Dual-Band Bandpass Filter With Controllable Bandwidths Using Two Coupling Paths

Sch. of Electron. & Inf. Eng., South China Univ. of Technol., Guangzhou, China
IEEE Microwave and Wireless Components Letters (Impact Factor: 1.78). 12/2010; DOI: 10.1109/LMWC.2010.2066553
Source: IEEE Xplore

ABSTRACT This letter presents the designs of dual-band bandpass filters using two coupling paths to control the bandwidth of each passband. One coupling path only delivers signals at the upper passband frequency whereas the other one couple signals at both passbands. Utilizing this method, the two bandwidths can be adjusted. The filters make use of stub-loaded resonators and it is convenient to tune the passband frequencies. Therefore, both the frequency and bandwidth of each passband can be easily controlled. For demonstration purpose, two example filters are implemented with different bandwidths. The experimental results are presented to verify the proposed method.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Two compact dual-band bandpass filters with T-shaped resonators are designed in this paper. The proposed filters are four-stage design composed by four T-shaped resonators in conjunction with the microstrip lines in the I/O ports. The location of the two passbands can be adjusted by suitably changing the impedance ratio and the length of the T-shaped resonators. For comparison, two different feeding structures are employed, saying, coupled-line feeding and tapped-line feeding patterns. For better energy input in the second pattern, the two resonators connected with the tapped-lines are asymmetric. For demonstration, one dual-band filter was designed at 2.45 GHz and 5.8GHz. The measured results show that the filter has return loss of -22 dB at 2.51 GHz and -18.6 dB at 5.81 GHz, and the 3-dB fractional bandwidth of the two passbands are 6.8% and 4.48%, respectively.
    Microwave Conference Proceedings (APMC), 2012 Asia-Pacific; 01/2012
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, a multi-layer dual-band bandpass filter using aperture-coupling is proposed. Two coupling paths are formed with the two apertures which exist between two dual-mode resonators. The coupling coefficients can be adjusted without changing the shape of resonators. The bandwidth of the second passband can be adjusted without affecting the bandwidth of the first passband using the size of an aperture between stubs of the dual-mode resonator. The aperture coupling mechanism is theoretically analysed. The dual-mode bandpass filter for the 2.4 GHz WLAN, 3.5 GHz WiMax was designed and fabricated. The fabricated filter shows centered 2.45 GHz and 3.5 GHz with 9 % and 8 % of the bandwidth.
    The Journal of Korean Institute of Electromagnetic Engineering and Science. 01/2012; 23(5).
  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents a new class of dual-, tri- and quad-band BPF by using proposed open stub-loaded shorted stepped-impedance resonator (OSLSSIR). The OSLSSIR consists of a two-end-shorted three-section stepped-impedance resistor (SIR) with two identical open stubs loaded at its impedance junctions. Two 50- Ω tapped lines are directly connected to two shorted sections of the SIR to serve as I/O ports. As the electrical lengths of two identical open stubs increase, many more transmission poles (TPs) and transmission zeros (TZs) can be shifted or excited within the interested frequency range. The TZs introduced by open stubs divide the TPs into multiple groups, which can be applied to design a multiple-band bandpass filter (BPF). In order to increase many more design freedoms for tuning filter performance, a high-impedance open stub and the narrow/broad side coupling are introduced as perturbations in all filters design, which can tune the even- and odd-mode TPs separately. In addition, two branches of I/O coupling and open stub-loaded shorted microstrip line are employed in tri- and quad-band BPF design. As examples, two dual-wideband BPFs, one tri-band BPF, and one quad-band BPF have been successfully developed. The fabricated four BPFs have merits of compact sizes, low insertion losses, and high band-to-band isolations. The measured results are in good agreement with the full-wave simulated results.
    IEEE Transactions on Microwave Theory and Techniques 01/2013; 61(9):3187-3199. · 2.23 Impact Factor