Millimeter-wave bandpass filter for 5G-N257 band based on thin-film IPD process

This letter presents the design of a millimeter-wave bandpass microstrip filter for 5G, using a thin-film integrated passive device (IPD) process, in accordance with the principles of microwave theory and technique. The proposed filter features a double-layer microstrip structure, which enables coverage of the 5G n257 frequency band. By incorporating metal-insulator-metal (MIM) capacitors through the overlap of the upper and lower metal layers, the filter size is effectively reduced. Hybrid coupling between two resonators is introduced to generate two transmission zeros, resulting in a second-order bandpass filter. The proposed microstrip millimeter-wave fil ter achieves miniaturization while ensuring excellent performance. Moreover, the center frequency and bandwidth of the passband can be flexibly designed by adjusting the overlap area between the upper and lower layers and the coupling line. In this study, a 5G millimeter-wave bandpass filter is designed with a center frequency of 28 GHz, a 3 dB bandwidth of 10.7%, and an insertion loss of 2.11, demonstrating the effectiveness of the proposed approach.