Browsing by Author "Hwang, RB"

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A beam adjustable leaky-wave antenna using a moveable dielectric slab inside a waveguide
(2005-12-01)
Hsiao, CC
;
Hwang, RB
;
電信工程研究所
;
Institute of Communications Engineering
In this paper, we presented a beam adjustable antenna made up of a slit waveguide and a dielectric slab. In order to change the radiation main-beam angle, we changed the phase constant of the waveguide mode by inserting a dielectric slab for perturbing its field distribution. The direction of radiation main-beam can be steered by dynamically changing the position of the dielectric slab. For the theoretical analysis, the dispersion relation, including the phase and attenuation constants, was determined by solving the transverse resonance equation. An agreement between the theoretical and experimental radiation pattern verities the beamsteering mechanism. Up to 23 degrees beam-steering angle can be achieved using this approach.
A broadband CPW-fed T-shaped antenna for wireless communications
(2004-12-01)
Hwang, RB
;
電信工程研究所
;
Institute of Communications Engineering
A novel broadband, dual-polarised coplanar-waveguide-fed T-shaped uniplanar antenna is presented. The raidation mechanism of such an antenna has been investigated, based on a full-wave numerical analysis and experimental measurement. In addition, the equivalent transmission line model incorporated with lumped-circuit elements is also presented to account for its radiation characteristics. Its performance has also been evaluated by integrating a 4-element CPW-fed T-shaped uniplanar antenna array with a simple beam forming network - a 4 x 4 Butler matrix. Its compact, low cost, easy-to-fabricate features together with good radiation characteristics are promising for application in wireless communication systems.
A low-cost electrical beam tilting base station antennas for wireless communication system
(2004-01-01)
Hwang, RB
;
Chang, YJ
;
Lai, MI
;
友訊交大聯合研發中心
;
D Link NCTU Joint Res Ctr
A multifunctional feeding network is presented in this paper. It contains a one-to-eight Wilkinson-based power divider and eight microstrip lines backed with slot array. In addition, the moveable card printed with seven metal strips servs as a novel phase shifter. By dynamically moving the card, we can adjust the number and shielding area of the slot array and then alter the distribution of phase angle at each port of the feeding network accordingly. For example, in our application, we can have a progressive phase difference between the ports of feeding network and dynamically adjust them by changing the degree of perturbation on the slots array. The characteristic of beam tilting has been carefully examined by measuring the phase angle at each port and also by the far-field radiation pattern of the patch antenna array integrated with this novel phase shifter, in various perturbation conditions. The reliable, easily fabricated, and low-cost characteristics show its potential applications in the base-station antenna design.
Analysis of plane-wave scattering by bigratings
(1998)
Peng, ST
;
Hwang, RB
;
電信工程研究所
;
Institute of Communications Engineering
We present here a rigorous analysis of the plane-wave scattering by a class of bigratings, each of which consists of two separated gratings that may have different periods and different orientations. Inherently, this is a three-dimensional boundary value problem, regardless of the incidence condition. An exact formulation based on the method of mode matching is carried out, taking into account the effect of polarization couplings. Numerical results are shown for identifying physical phenomena associated with the class of bigrating structures. In particular, Wood's anomalies in the presence of a bigrating are carefully examined and the results are interpreted in terms of those well known for single gratings.
Anomalous absorption of resonance-type periodic structures
(2000)
Peng, ST
;
Hwang, RB
;
Shih, HY
;
交大名義發表
;
National Chiao Tung University
We present here a study on scattering characteristics of resonance-type periodic structures, taking into account the effects of structure dispersion and material loss. The phenomena of anomalous absorption are systematically investigated on the basis of the guiding characteristics of the structures. In particular, the effect of dispersion is carefully examined.
Correlation between a negative group velocity and a slanted stop band in two-dimensionally periodic structures
(2006-02-10)
Hwang, RB
;
電信工程研究所
;
Institute of Communications Engineering
[1] In this paper, we employed the rigorous mode-matching method to carry out the calculation for the scattering characteristics of a two-dimensionally periodic structure made up of metallic rectangular cylinders. From the scattering characteristics, the interesting phenomenon of an anomalous dispersion was observed to possess negative group velocities. In order to understand the underlying physics involved, we begin with the investigation of the band structure associated with the corresponding structure of infinite extent; thereby, the band structures are classified into two types: vertical stop band that is mainly due to the effect of periodicity in a single direction and slanted stop band that is due to the combined effects of periodicities in two directions. Notably, the negative group velocity ( delay) within the slanted stop band of a two-dimensional periodic structure was directly related to the experimentally measurable scattering characteristics of the finite structure.
Frequency-selective transmission by a leaky parallel-plate-like waveguide
(2006-01-01)
Hwang, RB
;
Hsiao, CC
;
電信工程研究所
;
Institute of Communications Engineering
The phenomena of high frequency-selective transmission of a plane wave by a dielectric two-dimensional (2-D) periodic waveguide, comprising a uniform dielectric layer sandwiched by two finite thickness 2-D periodic structures served as the waveguide wall is described. This structure is termed a leaky arallel-plate-like waveguide because the waveguide walls are U perfect reflection mirrors. The scattering characteristics and dispersion relation, including the phase and attenuation constants, of the 2-D periodic waveguide are thoroughly analyzed with the modal transmission-line method and Floquet theory. The extraordinary open stopbands caused by the contra-flow coupling between a leaky parallel-plate-like waveguide and the leaky waves, which are generated by 2-D periodic structures (waveguide walls), are displayed in the form of the Brillouin diagram. The phase-match condition is used to verify the resonant coupling between the incident plane wave and the leaky parallel-plate-like waveguide modes. Specifically, the transmission peak frequencies are accurately predicted.
Guidance characteristics of two-dimensionally periodic impedance surface
(1999-12-01)
Hwang, RB
;
Peng, ST
;
友訊交大聯合研發中心
;
D Link NCTU Joint Res Ctr
In this paper, we present an exact formulation for the three-dimensional boundary-value problem of waveguiding by a two-dimensional periodic impedance surface in a uniform medium. The dispersion characteristics of such a structure are rigorously analyzed in terms of the complete set of both TE- and TM-polarized plane waves in the uniform medium. The results are systematically expressed in the form of the Brillouin diagram; thereby, in comparison to the one-dimensional case, a host of new and interesting phenomena are identified and physically explained.
Guided waves on 2D periodic structures and their relation to planar photonic band gap structures
(2000-05-01)
Hwang, RB
;
Peng, ST
;
友訊交大聯合研發中心
;
D Link NCTU Joint Res Ctr
We present here a study on the propagation characteristics of two-dimensional periodic structures. The method of mode matching is employ cd to formulate the boundary-value problem in an exact fashion, and a perturbation analysis is carried out to explain the wave phonomena associated with photonic band gap structures. The dispersion curves of 2D periodic medium and 2D periodic impedance surface are investigated in detail.
Guiding characteristics of periodic impedance surface
(2000)
Hwang, RB
;
Peng, ST
;
友訊交大聯合研發中心
;
D Link NCTU Joint Res Ctr
In this paper, we present a systematic analysis of the dispersion characteristics of two-dimensionally periodic impedance surfaces. The method of mode matching is employed analyze the boundary-value problem rigorously in terms of the complete set of both TE- and TM- polarized plane ts aves in the uniform medium above the impedance surface. Numerical results are obtained extensively and are presented graphically in the form of phase diagram, to explain various physical effects that are peculiar to the class of structures under consideration. More importantly, the unique characteristics of slanted stopband of 2D periodic structures are investigated to develop useful criteria for practical de-sign and to identify potential applications.
Negative group velocity and anomalous transmission in a one-dimensionally periodic waveguide
(2006-02-01)
Hwang, RB
;
電信工程研究所
;
Institute of Communications Engineering
This study presents a theoretical investigation of the negative group velocity (NGV) and anomalous transmittance of waves in the stop band of a corrugated parallel-plate waveguide (CPPWG). The two different schemes, scattering analysis for a finite CPPWG and the dispersion relation of an infinite CPPWG, were used to investigate the physical insight of the wave process. The NGV zone corresponds to the stopband slanted at an angle on the Brillouin diagram, following the mutual verification of the results obtained by the two different approaches. This class of stopband is caused by the contra-flow interaction between the fundamental mode and the space harmonics of higher-order modes. Additionally, fluctuation was also found in the transmitted coefficient within the conventional stopband, caused by the excitation of the first higher-order mode within the stopband of the fundamental mode.
Performance evaluation of a bigrating as a beam splitter
(1997-04-01)
Hwang, RB
;
Peng, ST
;
交大名義發表
;
電信工程研究所
;
National Chiao Tung University
The design of a bigrating for use as a beam splitter is presented. It is based on a rigorous formulation of plane-wave scattering by a big-rating that is composed of two individual gratings oriented in different directions. Numerical results are carried out to optimize the design of a bigrating to perform 1 x 4 beam splitting in two dimensions and to examine its fabrication and operation tolerances. It is found that a bigrating can be designed to perform two functions: beam splitting and polarization purification. (C) 1997 Optical Society of America.
Scattering and guiding characteristics of waveguides with two-dimensionally periodic walls of finite thickness
(2003-10-23)
Hwang, RB
;
Peng, ST
;
友訊交大聯合研發中心
;
D Link NCTU Joint Res Ctr
[1] Electromagnetic wave propagation along waveguides having two-dimensionally (2-D) periodic walls with finite thickness is formulated here as an exact boundary-value problem. The dispersion relation of such a class of waveguide is systematically analyzed in terms of both phase and attenuation constants. In addition, the contour map of field components and Poynting vector are also demonstrated in this paper to verify the guiding characteristics of such a class of waveguides. In particular, the strong couplings between an incident plane wave and waveguide modes phase-matching condition are carefully examined and are employed to identify the existence of waveguide modes.
Scattering characteristics of two-dimensionally periodic impedance surface
(2000-10-01)
Hwang, RB
;
友訊交大聯合研發中心
;
D Link NCTU Joint Res Ctr
We present here an exact formulation for the three-dimensional (3-D) boundary-value problem of plane wave scattering by a two-dimensionally (2-D) periodic impedance surface in a uniform medium. The scattering characteristics of such a structure are rigorously analyzed in terms of the complete set of both TE- and TM-polarized plane waves in the uniform medium. Extensive numerical results are given to illustrate physical phenomena associated with the structure.
Small perturbation analysis of diffracted holographic gratings
(1996-04-15)
Hwang, RB
;
Wei, CC
;
電信工程研究所
;
Institute of Communications Engineering
Plane-wave scattering by a holographic grating is presented. The grating layer can be considered as a perturbation imposed on the uniform medium. Based on the perturbation analysis, this perturbation becomes the source of a diffraction wave and the boundary-value problem can be translated into the equivalent transmission-line equations with distributed current source; therefore, the Green function technique is utilized here to calculate the fields in the grating layer. The numerical examples are carefully compared and found to agree quite well with exact results obtained by rigorous treatment.
Small perturbation analysis of diffracted holographic gratings
(1996-04-15)
Hwang, RB
;
Wei, CC
;
電信工程研究所
;
Institute of Communications Engineering
Plane-wave scattering by a holographic grating is presented. The grating layer can be considered as a perturbation imposed on the uniform medium. Based on the perturbation analysis, this perturbation becomes the source of a diffraction wave and the boundary-value problem can be translated into the equivalent transmission-line equations with distributed current source; therefore, the Green function technique is utilized here to calculate the fields in the grating layer. The numerical examples are carefully compared and found to agree quite well with exact results obtained by rigorous treatment.
Small perturbation analysis of oblique incidence in dielectric gratings
(1998-12-20)
Hwang, RB
;
Jen, DK
;
電信工程研究所
;
Institute of Communications Engineering
In this paper, the method of first-order perturbation is proposed to investigate the plane-wane scattering by dielectric gratings with a small modulation index at oblique incidence. Under the assumption of small perturbation, the cross coupling between the fields of the polarizations (TE and TM) due to the oblique incidence cart be represented by the TE and TM transmission lines fed by distributed current and (or) voltage sources, respectively. The results show good agreement with that obtained by a rigorous formulation. (C) 1998 John Wiley & Sons, Inc.
Surface-wave suppression of resonance-type periodic structures
(2000)
Hwang, RB
;
Peng, ST
;
Chen, CC
;
電信工程研究所
;
Institute of Communications Engineering
Periodic structures of the resonance type are investigated with a focus on the utilization of structure dispersion to achieve a wide-band operation for the surface-wave suppression. Both approximate and exact formulations are presented to illustrate wave processes involved in the resonant structure and to develop useful criteria for design purpose.
Surface-wave suppression of resonance-type periodic structures
(2003-06-01)
Hwang, RB
;
Peng, ST
;
電子與資訊研究中心
;
Microelectronics and Information Systems Research Center
Periodic structures of the resonance type are investigated with a focus on the utilization of structure dispersion to achieve a wide-band operation for the surface-wave suppression. Both approximate and exact formulations are presented to illustrate wave processes involved in the resonant structure and to develop useful criteria for design purpose. In addition, experiments are performed to verify the phenomena with stopband and leakage associated with the resonance-type periodic structures.
Switched Beam System for low-tier wireless communication systems
(2001)
Chang, YJ
;
Hwang, RB
;
友訊交大聯合研發中心
;
D Link NCTU Joint Res Ctr
In this paper, we present a switched-beam antenna including a 4 by 4 Butler matrix and novel, compact, broadband CPW-fed uniplanar monopole array antennas at ISM band that were all fabricated with FR4 substrate. The lost cost and fairly good performance undoubtedly confirm its promising application in the low-tier wireless communication system such as PHS, DCS and Wireless LAN.