A compact composite right/left-handed (CRLH) bandpass filter with wide out-of-band rejection, which utilizes a substrate integrated waveguide (SIW) and modified complementary split-ring resonators (CSRRs) is presented. By incorporating two sets of CSRRs resonators (the top and bottom CSRRs) into SIW cavity, the proposed filter obtains a high selectivity. Besides, the filter has the CRLH property, and no additional areas are required because of the structure of the top CSRRs and the gap between them. At the same time, two slots of etched units used in feeding lines are replaced to obtain a wide out-of-band rejection. Finally, the measured results show that the filter has a wide stopband with rejection over 20 dB up to 4.3 times of the center frequency, implying that the experimental results are in good agreement with simulated ones.
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