Design of compact semi-lumped mixed bandpass filter with wide stopband for 5G application

This article designs a semi-lumped mixed micro-strip bandpass filter with wide stopband for 5G wireless communication applications. The stopband of the proposed filter can be extended to the 5G millimeter wave frequency band with excellent out of band suppression, delicate structure, and compact size. This article analyzes the lumped device model under high-frequency conditions and achieved co-simulation of circuit model and field model. Finally a wide stopband bandpass filter composed of a cross loaded resonator mixed lumped LC parallel resonant circuit is implemented. The center frequency of the filter is located at 4.08 GHz, with a passband coverage of 3.96 GHz to 4.2 GHz. The designed passband locates in the N77 frequency band currently applied for 5G indoor coverage. The filter has extremely wide stopband suppression characteristics and upper stopband range exceeding 20 dB suppression level up to 22 GHz is approached. In addition, the filter has a compact device size of only 5.125 mm×7.625 mm effective circuit size, a lower insertion loss level (0.54 dB) and good selectivity which is suitable for 5G communication system application.