Radiation Pattern Research Articles

Far-field pattern accuracy improvement in planar near-field measurement using infinitesimal dipole modeling

This paper discusses the challenges in accurately measuring the far-field performance of array antennas, which have become more complex and larger due to recent trends in increasing the number of elements and the antenna size. The far-field measurement method, which is a general method for measuring a radiation pattern in a far-field, is difficult to be utilized at a high frequency due to limitations in physical chamber size and difficulty in diagnosing an antenna. In order to improve these problems, a near-field measurement method is used as an alternative. Even though using a near-field measurement, the accuracy of the derived far-field pattern is reduced at low elevation angles due to zero-padding of data outside the measurement area. The integration of the near-field measurement with the source reconstruction is a promising approach to enhance the measurement limits of the far-field pattern analysis. This paper aims to extend the previous work to accurately predict the far-field radiation pattern, especially in the low elevation angles. The verification of the proposed method is performed for a standard gain horn and 4 by 4 patch array antennas, with and without beam steering.

Drone direction estimation: phase method with two-channel direction finder

This scientific article presents a block diagram of a two-channel radio direction finder that effectively uses the phase method to determine the direction of the signal source. The main attention is paid to the mathematical model of the formation of the cardioid radiation pattern of biconical antennas, which have unique directivity characteristics. These features significantly affect the accuracy and reliability of the bearing determination process. The developed algorithm aims to accurately determine the direction of motion of an unmanned aerial vehicle, especially in the context of a two-channel radio receiver and a five-element antenna system. This antenna system provides unique capabilities for increased resolution and directional accuracy. The article also touches on the issue of software implementation of the developed algorithm, which is aimed at increasing the number of generated bearing estimates in conditions of limited time for observing an unmanned aerial vehicle. Thus, the proposed method is of interest in the field of precision direction finding in the context of small unmanned vehicles.

Multimodal planar monopole filtenna for 5G applications

This paper presents a novel planar filtering antenna (filtenna) with simple layout based on tightly-coupled different-length monopoles. Its design methodology is based on an even-mode/odd-mode decomposition of the monopole currents, and the combination of both modes in a multimodal circuit model that facilitates the design and tuning of the antenna and the accompanying feeding network, since most of the process is performed using fast circuit simulations. The circuit model casts light into the interaction between conducting and radiating modes in the bulk of the antenna, and on how this interaction can be used to propose feedback loops that increase and define the radiation band. Using these modal tools, a filtenna was designed and fabricated to fully cover the new 5G frequency bands (n77, n78 and n79) from 3 to 5 GHz that are currently being adopted by many countries for high-capacity data transmission. It features a 62.9% FWB, dipole-like radiation patterns, good out-of-band rejection up to 10 GHz, and a very good trade-off between design/structural-simplicity and bandwidth.

Design of Compact Size Tri-Band Stacked Patch Antenna for GPS and IRNSS

Abstract: This paper introduces a low-profile, compact tri-band microstrip patch antenna designed for GPS and IRNSS applications. The proposed antenna operates at frequencies of 1.57 GHz, 1.22 GHz, and 1.77 GHz. The antenna configuration consists of a patch antenna with a slip slot or manderline to generate three frequency bands while maintaining an acceptable radiation pattern. The focus of the study is to enhance the antenna's gain across all three frequency bands. This design aims to offer a versatile solution for navigation systems, leveraging the tri-band capability to accommodate different satellite signals and improve overall performance in GPS and IRNSS applications.

Radiation Pattern Reconfigurable Arch-Shaped Dual-Band Antenna for Wi-Fi and WLAN Applications

This paper describes the design and analysis of a reconfigurable radiation pattern dual-band antenna for Wi-Fi and WLAN applications. The antenna patch comprises two parts: the upper part, which consists of three symmetrical oval rings, and the lower part, which is shaped like a lotus flower. By controlling the ON and OFF states of lumped p-i-n switches to control the direction of the radiation beams, the proposed pattern reconfigurable antenna achieves three reconfigurable states. The beam's direction change is performed by two switches that are connected in the gap between the feedline and the arch. The proposed antenna operates at 2.4 and 5.5 GHz, covering the bands from 2.1882 to 2.55 GHz and from 5.31 to 5.96 GHz, respectively. Additionally, the directivity over the working bands is about 1.92 to 4 dBi while the gain lies in the range of 1.66 to 3.5 dB. Moreover, the voltage standing wave ratio (VSWR) varies from 1 to 1.20. The size of the antenna is 47×59.5 mm2 which is printed on a 1.6 mm thickness FR-4 substrate of 4.4 relative permittivity. Computer simulation technology Microwave Studio is used to design and study the recommended constructions. The proposed design achieves an acceptable value of VSWR, stable gain, and good directivity, which makes it a suitable choice for future radiation pattern reconfiguration applications. The proposed antenna is distinguished by a simple shape, compact size, respectable return loss, good radiation characteristics, and high efficiency. The obtained results from measurements are quite close to the simulations.

Optimizing inset-fed rectangular micro strip patch antenna by improved particle swarm optimization and simulated annealing

ABSTRACT The recent wireless communication systems require high gain, lightweight, low profile, and simple antenna structures to ensure high efficiency and reliability. The existing microstrip patch antenna (MPA) design approaches attain low gain and high return loss. To solve this issue, the geometric dimensions of the antenna should be optimized. The improved Particle Swarm Optimization (PSO) algorithm which is the combination of PSO and simulated annealing (SA) approach (PSO-SA) is employed in this paper to optimize the width and length of the inset-fed rectangular microstrip patch antennas for Ku-band and C-band applications. The inputs to the proposed algorithm such as substrate height, dielectric constant, and resonant frequency and outputs are optimized for width and height. The return loss and gain of the antenna are considered for the fitness function. To calculate the fitness value, the Feedforward Neural Network (FNN) is employed in the PSO-SA approach. The design and optimization of the proposed MPA are implemented in MATLAB software. The performance of the optimally designed antenna with the proposed approach is evaluated in terms of the radiation pattern, return loss, Voltage Standing Wave Ratio (VSWR), gain, computation time, directivity, and convergence speed.

Metamaterial-Inspired Electrically Compact Triangular Antennas Loaded with CSRR

In this paper, simulation of two distinct kinds of metamaterial (MTM) antennas are proposed for fifth generation (5G) indoor distributed antenna systems (IDAS). Both antennas operate in the sub-6 GHz 5G band, i.e., 3.5 GHz and to analyze various factors like gain, directivity, return loss, radiation intensity for the frequency of 3.5 GHz. The simulation of this metamaterial antenna is carried out in ANSYS HFSS v2021. Results like return loss, radiation pattern, 3D polar plot, side lobe level, beamwidth, radiated power, accepted power have been obtained using HFSS v2021. This research on metamaterial gives a great view on how it can be designed and used at 3.5GHz frequency has a measured gain/bandwidth characteristic of 100 MHz/2.6 dBi and 700 MHz/2.3 dBi, respectively. The main advantage of this antenna is it can be used as both transmitting and receiving antenna. Key Words: Metamaterial, CSRR, return loss, triangular CSRR

Parasitic Loaded Shorting Pin Based Compact Multi-slot LoRa Antenna for Military Application

In this paper, work on a compact multi-slot patch antenna with a parasitic load and shorting-pin has been presented for its use in long range (LoRa) defense applications. Initially the antenna is designed and simulated using HFSS and a parametric study has been carried out for achieving an optimized antenna configuration. This is followed by the fabrication of antenna prototype based on the optimal performances obtained from the simulated results. Further, the return loss along with free space co-polar and cross-polar radiation pattern measurements has been carried out for the fabricated antenna. The experimental results show a good comparison with that of the simulated one. The proposed antenna resonates at an operating frequency of 866 MHz, providing a -10 dB bandwidth from 856 MHz-877 MHz, which covers the wireless standard used for LoRa technology. Finally, a comparative analysis of the proposed antenna with the recently reported works is presented.

Prediction of Resonant Frequency of an Equilateral Triangular Microstrip Antenna Using Conformal Mapping Technique

In this manuscript, Conformal Mapping Technique (CMT) is applied to predict the resonant frequency of an Equilateral Triangular Microstrip Antenna (ETMA). The ETMA is mapped into a simple circular geometry with the aid of CMT. The wave equation is solved in the transformed domain using Galerkin technique to obtain the approximate solution of eigenfunction and eigenvalue. Twenty-three measured data are collected from the open literature to validate our theory. Our theoretical results are also compared with several CAD models to show the effectiveness of the present theory. It is found that our proposed theory can predict the resonant frequency of the ETMA with an error of less than 1.5%, whereas those CAD models can produce a large error (sometimes, 10-19% error). Internal field patterns, input impedance, far-field radiation patterns, quality factor, bandwidth gain, and directivity of the ETMA for the dominant mode are also investigated using CMT.

Metasurface Loaded Ceramic based MIMO Antenna with Improved Gain and Circular Polarization Characteristics

Abstract In this communication, the conceptualization involves the design of a multiple input multiple output (MIMO) (dual-port) ring dielectric resonator antenna and the integration of a meta-surface onto this configuration. It introduces three distinctive attributes, which characterize the novelty of the proposed design: (a) facilitates the conversion of linearly polarized waves into circularly polarized counterparts; (b) contributes to a substantial enhancement in gain in between the working band; and (c) there is notable improvement in the isolation between the antenna ports to more than 25 dB. The experimental measurements validate the simulated results of proposed design and confirms its applicability in between 2.45–3.0 GHz. Notably, a 3-dB axial ratio is created in the frequency span of 2.56-2.99 GHz, along with an impressive gain of approximately 8.3 dBi. Its consistent radiation pattern and excellent diversity performance make it suitable for WiMAX (2.6 GHz) use.

Development and comprehensive evaluation of a dual-port textile UWB MIMO antenna for biomedical use

In this paper, a textile two-port multi-input multi-output (MIMO) half-circle antenna with corrugated borders is designed and fully analyzed for nearfield ultra-wideband biomedical diagnostic applications. The orthogonal polarization technique is introduced for mutual coupling reduction, signal quality, and imaging accuracy improvement. A low pass filter with significant out-of-band rejection is inserted between the two MIMO structural elements to improve the isolation from element to element. For simple system integration, A 50 ohms feed coplanar waveguide is suggested for each element. The entire antenna is constructed using textile materials, with the radiating element composed of conductor fabric. The substrate, on the other hand, is crafted from cotton material which possesses a relative permittivity of and a tan δ value of 0.025. The size of each antenna element has low-profile dimensions of 40 × 40 × 0.3 mm3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${mm}^{3}$$\\end{document}. The measured results obtained demonstrate an extremely broad bandwidth extends from 2.5 GHz to 12 GHz. Omnidirectional radiation pattern is obtained, with 6 dBi maximum gain and 96% efficiency. In order to ensure flexibility, a range of bending conditions were analyzed, and the durability was assessed through wash ability testing. Safety was confirmed by measuring the specific absorption rate. Furthermore, time domain and MIMO performance assessments were performed to ensure its suitability for imaging systems.

Scaled Model for Studying the Propagation of Radio Waves Diffracted from Tunnels

One of the major challenges in designing a wireless indoor–outdoor communication network operating in tunnels and long corridors is to identify the optimal location of the outside station for attaining a proper coverage. It is required to formulate a combined model, describing the propagation along the tunnel and the resulting diffracted outdoor pattern from its exit. An integrated model enables estimations of the radiation patterns at the rectangular tunnel exit, as well as in the free space outside of the tunnel. The tunnel propagation model is based on a ray-tracing image model, while the free-space diffraction model is based on applying the far-field Fraunhofer diffraction equation. The model predictions of sensing the radiation intensity at the tunnel end and at a plane located at a distance ahead were compared with experimental data obtained using a down-scaled tunnel model and shorter radiation wavelength correspondingly. This down-scaling enabled detailed measurements of the radiation patterns at the tunnel exit and at the far field. The experimental measurements for the scaled tunnel case fit the theoretical model predictions. The presented model accurately described the multi-path effects emerging from inside the tunnel and the resulting outdoor diffracted pattern at a distance from the tunnel exit.

Fractioned-pattern radiation mapping, Part I: modeling

Here, we present a technique that predicts the radiation’s distribution in any optical system. It is based on decomposing the emitting source power by assigning a fraction of the total power to each emitted ray. All kinds of power losses in the rays’ optical paths are considered. Fractioned radiation patterns are created in the last optical system surface, each associated with a single ray. We refer to fractioned patterns as those that conform to a whole radiating pattern. Thus, the irradiance of the completely illuminated surface is calculated by adding the optical system’s fractioned radiation maps. This method is non-zero étendue. The result presented here allows for predicting the radiation patterns accurately with a handful of equations and can help design any image and non-image-forming optical systems.

Effect of coil diameter on water disinfection efficiency in a helical photoreactor using ultraviolet-C light emitting diodes

ABSTRACT This study investigated the disinfection efficiency of a photoreactor equipped with a helical water flow channel and ultraviolet-C (UV-C) light emitting diodes (LEDs). Theoretical simulations and biodosimetry tests were conducted to investigate the effects of coil diameter and flow rate on the reactor’s performance in inactivating Escherichia coli. The interplay between hydrodynamics and UV radiation was analyzed to determine the UV fluence absorbed by the microbes. The simulations revealed that, primarily due to the specific radiation pattern of the UV LEDs, the coil diameter strongly influenced the distribution of irradiance in the water and the UV fluence received by microbes. The experimental results indicated that the photoreactor achieved the highest inactivation value of 2.8 log when the coil diameter was 48 mm for a flow rate of 40 mL/min; this log value was superior to those for coil diameters of 16, 32, 64, and 80 mm by approximately 1.9, 0.4, 0.5, and 0.7 log units, respectively. This optimal coil diameter leading to the maximal UV irradiance and the highest degree of irradiance uniformity along the flow channel. This study offers design guidelines for constructing a high-efficiency water disinfection reactor with a helical flow channel configuration.

Analysis of far-field radiation pattern by a current loop in hyperbolic material

Analysis of far-field radiation pattern by a current loop in hyperbolic material

A Wide Bandwidth Vivaldi Antenna Suitable for 5G/6G Communication Utilizing a CMOS 0.18 μm Process

This text proposes a Vivaldi structure array antenna, using a power divider structure. The composition includes an antenna array with four antennas, suitable for a wideband array structure antenna in the 100 GHz frequency band. The goal is to address the challenges faced by monolithic systems in modern wireless communications, particularly the issue of the inapplicability of antennas on silicon substrates. The Vivaldi antenna was chosen for its wide bandwidth, high efficiency, and stable radiation pattern. It combines the characteristics of a wide scanning angle and ultra-wide bandwidth. Through integration with CMOS technology, the developed antenna achieved a bandwidth of 85.47–102.40 GHz. The peak gain reached −4 dBi, corresponding to a bandwidth of 17.7%. And the antenna volume was only 1.2 mm × 1.2 mm, demonstrating its immense potential in high-frequency wireless applications.

Laser-assisted screen-printing of graphene folded reflectarray antenna for millimeter-wave applications

Antennas operating at high frequency bands are sought after for applications in 5G, satellite, radar, and other communication systems. Graphene, a two-dimensional material known for its exceptional conductivity, mechanical strength, and chemical stability, is anticipated to serve as a viable substitute for copper in antenna applications. However, researches on graphene antennas at millimeter-wave and higher frequencies are mainly limited to theory and simulation, due to the fabrication challenges of achieving high-precision graphene patterns. Herein, we present the design and fabrication of a graphene folded reflectarray antenna (FRA) operating at millimeter-wave. The FRA is fabricated using screen-printing of graphene ink on an RT5880 substrate, followed by laser engraving for precise patterning. The main reflector has 918 patch units, and the polarizing grids have line widths and spacings of 100 μm. Measurements demonstrate that the antenna has a realized peak gain of 21.37 dBi at 37.5 GHz. The radiation patterns show a 3 dB beamwidth of 6° and 4° in the E-plane and H-plane respectively, with cross-polarization more than −18 dB. The laser-assisted screen-printing method provides a feasible strategy for the precision manufacture of graphene communication devices.

Low profile cavity-embedded ultra-wideband UHF array antenna with end-fire beams

A low profile, vertically polarized, ultra-wideband array antenna with end-fire beams operating in an ultra-high frequency (UHF) band is developed in this paper. The array antenna consists of 1×16 log-periodic top-hat loaded monopole antenna arrays and is feasible to embed into a shallow cavity to further reduce the array height. Capacitance is introduced in the proposed antenna element to reduce profile height and the rectangular top hats are carefully designed to minimize the transverse dimension. Simulated results show that when the antenna array operates in a frequency range of 300 MHz–900 ​MHz, the end-fire radiation pattern achieves ±45° scanning range in the horizontal plane. Then prototypes of the proposed end-fire antenna element and a uniformly spaced linear array (1×2) are fabricated and validated. The end-fire antenna array should be suitable for airborne applications where low profile and conformal scanning phased antenna arrays with end-fire radiations are required. This design is attractive for airborne platform applications that are used to search, discover, identify, and scout the aerial target with vertically polarized beams.

Slots and stubs incorporated annular ring-shaped compact microstrip antenna with circular polarization characteristics for wireless UWB communication systems

A circularly polarized (CP) antenna with ultra-wideband resonance and a broad axial ratio bandwidth is designed for UWB communication systems. The prescribed design comprises of a modified annular ring-shaped radiator and a modified step-graded slots loaded partial ground plane. The projected antenna is prototyped on FR4 substrate of 35 × 30 × 1.6 mm3. To achieve wide axial ratio bandwidth, a rectangular vertical slot is inserted into the radiating patch and two stubs are embedded into the monopole ground plane, which is configured with step graded rectangular slots. The simulation results are verified by testing the fabricated protype. The proposed design operates at UWB spectrum with an ultra-wide impedance bandwidth (IBW) of 134.57%, centered at 10.7 GHz, covering 3.5 GHz to 17.9 GHz frequency spectrum. Furthermore, it demonstrates circular polarization characteristics with a broad axial ratio bandwidth (ARBW) of 96.29% expanding from 3.5–10 GHz (6500 MHz). Its peak gain reaches to 8.7 dBi and a maximum radiation efficiency of 95% is achieved within the operating band. The results (measured and simulated) obtained in terms of S11, axial ratio, gain and efficiency and radiation patterns exhibit high agreement. The presented antenna could be a suitable choice for 5.5 GHz Worldwide Interoperability for Microwave Access (Wi-Max), 5.2/5.8 GHz Wireless local area network (WLAN), X-band satellite communication (downlink: 7.25–7.745 GHz, uplink: 7.9–8.4 GHz), UWB communication systems, and other applications in microwave C, X, Ku bands due to its superior characteristics.

An Electronically Reconfigurable Highly Selective Stop-Band Ultra-Wideband Antenna Applying Electromagnetic Bandgaps and Positive-Intrinsic-Negative Diodes.

In this article, an ultra-wideband (UWB) antenna featuring two reconfigurable quasi-perfect stop bands at WLAN (5.25-5.75 GHz) and lower 5G (3.4-3.8 GHz) utilizing electromagnetic bandgaps (EBGs) and positive-intrinsic-negative (P-I-N) diodes is proposed. A pair of EBG structures are applied to generate sharp notch bands in the targeted frequency spectrum. Each EBG creates a traditional notch, while two regular notches are combined to make a quasi-perfect, sharp, notch band. Four P-I-N diodes are engraved into the EBG structures to enable notch band reconfigurability. By switching the operational condition of the four diodes, the UWB antenna can dynamically adjust its notching characteristics to enhance its adaptability to various communication standards and applications. The antenna can be reconfigured as a UWB (3-11.6 GHz) without any notch band, a UWB with a single sharp notch (either at WLAN or 5G), or a UWB with two quasi-perfect notch bands. Moreover, the antenna's notch bands can also be switched from a traditional notch to a quasi-perfect notch and vice versa. To confirm the validity of the simulated outcomes, the proposed reconfigurable UWB antenna is fabricated and measured. The experimental findings are aligned closely with simulation results, and the antenna offers notch band reconfigurability. The antenna shows a consistently favorable radiation pattern and gain. The dimension of the presented antenna is 20 × 27 × 1.52 mm3 (0.45 λc × 0.33 λc × 0.025 λc, where λc is the wavelength in free space).