Browsing by Author "Lok, U-Hou"

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New Dual-Mode Dual-Band Bandpass Filter With Quasi-Elliptic Function Pass bands and Controllable Bandwidths
(2010)
Lin, Tsu-Wei
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Lok, U-Hou
;
Kuo, Jen-Tsai
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傳播研究所
;
Institute of Communication Studies
New dual-mode dual-band bandpass filters with quasi-elliptic function responses are devised based on a single stepped-impedance resonator. The center of the resonator is grounded through a short high-impedance section which is equivalent to an inductor for providing coupling between the resonant modes. In addition, in order to increase the degree of freedom for the dual-band design, an interdigital capacitor is introduced so that both center frequencies and bandwidths of the two passbands can be controlled. Moreover, with the aid of source-load coupling, two extra transmission zeros can be created close to the passband edges and hence greatly improve the filter selectivity between the two passbands. Two filters are fabricated and measured to validate the proposed idea. The measured results show good agreement with the simulation.
Novel corrugated coupled-line stage with ideal frequency response and its application to bandpass filter design with multi-harinonic suppression
(2007)
Kuo, Jen-Tsai
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Lok, U-Hou
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Wu, Meng-Huan
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電信工程研究所
;
Institute of Communications Engineering
Coupled-line stages are designed with corrugated periods to accurately allocate inherent transmission zeros at three leading even harmonics of design frequency, f(0). The corrugation pattern is finely trimmed so that phase velocities of the two eigenmodes can be simultaneously equalized at these frequencies. By decreasing munber of coupled periods in a stage, frequencies of the zeros can be arbitrarily scaled up to a certain extent In this way, a parallel-coupled line bandpass filter with a cascade of several such stages cant be synthesized to be free of spurious harmonics up to at least 10f(0,) with aid of tapped input/output coupling scheme. The measured data of the fabricated bandpass filter show a rejection level of better than 30 dB in the upper stopband up to 18f(0).
Quadruple-mode coupled-ring resonator bandpass filter with quasi-elliptic function passband
(2008-03-01)
Lok, U-Hou
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Chiou, Yi-Chyun
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Kuo, Jen-Tsai
;
電信工程研究所
;
Institute of Communications Engineering
Quadruple-mode coupled-ring resonator is used to design quasi-elliptic function bandpass filters (BPFs) with a relatively wide bandwidth. The resonator consists of a pair of coupled rings with two open stubs symmetrically tapped to the inner ring. The stubs are used to move a transmission zero near the center frequency to lower transition band. It is believed that it is the first ring resonator BPF-based on the coupled-ring to create four transmission poles and four transmission zeros. Two filters with relative bandwidths of 10% and 15% are fabricated and measured. Good agreement between simulation and measurement is obtained.