Browsing by Author "Itoh, T"

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A periodic microstrip radial antenna array with a conical beam
(2003-04-01)
Chen, KC
;
Qian, YX
;
Tzuang, CKC
;
Itoh, T
;
電信工程研究所
The analysis and design of a microstrip antenna array with a conical beam are presented. The antenna array employs a periodic structure derived from the microstrip on a perforated ground plane. The microstrip antenna array consists of eight leaky lines evenly distributed around a circle. Each line radiates mainly a pair of forward and backward beams, forming a conical beam. The new leaky line design employs the concept of space-harmonic modulation on the EH0 mode launched at the common joint of the antenna array. The scattering and dispersion characteristics of the leaky line are thoroughly investigated. The fact that the perturbation of the antisymmetric holes made by photolithographic etching excites the leaky EH1 mode is theoretically and experimentally validated. Scattering analyses of the surface currents on the microstrip, however, reveal in detail the physical operation of the leaky line. The dispersion characteristics are, thus, established and shown in a Brillouin diagram, indicating the role of each space harmonic, denoted by its complex propagation constant gamma(m,n)(+/-). gamma(m,n)(+/-) represents a traveling-wave component of the nth higher-order spatial component in association with the EHm mode: the superscript, + signifies a forward (backward) traveling wave. For the particular leaky line design, gamma(0)(+),(-1) and gamma(1,0)(+) space barmonics, both showing odd-symmetric field polarization, and both outside the triangular Brillouin region, form the backward and forward leaky waves, respectively. When the leaky lines are evenly and collinearly tied, an 11.5-GHz radial antenna array prototype is formed, and emits a conical beam, showing a 3-dB beamwidth of 24degrees at the flare angle of 31degrees.
Hybrid-mode computation of propagation and attenuation characteristics of parallel coupled microstrips with finite metallization thickness
(1997-02-01)
Kuo, JT
;
Itoh, T
;
電信工程研究所
;
Institute of Communications Engineering
The hybrid-mode mixed spectral domain approach (MSDA) is formulated to investigate the dispersion nature of multiple coupled microstrip lines with arbitrary metallization thickness, Incorporated into the solution procedure, a new set of basis functions with delta(-1/3) field singularity near conductor edges is found to be effective in calculating both the phase and attenuation constants, The computation of conductor loss is based on the perturbation procedure, Over a broad band of frequency spectrum, excellent agreement is obtained between the calculated results and existing experiment data for the metallic losses of a single microstrip and effective dielectric constants of coupled lines, The influence of finite metallization thickness on the frequency dependent modal propagation and attenuation characteristics is presented for both a three-line and four-line structure.
Leaky properties of microstrip above a perforated ground plane
(1999)
Chen, KC
;
Tzuang, CKC
;
Qian, YX
;
Itoh, T
;
電信工程研究所
A leaky line is proposed. The leaky line emits leaky wave by feeding the bound mode that is not supposed to leak. The proposed guiding structure consists of a microstrip above a perforated ground plane with etched holes positioned anti-symmetrically. A prototype is built and tested to verify the concept. The two-port scattering parameters of the leaky line employing the well-known full-wave integral equation method agree well with the measured data. The investigation of RPA (relative power absorbed) and G(A,max) (maximum available power gain) of the prototype points to a substantial excitation of the EH1 leaky mode, over 50% leakage of input energy for the 72 mm long prototype at 6.5 GHz.
Modal characteristics of planar transmission lines with periodical perturbations: Their behaviors in bound, stopband, and radiation regions
(2005-01-01)
Chen, YC
;
Tzuang, CKC
;
Itoh, T
;
Sarkar, TK
;
電信工程研究所
This paper presents the modal characteristics of one-dimensional periodical transmission lines, including the microstrip with even-symmetric periodical perturbations, the microstrip on an electromagnetic bandgap (EBG) surface without via holes, and the electric-magnetic-electric (EME) microstrip, in the bound, stopband, and radiation regions. The Brillouin diagram, or the so-called kappa - beta diagram, is employed to represent the dispersion characteristics of the periodical transmission lines. The matrix-pencil method is applied to analysis the surface currents J(s) obtained by invoking the method of moment simulation, and the results are verified by the finite-element method analyzes. The complex modes in the form of +jalpha +/- beta and -jalpha +/- beta could be observed in the microstrip with even-symmetric periodical structure and form the stopband of the periodical microstrip. In the case study of the microstrip on the EBG surface, the complexity of the modal behaviors could be illustrated in the stopband. The complex mode pair in the form of +jalpha +/- beta exists in the stopband. In the stopband of the EME microstrip, the complex mode in the form of +jalpha +/- beta appears. Energy vanishes due to the space-wave leakages near the corner frequencies of the stopband of the microstrip on the EBG,ground plane and the EME microstrip. The dispersion characteristics of three case studies exhibit the different modal behaviors although the scattering analyzes show the similar results in the passband, stopband, and radiation regions.