Coupled-Line Bandpass Filters With Stopband Extension and Multiple Transmission Zeros
Date Issued
2006
Date
2006
Author(s)
Wu, Chao-Huang
DOI
en-US
Abstract
In this dissertation, a new class of coupled-line bandpass filters (BPFs) with stopband extension and better selectivity, including several microstrip and two coplanar-waveguide (CPW) structures, is presented. These BPFs can find applications in various wireless communication systems.
First of all, in Chapter 2, the basic coupled-line BPFs are proposed according to the fundamental concepts of filters and equivalent-circuit models of coupled-line sections. By adding the lumped-element-inverters into conventional coupled-line BPFs, the order of proposed coupled-line BPFs are double of conventional coupled-line BPFs without increasing the circuit area, and no repeated passband is observed at twice center frequency.
For the stopband extension, in Chapter 3, the basic coupled-line BPFs are extended to implement the novel microstrip coupled-line BPFs with extended rejection band, using the transmission zeros inherently associated with the shortened coupled sections to suppress the odd spurious harmonics. This technique has the advantage of compact circuit size without increasing the insertion loss.
For the selectivity improvement, several compact microstrip coupled-line BPFs with capacitive or inductive cross-couplings to create multiple transmission zeros are proposed in Chapter 4. The locations of transmission zeros can be adjusted by varying the values of cross-coupled capacitances or inductances so as to improve the filter selectivity.
Finally, in order to overcome the drawbacks of microstrip structures, two compact coupled-line coplanar-waveguide bandpass filters with good selectivity and stopband responses are proposed in Chapter 5. By using the quarter-wavelength resonators in implementation, the filter size can be reduced by half and no spurious passband is observed at twice the center frequency when compared with the conventional parallel-coupled bandpass filters based on half-wavelength resonators. In addition, the concepts in Chapters 3 and 4 are also adopted in the CPW filters design so as to achieve stopband extension and better selectivity.
Subjects
濾波器
耦合線
傳輸零點
截止帶
filter
coupled-line
transmission zeros
stopband extension
Type
thesis
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