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Highly Selective Differential-Mode Wideband Bandpass Filter for UWB Application. 趙士傑 2011/9/8. Ref: T. B. Lim and L. Zhu, IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS , vol. 21, no. 3, pp. 133-135, 2011. Introduction.
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Highly Selective Differential-Mode Wideband BandpassFilter for UWB Application 趙士傑 2011/9/8 Ref: T. B. Lim and L. Zhu, IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, vol. 21, no. 3, pp. 133-135, 2011
Introduction FCC authorizes the unlicensed use of UWB in the range of 3.1 to 10.6 GHz As a key component to regulate the specified UWB spectrum, the bandpassfilters with high performance, compact size and low cost are highly demanded Little research has been done on exploration of a wideband differential-mode BPF to meet the prompt needs in development of such a balanced RF front-end
Introduction (cont.) • The broadside coupled coplanar striplines • differential-mode BPF with a fractional bandwidth greater than 110% • in the absence of the ground plane, this filter cannot directly integrate with other differential-mode active circuits • Microstrip line • poor frequency selectivity
Simulated frequency response f0=4.1GHz Z1=Z3=54.3Ω Z2=52.8Ω Z12=Z23=52.4 Ω
Proposed differential-mode BPF To sharpen the out-of-band rejection skirt, the first and third shunt stubs are then stretched by three times
Simulated frequency responses With λg/2 connecting lines Common-mode frequency responses
Schematic of the proposed differential-mode wideband bandpass filter
Conclusion A novel differential-mode BPF with good common-mode suppression is proposed and designed on microstrip line The differential-mode filter is constituted by installing two3λg/4vertical arms on the two sides and one λg/4 vertical arms in a branch-line structure The proposed filter exhibits a wide passband in the lower UWB band As the connecting lines are stretched from λg/4 to λg/2 in filter, a five-pole filter is realized with good out-of-band rejection skirt and good in-band common-mode suppression Measured results achieve a differential-mode passband in the range of 2.8–5.3 GHz where the common-mode attenuation is close to 20.0 dB