Conical Monopole Antenna Research Articles

Conical Monopole Antenna With Integrated Tunable Notch Filters

With increasing radio spectrum being allocated to wireless communications, multiband and ultrawideband systems are becoming much more prevalent. Such broadband systems are susceptible to interference, or can inadvertently radiate out-of-band emissions, so significant filtering is required at RF front-ends. With this motivation, a broadband conical monopole antenna with integrated tunable notch cavity filters is presented. The antenna is a complex structure but it can be conveniently realized with lightweight perforated alloy surfaces using 3-D printing. This coax-fed antenna is demonstrated to maintain its omnidirectional azimuthal pattern with a very wide notch-tuning range, resulting in a versatile broadband antenna.

Distinguishing polymeric insulators PD sources through RF PD measurement

A better performance and consequently the widespread use of polymeric insulators in different parts of the power grid can increase their role in the grid reliability. The accumulation of contamination and housing-erosion are the two most effective factors in undermining the performance of this type of insulators. Therefore, electric utilities need to identify contaminated insulators for washing and cracks in polymeric housing to replace them with healthy specimens. This paper discusses the impact of contamination layer and housing-erosion of polymeric insulators on the partial discharges (PD) at the insulator surface, through RF-PRPD (phase resolved partial discharge) patterns. The existence of different sources of PDs in a real environment (transmission line or station) makes it difficult to use the PRPD patterns to distinguish them from each other. Therefore, using a conical monopole antenna, the simultaneous PD signals and the related RF-PRPD pattern of samples under test are captured. The grayscale image was obtained using the time-frequency matrix of the PD signals transform, by wavelet. Then, features are extracted and selected from grayscale image. By clustering of the PD signals, the resulted RF-PRPD sub-patterns are well separated and provided the necessary means to distinguish among the status of different samples under test.

Suppressed Band Characteristics of an UWB Conical Monopole Antenna with Split Loops Based on the Equivalent Circuit

In this study, the principle of band suppressing an UWB antenna by attaching a small resonator is explained by developing its equivalent circuit. The realized UWB antenna is a conical monopole antenna that contains a split loop for band suppression. The conical monopole antenna corresponds to a transmission line terminated with load impedance, and the split loop is an LC resonator. The coupling between the conical monopole antenna and the split loop is represented as mutual inductance. Equivalent circuits for the UWB antenna suppressing single band [WLAN] and dual band [WLAN, WiMAX] have been suggested, and these equivalent circuits provide insight into the performance characteristics of the developed band suppressed UWB antenna to which a small sized resonator is installed. Simulation and measurement results on the input impedance and VSWR of the proposed equivalent circuit are closely matched. Thus, the validity of the equivalent circuit is confirmed. The measurement results demonstrate that the proposed antenna exhibits a gain of over 3 dBi in the working band and has an omnidirectional radiation pattern. Band rejection has been also implemented by split loops.

Carbon Fiber Reinforced Polymer with Shredded Fibers: Quasi-Isotropic Material Properties and Antenna Performance

A carbon fiber reinforced polymer (CFRP) laminate, with the top layer consisting of shredded fibers, is proposed and manufactured. The shredded fibers are aligned randomly on the surface to achieve a more isotropic conductivity, as is desired in antenna applications. Moreover, fiber shreds can be recycled from carbon fiber composites. Conductivity, permittivity, and permeability are obtained with the Nicolson-Ross-Weir method from material samples measured inside rectangular waveguides in the frequency range of 4 to 6 GHz. The decrease in material anisotropy results in negligible influence on antennas. This is shown by measuring the proposed CFRP as ground plane material for both a narrowband wire monopole antenna for 5.9 GHz and an ultrawideband conical monopole antenna for 1–10 GHz. For comparison, all measurements are repeated with a twill-weave CFRP.

Concealed CFRP Vehicle Chassis Antenna Cavity

A concealed vehicular carbon fiber reinforced polymer cavity in the roof that contains antennas is proposed, prototyped, and measured. Compared to state-of-the-art roof-mounted shark-fin modules, this offers significantly more room for antennas and radio frequency hardware, thus enabling a smooth transition of vehicular connectivity towards 5G. Three antennas were prototyped and embedded in the cavity: two laser direct structured antennas (inverted-F antenna for 2 GHz, monopole for 5.9 GHz), as well as a broadband conical monopole antenna milled from brass that characterizes the feasible frequency range from 2 to 6 GHz by measurement. It is shown that near-omnidirectional radiation from the concealed automotive antenna cavity is achievable.

指数テーパ線路型コニカルモノポールアンテナのリターンロスに関する実験的検討

Exponential tapered line type conical monopole antenna is proposed as a radiator of electromagnetic wave due to electrostatic discharge (ESD). The electromagnetic wave radiated by discharge such as ESD is broadband and influenced by lead lines connected to discharge electrodes. Therefore, the broadband antenna, which can lay on the electrodes to the antenna input and withstand the high voltage, is required instead of lead lines. The proposed antenna is the conical monopole antenna having an exponential tapered line structure. The characteristic impedance of the antenna changes from 50Ω to the free space impedance according to exponential function. The return loss and input impedance of the conical monopole antenna were measured by a network analyzer in the frequency range from 300kHz to 9GHz. As a result of experiment, the return loss was less then -20dB and the input impedance was 50Ω in frequency range from 1.6GHz to 9GHz. The results of the experiment are compared with the linear tapered line type monopole antenna that the characteristic impedance changes from 50Ω to the free space impedance linearly. The return loss of the conical monopole antenna was lower than that of the linear tapered line type monopole antenna.

An UWB Conical Monopole Antenna for Multiservice Wireless Applications

A novel formation of a conical monopole antenna is presented for ultra-wideband (UWB) and multiple other wireless services. The proposed antenna design is compatible with many wireless standards, including Wi-Fi (2.4 GHz), Bluetooth (v1.0-v4.0), WiMAX ( ~ 2.5-5.5 GHz) and Bluetooth 4.0 or Wireless USB (3.1-10.6 GHz). It is also has a suitable frequency response for close range radar and satellite communication in the X band ( ~ 8-12 GHz) and Ku band ( ~ 12-18 GHz) applications. The proposed design is approximately 0.24λ in length with respect to the lowest frequency boundary at the 2.4 GHz Wi-Fi band. The structure consists of two mechanical parts, which are the cone and a cylindrical block (disc). The proposed conical monopole antenna displays a fractional bandwidth of 8.3:1 and a simulated maximum efficiency of over 95% across the whole frequency range. The radiation patterns are largely omnidirectional. Furthermore, it displays a useful level of gain across the impedance bandwidth and the time domain response indicates promising performance for radar and impulse radio. In short, the proposed conical monopole offers ultra-broad bandwidth with omnidirectional radiation patterns, in a reasonably small and easy to construct structure.

동축 프로브 급전구조에 대한 FDTD 전원 모델들의 상호 관계에 관한 비교 연구

RF 및 마이크로파 대역에서 동축 프로브 급전구조에 대한 효율적인 유한 차분 시간 영역(FDTD: Finite-Difference Time-Domain) 해석을 위한 등가 전원 모델링 기법들의 상호 관계를 연구하였다. 기존에는 델타 갭(delta-gap) 또는 자기 프릴(magnetic-frill) 개념을 FDTD에 도입한 등가 전원 모델들이 여러 연구진에 의해서 개발되었다. 이러한 등가 전원 모델들의 FDTD 구현 방법과 모의 계산의 정확성은 서로 조금 다르다는 정도로만 잘 알려져 있었다. 본 논문에서는 준정적 근사(quasi-static approximation)하에서 동축-프로브 급전 구조에 대한 FDTD 등가 전원 모델들의 상호 관계를 제시하였다. FDTD 등가 전원 모델들의 적용방법에 따라 동축 급전된 원추형 모노폴 안테나의 시간영역과 주파수영역 응답을 수치계산하였다. 또한, FDTD 모의계산의 정확성과 효율성에 대한 비교 결과를 제시하였다. For an efficient finite-difference time-domain(FDTD) analysis of coaxial-probe feeding structures in radio frequency(RF) and microwave bands, an interrelation between equivalent source modeling techniques is investigated. In existing literature, equivalent source models with delta-gap or magnetic-frill concepts have been developed by many researchers. It is well known that FDTD implementation and computational accuracy of these source models are slightly different. In this paper, the interrelation between FDTD equivalent source models for coaxial feeding structures under the quasi-static approximation(QSA) is presented. As a function of FDTD equivalent source models, time-domain and frequency-domain responses of a coaxial-probe fed conical monopole antenna are calculated numerically. And comparison results of computational accuracy and efficiency are provided.

Filter-Antenna Consisting of Conical FSS Radome and Monopole Antenna

A filter-antenna consisting of a monopole antenna and a conical frequency selective surface (FSS) radome was designed and investigated. A coupled-resonator spatial filter (CRSF) was used to design an FSS array with stable performances, and then a specific geometrical layout was proposed to construct a conical FSS radome. We technically investigated the combination of a monopole antenna and the conical FSS radome. Both the simulated and measured results show that the proposed filter-antenna keeps the input reflection coefficient, radiation pattern of the monopole antenna within the designed passband, and reflects out-of-band signals. Such properties of the filter-antenna will exhibit anti-interference capability and low RCS, which can be widely used in military applications.

WIDEBAND CONICAL MONOPOLE ANTENNA WITH INTEGRATED STOPBAND FILTER

This paper presents a conical monopole antenna with two C-shaped slots to provide a frequency stopband to suppress interference. Compared to previous work reported in the literature, the antenna provides increased gain suppression to vertically polarised signals within the notch-band of up to 41.5dB in four speciflc directions. It also yields omni-directional radiation patterns at frequencies throughout the operating band, outside the rejection band. The four null directions in vertically polarised plane at the notched band frequency are explained by an analysis of simplifled equivalent current sources. The efiect of difierent length of slots has been investigated. Two methods to control the stop band directions are also discussed.

Improved band‐notched wideband conical monopole antenna

AbstractRecently, wideband antennas with band‐notched behavior have attracted increasing interest. This paper presents a conical monopole antenna with four C‐shaped slots to achieve improved band‐rejection behavior with at least 28 dB of gain suppression. Compared to previous work reported in the literature, the antenna provides a relatively wide rejection band with increased gain suppression, at the notch‐band center frequency. The antenna also provides an omnidirectional radiation pattern at frequencies within the operating band. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26132

Wideband conical monopole antenna with frequency band-notched behaviour

Wideband antennas with band-notched behaviour have recently attracted increasing interest. Presented is a conical monopole antenna with two C-shaped slots. Compared to previous work reported in the literature, the antenna provides a notch band with increased gain suppression within the notch band, combined with omnidirectional pattern at frequencies throughout the operating band.

Optimisation of a sensor for onsite detection of partial discharges in power transformers by the UHF method

Among the different solutions which allow onsite partial discharge measurement in energized power transformers, the UHF technique is gaining general interest. In order to apply this method in existing transformers, it is considered advantageous to design a UHF sensor to be fitted inside the transformer tank. This paper describes the constraints affecting the development of such sensor and the process followed to optimize its design. During this process, different solutions for broadband UHF antennas were analysed. The selection was based on computer simulation and experimental results. Computer simulation was used to evaluate differences in radiation pattern, antenna impedance, gain and effective area. Measurements of the antenna response to different partial discharge sources in oil were performed using an oil dielectric breakdown test set in an electromagnetic shielded laboratory. A group of selected antennas were then tested in a power transformer simulating the broadband signals generated by partial discharges by injecting controlled voltage pulses in the transformer. Finally, a sensor based on a conical monopole antenna structure was built and attached to a specially designed housing to be fitted inside the transformer tank through the drain valve. This final prototype was benchmarked during a high voltage factory test of a power transformer which showed a significant partial discharge activity.

A Conical-Cylindrical Monopole Antenna

In this paper, a monopole antenna of conical-cylindrical compound shape is presented. The conventional circular conical monopole antenna is modified by placing a cylinder at the top of the inverted cone. The cylindrical portion is useful in the wide band impedance matching, in adjusting the antenna gain in the horizontal direction, and in reducing the cone diameter. The dependence of the antenna performance on various geometric parameters is investigated using a commercial electromagnetic simulation software, from which an optimum design of the antenna is derived. The diameter of the circular ground plane is minimized to 115 wavelength at the lowest operating frequency. The antenna proposed in this study shows a reflection coefficient less than -10 dB and a 1<TEX>${\sim}$</TEX>6 dBi gain over 3<TEX>${\sim}$</TEX>20 GHz frequencies. The antenna shows a circular-symmetric radiation pattern in the horizontal plane and a null-free pattern in the vertical direction over the whole operating frequency range.

A multiband conical monopole antenna derived from a modified Sierpinski gasket

The Sierpinski gasket monopole is known to exhibit a certain degree of periodic multiband behavior in terms of its input impedance characteristics. However, its overall performance properties are somewhat less than desirable. Specifically, the Sierpinski gasket monopole exhibits a relatively narrow bandwidth in each of its operating bands and its radiation patterns exhibit poor omnidirectionality because of the asymmetrical two-dimensional (2D) bow-tie shape of the antenna. Here, a multiband conical monopole antenna is presented that is designed to operate in the same frequency bands as the Sierpinski gasket. The conical monopole antenna, being a symmetrical three-dimensional (3D) structure, offers increased impedance bandwidth and improved radiation pattern performance.

Folded conical helix antenna

A novel conical monopole antenna composed of multiple spiral wires for the HF to VHF frequency bands is presented. The antenna exhibits broad bandwidth and good efficiency in an electrically small package. Broadbanding and impedance matching techniques used during the design process of this antenna are described. Measured data from a VHF version of this antenna is shown. The performance of this antenna is then compared to the performance of other electrically small antennas.

Optimization of a conical antenna for pulse radiation: an efficient design using resistive loading

The conical monopole antenna with a section of continuous resistive loading is considered as a radiator for temporally short, broad-bandwidth pulses. The geometrical details of the coaxial feed and the resistive loading are varied to optimize this structure for pulse radiation. Compared with the perfectly conducting cone, the optimized resistive cone radiates a better reproduction of the pulse excitation with no loss in amplitude, and has internal reflections that are much smaller in amplitude. Graphical displays of the field surrounding the antenna are used to give insight into the physical processes for transient radiation from this antenna. Experimental models were constructed to verify the optimization and demonstrate the practicality of the design. Measurements of both the reflected voltage in the feed line and the time-varying radiated field are in excellent agreement with the theoretical calculations.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Broad-band characteristics of rotationally symmetric antennas and thin wire constructs

The rotationally symmetric monopole antenna is given by a set of simultaneous equations on the rotationally symmetric surface current of a conductor, separated with respect to the variable of the envelope length on the surface of the rotationally symmetric antenna and the variable in the direction of revolution. The structure is analyzed in detail by means of an extended moment method based on the present theory. As an application, this analysis is applied to a conical monopole antenna. Studies are performed to find body shapes providing broadband characteristics. It is found that the antennas with lengthwise cross sections approximated by straight lines, ellipses, and circles have an impedance of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50 \Omega</tex> over a wide frequency band. When these shapes are replaced with wire elements for analysis, 16 elements are found sufficient to approximate the characteristics of the rotationally symmetric antenna. Theoretical calculations and experimental results are compared. Agreement is excellent and the method is found useful.

Broadband characteristics of bodies of revolution

AbstractA monopole antenna consisting of a body of revolution is given by a set of simultaneous equations on the rotationally symmetric surface current of a conductor separated with respect to the variable of the envelope length on the surface of the body of revolution and the variable in the rotating direction. The structure is analyzed in detail by means of an extended moment method based on the present theory.As an application, this analysis is applied to a conical monopole antenna. Studies are performed to find body shapes providing broadband characteristics. It is found that antennas with cross sections approximated by straight lines, ellipses and circles have an impedance of 50 ω over a wide range of frequency. When these shapes are replaced with wire elements for analysis, 16 elements are found sufficient to provide the characteristics for the bodies of revolution. Theoretical calculations and experimental results are compared. Agreement is excellent and the method is found useful.

Monopole antenna above a hemisphere

Antenna imaging by a finite ground is investigated analytically and numerically by considering a conical monopole antenna above a finite hemispherical ground of variable radius. The ratio <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y_{t}/Y_{t \infty}</tex> of the terminating admittance of the antenna over a finite to that over an infinite ground is evaluated and plotted versus the ground radius for various monopole lengths. The plots provide a quantitative measure of the effectiveness of finite screens in imaging antennas.