Notch-Band Implemented UWB Bandpass Filter

Daisuke KURITA  Keren LI  

IEICE TRANSACTIONS on Electronics   Vol.E90-C   No.12   pp.2226-2231
Publication Date: 2007/12/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e90-c.12.2226
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Recent Technologies for Microwave and Millimeter-wave Passive Devices)
UWB,  bandstop filter,  notch-band,  bandpass filter,  in-line stub,  

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In this paper, a notch-band implemented UWB bandpass filter was proposed. The filter was realized by integrating a full ultra-wideband bandpass filter using broadside coupling structure with a bandstop filter using in-line open stub. The in-line open stub was installed in the removed area in the broadside coupled microstrip conductors, which demonstrated a narrow notch-band performance. The proposed filters were designed based on the electromagnetic simulation and fabricated using a wet etching system. Parameter study of length dependence of the notch-band was carried out. The first resonant frequency of the in-line stub appears when the length is approximately equal to one quarter of the guided wavelength. Based on this fact, the notch-band can be adjusted to almost any specified band in the UWB passband. A three-section notch-band implemented filter demonstrated good characteristics: its full frequency bandwidth form 2.8 GHz to 10.2 GHz, good insertion loss of 0.6 dB and 1.0 dB at the centers of the first and second bands respectively, and flat and small group delay of less than 0.40 ns over main pass band, and a large attenuation stopband about 55 dB at 5.63 GHz. A lowpass filter was also introduced in order to improve the out-band performance, by which the measured results show an excellent attenuation better than 30 dB from 10.4 GHz to 17.8 GHz.