VHF Antenna Research Articles

0.16BaFeO3-0.84MgFe2O4 hexa-spinel composited ferrites with enhanced magneto-dielectric properties for miniaturized high-frequency antennas

we deeply dived multi-phase-based 0.16BaFeO3-0.84MgFe2O4 ferrite for VHF antennas. The structural and magneto-dielectric properties synthesized at various temperatures (1100 °C, 1125 °C, 1150 °C and 1175 °C) were investigated. The results demonstrated the coexistence of hexagonal and cubic spinel phases. Microstructure analysis indicated higher temperature induced lager grain size and denser structure. Meanwhile, both the saturation magnetization (from 28 to 25 emu/g) and coercivity (19–5 Oe) decreased. In addition, real permeability (μ′) and permittivity (ε′) arose at higher temperature, promising equivalent permeability and permittivity. What's more, relatively low magnetic and dielectric losses (tanδμ ∼10−2 to 10−3 and tanδε ∼10−3 to 10−4) promote low energy loss. Finally, a miniaturized antenna with relative bandwidth of 14.6 %, peak gain of 0.98 dB, and radiation efficiency of 74.6 % was simulated based on the processed ferrites. In conclusion, the presented investigation greatly improves the magneto-dielectric response, which paves the way to realize high performance in VHF antenna application.

Real time AIS tracking system for fishermen using microcontroller-based approach

Fishing activities in the waters of Banyuwangi are relatively intense. Local fishermen often venture 50 nautical miles from the coastline using small boats. These boats are lacking adequate communication and navigation equipment, causing difficulties in obtaining assistance during emergencies. This study aims to develop an Automatic Identification System (AIS) device to be installed on fishing boats. The AIS device developed for this research incorporates the STM32F4 microcontroller, CMX7032 Evaluation Board, VHF Antenna, and Global Positioning System (GPS) as its main components. The integration and configuration of each component will be elaborated in this paper. Performance testing has yielded promising results, as the AIS device was capable of transmitting data up to 10 nautical miles from the Base Station. Utilization of AIS technology would enhance safety and communication among fishermen. Through careful integration and configuration of these components, the AIS device effectively ensures that the fishermen’s positions are accurately tracked and communicated. The successful development and testing of this device underscore its potential to bridge the communication gap, offering timely assistance and enhancing the overall safety of these seafarers.

Magnetodielectric Material for VHF Antenna Devices Tunable by a Low DC Magnetic Field

This study presents the performance of a magneto-dielectric material (MDM) specially developed to enable the tunability of antenna devices operating in the VHF band. A current flowing through the sample, which creates a DC magnetic field inside the sample with the same symmetry as the magnetic domains, controls the magnetic susceptibility variation of the MDM. By changing the magnetization state of the MDM with a low DC magnetic field of 740 A.m-1, a tunability of 40% can be observed. The MDM tunability at VHF frequencies is also highlighted by microwave measurements for different magnetization states.

Suppresion of Log‐Periodic Dipole Antenna Spurious Radiation by Lumped Element Loading for Radioastronomical Application

AbstractLog‐Periodic Dipole Antennas have been known to provide good performance over large fractional bandwidths. However, optimized designs of log‐periodic antennas, in particular for radioastronomy and remote sensing, need to tackle the spurious radiation of secondary dipole harmonics that can compromise the gain smoothness and therefore the ability to detect natural spectral features emitted by the probed sources. A new, low‐cost method applicable also at a post‐design stage is proposed in this paper, which relies on loading some of the dipoles with appropriate lumped circuit elements in order to avoid this unwanted feature while preserving the desired performance characteristics. Application is found on the log‐periodic dipole antenna selected for the low‐frequency instrument of the SKA (Square Kilometer Array), and general guidelines are described for other designs. An experimental test using a transmitting VHF antenna and the antenna under test with new RLC loaded dipoles confirms our solution.

Comparative evaluation of implementation options for partial radiators for antenna systems of urban radio centers under severe restrictions on placement conditions

In connection with the active development of urban infrastructure and the expansion of residential areas, it becomes necessary to provide corporate mobile radio communications with a large coverage area. In this regard, a number of problems arise, since in most cases special television towers and cellular communication masts are already occupied, and the location on high-rise buildings that are not adapted for antenna placement has rather severe restrictions. Calculation and study of the characteristics of PIFA type antennas placed on high-rise buildings under severe restrictions on placement conditions. Results. The results of calculations of antennas of the PIFA type are obtained, taking into account the environment. A technical solution for a dual-band PIFA VHF antenna is proposed. It is shown that with duplex operation isolation of at least 20 dBm, VSWR of no more than 2 with a bandwidth of 3 MHz is achieved.

Метод синтеза широкополосных устройств с оптимальной характеристикой коэффициента преобразования мощности, согласующих изменяющийся во времени импеданс нагрузки.

A method is proposed for the synthesis of broadband matching devices that adapt radio engineering systems to the changing load impedance in a wide range of natural conditions of their operation. The results of experimental studies of the effect of operating conditions on the impedance of VHF and UHF radio antennas with matching devices are presented. An invariant of the sensitivity of the reflection coefficient function to changes in the load impedance is obtained, on the basis of which a complex criterion for the synthesis of broadband matching devices is developed. A broadband matching circuit was synthesized for the AD-44/CW-TA-30-512 antenna device, which provides a gain in the potentially achievable radio line range of up to 5% in relation to the standard matching device. An analytical mathematical model of a broadband matching device is developed and based on it, a matching device adaptive to the changing impedance of the AD-25/CW-3512 antenna is synthesized, providing an average gain in the potentially achievable range of the radio line from 2% to 15% in the framework of the presented experimental studies.

Engineering Synthesis of VHF Antenna Matching Structures with Feeder Line Segments

Системно рассмотрены инженерные методы синтеза структур согласования УКВ-антенн с использованием отрезков фидерных линий. При этом выбор согласующих структур ограничен применением реактивных элементов и отрезков линий передачи. Обсуждаются возможности и варианты расширения частотной полосы пассивного согласования на таких элементах. Наглядность материала обеспечивается его представлением на комплексной диаграмме Смита.Для использования эквивалентных электрических схем с сосредоточенными реактивными элементами приведены варианты их аналогов в виде шлейфов из замкнутых и разомкнутых отрезков линий передачи, а также показаны возможности создания эквивалентных последовательных и параллельных колебательных контуров с помощью агрегированных двухэлементных шлейфов.Рассмотрено создание реактивных сопротивлений с помощью вставок из отрезков линий. Выбором параметров последовательно включенных вставок можно создавать разные эквивалентные структуры из последовательно и параллельно включенных емкостей и индуктивностей, последовательных и параллельных колебательных контуров. Вставка отрезка линии передачи после нагрузки дополнительно позволяет перераспределять активную и реактивную составляющие входного сопротивления без изменения КСВ, включая изменение знака реактивной составляющей. При этом для упрощения реализации широкополосного согласующего устройства рекомендуется входное сопротивление перемещать ближе к горизонтальной оси в левой полуплоскости диаграммы Смита, так как в ней сопротивление изменяется меньше по сравнению с правой полуплоскостью.С помощью диаграммы Смита приведены разные варианты синтеза двухэлементных согласующих структур с использованием отрезков линий передачи, приведены методики их расчета. Обсуждается задача расширения полосы согласования на основе многоконтурных схем со структурой полосовых фильтров. Для иллюстрации влияния структуры согласующего устройства на ширину полосы согласования представлены результаты моделирования инженерно предложенных структур для случая укороченной антенны.

Ferrite-Loaded Spidron Fractal Loop VHF Antenna for UAV Applications

In this letter, an electrically small Spidron fractal loop antenna operating in the VHF band is proposed. The ferrite material, which consists of a nickel-zinc combination, is loaded into inside of the loop antenna to increase the gain of the antenna in the low frequency band. To minimize the magnetic loss of the ferrite in the high frequency band, the amount and configuration of the ferrite are optimized using a genetic algorithm. Through this optimization step, the amount of the ferrite is decreased to 37.5% and the gain of the antenna in the high frequency band is improved. The size of the proposed antenna is 0.0242 × 0.0242 × 0.0051 λL3 at the lowest operating frequency. The proposed antenna was fabricated to verify the performance, and the simulated and measured results are in good agreement. The measured peak gains varied from −31.6 to −1.9 dBi within the measured frequency band. To examine the performance of the proposed antenna mounted on an unmanned aerial vehicle model (UAV), the antenna on a UAV was also simulated and the results were discussed. The simulated realized peak gains of the antenna on the UAV and on flat ground are similar.

Electric field change and VHF waveforms of Positive Narrow Bipolar Events in Mississippi thunderstorms

Positive Narrow Bipolar Events (+NBEs) in Mississippi thunderstorms were studied using fast antennas (FA, bandwidth 16 Hz - 2.6 MHz) and VHF antennas (Log-RF, bandwidth 186–192 MHz). The waveform characteristics of 201 positive NBEs were determined using both sensors. The +NBEs were classified in two ways: by FA waveform into Types A-D and by +NBE occurrence relative to other lightning events into three groups called Isolated, Not-Isolated, and INBE. (An INBE initiates an intracloud flash.) The FA waveform properties of 188 positive NBEs were mainly in reasonable agreement with previous studies. The VHF waveform properties of +NBEs have not been studied previously. The VHF powers of 201 positive NBE ranged from 0.1–88.4 kW with an average value of 7.8 kW. Types C and D positive NBEs tended to be more energetic (average VHF powers of 9.2 and 13.2 kW) than Types A and B (average powers of 1.9 and 4.0 kW). The INBE group of +NBEs had a larger range of VHF powers (0.2–88.4 kW) than the combined power range of the Not-Isolated and Isolated groups (0.1–26.7 kW). The INBE group also had a larger average peak power (9.9 kW) than the Not-Isolated and Isolated Groups (4.0 and 8.7 kW, respectively). However, 53% of INBEs had peak VHF power < 5 kW, so an INBE does not require a large power to initiate an intracloud flash. For 90% of the 201 positive NBEs the magnitude of the time difference between the FA peak amplitude and the Log-RF peak power was ≤2 μs, but the FA peak amplitude showed almost no correlation with the Log-RF peak power.

A Low-Profile Ferrite Dipole VHF Antenna for Integrated Mast Applications

In this paper, an extremely low-profile ferrite dipole antenna operating on the VHF band (30–300 MHz) is proposed. The design antenna consists of 44 plate-type ferrite cells arranged into two stacked ferrite layers: a bottom ferrite layer with 2 × 12 grid cells and a top ferrite layer with 2 × 10 grid cells. The antenna is excited by an electric loop feeding structure and maximum gain performance is achieved when the loop feeding structure has five loops. To validate the performance of the proposed antenna, an antenna prototype is fabricated and tested at an outdoor range. The antenna weighs 1.45 kg and has electrical dimensions of approximately 0.0636 × 0.0112 × 0.0008 λ L 3 at the lowest operating frequency of 30 MHz. The measured realized gain varies from −31.48 to −2.44 dBi within the VHF band. Reasonable agreement is also obtained between the measurement and simulation results. To assess the performance of the proposed antenna, it was mounted on the integrated mast of an offshore patrol vessel (OPV) model. The antenna on the OPV was also simulated and the results discussed.

Experimental Study of Measuring Radiation Patterns for VHF and UHF Antennas

This paper discusses the experiment of measuring antenna radiation patterns using hardware and software that has been made previously. The antenna measured is the Half Wave Open Dipole antenna that works at VHF frequencies as Antenna Under Testing (AUT). The hardware used is Module-1 and Module-2 which have previously been tested for functionality, and the software is the Antenna Radiation Pattern application that is created using the Visual Basic programming language in the Microsoft Visual Studio package. Radiation pattern measurement experiments were carried out under various conditions, namely (1) without RF signals; (2) with RF signal and the position of the transmitting antenna is 0o with AUT; (3) with the RF signal and the position of the transmitting antenna at an angle of 90o to AUT; and (4) simulation of electromagnetic wave interference when making measurements. Based on the results of experiments conducted, it can be concluded that the Antenna Radiation Pattern application has functioned well and can describe the AUT radiation pattern. Future work of this research is the measurement of radiation patterns for other types of antennas and refinement of applications for the measurement of various antenna parameters.

Drag coefficients of lattice towers with VHF antennas on wind tunnel

En el presente articulo se exponen algunos de los principales aspectos a que se deben considerar para el desarrollo de ensayos estaticos a torres reticuladas con el empleo de tuneles de viento. Se describe, como caso de estudio, un ensayo realizado a un modulo de torre de seccion cuadrada con presencia de antenas VHF, con el objetivo de obtener los coeficientes de arrastre para el modulo y para las antenas de forma independiente, asi como los factores de interferencia para el modulo de torre con las antenas VHF incorporadas ensayados de forma simultanea. Los resultados muestran valores de factores de interferencia mayores de uno para la direccion de viento a 45 grados lo que permite concluir que es necesario calcular la carga de viento de la torre reticulada con las antenas colocadas y no de forma independiente, superponiendo los valores de coeficientes de arrastre, pues se subestima la accion del viento sobre la estructura.

Design and Fabrication of VHF Band Small Antenna Using Composite Right/Left-Handed Transmission Lines

This paper presents a small VHF antenna using a composite right/left-handed (CRLH) transmission lines. The proposed antennas have 3 and 7 unit cells that consist of interdigital capacitors and shunt spiral inductors. The size of the antenna with 3 unit cells is 0.039λ × 0.025λ × 0.0008λ (72.9 × 47.5 × 1.52 mm3) at 161 MHz and its peak gain is − 33 dBi. To enhance the gain, the antenna with 7 unit cells is fabricated. Its size is 0.089λ × 0.025λ × 0.0008λ (167.2 × 47.5 × 1.52 mm3) at 161.4 MHz and its peak gain is − 26.5 dBi. The radiation pattern of both antennas is omni-directional. The electrical size in kr of each antenna is 0.055 and 0.11, respectively. The effects of frequency characteristic of lumped elements on the impedance matching are discussed.

Optimization of Ni0.95−xZnxCo0.05Fe1.90Mn0.02O4 ceramics with promising magneto-dielectric properties for VHF antenna miniaturization

Magnetic, dielectric and DC conductive properties of Ni[Formula: see text]ZnxCo[Formula: see text]Fe[Formula: see text]Mn[Formula: see text]O4 (with [Formula: see text]-0.20 at an interval of 0.05) ferrite ceramics were studied, in order to develop magneto-dielectric materials with almost equal values of relative permeability and permittivity, for the miniaturization of HF (3–30[Formula: see text]MHz) and VHF (30–90[Formula: see text]MHz and 100–300[Formula: see text]MHz) antennas. The ferrite ceramics were prepared by using the conventional two-step sintering process. The real part of relative permeability is increased almost linearly with increasing concentration of Zn, while that of relative permittivity keeps nearly unchanged. It is found that promising magneto-dielectric materials, with close values of real permeability and permittivity over 30–90 MHz (VHF), can be obtained for the samples at Zn concentrations between [Formula: see text] and [Formula: see text].

Aerodynamic and structural design of winglet with integrated VHF antenna

A new optimized winglet of a small aircraft is used to develop the solutions for structure, VHF antenna, systems as lights and lightning protection. The aerodynamic optimization has been based on the Design of Experiment and Response Surface method in order to find out the suitable shape of the winglet from the aerodynamic, structure and the basic operating frequency range for VHF radio communication points of view. The winglet’s structure has been designed based on the aerodynamic loads and took into account the appropriate technology. The improvement of the aerodynamic characteristics and handling qualities of the aircraft are discussed and the integration concepts and production moulds are presented.

A New Method of VHF Antenna Gain Measurement Based on the Two-ray Interference Loss

Antenna gain is an important index of wireless communication system, how to accurate measurement of antenna gain is a difficult problem. There are many factors affecting the VHF antenna gain test accuracy in the outdoor test site. Ground reflected wave is the most important source of error. A new method is proposed in this paper to measure the antenna gain by using a two-ray interference loss to modify, which improved the antenna gain accuracy.

Novel Bio-Logging Tool for Studying Fine-Scale Behaviors of Marine Turtles in Response to Sound

Increases in the spatial scale and intensity of activities that produce marine anthropogenic sound highlight the importance of understanding the impacts and effects of sound on threatened species such as marine turtles. Marine turtles detect and behaviorally respond to low-frequency sounds, however few studies have directly examined their behavioral responses to specific types or intensities of anthropogenic or natural sounds. Recent advances in the development of bio-logging tools, which combine acoustic and fine-scale movement measurements, have allowed for evaluations of animal responses to sound. Here, we describe these tools and present a case study demonstrating the potential application of a newly developed technology (ROTAG, Loggerhead Instruments, Inc.) to examine behavioral responses of freely swimming marine turtles to sound. The ROTAG incorporates a three-axis accelerometer, gyroscope, and magnetometer to record the turtle’s pitch, roll, and heading; a pressure sensor to record turtle depth; a hydrophone to record the turtle’s received underwater acoustic sound field; a temperature gauge; and two VHF radio telemetry transmitters and antennas for tag and turtle tracking. Tags can be programmed to automatically release via a timed corrodible link several hours or days after deployment. We describe an example of the data collected with these tags and present a case study of a successful ROTAG deployment on a juvenile green turtle (Chelonia mydas) in the Paranagua Estuary Complex, Brazil. The tag was deployed for 221 minutes, during which several vessels passed closely (<2km) by the turtle. The concurrent movement and acoustic data collected by the ROTAG were examined during these times to determine if the turtle responded to these anthropogenic sound sources. While fine-scale behavioral responses were not apparent (second-by-second), the turtle did appear to perform dives during which it remained still on or near the sea floor during several of the vessel passes. This case study provides proof of concept that ROTAGs can successfully be applied to free-ranging marine turtles to examine their behavioral response to sound. Finally, we discuss the broad applications that these tools have to study the fine-scale behaviors of marine turtles and highlight their use to aid in marine turtle conservation and management.

Electromagnetic Characterization of Aircraft Composite Materials and its Effects on the Antenna Performance

This paper presents an electromagnetic characterization of aircraft composite materials, as well as numerical and experimental analyses of its effects on the antenna performance. Two uncalibrated S-parameters characterization methods have been applied for retrieving the complex electrical permittivity in the L- and C-band, namely: Air-region method and Sample-shifted method. Dielectric constants of 4.6 and 1.84 and loss tangent of 2.0x10 -2 and 6.1x10 -2 have been obtained for fiberglass and honeycomb composite materials, respectively. A 3.0-meters prototype of an Embraer light jet aircraft dorsal fin was fabricated and used in the experiments in a semi-anechoic chamber in order to evaluate the impact of installing aeronautical VHF and L-band antennas on a fuselage made of composite materials.

VHF antenna pattern characterization by the observation of meteor head echoes

Abstract. The Middle Atmosphere Alomar Radar System (MAARSY) with its active phased array antenna is designed and used for studies of phenomena in the mesosphere and lower atmosphere. The flexible beam forming and steering combined with a large aperture array allows for observations with a high temporal and angular resolution. For both the analysis of the radar data and the configuration of experiments, the actual radiation pattern needs to be known. For that purpose, various simulations as well as passive and active experiments have been conducted. Here, results of meteor head echo observations are presented, which allow us to derive detailed information of the actual radiation pattern for different beam-pointing positions and the current health status of the entire radar. For MAARSY, the described method offers robust beam pointing and width estimations for a minimum of a few days of observations.

Study of Masking Effect of Cable and Practical Analysis of FM, VHF and UHF Broadcasting Antenna

Study of Masking Effect of Cable and Practical Analysis of FM, VHF and UHF Broadcasting Antenna