Unidirectional Antenna Research Articles

Single-Motor Controlled Mechanically Frequency Reconfigurable Unidirectional Antenna Array With Stable Radiation Patterns

Single-Motor Controlled Mechanically Frequency Reconfigurable Unidirectional Antenna Array With Stable Radiation Patterns

Visible-Light Uniform and Unidirectional Grating-Based Antennas for Integrated Optical Phased Arrays

Visible-Light Uniform and Unidirectional Grating-Based Antennas for Integrated Optical Phased Arrays

Metal‐loaded slot antenna with flat gain and one‐sided radiation

AbstractA metal‐loaded double‐layer unidirectional radiation slot antenna with flat gain is proposed for millimeter‐wave (mm‐wave) operations. Our presented antenna is constituted of a slot antenna with metal vias, an inner floating metal, a metal line, and ground patch. With the help of inner metal excited by the coupling of the slot antenna, an additional resonance point around 26 GHz could be obtained and the antenna gain is enhanced. To verify the design, the antenna has been fabricated with the prepreg technology. The whole fabricated size is only 0.62 × 0.62λ0² with a thickness of 0.057λ0 (λ0 is the free‐space wavelength at 26 GHz). The measured impedance bandwidth is from 25.1 to 26.55 GHz. Moreover, the proposed antenna obtains a wide flat gain (5.78 ± 0.48 dBi) within the bandwidth and stable one‐sided radiation patterns. The above characteristics show that the proposed antenna is a competitive choice for mm‐wave systems.

Design, Fabrication and Performance Analysis of a Compact Unidirectional Quasi-Yagi Antenna for High Gain and High Directivity at 6.2 GHz

Design, Fabrication and Performance Analysis of a Compact Unidirectional Quasi-Yagi Antenna for High Gain and High Directivity at 6.2 GHz

Broadband unidirectional twin-element MIMO antenna scheme for mid-band 5G and WLAN laptops

This research proposes a broadband unidirectional twin-element multiple-input-multiple-output (MIMO) antenna scheme for mid-band 5G and WLAN applications. The twin-element antenna scheme comprises two single-element antennas, and each single-element antenna consists of a T-shaped hemispherical feeding patch, left- and right-arm radiating patches, and a conjoined triangular ground plane. The twin-element MIMO antenna scheme is integrated with a laptop model functioning as the reflector. The measured impedance bandwidth (|S11|, |S22|≤ − 6 dB) are 55.32%, covering 3.4–6.0 GHz, and the measured mutual coupling (|S12|) is less than − 15 dB. The measured gain at the center frequency (4.5 GHz) is 4.585 dBi. Besides, the measured xz- and yz-plane cross-polarization levels are below − 25 dB and − 15 dB, respectively. The half-power beamwidth (HPBW) in the xz-plane at 3.5, 4.5, and 5.5 GHz are 99°, 92.8°, and 84.2°, and the corresponding HPBW in the yz-plane are 102°, 78°, and 102°. The measured xz- and yz-plane back lobe levels are below − 15 dB across the entire operating frequency band (3.5–5.5 GHz). The radiation pattern of the twin-element MIMO antenna scheme is of unidirectionality. Furthermore, the envelope correlation coefficient and diversity gain of the twin-element antenna scheme are < 0.001 and > 9.99 dB, respectively. The proposed broadband unidirectional twin-element MIMO antenna scheme is thus operationally suitable for mid-band 5G/WLAN communication systems. Essentially, this research is the first to propose a broadband twin-element MIMO antenna scheme for mid-band 5G/WLAN applications.

A Robust Low-Profile, Electrically Small, Unidirectional Mixed-Multipole Antenna Integrated With a Ground Surface

A Robust Low-Profile, Electrically Small, Unidirectional Mixed-Multipole Antenna Integrated With a Ground Surface

DESIGN OF A REFLECTOR ANTENNA IN THE FORM OF A TRUNCATED PARABOLOID

One of the fastest developing areas of radioelectronics are antennas and microwave devices. Antennas are one of the most important functional blocks of different radio engineering systems. Parabolic antennas are the most common unidirectional microwave antennas in radar systems, radio communication and radio astronomy. A parabolic antenna in the form of truncated paraboloid is developed. The antenna is designed, and its characteristics are calculated using one of the most modern software for electrodynamics modeling, FEKO, which represents a new approach to the design of three-dimensional microwave devices. The visualized results of calculations of a parabolic antenna in the form of a truncated paraboloid, which are displayed in the form of graphs. As a radiator for the designed antenna a circular open-ended waveguide is chosen, which consists of two parts – the rectangular and the circular waveguides. For the developed antenna, the radiation patterns in the polar system in E and H planes, and the gain and voltage standing wave ratio (VSWR) are presented, designed in FEKO software. The value of the main lobe of the pattern at half power 〖2θ〗_0,5 and 〖 2φ〗_0,5 is calculated. The structure of the real antenna is shown. The results of comparisons of the values of dependency of VSWR on the frequency and radiation patterns of real and designed antennas are introduced. The parameters of the developed antenna were measured using the NI PXI-5630 network vector analyzer and the NI USRP-2901 radio device. The results of experimental studies have shown their compliance with the results of modeling. The developed antenna operates in the 4.6...6 GHz frequency range.

Magnetic-electric dipole circularly polarized antenna with unidirectional radiation pattern with improved characteristics

Abstract In this paper, a compact unidirectional antenna consisting of a planar electric dipole and a shortened connecting element is introduced. This antenna is excited by a Γ-shaped feeding line. A wide impedance bandwidth in the frequency range of 1.3–3.3 GHz is observed in the output performance. Sufficient main lobe and low level back lobe have been introduced as other characteristics of the structure, based on radiation patterns. The antenna design process is evaluated step-by-step and using parametric study based on the antenna geometry. One of the main features of the desired antenna is the realization of circular polarization in a high percentage of the operational bandwidth 1.5–3.3 GHz. The radiation patterns of the orthogonal planes E-field and H-field along with the left-handed and right-handed circular polarization patterns for the desired antenna have been extracted and analyzed. A three-dimensional structure in the form of stacked stepped disks (SSD) is introduced to increase overall performance of antenna. There is an acceptable similarity between the E-field and H-field page patterns, which shows the accuracy of the design process. On the other hand, for studying the circular polarization, left-handed and right-handed patterns based on the main beam direction and orthogonal polarization level have acceptable performance. The maximum overall gain of the antenna in the designed frequency band is near to 13 dB.

A Simple ±45° Polarized Patch Antenna Array Based on Single-Sided PCB for Wi-Fi 6/6E Application

A high gain, broadband, and ±45° polarized patch antenna array with a quite simple configuration for Wi-Fi 6/6E application is proposed in this article. The antenna consists of a substrate board and a metal layer. All the patches and feeding circuits are printed on the bottom surface of the board. The patches are excited by T-shaped dipoles which are driven by parallel dual-lines. The parameters of the dipoles and parallel dual-lines are specially designed to achieve a broadband covering both 5 GHz and 6 GHz bands of Wi-Fi 6/6E. A prototype was fabricated and tested to validate the concept. In agreement with the simulated results, the measured bandwidth with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> < -10 dB for two ports are both 5.00 - 7.50 GHz, with the isolation higher than 22 dB. Besides, the measured gains for two ports are higher than 9.80 and 9.38 dBi over the operating band. Compared with other unidirectional antennas, the proposed antenna shows great advantages in high gain, low cost, and easy processing.

Superdirective Unidirectional Mixed-Multipole Antennas: Designs, Analysis, and Simulations

Highly directive antenna systems that will address the needs of space-limited Internet-of-Things devices and their NextG applications are in demand. Compact high-frequency high-directivity alternatives to complex, power hungry phased arrays are desired. Several compact, unidirectional mixed-multipole antennas (UMMAs) based upon mixtures of primarily dipoles and quadrupoles are reported. The simulated performance characteristics of these 28 GHz near-field resonant parasitic (NFRP) antennas, notably their large peak directivities and front-to-back ratios, are presented; they are all demonstrated to be superdirective while having attractive radiation efficiencies. Uniform endfire arrays of active closely-spaced equal-length idealized wire dipoles are exemplified as reference cases. The Rayleigh quotient (RQ) method typically used to determine their amplitude coefficients is extended for the first time to achieve unidirectional versions. Comparisons between these unconstrained and constrained RQ-designed arrays are made. While the performance characteristics of the single-source broadside-radiating UMMAs approach those of the reference arrays, a direct comparison of a realizable UMMA with the analogous unequal-length, non-uniformly-spaced idealized dipole array demonstrates its superiority. A two-element UMMA array that is scalable to a larger number of elements is also presented and shown to be superdirective, illustrating that the attractive properties of its individual elements are maintained even when mutual coupling occurs.

Formulas for Beam Shift and Beam Narrowing in 1-D Leaky-Wave Antennas Due to Element Pattern

The radiation pattern of one-dimensional (1-D) unidirectional leaky-wave antennas (LWAs) is typically derived from the analysis of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">space factor</i> (SF) only. However, when the antenna aperture is characterized by a longitudinal radiating current, a cosine-type <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">element pattern</i> term has to be included: this factor may considerably affect the beam properties. Specifically, the beam peak is shifted and the beamwidth is narrowed when the element pattern is included. These effects are more prominent as the antenna size decreases and the beam angle increases. Approximate but accurate analytical formulas are here provided and numerically validated to predict the beam angle and the half-power beamwidth for these kinds of 1-D unidirectional LWAs when the element pattern is included.

Sniffer for Detecting Lost Mobiles

The main goal of this Endeavour is to use sniffer technology to track down a misplaced cell phone. Regularly thousands of adaptable get misplaced. Security for mobile devices is necessary since portable companies are now building mobile devices with IMEI to locate the mobile device, but this system is not very effective. Hence, sniffer technology is applied. This device, which combines a Sniffer Base Station, an Unidirectional Antenna, and Tracking Software, can be referred to as a Base Station. To maintain the recurrence, the Sniffer Base Station is used. Recurrence is a VHF extension at 900 MHzTo exchange the flag relating to the desired recurrence for receiving and transmitting signals, unidirectional radio wire is employed. The most important component of cell phone monitoring is the programming. Because of the way this programming is laid out, the IMEI of the device is read from its Memory. It checks for a signal from a device that responds to a flag sent by sniffer technology. The IMEI number, which stands for “International Mobile Station Equipment Identity,” identifies a device that uses GSM technology.

Gain and bandwidth enhancement of low‐profile unidirectional radiation spiral slot antenna

AbstractA novel simple antenna based on substrate integrated coaxial‐like waveguide (SICW) is presented to enhance the gain and bandwidth of circularly polarized (CP) antenna with unidirectional radiation. The stepped inner metal strip is introduced in SICW, which results in a stronger radiation gain and wider axial ratio bandwidth. In addition, unlike traditional spiral antennas, the slot spiral antenna can be directly fed by a coaxial line at the inner port of the waveguide. As SICW can make the antenna directly realize unidirectional radiation, the extra reflector is not needed, and the antenna has a low profile of ( is the free space wavelength at the lowest frequency). The simulation and measurement results show that by using SICW with a stepped inner metal strip, the overlapping bandwidth of CP antenna can be increased significantly from 57.3% (2.7–4.85 GHz) to 71.6% (2.6–5.5 GHz) and the boresight gain of the antenna is improved 2 dBi over the entire frequency band.

Smart Magnetic Optical Antenna for Automatic Nanoalignment and Photon Beaming from Prepatterned Single Quantum Dot Nanospot.

We present a unidirectional dielectric optical antenna, which can be chemically synthesized and controlled by magnetic fields. By applying magnetic fields, we successfully aligned an optical antenna on a prepatterned quantum dot nanospot with accuracy better than 40 nm. It confined the fluorescence emission into a 16-degree wide beam and enhanced the signal by 11.8 times. Moreover, the position of the antenna, and consequently the beam direction, can be controlled by simply adjusting the direction of the magnetic fields. Theoretical analyses show that this magnetic alignment technique is stable and accurate, providing a new strategy for building high-performance tunable nanophotonic devices.

Low-Profile and Wideband Unidirectional Antenna With Ferrite Loading for UHF Applications

A low-profile and wideband unidirectional antenna with ferrite loading is presented for ultrahigh-frequency (UHF) applications. This design comprises a slotted bowtie antenna with parasitic elements placed 50 mm over a ground plane. A small amount of ferrite loaded on the center of the ground plane plays a crucial role in improving the performance of the low-profile antenna. The ferrite used here is a new type of magnetodielectric material with relatively high permeability and permittivity, as well as low magnetic and dielectric loss. The loaded ferrite introduces an additional phase change of the electromagnetic field reflected by the ground to improve the impedance matching, bandwidth, efficiency, and gain of the low-profile antenna. The evolution process and mechanism of the proposed antenna are elaborated. For validation, an optimized antenna prototype was fabricated and measured. The measured results are consistent well with their simulations, which shows the realized gain of 7.2–9 dBi over <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert \text{S}_{11}\vert \le -10$ </tex-math></inline-formula> dB impedance bandwidth of 38% (480–705 MHz). The overall profile of this antenna is only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.08\lambda _{0}$ </tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> is the free-space wavelength at the lowest frequency of operation.

Design of pattern-reconfigurable circularly polarized unidirectional antenna based on quasi-radiator for ISM applications

A pattern-reconfigurable circularly polarized antenna for 2.45 GHz industrial, scientific, and medical (ISM) band applications is designed in this work. The proposed antenna consists of a slotted-stepped monopole connected to a rectangular ground plane via a shorting side-stub. This converts the omnidirectional radiation pattern of the antenna into stable unidirectional radiation. To dynamically steer the realized pattern, two switchable RF PIN diodes are jointly incorporated into the side-stubs to achieve symmetrical radiations in specific operating modes. In this way, the radiation patterns can be simultaneously tuned in the ±y directions by the simple switching of the PIN diodes ON and OFF. The fabricated prototype achieves an S11 smaller than -10dB within the 3dB axial ratio (AR) bandwidth with stable far-field patterns. The antenna maintains a low-profile and compact size of 0.055λ02 which makes it suitable for body-centric wireless communication (BWC) and personal wireless area networks.

Characteristic Mode Inspired Single-Plate Unidirectional Antenna Using Complementary Characteristic Radiation

Based on characteristic mode theory (CMT), a novel single-plate complementary antenna with a unidirectional radiation pattern is proposed in this communication. The proposed antenna is composed of an isosceles right triangular conductive slab (IRTCS), three inductive coupling elements (ICEs), and a feeding network. By exciting two complementary current modes of IRTCS simultaneously, the radiation of IRTCS can be tailored. More specifically, ICEs can stimulate the electric dipole and magnetic dipole current modes of IRTCS concurrently through appropriate excitation, thereby realizing an endfire radiation pattern by combining the two complementary characteristic fields with suitable modal weighting coefficients (MWC). For proof of concept, a prototype is fabricated, and the measured results demonstrate that a good unidirectional radiation pattern is achieved with a front-to-back ratio (FBR) larger than 20 dB, which verifies the feasibility and reliability of the proposed method. Compared with the conventional complementary antennas or Huygens source antennas which need two different radiating sources to realize the electric and magnetic dipole radiations individually, the proposed method reuses the radiating aperture and achieves the unidirectional radiation by a single radiating aperture.

Optimization of 1-D Unidirectional Leaky-Wave Antennas Based on Partially Reflecting Surfaces

In a previous work, we derived optimum conditions for the design of finite-size 1-D unidirectional leaky-wave antennas (LWAs) in the general case. The bandwidth and the gain–bandwidth figure of merit are, however, structure-specific and have not been discussed yet. A practical case that is widely investigated in the literature is that of 1-D unidirectional LWAs based on partially reflecting surfaces (PRSs). In this work, we not only evaluate these features for this specific class of antennas, but we also derive design rules for optimizing the PRS impedance and cavity height to get maximum gain. Numerical results and full-wave simulations are finally proposed for a realistic example based on a metal strip-grating structure, to validate the theoretical findings.

Multipole-Based Electrically Small Unidirectional Antenna With Exceptionally High Realized Gain

Electrically small, high-directivity antennas are in demand for a variety of current and future wireless applications. An electrically small directive antenna (ESDA) that requires only one specially engineered port to excite a set of multipoles is demonstrated in this article. Four 90° copper sectors are combined with additional structures and fed with a coaxial cable. Two resonant quadrupoles (equivalent to two pairs of resonant electric dipoles) and one magnetic dipole are excited. Both high radiation efficiency and good impedance matching are achieved. Theoretical calculations, numerical simulations, and experimental measurements are shown to be in good agreement. An optimized prototype is designed, fabricated, and tested. The measured results confirm that it is a supergain system. The unidirectional ESDA has a peak directivity of 6.71 dBi, a peak realized gain of 6.31 dBi, radiation efficiency of 94.5%, and a front-to-back ratio of 14.89 dB at its resonance frequency, 814 MHz. Its height is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.06 \lambda _{\mathrm{ res}}$ </tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ka = 0.98$ </tex-math></inline-formula> . These measured realized gain and directivity values exceed both the Harrington and Kildal–Best <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ka$ </tex-math></inline-formula> -based upper limits.

A portable non-invasive microwave based head imaging system using compact metamaterial loaded 3D unidirectional antenna for stroke detection

A metamaterial (MTM) loaded compact three-dimensional antenna is presented for the portable, low-cost, non-invasive microwave head imaging system. The antenna has two slotted dipole elements with finite arrays of MTM unit cell and a folded parasitic patch that attains directional radiation patterns with 80% of fractional bandwidth. The operating frequency of the antenna is 1.95–4.5 GHz. The optimization of MTM unit cell is performed to increase the operational bandwidth, realized gain, and efficiency of the antenna within the frequency regime. It is also explored to improve radiation efficiency and gain when placed to head proximity. One-dimensional mathematical modelling is analyzed to precisely estimate the power distribution that validates the performance of the proposed antenna. To verify the imaging capability of the proposed system, an array of 9 antennas and a realistic three-dimensional tissue-emulating experimental semi-solid head phantom are fabricated and measured. The backscattered signal is collected from different antenna positions and processed by the updated Iterative Correction of Coherence Factor Delay-Multiply-and-Sum beamforming algorithm to reconstruct the hemorrhage images. The reconstructed images in simulation and experimental environment demonstrate the feasibility of the proposed system as a portable platform to successfully detect and locate the hemorrhages inside the brain.