Browsing by Author "Liu, Chun-Chih"

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Compact Zeroth-Order Resonant Antenna Based on Dual-Arm Spiral Configuration
(2012)
Liu, Chun-Chih
;
Chi, Pei-Ling
;
Lin, Yu-De
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電機工程學系
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Department of Electrical and Computer Engineering
A miniaturized and zeroth-order resonant composite right/left-handed (CRLH) antenna based on dual-arm spiral structure is presented. The proposed dual-arm spiral unit cell is able to implement and tailor the CRLH lumped elements easily in a compact fashion. Particularly, the gap coupling between the spiral arms contributes to the series capacitance C-L and the metallic via-hole at the end of one arm results in the shunt inductance L-L. The resonant frequency and thus the miniaturization factor can be simply engineered by the spiral parameters that determine the corresponding circuit elements. The proposed CRLH antenna is composed of two unit cells, each of which occupies only 0.066 lambda(0) x 0.053 lambda(0) at the operating frequency. From the experimental results, this compact antenna exhibits the dipole-like radiation patterns and has a peak gain of -0.53 dBi. The measured and simulated results are provided, and good agreement is achieved.
Novel Dual-Band Quasi-0-dB Coupled-Line Coupler Using the Composite Right/Left-Handed Transmission Lines
(2014-02-01)
Chi, Pei-Ling
;
Liu, Chun-Chih
;
電機資訊學士班
;
Undergraduate Honors Program of Electrical Engineering and Computer Science
A novel edge-coupled symmetric coupled-line coupler featuring the quasi-0-dB couplings at adjacently dual frequencies is presented based on the composite right/left-handed (CRLH) transmission lines. The fulfillment of dual-frequency quasi-0-dB couplings is derived from the complete backward and complete forward coupling phenomena at the higher and lower operating frequencies, respectively. To this end, the dispersion relations of the even and odd-mode CRLH lines have to be engineered in a particular manner so that: 1) the substantial attenuation level for each mode; 2) the 180 degrees phase difference between the even and odd-mode reflection coefficients in the overlapped stopband region are obtained to accomplish the complete backward coupling; 3) the enabling curve intersection for the even and odd-mode Bloch impedances; and 4) the considerable difference between the even and odd-mode propagation constants in the left-handed regions are obtained to suppress the impedance coupling and attain strong forward coupling. Based on a thorough analysis on the even and odd-mode dispersion characteristics and Bloch impedances of the coupled lines, the operating principle and design procedure for the proposed coupler with dual-band complete couplings can be fully explained and greatly simplified. A symmetric CRLH coupled-line coupler consisting of seven coupled unit cells was experimentally developed and a shielding (metal) box was used to prevent radiation loss in the forward coupling band. Experimental results show that the maximum coupling levels are -1.3 and -0.9 dB, corresponding to the 3-dB fractional bandwidths of 15.8% and 10.8% at the lower and higher operating frequencies, respectively. Good agreement is obtained between the simulated and experimental results.