Omnidirectional Radiation Performance Research Articles

Design of a planar microstrip antenna with wide bandwidth and omnidirectional radiation patterns using tightly coupled structures

AbstractA wideband planar microstrip antenna with good horizontally polarized omnidirectional radiation performance is presented. Using tightly coupled structures, six planar dipole elements are deployed in a circular pattern, and radiation is synthesized into a horizontal omnidirectional radiation pattern by superposing the far‐field pattern of the six dipoles. Owing to the tight coupling between radiating elements, the proposed antenna has a wide operating band. The radiating elements are printed on a printed circuit board and excited by a balun with uniform magnitude and synchronized current. A prototype is manufactured and measured. The measurement results show that the impedance bandwidth of the proposed antenna is 102. The gain variation of the horizontal omnidirectional pattern is less than 1.2 dB in the 1.27–3.89 GHz band. Within the operating frequency band, the total efficiency and radiation efficiency are greater than 82% and 88%, respectively. The diameter of the antenna is 0.48, where is the wavelength corresponding to the lowest frequency in the operating band.

Bandwidth‐enhanced horizontally polarized omnidirectional slot antenna based on single‐ridge trapezoidal waveguide

AbstractThis letter presents a Ku‐band horizontally polarized (HP) omnidirectional antenna based on single‐ridge trapezoidal waveguide (STW). Four groups of longitudinal slots are etched on a pair of back‐to‐back arranged STWs to achieve the HP omnidirectional radiation performance. The number and distribution of each radiation slot group are optimized to reduce the gain variation. An out‐of‐phase stripline power divider cascaded with two probe‐based vertical power dividers is used to excite all radiating slots in a series‐parallel hybrid structure, which helps to enhance the boresight radiation bandwidth. For demonstration, a prototype covering 14.5 to 15.5 GHz is designed, fabricated, and measured. Experimental results show that the good impedance matching (|S11|←14 dB) and the measured out‐of‐roundness for the omnidirectional radiation pattern are less than 4.4 dB within the desired frequency band. High gain and wideband omnidirectional radiation characteristics can provide a wide range of coverage and good signal transmission performance for outdoor wireless communication systems.

Low-Profile Ultra-Wideband Dual-Polarized Omnidirectional Antenna for Indoor Base Station

A low-profile ultra-wideband omnidirectional antenna with dual polarizations for indoor mobile communication is presented. The horizontally polarized (HP) omnidirectional element is introduced by using twelve I-shaped slot antennas, which are arranged in a circle-shaped array and excited by a 1-to-12 power divider. The vertically polarized (VP) omnidirectional performance is introduced by using a dual-M-shaped monopole with a small ground plane. To enhance the impedance matching within an ultra-wide bandwidth, a top metal disk with four chunks, a bottom metal loop and a ring slot embedded in the ground plane are employed for the design of the VP element. After replacing the metal disk of the VP element with the designed HP element, the omnidirectional antenna with dual polarizations is then simply achieved. By utilizing this new method, an ultra-wideband dual-polarized omnidirectional antenna for indoor mobile communications is designed, manufactured and measured. It has an ultra-wide bandwidth of 117% (1.44-5.5 GHz), a high isolation of 30 dB, and a low profile of 0.16λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> denotes the wavelength at the lowest frequency of the operating band). Good omnidirectional radiation performance with gain variation < 2.6 dBi is obtained for both HP and VP ports over the ultra-wide operating band.

A Flexible Bi-Stable Composite Antenna with Reconfigurable Performance and Light-Responsive Behavior

An integrated solution providing a bi-stable antenna with reconfigurable performance and light-responsive behavior is presented in this paper for the first time. The proposed antenna includes a radiation layer with conductivity, which is integrated onto the bi-stable substrate. First, the effect of the radiation layer material and substrate layer parameters on antenna performance was studied. The experiment showed that an antenna with CNTF has a wider impedance bandwidth than one with CSP, namely 10.37% versus 3.29%, respectively. The resonance frequency increases gradually with the increase in fiber laying density and fiber linear density. Second, the influence of state change of the substrate layer on the antenna radiation pattern was studied. The measured results showed that the maximum radiation angle and gain of states I and II are at 90°, 1.21 dB and 225°, 1.53 dB, respectively. The gain non-circularities of the antenna at states I and II are 4.48 dB and 8.35 dB, respectively, which shows that the antenna has good omnidirectional radiation performance in state I. The display of the array antenna, which shows that the array antenna has good omnidirectional radiation performance in state A, with gain non-circularities of 4.20 dB, proves the feasibility of this bi-stable substrate in reconfigurable antennas. Finally, the antenna deforms from state I to state II when the illumination stimulus reaches 22 s, showing good light-responsive behavior. Moreover, the bi-stable composite antenna has the characteristics of small size, light weight, high flexibility, and excellent integration.

An omnidirectional filtering dielectric resonator antenna based on metal patches

A novel filtering dielectric resonator (DR) antenna (DRA) is designed in this article. By using a single-layer planar feed structure, the TM01δ and TM011+δ modes of a cylindrical DR are excited. The proposed filtering DRA achieves a good omnidirectional radiation performance and a flat gain response. By loading a crossed patch with four shorting pins on the feed structure, the lower edge of the passband obtains a steep roll-off rate. By plating four metal patches on the side wall of the DR, a radiation null (RN) is successfully introduced at the upper sideband of the DRA. The suppression levels of the proposed filtering DRA in the lower and upper stopbands are above 18 dB. Therefore, the proposed filtering DRA achieves filtering function without additional circuits. For demonstration, a prototype DRA is fabricated and measured. The simulated and measured results are basically consistent.

Design of an omnidirectional transmit/receive antenna pair using mushroom‐like electromagnetic band‐gap structure

This paper presents a transmit-receive (T/R) antenna pair with omnidirectional and broadband radiation performance. The proposed antenna combines a patch with mushroom-like electromagnetic band-gap (EBG) structures. The mushroom structures are utilized to enhance the radiation characteristics such as impedance bandwidth, directivity, and gain. Two T/R antennas with 3 × 3 and 5 × 5 arrays working in K-band are designed and fabricated, the transmit (TX) and receive (RX) antennas are printed on a single-layer grounded dielectric substrate. Both the TX and RX antennas consist of an array of mushroom-like EBG structures around the monopole microstrip antenna, which is loaded with four stubs and fed by a 50 Ω coaxial probe. The dimensions of the fabricated prototype 3 × 3 array antenna are 3.58 λ 0 × 1.61 λ 0 ( λ 0 -the wavelength in free space at 24 GHz). The TX/RX measured impedance bandwidth ( ∣ S 11 ∣ < −10 dB) are 9.58% (23.6 ~ 25.9 GHz), 12.08% (22.8 ~ 25.7 GHz), respectively. The measured peak gain is 3.45 dBi at 24.8 GHz. For the 5 × 5 array antenna, the aperture size is 5.58 λ 0 × 2.61 λ 0 . The measured impedance bandwidth ( ∣ S 11 ∣ < −10 dB) is 9.17% (23.65 ~ 25.85 GHz) and 12.71% (22.65 ~ 25.7 GHz) for the TX and RX, respectively. The measured peak gain increases by nearly 2 dB. Measurement results show that both antennas have a TX/RX isolation level better than 20 dB and achieve monopole-like omnidirectional patterns over its operating frequency band.

Low-profile dual-band pixelated defected ground antenna for multistandard IoT devices

A low-profile dual-band pixelated defected ground antenna has been proposed at 3.5 GHz and 5.8 GHz bands. This work presents a flexible design guide for achieving single-band and dual-band antenna using pixelated defected ground (PDG). The unique pixelated defected ground has been designed using the binary particle swarm optimization (BPSO) algorithm. Computer Simulation Technology Microwave Studio incorporated with Matlab has been utilized in the antenna design process. The PDG configuration provides freedom of exploration to achieve the desired antenna performance. Compact antenna design can be achieved by making the best use of designated design space on the defected ground (DG) plane. Further, a V-shaped transfer function based on BPSO with fast convergence allows us to efficiently implement the PDG technique. In the design procedure, pixelization is applied to a small rectangular region of the ground plane. The square pixels on the designated defected ground area of the antenna have been formed using a binary bit string, consisting of 512 bits taken during each iteration of the algorithm. The PDG method is concerned with the shape of the DG and does not rely on the geometrical dimension analysis used in traditional defected ground antennas. Initially, three single band antennas have been designed at 3.5 GHz, 5.2 GHz and 5.8 GHz using PDG technique. Finally, same PDG area has been used to design a dual-band antenna at 3.5 GHz and 5.8 GHz. The proposed antenna exhibits almost omnidirectional radiation performance with nearly 90% efficiency. It also shows dual radiation pattern property with similar patterns having different polarizations at each operational band. The antenna is fabricated on a ROGERS RO4003 substrate with 1.52 mm thickness. Reflection coefficient and radiation patterns are measured to validate its performance. The simulated and measured results of the antenna are closely correlated. The proposed antenna is suitable for different applications in Internet of Things.

Structural Design and Electrical Characteristics Analysis of Mid-Load Whip Antenna

In order to facilitate the integration of the offshore surface antenna and reduce the manufacturing cost, the resonance shortening length and omnidirectional radiation performance of a centrally loaded whip antenna are analyzed. By calculating the impedance characteristics of each part of the midload whip antenna, the shortened length of the antenna in the resonance state is obtained; the superimposed field strength of the midload whip antenna to the far field is calculated and its radiation performance is analyzed; the simulation is carried out by using FEKO electromagnetic simulation software. Through the field test, the reflection coefficient and resonant frequency of the antenna before and after shortening are compared, and the directivity of the midload whip antenna and the traditional whip antenna is compared. The simulation and experimental results show that under the preset frequency of 75 MHz, the reflection coefficient of the shortened midload whip antenna decreases by 4.414 dB and 19.09 dB, respectively. The optimal operating frequency is about 68.6 MHz–79.4 MHz, and the bandwidth is 10.8 MHz. Compared with the traditional whip antenna, the midload whip antenna at the radiation null point receives a larger field strength.

A Pattern-Reconfigurable Dielectric Resonator Antenna Based on Switchable Directors

A novel pattern-reconfigurable dielectric resonator antenna (DRA) with compact structure and high efficiency is proposed in this letter by introducing a pair of switchable directors. The switchable directors are arranged on both sides of an omnidirectional DRA, which operates in the TE01δ mode. Their directing function can be controlled by switching the <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> / <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> status of the p-i-n diodes so that one omnidirectional radiation pattern and two unidirectional endfire patterns are provided in the azimuthal plane. To verify this idea, a prototype of the proposed antenna is fabricated and measured. Good agreement between the simulated and measured results can be observed. The peak gain in endfire status reaches 4.5 dBi and the front-to-back ratio is more than 12 dB. Meanwhile, the gain variation of the omnidirectional pattern in the azimuth plane is less than 2 dB, which shows good omnidirectional radiation performance.

An Ultra-Wideband CPW Fed Slot Antenna for IoT Applications

An Ultra-wideband (UWB) radio is a fast-emerging technology. It is offering several unique attractive features that promotes major advances in wireless communications, networking, imaging, radar and positioning systems. Here, an Ultra-Wideband Coplanar Waveguide fed Monopole antenna for IoT Applications is proposed. The bandwidth of the antenna is enhanced due to the partial rectangular patch and the round corner of the rectangular slot. To validate the simulation results, prototypes of the proposed antenna are fabricated and tested. Based on the results, good agreement has been achieved between the measurement and simulation. The antenna prototype with a total size of 138 mm × 40 mm achieves good impedance matching, constant gain and stable radiation patterns. The impedance bandwidth of the antenna reaches up from 600 MHz to 6.0 GHz for S11 with good omnidirectional radiation performance has also been achieved.

A Compact 8-States Frequency Reconfigurable UWB Antenna

To meet the anti-interference and multi-function requirements of the antenna, a compact 8-states frequency reconfigurable ultra-wideband (UWB) monopole antenna is proposed. The antenna consists of a coplanar waveguide structure (CPW), defected ground structure (DGS), rectangular radiation patch, and stepped feed line. Band rejections at the C band, WLAN, and X band are generated by two C-slots and inverted U-slot, respectively. Three PIN diodes are connected across the C-slots and inverted U-slot. By controlling the on/off state of PIN diodes to realize notch reconfiguration. The antenna size is only 22 mm $\times 13$ mm $\times0.8$ mm. The measured results show that the antenna can work in 8 states. The impedance bandwidth of UWB mode is 2.82-13.25 GHz, the relative bandwidth is 129.8%. The notch band is 3.19-4.58 GHz, 5.26-6.21 GHz, and 7.87-8.73 GHz, respectively. The antenna has stable gain, good omnidirectional radiation performance, and can switch freely between UWB mode and each notch band mode.

Low-Profile Omnidirectional WIFI Antennas With Pattern Reconfigurability Inspired by Meta-Resonators

A family of low-profile, omnidirectional antennas inspired by metamaterial resonators (meta-resonators) for WIFI applications is proposed. Two novel meta-resonators with an inductive feeding are presented. They can be considered as an LC resonant tank. Arbitrary size miniaturization could be obtained. Three rotated metamaterial unit cells constitute a ring-shaped structure, which generates a horizontally polarized, omnidirectional radiation. A direct microstrip power divider is used to excite them in-phase, achieving a small and low-profile magnetic dipole-like antenna. Their working principles are illustrated in detail by equivalent circuit and current distribution. Two omnidirectional antennas based on different meta-resonators and one pattern-reconfigurable antenna are fabricated and measured, respectively. Their measured −10 dB frequency bandwidth, peak gain, and radiation efficiency are greater than 2.4–2.48 GHz, 1.17 dBi, and 80%, respectively. They demonstrate superior advantages in terms of a miniaturized/low-profile size, simple structure, good bandwidth, and omnidirectional radiation performance, which are well positioned for 2.40 GHz WIFI router or indoor communications.

High-Gain Conical-Beam Traveling-Wave Array Antenna Based on a Slotted Circular Waveguide at $Ku$ -Band

A high-gain conical-beam traveling-wave array antenna based on a slotted circular waveguide is designed at the higher part of Ku-band. A single radiating element is formed by a ring of eight equally spaced slots fed by a circular waveguide. The excitation of the nonfundamental TM01 mode provides a uniform feeding distribution to each slot, generating an omnidirectional radiation performance. Thus, an array antenna formed by 48 rings of slots is proposed following the design rules of traveling-wave arrays. Every ring is properly designed to achieve a uniform power distribution and consequently maximum directivity for the array antenna performance. The distance between elements is also adjusted to obtain the better input matching response and mitigate the grating lobe appearance, generating a high-gain conical-beam radiation performance suitable for satellite and fifth-generation communications. The proposed antenna design has been manufactured in plastic material by using a 3-D printing process and plated by a spray metallization process. A -10 dB impedance bandwidth higher than 23%, high-gain values around 13.5 dB, or total efficiency higher than 98% has been achieved for the whole frequency band.

Compact Wideband Folded Dipole Antenna With Multi-Resonant Modes

A compact and wideband folded dipole antenna with multi-resonant modes is presented in this paper. Three resonant modes are obtained by using a modified planar folded dipole and its coupled feeding structure. Incorporating the shorting pins and parasitic patches, multiple resonant modes in the antenna are manipulated, shifted, and then combined to increase the impedance bandwidth. Using this concept, a prototype of a multi-mode folded dipole is designed, fabricated, and measured. The experimental results show that the proposed antenna achieves a bandwidth of 80% from 1.57 to 3.68 GHz, while occupying a compact size of $0.3\lambda _{0}\times 0.15\lambda _{0}\times 0.05\lambda _{0}$ ( $\lambda _{0}$ is the wavelength in free space at the lowest operating frequency). Furthermore, a simple and effective design to achieve good omnidirectional radiation performance is developed by placing two proposed folded dipoles back to back. The antenna exhibits a flat gain variation of less than 1.27 dB over a broad bandwidth (82%) in the horizontal plane. Such a compact, wideband, planar antenna is a promising candidate for indoor signal coverage, wireless access points, and micro base stations in 2G/3G/4G/5G and WLAN/WiMAX wireless communication systems.

Realization of acoustic omnidirectional radiation with annular anisotropic zero-density metamaterial

Acoustic metamaterials are artificial structures with unique properties that offer great flexibility for manipulating acoustic waves. In this manuscript, we describe the fabrication of an annular anisotropic metamaterial with an azimuthal effective density approaching zero and demonstrate its robust omnidirectional radiation performance. Locating two sources at a distance from one another or placing a cross-shape obstacle between them inside the cavity of the metamaterial produces acoustic omnidirectional radiation over a wide frequency range. This is quite different from the behavior in the cavity mode. This anisotropic zero-density metamaterial can be considered as a source shifter, which may have applications in acoustic manipulation, acoustic communication, cloaking, and sonar systems.

Dual-Polarized Omnidirectional Antenna With High Isolation Based on the Theory of Characteristic Modes

A dual-polarized antenna with omnidirectional radiation and high isolation performance is proposed in this paper. The proposed antenna consists of courtyard-shaped metal frame, feeding network, and metal background. Working mechanism of the proposed antenna is analyzed by the theory of characteristic modes. Two orthogonal polarizations can be achieved by utilizing the orthogonal current distributions on the courtyard-shaped metal frame. In order to obtain the horizontal-polarized mode, eight slots etched on the walls of the courtyard-shaped metal frame are excited. A feeding network is placed at the inner part of courtyard-shaped metal frame for a compact design. Measured results show that the proposed antenna can cover the impedance bandwidth of 1.80–2.81 GHz for both polarizations with their corresponding isolations better than 35 dB. A peak gain of 7 dBi and a gain ripple less than 3 dB in the horizontal radiation plane are achieved. The proposed antenna can be applied in the indoor wireless communication.

Estimation of resonant frequency and bandwidth of compact unilateral coplanar waveguide‐fed flag shaped monopole antennas using artificial neural network

ABSTRACTNeural network based estimation of resonant frequency and bandwidth of compact unilateral coplanar waveguide (CPW)‐fed flag shaped printed monopole antennas is presented. The proposed antennas are similar to CPW‐fed antenna; however, by replacing unilateral CPW feed instead of CPW feed, compactness of about 48.615 percent is achieved. These are designed on an inexpensive FR4‐epoxy substrate with dielectric constant of 4.4 and thickness of 1.6 mm. Resonant frequencies and bandwidths of the flag shaped antennas with different dimensions are computed using method of moment electromagnetic solver IE3D 15.10 and they have been given as training and test data for the proposed multilayered perceptron feed forward neural network with Levenberg–Marquardt training algorithm to estimate the resonant frequency and bandwidth of the proposed antennas. The estimated values of resonant frequency and bandwidth with average percentage of error are 1.275 and 0.325, respectively. For verification, the proposed antenna is fabricated and measured with resonant frequency 5.78 GHz and bandwidth of 1.0 GHz for HiperLAN/2 and IEEE802.11a applications. It has impedance bandwidth from 5.0 to 6.0 GHz for return loss lower than −10 dB and good omnidirectional radiation performance over entire frequency range, with a compact size of 11.07 × 27.5 × 1.6 mm3. Various features such as compactness, simple geometry, and low cost, uniplanar structure make the antennas suitable for modern wireless communication systems. This approach replaces the use of very complicated analysis. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:337–342, 2015

Research on a Novel Folded Monopole With Ultrawideband Bandwidth

In this letter, a novel folded monopole antenna with an ultrawideband (UWB) bandwidth and omnidirectional radiation performance has been proposed. An inverted “S”-type structure was formed by folding the planar monopole, which not only realizes dimension reduction, but also contributes to a decrease in the size of the ground plane; the proposed monopole antenna, meanwhile, has a more circular radiation pattern with the frequency ratio of 3.4:1, compared to the planar monopole antenna. Simulation has been carried out together with the measurement of the fabricated antenna. Good agreement between the measured and simulated results can be observed, showing that the antenna is capable of working in the frequency range from 3.1 to 10.6 GHz with return loss less than -10 dB.

Quad band‐notched ultrawideband antenna with a modified H‐shaped resonator

In this study, a novel planar ultrawideband antenna, with a quad band-notched function, is investigated. The proposed antenna consists of a circular-shaped radiating element, a 50 Ω microstrip feed line, a modified H-shaped resonator, and a partially truncated ground plane. The proposed H-shaped resonator, with quadruple resonance characteristics, is realised without any change in its size but instead, by modifying the simplified composite right/left-handed resonator with dual resonance characteristics. By embedding the modified H-shaped resonator beside the microstrip feedline, band-rejected filtering properties in the wireless local area network /worldwide interoperability for microwave access bands are generated. By changing the modified H-shaped resonator's dimensions, the proposed antenna shows variable quadplex-filtering characteristics, such as band-notch frequency and its bandwidth. The measured results show that the proposed antenna design exhibits a 10 dB return loss bandwidth from 2.12 to 13.63 GHz, excluding the rejection bands. Very sharp notch and high band-rejection are achieved, and relatively stable omnidirectional radiation performance over the entire frequency range is also obtained.

DESIGN OF WIRELESS POWER TRANSFER SYSTEMS USING MAGNETIC RESONANCE COUPLING FOR IMPLANTABLE MEDICAL DEVICES

E-cient and compact wireless power transfer (WPT) systems are proposed and designed for recharging small implantable medical devices. They use the magnetic resonance coupling scheme to transfer power over a relatively large distance. The receiver resonator coil and the load loop are designed in correspondence to size restriction of implantable devices. The dimensions of the coils are optimized and efiective values of the lumped capacitors are investigated and flne-tuned for e-ciency enhancement. Three design conflgurations of the WPT system, each consisting of two coils at the transmitter and two coils at the receiver, are designed and fabricated. The transfer e-ciency is measured over difierent transmission distances and with difierent orientation angles of the receiver coils. The measurement results show good agreements with the simulations and illustrate that the proposed WPT systems exhibit nearly omnidirectional radiation performance. Furthermore, the receiver coils are implanted inside of a biological object to show the power can be transferred efiectively.