Dual-Band Bandpass Filter With Controllable Bandwidths Using Two Coupling Paths
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.
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ABSTRACT: Dual-band bandpass filters with controllable fractional bandwidths (FBWs) are constructed by cascading the multiple λ/2 stepped-impedance resonators (SIRs) through the distributed parallel-coupled microstrip lines (PCMLs). By suitably choosing the aspect ratio of two strip widths or impedances in the SIR, the first two resonant frequencies are allocated to 2.4 and 5.2 GHz for dual-band filter application. These PCMLs with different overlapped lengths are investigated to show their distributed coupling performance in terms of explicit J-inverter susceptances. For the first time, it implies that the coupling degrees at two resonances can be adjusted with freedom to control the FBWs of these dual pass bandwidths. Then, the three one-stage dual-band SIR circuits are characterized to initially exhibit the dual-band performances in terms of S-parameters. In final, the three two-stage filters are optimally designed and fabricated to demonstrate in reality the dual-band performance with controllable FBW parameters.Microwave Symposium Digest, 2005 IEEE MTT-S International; 07/2005
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ABSTRACT: This paper presents the design of a new dual-band filter with very wide upper stopband. The proposed circuit offers a simple and compact structure with low insertion loss. Spurious suppression is achieved by using specially designed coupling and resonator sections. Moreover, a systematic analysis is applied to the proposed topology with closed-form design equations derived. For verification purposes, the measured performance of a microstrip filter operating at 1 and 2 GHz is shown with stopband attenuation of greater than 20 dB over the frequency range from 2.5 to 8.0 GHz.IEEE Transactions on Microwave Theory and Techniques 07/2008; · 2.23 Impact Factor
Conference Proceeding: Dual-band coupling and feed structure for microstrip filter design[show abstract] [hide abstract]
ABSTRACT: A new configuration of dual-band filter design is presented in this paper. Stepped-impedance transmission-line sections are used as the tunable dual-band resonators. New coupling structures and matching networks at input and output are also proposed to achieve a dual-band characteristics. Three filters with their second passband at 1.5, 2, and 2.5 times the fundamental frequency are designed as examples, and they are all verified by experimental results.Microwave Symposium Digest, 2004 IEEE MTT-S International; 07/2004