Browsing by Author "Chi, CH"

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A new class of wideband multisection 180 degrees hybrid rings using vertically installed planar couplers
(2006-06-01)
Chi, CH
;
Chang, CY
;
電信工程研究所
;
Institute of Communications Engineering
A new class of wideband multisection 180 degrees hybrid rings using the vertically installed planar (VIP) coupler is proposed. On the basis of the reconfigured ideal single-section 180 degrees hybrid ring (i.e., the 180 degrees hybrid ring with an ideal phase inverter), the multisection 180 degrees hybrid rings can be realized by properly cascading of single-section 180 degrees hybrid rings. Compared with the conventional hybrid ring, the two-section hybrid rings exhibit wide bandwidth, size reduction, and easily achievable high power-division ratios. Design equations based on the equal-ripple functions are derived. Design curves for the equal and unequal power-division ratio are also described. In addition, a cascade of single-section cascadable hybrid rings with a unit element at each I/O port can be used for bandwidth enhancement. Good agreement is obtained between the experimental and simulated results.
Miniaturized spurious passband suppression microstrip filter using meandered parallel coupled lines
(2005-02-01)
Wang, SM
;
Chi, CH
;
Hsieh, MY
;
Chang, CY
;
電信工程研究所
A novel meandered parallel coupled-line structure is proposed to suppress the first spurious passband of a microstrip bandpass filter. The meandered parallel coupled line can equalize the modal transmission phases at any interested frequency such as first spurious passband frequency due to its dispersive response. Several filters are designed and fabricated on a substrate with a dielectric constant of 10.2 and a thickness of 50 mil (1.27 mm) to demonstrate the validity of the proposed method. The example filters are chosen to be of large fractional bandwidth and with a relatively high dielectric-constant substrate where, in these cases, the first spurious passband near twice of the passband frequency (2f(o)) seriously degrades the conventional parallel coupled filter's upper stopband performance. The upper stopband performance of the proposed filters drastically improves that the measured first spurious passband are suppressed to better than -50 dB for all example filters. Besides, a meandered coupled line not only suppresses the filter's first passband, but also largely shrinks its length. The characteristics of the proposed structure and the design procedures of the filter are described in detail.