IPD dual-band filter chip with a large frequency ratio for 5G microwave and millimeter-wave applications

Abstract

In this paper, a dual-band integrated passive device (IPD) filter with an almost arbitrary large frequency ratio is proposed and it has passbands at sub-6GHz and millimeter-wave frequencies. The method to design this kind of filter is summarized. A comprehensive qualitative analysis shows how the coupled lines are used to separate high-frequency (HF) and low-frequency (LF) signals and multiple open stubs as well as LC resonators are involved in this kind of filter. According to the odd- and even-mode analytical methods, the relationship between critical transmission zeros (TZs) and circuit parameters of the dual-band filter is explained. A good selectivity is achieved to suppress intermodulation signals. A prototype of the dual-band filter chip working at 4.80 GHz and 28.29 GHz with 3-dB fractional bandwidths of 53.81% and 24.52% is implemented, indicating that it supports more 5G bands than previous designs and has a good application prospect.