New cross-coupled bandpass filters using half-wavelength (λ/2) and branch-line resonators are proposed. The branch-line resonators are made of two quarter-wavelength (λ/4) resonators in which a shorted circuit is realized by one open stub. In the first case, a non-0°feed structure at the input and output resonators is used to produce one pair of transmission zeros near the passband to improve the selectivity. In the second case, good selectivity and improved stopband rejection can be achieved at the same time by utilizing a 0° feed structure. Specifically, the proposed filters can simplify the manufacturing process of the conventional cross-coupled filters using λ/2 and λ/4 resonators without increasing circuit area significantly.
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