A dual-mode dual-band bandpass filter with high cutoff rejection using asymmetrical transmission zeros technique is presented here. Two dual-mode filters are combined to form a dual-band filter by sharing the input and output coupled-feed line, which is more flexibility-designed and maintains a small circuit size. Controllable asymmetrical transmission zeros (TZs) at lower- and upper-sideband locations of dual-band filters are designed to achieve the high-selectivity dual-mode dual-band bandpass filter. Unwanted signals are suppressed by the places of the TZs between the first and second passband, which give much-improved signal selectivity for the dual-band bandpass filter. The two passbands are centered at 1.8 and 2.4 GHz, respectively. The first and second passbands' insertion losses are only 0.9 dB and 1.1 dB, and the measured return losses are better than 20 dB. Three transmission zeros are located between both passbands, which achieve the rejection levels about 40 dB attenuations from 1.9 to 2.3 GHz.
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