Browsing by Author "Hwang, R. B."

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A band-pass filter consisting of two substrate integrated waveguide cavities coupled by an aperture on their common side wall
(2007-08-01)
Hwang, R. B.
;
Chang, C. W.
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電信工程研究所
;
Institute of Communications Engineering
In this article, we present a substrate-integrated waveguide-based band-pass filter with wide stop-band rejection property. This band-pass filter is made up of two substrate-integrated waveguide cavities, which couple to each other by all aperture on their common waveguide side wall. By using the empirical formula [19] for obtaining the equivalent rectangular waveguide dimensions, the substrate integrated waveguide structure could then be properly approximated by a closed rectangular waveguide. We employed the rigorous mode-snatching method to analyze the electromagnetic boundary-value problem of the structure containing multiple discontinuities. In comparison with the conventional end-to-end coupled cavity filters, we find that out-new-side-wall-coupled cavity filter can suppress the second resonance frequency and therefore, provide a considerably wide rejection band. It is interesting to note that the suppression of the second resonance frequency can be achieved by properly shifting the second cavity in lateral direction. To explore its physical insight, the resonant modes in the substrate integrated waveguide cavities are carefully inspected. for realizing the physical picture of wave process taking place in the two cavities system. In addition to the theoretical analysis, we have fabricated the filters and measured their scattering parameters. The good agreement between the theoretical and measured results validates the accuracy of numerical computation, and also shows the promising performance of the proposed filters. (c) 2007 Wiley Periodicals, Inc.
A Novel Monopulse Antenna Using an Artificial Magnetic Conductor in Metallic Corner Reflectors
(2015)
Tsai, Y. L.
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Hwang, R. B.
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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 monopulse antenna composed of corner reflectors was designed, fabricated, and measured. The antenna consists of two corner reflector antennas: the first is used for the sum pattern and the second is used for the difference pattern. The corner reflectors for the sum pattern antenna are made of two sheets of metallic plates arranged orthogonally to each other. Replacing one sheet of the corner reflector of the sum antenna with an artificial magnetic conductor (AMC) sheet transforms it into an antenna for the difference pattern. This proposed antenna design realizes a monopulse antenna system that does not require a complex multiple mode excitation network and phasing circuitry. The experimental results reveal that the peak gain of the difference antenna was 10.6 dBi, the null depth of the difference antenna was lower than -25 dB, the field of view was approximately 22 degrees, and the side lobe level was approximately -13 dB at 2.6 GHz. With the achieved specifications, this antenna system has considerable potential in target localization and angle tracking applications.
Leaky wave phenomena of a conductor-back dielectric slab covered with a two-dimensionally electromagnetic band gap superstrate
(2007-07-18)
Hwang, R. B.
;
電信工程研究所
;
Institute of Communications Engineering
[1] This paper presents the leaky wave phenomena associated with a waveguide structure that consists of a conductor-back dielectric slab covered with a superstrate made up of a two-dimensionally ( 2-D) electromagnetic band gap ( EBG) structure. A guided wave has its energy bounced back and forth between the metallic ground plane and the EBG structure that is taken as a frequency-selective reflection mirror. Because of the finite thickness of the 2-D EBG superstrate, the guided wave will leak or radiate some of its energy into the air region above the waveguide structure to become a leaky wave. By the mode-matching method and the transverse resonance technique, the overall waveguide structure is formulated as a rigorous electromagnetic boundary value problem to yield an exact dispersion relation of the waveguide so that the complex propagation constant of a guided mode can be accurately determined, including the phase and attenuation constants. Additionally, the electric field distribution inside the waveguide and the far-field radiation pattern were also calculated to demonstrate the leaky wave phenomena of this waveguide from a microscopic point of view. On the basis of the excitation of leaky waves, the phenomenology concerning a class of directive antennas with EBG structure as superstrate was clarified in this research.
Side wall coupling via-hole array cavity band-pass filter
(2007)
Hwang, R. B.
;
電信工程研究所
;
Institute of Communications Engineering
In this paper, we present a substrate integrated waveguide-based band-pass filter with wide stop-band rejection property. This band-pass filter is made up of two substrate integrated waveguide cavities, which couple to each other by an aperture on their common waveguide side wall. We employed the rigorous mode-matching method to analyze the electromagnetic boundary-value problem of the structure containing multiple discontinuities. In comparison with the conventional end-to-end coupled cavity filters, we found that our new side-wall-coupled cavity filter can suppress the second resonance frequency and, therefore, provide a considerably wide rejection band. It is interesting to note that the suppression of the second resonance frequency can be achieved by properly shifting the second cavity in lateral direction.
Spatial Beam Splitter Design Using Fishnet-type Periodic Structure
(2010)
Hsu, N. C.
;
Chin, C. Y.
;
Hwang, R. B.
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電子物理學系
;
Department of Electrophysics
In this paper, we present a metamaterial-based beam splitter. Such a power splitter was made up of a metamaterial sandwiched by two metallic plates. The metamaterial consists of three-dimensional (3D) fishnet arranged in a two-dimensional square lattice. As is well known from Snell's law, the refracted wave tends to be normal to the interface when the wave is incident from a medium having effective refractive index much smaller than unity into the air region. We properly synthesize the metamaterial having effective refractive index smaller than unity. Furthermore, a line source made by a monopole was embedded in the metamaterial to excite four beams propagating toward four directions. In addition to the calculation of wave-propagating characteristics in the metamaterial, we also implemented a beam-splitting structure invoking the unique characteristic of the metamaterial. The electric-field radiating pattern was measured to prove its spatially beam-splitting characteristics. Metamaterial is an artificially engineered structure which obtains its properties from its structure rather than directly from its composition. Generally, a metamaterial is synthesized by embedding specific inclusions, for example, periodic structures, in a host medium. The applications of metamaterial in waveguides and antennas designed were intensively developed [1, 2]. A metamaterial with zero-index was demonstrated to have the capability to narrow the far-field pattern associated with an antenna located within it. Besides, a matched zero-index slab could be used to transform curved wave fronts into planar ones [3]. The metamaterial made up of wire medium has been studied intensively, particularly on its effective refractive index, permittivity and permeability. Specifically, the structure composed of metallic mesh wires, which has very small electrical length in the period and wire thickness, can be characterized as a homogeneous medium with a low plasma frequency [4].