A Novel Miniaturized Image Rejection Bandpass Filter Basing on Stepped-impedance Resonators

|In order to meet the requirements for the suppression of mirror frequencies in the 5G RF front end, this paper proposes a novel miniaturized image rejection bandpass (cid:12)lter by loading Stepped-Impedance Resonators (SIR). By analyzing the relationship between the impedance ratio of a half-wavelength SIR and its electrical length, we have designed an improved second-order bandpass (cid:12)lter, which reduces the size by 34.3% compared to traditional (cid:12)ve-order hairpin (cid:12)lters. In order to further enhance the performance of the (cid:12)lter, the use of a radial stub, as opposed to the traditional rectangular open stub, allows for the generation of a wider band transmission zero, which can be analyzed using lumped equivalent circuits. This integration improves the stopband rejection of the (cid:12)lter. The results show that the passband range is 5.35 GHz{6.64 GHz; the rejection in the stopband range 8.10 GHz{ 11.98 GHz is over 45 dB; and the size is only 0.385 (cid:21) g (cid:2) 0 : 295 (cid:21) g .