectangular monopole antenna and a slot antenna fed by two microstrip lines, respectively. To improve the impedance matching, a circular coupling structure is designed to feed the tapered slot antenna. The parasitic resonance introduced by the ground stub helps to extend the impedance bandwidth of monopole antenna at the upper UWB band. Commonly used complex decoupling or coupling structures are eliminated that endow the proposed antenna minimized foot print, which is preferred in mobile handset. Although without decoupling structure, high isolation is obtained between two antenna elements. Simulation and measurement verify the antenna’s desirable performance, showing a broad impedance bandwidth of 3.1–10.6 GHz with |S11| &lt; −10 dB and |S21| &lt; −20 dB over 3.4–10.6 GHz, and |S21| &lt; −18 dB from 3.1–3.4 GHz.

Design of dual band and wideband circularly polarised slot antenna for wireless applications

ABSTRACTIn this paper, two circularly polarised (CP) antennas are proposed. One is dual band CP (DBCP) while the other is wideband CP (WBCP). Both the slot antennas are coplanar waveguide-fed corner truncated structure with an L-shaped radiating patch. The CP bandwidth is significantly improved by connecting one end of the L-shaped patch to the ground plane which also resulted in miniaturisation of the antenna with a size of 48 × 43 mm. DBCP is generated by adding an extra rectangular stub to the ground plane while WBCP by cutting two additional slots in the ground plane. The dual band antenna has a measured impedance bandwidths (S11 < −10 dB) of 34% (2.2–3.1 GHz) and 42% (4.6–7.1 GHz) while the corresponding 3 dB axial ratio bandwidths (ARBWs) are 34% (2.2–3.1 GHz) and 28.6% (4.8–6.4 GHz). The measured impedance bandwidth and ARBW of the wideband antenna are 102% (2.2–6.8 GHz) and 93% (2.3–6.3 GHz), respectively.

Compact and High-Gain UHF/UWB RFID Reader Antenna

A linearly polarized, dual-port, and dual-band radio frequency identification reader antenna is designed to simultaneously operate at ultrahigh frequency (UHF) and ultra-wideband bands for positioning systems. A hybrid design using patch and slot structures within a shared radiating aperture is proposed and demonstrated to achieve a high gain and wideband operation with a limited profile. The size of the total antenna is 200 mm × 10 mm. The measured impedance bandwidth of the UHF antenna ranges from 0.890 to 0.907 GHz with a minimum antenna gain of 9 dBi. The measured impedance bandwidth of the ultra-wideband antenna can cover the frequency band from 3 to 4.99 GHz with a minimum antenna gain of 9 dBi. The antenna gains near two WLAN bands are less than -15 dBi at 2.45 GHz and -5 dBi at 5.8 GHz, respectively. The mutual coupling between the two ports is less than -30 dB over the two bands.

Analysis of Wideband Circularly Polarized Ferrite-Loaded Antenna Based on Unidirectional Resonant Modes

We propose a wideband circularly polarized antenna that consists of a metallic patch and some parasitically coupled elements mounted on a grounded dielectric-ferrite substrate. The metallic patch is fed by a proximity-coupled feed line placed between the ferrite and the dielectric layers. The parasitically coupled elements are included to improve the impedance bandwidth of antenna and are excited through the metallic patch. The antenna utilizes the resonant modes of the structure, which rotate only in the clockwise or counter-clockwise direction. A semi-analytical solution based on the magnetic wall approximation shows that the resonance frequencies of the clock- and counter-clockwise resonant modes differ significantly when operating in the frequency range where the effective permeability of the ferrite layer is negative. Moreover, there is a good agreement between the model presented and full-wave numerical simulations. For the proposed antenna, the results show that the radiation bandwidth is more than 15.5% and the 3 dB axial ratio bandwidth is more than 50%. The proposed antenna is easy to design and fabricate, does not require a complicated feeding network, and has a wideband and wide-angle circular polarization.

Dual port disc monopole antenna for wide‐band MIMO‐based wireless applications

AbstractIn this article, design and implementation of a wide‐band dual port monopole antenna based on single circular disc radiating element has been presented for Multi Input Multi Output (MIMO) configured 4G mobile and wireless communication systems. The proposed antenna uses a partial ground plane with two rectangular grooves which lie exactly below the respective 50 Ω microstrip feeding lines in order to obtain enhanced antenna's impedance bandwidth of 2‐6 GHz. A circular cut with 14 mm radius and centered at intersection of two partial rectangular ground planes is etched to reduce port to port RF coupling. The implemented dual port monopole antenna on 1.575 mm thick RT/Duroid 5880 substrate (with ɛ = 2.2, tangent loss = .001) provides &gt;15 dB RF interport isolation for antenna's 10 dB impedance bandwidth of 2–6 GHz with measured gain variations of 2–6 dBi for each port excitation. In addition to interport isolation measurement for dual port antenna, the envelope correlation coefficient over the required frequency range has been calculated and plotted using S11, S22, and S21 measurement results to endorse the performance of dual port implemented antenna for diversity applications.

Compact size flexible UHF RFID tag antenna for racing pigeon ring applications

A very small size radio frequency identification (RFID) tag antenna specifically designed for racing pigeon ring applications is proposed. The structure of this UHF tag is a closed-loop type printed on a 30 × 8 mm2 polyimide film of thickness 0.063 mm. Thus, it can be wrapped into a double layer plastic cylindrical ring of size similar to those used for racing pigeon. By simply tuning the inner width of the loop, good conjugate matching between the tag chip input impedance and the tag antenna can be achieved. When mounted onto a real preserved dried pigeon feet specimen, the measured impedance bandwidth of the tag antenna was 901-929 MHz. Further experimental results have also shown that the proposed antenna has a maximum reading range of up to 50 cm.

Wideband Shorted Patch Antenna Under Radiation of Dual-Resonant Modes

A novel design concept of enhancing the impedance bandwidth of a single-layer shorted microstrip patch antenna (MPA) is proposed under simultaneous radiation of the one- and three-quarter wavelength resonant modes (TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0,1/2</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0,3/2</sub> modes). Initially, a conventional MPA with the shorting wall is studied to demonstrate that none of the redundant modes can be excited between the dual-resonant modes. Then, a pair of shorting pins are appropriately installed underneath the patch to progressively turn up the resonant frequency of TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0,1/2</sub> mode without significant influence on that of TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0,3/2</sub> mode. After that, a V-shaped slot is etched out on the patch to dramatically reduce the resonant frequency of TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0,3/2</sub> mode with little effect on that of TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0,1/2</sub> mode. With the use of these arrangements, the dual-desired radiative resonant modes are gradually moved in proximity to each other, thus widening the impedance bandwidth under emergence of dual resonant poles. In order to validate the principle and design method, the proposed antenna is designed, fabricated, and measured. The measured results demonstrate that the impedance bandwidth of the proposed shorted patch antenna has been extended to about 11.8%, and it is about 1.82 times of 6.5% of the traditional shorted MPA. Meanwhile, the fabricated antenna exhibits other attractive performances including stable radiation pattern, same polarization, and a low-profile property with the height of 0.042 free-space wavelength.

Resonant slot antenna array on a ridge gap waveguide

The design of a resonant slot array antenna in a single layer ridge gap waveguide is presented. Linear and planar array configurations are developed. The linear array includes eight series slots in the ridge gap waveguide that is powered by a coaxial transmission line. The planar antenna array is developed by incorporating a power divider of four branches in the ridge gap waveguide layer. Each branch of the power divider feeds the linear array. The planar antenna detail design for Ku-band is provided, and the manufactured antenna is measured. The antenna impedance bandwidth of 7% at 13.5 GHz centre frequency, the gain of 20.5 dBi and the side lobe level of <14 dB are obtained.

Ferrite Coating Design for Near-Ground HF Bowtie Antenna

An effective technique is proposed to extend the impedance bandwidth of a near-ground antenna without significantly degrading the realized gain in this communication. This is achieved by coating the ground plane under the antenna with ferrite tiles. Since the current density is found to indicate the magnetic field and image current density on the ground, ferrite tiles are used to coat the ground plane in regions where there is a high current density concentration. In addition, the end loading is also implemented to extend the bandwidth of the antenna at the lower frequency bound. An HF low-profile antenna is used to verify the proposed method. The height of this antenna can be reduced to $0.023\lambda $ using the ferrite tiles, and the lower bound of the bandwidth can be reduced from 7 to 2 MHz. The HF broadband antenna is fabricated, and the measurement is performed to verify the simulated results.