Browsing by Author "Kehn, Malcolm Ng Mou"

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A Bisected Miniaturized ZOR Antenna With Increased Bandwidth and Radiation Efficiency
(2013)
Yang, Shu-Yen
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Kehn, Malcolm Ng Mou
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電機資訊學士班
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電機工程學系
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Undergraduate Honors Program of Electrical Engineering and Computer Science
A compact planar, via-free, and bisected zeroth-order resonator (ZOR) antenna based on bisected interdigital capacitor-loaded transmission line (B-CL-TL), with improved bandwidth and higher radiation efficiency is proposed. Strong miniaturization and increase of bandwidth and efficiency are obtained by dissecting the initial design by half without incurring compromise. The antenna consists of two cascaded coplanar interdigital capacitors as series capacitors shorted to the ground plane at one end. A meander-line inductor is implemented for matching. A fabricated prototype has dimensions of 0.11 lambda(0) x 0.18 lambda(0) x 0.01 lambda(0) in total size, yielding an omnidirectional far-field pattern, and provides a 135-MHz bandwidth (6.1%) with a measured radiation efficiency of 76.8% at 2.21 GHz.
An Approximate Method of Obtaining Surface-wave Band Gap from Reflection Phase Plots for Mushroom Structures
(2014)
Chao, Wei-Chuan
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Kehn, Malcolm Ng Mou
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傳播研究所
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Institute of Communication Studies
This paper proposes an approximate method of obtaining the surface-wave band gap from reflection phase plots for mushroom structures. The upper bound of the band gap can be found by observing the first in-phase frequency on the reflection phase plot of TE plane waves under grazing incidence, and the lower bound of the band gap can be approximated by the three specific frequencies on reflection phase plots of TM plane waves: the first in-phase frequencies under normal and grazing incidence and the frequency where the first +90 degrees reflection phase occurs. By comparing surface-wave band gaps obtained from dispersion plots and from reflection phase plots through the approximate method in the commercial software CST, results show that the errors of estimated values are less than 10% in different cases of mushroom structures.
Analysis of Doubly-Stacked Rotated Gratings Using Asymptotic Corrugations Boundary Conditions
(2019-07-01)
Lai, Wei-Yu
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Kehn, Malcolm Ng Mou
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交大名義發表
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電機工程學系
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National Chiao Tung University
In this paper, we present a highly efficient analysis of double-layered stacked gratings that are rotated from each other by any arbitrary angle using the asymptotic corrugations boundary conditions (ACBC) along with classical vector potentials. By casting the resultant system of linear equations into a homogeneous matrix equation, the eigenvalue problem can then be solved, after which the surface-wave dispersion diagram may be generated. In addition to the solutions for modal resonances under sourceless conditions, reflection and transmission analyses of plane-wave incidences constituting source-driven problems are also presented for both normal and oblique incidences. The properties of copolarization and cross-polarization levels in those scenarios are also discussed. The results computed by the code written based on this proposed modal method are compared and validated with those simulated using a commercial full-wave solver. A prototype of the structure was also manufactured and measured.
Analysis of Strip-Grated Conducting Rod Using Asymptotic Strip Boundary Conditions
(2018-01-01)
Yang, Yueh-Chieh
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Kehn, Malcolm Ng Mou
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電信工程研究所
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Institute of Communications Engineering
In this paper, an analytical method that deals with the solutions for surface wave modes that propagate along a dielectric coated conducting cylinder loaded with a periodic array of metallic transverse strips is presented. The approach hinges on the asymptotic strip boundary conditions (ASBC) along with classical electromagnetic theory of vector potentials that dramatically simplify the formulation as compared to the use of traditional Floquet mode expansion. The method would be validated by presenting the consistency of the dispersion properties obtained from the ASBC method with those simulated by an independent full wave solver. The closed form field expressions have been derived successfully by this method.
Analysis of Strip-Grated Dielectric-Coated Rods by Asymptotic Strip Boundary Conditions for Studies of Dielectric Losses and Field Localization
(2019-05-01)
Yang, Yueh-Chieh
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Kehn, Malcolm Ng Mou
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
In this paper, the surface-wave modal analysis of the transverse strip-grated dielectric-coated metal rod is done by using the asymptotic strip boundary conditions (ASBC) along with classical vector potentials in the cylindrical coordinate system. The yielded solvable system of linear equations is then cast into a homogeneous matrix equation, from which the characteristic equation as well as field distributions in explicit functional forms may be obtained. Modal dispersion diagrams and field distributions generated by this method are compared and validated with those simulated by an independent commercial full wave solver. The time cost by the ASBC method is also compared with that of the simulation software, upon which the vast superiority in speed of the proposed technique over the benchmark tool is demonstrated, but yet preserving high accuracy. Parametric studies that portray the variations of dispersion properties with various geometric attributes are carried out. Comparisons with its counterpart transverse corrugated rod are also carried out, and studies of dielectric losses are presented as well. A prototype was fabricated and measured, the experimental results of which concur well with theoretical expectations.
Analysis of Strip-grating structure with ASBC
(2014)
Liang, Yung-Hsun
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Kehn, Malcolm Ng Mou
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傳播研究所
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Institute of Communication Studies
The strip grating on dielectric slab is a common periodic structure used in antenna design and microwave component applications. The asymptotic strip-loaded boundary conditions (ASBC) are applied on classical theory of vector potentials to analyze planar strip grating structure rapidly and easily. Dispersion diagram can be obtained by solving a transcendental characteristic equation, which is derived from matrix of system equations which are composed of vector potentials and ASBC. With the roots of the transcendental characteristic equation, we can sketch both TE and TM modes field distributions with closed form equation at any frequency or wave number point we need.
Analysis of Substrate Integrated Waveguides by Asymptotic Strips Boundary Conditions
(2014-01-01)
Yeh, Nan-Keng
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Kehn, Malcolm Ng Mou
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傳播研究所
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Institute of Communication Studies
There have been many papers about applications of substrate integrated waveguide (SIW). Only a few related to the use of mathematical methods to analyze SIW, however, were reported. We present an analytical method that is easy, quick and also accurate to obtain the modal dispersion diagrams and field distributions of SIWs. The closed-form characteristic equations and field expressions provide us insights into the modal behavior of the SIW, providing us the knowledge of the impact and influences which the various parameters have on the SIW, thereby saving a great deal of time in engineering and design often entailing lengthy simulations by full-wave solvers or even trial-and-error practices. We compare the dispersion diagrams and modal field distributions obtained by using our analytical method with those generated by CST Microwave Studio.
Analysis of Substrate Integrated Waveguides by Transverse Resonant Technique
(2014)
Yeh, Nan-Keng
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Kehn, Malcolm Ng Mou
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傳播研究所
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Institute of Communication Studies
There have been many papers about applications of substrate integrated waveguide (SIW). Only a few related to the use of mathematical methods to analyze SIW, however, were reported. We present an analytical method that is easy, quick and also accurate to obtain the modal dispersion diagrams and field distributions of SIWs. The closed-form characteristic equations and field expressions provide us insights into the modal behavior of the SIW, providing us the knowledge of the impact and influences which the various parameters have on the SIW, thereby saving a great deal of time in engineering and design often entailing lengthy simulations by full-wave solvers or even trial-and-error practices. We compare the dispersion diagrams and modal field distributions obtained by using our analytical method with those generated by CST Microwave Studio. transverse resonant technique
Compact Mikaelian Lens Design Using Metasurface Structure
(2016-01-01)
Syue, Cheng Jie
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Kehn, Malcolm Ng Mou
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Quevedo-Teruel, Oscar
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電信工程研究所
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Institute of Communications Engineering
Research on metasurfaces has been widespread recently because it can generate arbitrary permittivity and permeability which can be used to synthesize different types of flat surface-wave based lens for engineering applications such as nanofocusing, sensing, detection, and spectral imaging. In this paper, we use the periodic array of square metallic patches etched over a thin grounded dielectric sheet to synthesize a flat Mikaelian lens of rectangular shape that is narrower than contemporary circularly-shaped lens. The design is validated by simulation results, which demonstrate the effectiveness of the focusing.
Compact Mikaelian Lens Synthesized by Metasurfaces
(2018-03-01)
Yang, Jiun Wen
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Lai, Wei Yu
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Chou, Hai Cheng
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Kehn, Malcolm Ng Mou
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電機工程學系
Synthesized using metasurfaces, we propose the implementation of the rectangular Mikaelian lens, one that is not only just flat but now also thin, thus enabling impingent wavefronts to converge at focal points over shorter distances, a feature that no other contemporary types of circularly shaped lenses are able to achieve. The subsequent savings of space and weight afforded by this unique property could be invaluable. By further postprocessing of the fields extracted from the simulations, the degree of focusing attained by the lens is also quantitatively characterized, thus offering insights beyond mere visual inspection of field patterns. The phenomenon of power concentration has been successfully demonstrated with simulations that are well corroborated by results of measurements carried out on a manufactured prototype.
Corrugated Surfaces With Tailorable Dark Sectors Within Prescribed Frequency Bands
(2014-10-01)
Kehn, Malcolm Ng Mou
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交大名義發表
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National Chiao Tung University
Electromagnetic bandgap (EBG) surfaces have customarily been defined as being prohibitive of surface-waves within frequency ranges called bandgaps, for all directions along the surface, this latter specification being an understood presumed condition. However, not all practical applications require such an entire bandgap in terms of surface directions. Rather, there could be situations where surface-wave suppression is needed along directions only within an angular sector but are instead desirable towards others outside, over a frequency band, termed herein as a sectoral dark band (SDB). This work investigates this aspect using planar corrugated surfaces as the vehicle for study, in virtue of its ease of surface-wave modal analysis of dispersion by asymptotic corrugations boundary conditions (ACBC). A systematic design procedure for tailoring surfaces to any specified dark sector of weak signals prevailing over any prescribed band is presented.
Corrugated Waveguides With Stepped Ridges and Stratified Core for High-Power Transmission: Modal Analysis by Radial-Cavity and Concentric Multilayer Green\'s Functions
(2016-11)
Kehn, Malcolm Ng Mou
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
This paper presents a full-wave modal analysis of transverse corrugated circular waveguides with stepped ridges accompanied by segmented grooves and a waveguiding core that is stratified into concentric layers. The method is validated with the known results from literature and those generated by independent solvers. Its strengths over contemporary numerical alternatives such as the finite-element method (FEM) are also portrayed. Such a topology facilitates the study of ways for reducing metal losses and enhancing the aperture efficiency of the operational mode, especially in high-power high-frequency microwave applications, such as by implementing dielectric linings within the grooves or ceramic coatings over the surface of the corrugations, constituting just two cited examples amongst the many other forms of measures for potential performance enhancement which the technique is able to treat.
Corrugated Waveguides With Stepped Ridges and Stratified Core: Reduction of Metal and Aperture Losses and Study of Thermal and RF Breakdown
(2017-05-01)
Kehn, Malcolm Ng Mou
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交大名義發表
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National Chiao Tung University
Numerical results generated by computer codes written based on a full-wave modal analysis of transverse corrugated circular waveguides with segmented grooves and a waveguiding core that is stratified into concentric layers, as detailed in a previous paper, are presented here. It is shown that the reduction of metal losses and enhancement of the aperture efficiency of the operational mode can be achieved by ceramic linings of the groove floors as well as the surface of the corrugations. The benefits of chamfering the groove-floor coating are also demonstrated. Dielectric losses and thermal and RF breakdown are also studied.
Dual-Band Implantable Antenna Based on Short-Circuited SRR
(2010)
Sanchez-Fernandez, Carlos J.
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Quevedo-Teruel, Oscar
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Requena-Carrion, J.
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Inclan-Sanchez, L.
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Rajo-Iglesias, Eva
In this communication, an innovative dual band microstrip patch antenna is proposed for Implantable Medical Devices (IMD). Particularly, the covered bands are MICS (402-405MHz) and ISM (2.4-2.48GHz). The antenna has a multilayer configuration where the feeding line and radiating layer are located at different levels. The radiating element of the antenna is a Split Ring Resonator (SRR) coupled to a Spiral. Both elements are short-circuited to the ground plane to achieve size reduction. In addition, the effects of human body geometry and dielectric properties are studied. Three models are investigated: single-layer, three-layer and a realistic human body based on the Voxel Man dataset.
Dual-Band Patch Antennas Based on Short-Circuited Split Ring Resonators
(2011-08-01)
Quevedo-Teruel, Oscar
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Kehn, Malcolm Ng Mou
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Rajo-Iglesias, Eva
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
A study of an innovative antenna based on split ring resonators (SSRs) is presented. SSRs have been exhaustively used in the literature as the unit cell of periodic structures for obtaining left-handed media, whose interesting characteristics can be applied to waveguides or antennas. In this work, the authors propose the use of only one unit cell of a double SRR as a radiator. The double SRR is printed on a grounded dielectric slab, acting as the radiating element of a microstrip patch antenna, and grounded pins are used to short-circuit the structure for size reduction. A compact dual band antenna is obtained in this way. For example, a particular design making use of PP (epsilon(r) = 2.2) as substrate allows a size of 0.05 lambda(o) x 0.05 lambda(o) for the lower frequency of operation with an acceptable radiation efficiency. Simulated and measured results of return losses, gain and radiation efficiency of this new type of patch antenna are provided.
Efficient Analysis of Longitudinally Corrugated Rods Using Asymptotic Boundary Conditions for Investigation of Conductor Losses and Plasmonic Field Localization
(2019-05-01)
Chin, Chang Fu
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Kehn, Malcolm Ng Mou
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
This paper proposes an analytical modal method that provides quick yet accurate surface-wave solutions for tackling longitudinally corrugated conducting circular rods with dielectric-filled grooves. Using asymptotic corrugations boundary condition-the asymptotic corrugated boundary condition, this elegant albeit nonfull-wave approach offers a simple way to obtain not only the dispersion relation between the frequency and wavenumber but also the modal field distribution from the solution of the final system matrix for the amplitude coefficients. The proposed method is validated with an independent full-wave simulation software. Parametric studies for the field localization are carried, and the results of conductor losses as well as radial attenuation are also reported. The results of measurements conducted on a manufactured corrugated rod are presented at the end.
Enhancing the Efficiency of Compact Patch Antennas Composed of Split-Ring Resonators by Using Lumped Capacitors
(2012)
Pucci, Elena
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Rajo-Iglesias, Eva
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Kehn, Malcolm Ng Mou
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Quevedo-Teruel, Oscar
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電子工程學系及電子研究所
A new type of small patch antenna with low profile and enhanced radiation efficiency is proposed in this letter. The antenna is realized with a double layer of low-permittivity material (polypropylene, epsilon(r) = 2.2). The lower layer is used for the feeding of the antenna, and split ring resonators (SRRs) are printed on top of the upper layer acting as radiating elements. The compactness is provided by shorting the rings to the ground plane with two metal pins. Although this antenna presented initially a dual band of operation, it has been demonstrated how the use of a lumped capacitor in the inner ring can increase the total radiation efficiency of the antenna performing a single-band response. Therefore, when the two original operation frequency bands coincide, a manufactured prototype of the antenna demonstrated a measured radiation efficiency of 73% that can be provided at the operation frequency of 1.29 GHz.
Improved Characterization of High-Impedance Surfaces for Better Designs of Low Profile Antennas
(2012)
Huang, Chien-Jung
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Kehn, Malcolm Ng Mou
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傳播研究所
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Institute of Communication Studies
Low profile antenna designs using high impedance or artificial magnetic conducting ground planes composed of periodic structures have been receiving considerable research attention, but most if not all of them only use the reflection-phase of the normal incident plane wave to determine the high impedance frequency of operation. Considering the fact that the overlying antenna does not radiate toward only the normal direction, it is necessary to use numerous incident waves of different incident angles and polarizations to properly characterize the periodic structures for subsequently more appropriate antenna designs. Though in this paper the concept is built on planar corrugated surfaces [1], it can be extended to other periodic structures.
Improved Matching of Waveguide Focal Plane Arrays Using Patch Array Covers as Compared to Conventional Dielectric Sheets
(2009-10-01)
Kehn, Malcolm Ng Mou
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Shafai, Lotfollah
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
This paper presents the advantages of microstrip patch array covers as matching layers for waveguide arrays, as compared with the use of conventional dielectric sheets. It will be demonstrated that both types of covers can be tuned to improve the transmission levels of uncovered arrays at either low frequencies or over a very wide band. However, at low frequencies where the radiation performance tends to be poor due to strong mutual coupling between closely separated elements, the patch array cover offers itself as a lower profile and lighter weight matching structure. This makes it highly advantageous for use in space applications and satellite communications. In addition, it is also able to provide wider matching bandwidths than dielectric sheets.,Here, we present a rigorous analysis of such a patch array printed on a dielectric slab and placed over an array of sidewall loaded hard rectangular waveguides. Due to the desirable properties of its aperture field, this type of element serves as an ideal reference for conveying the properties of the two matching layers studied here. Also, to ensure the matching layer performance is independent of the array elements, optimized elements are used in all computations. The method of moments using spectral Green's functions for multilayer structures is employed. Two array operation scenarios are studied, which are the direct radiating phased arrays, and focal plane arrays (FPAs) as feeds for reflectors.
Modal Analysis of a Periodic Array of Metallic Pins Embedded within a Grounded Dielectric Substrate - An Asymptotic Solution for Vanishing Unit-Cell Size
(2012)
Chiou, Yi Jia
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Kehn, Malcolm Ng Mou
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傳播研究所
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Institute of Communication Studies
In this paper, it is shown that the TM mode characteristic equation of the pin-lattice embedded in grounded dielectric substrate obtained by vector-potential method is identical to that presented in a classical book [1] derived by the transverse resonance technique (TRT). Here, we derive the characteristic equation of a grounded plain dielectric substrate by analyzing the electric and magnetic field instead of TRT. With the same threshold, we can extend it to the rectangular waveguide with pin-lattice loaded on the sidewalls in the future.