Compact Quadruple-Mode FSIW Filtering Power Divider With High Isolation Using Embedded Capacitive Isolation Network

In this brief, a new compact filtering power divider (FPD) with high isolation utilizing embedded capacitive isolation network (CIN) is proposed, which is based on the quadruple-mode folded substrate integrated waveguide (FSIW) resonator. The dual-mode stepped-impedance stub-loaded resonator (SISLR) is the first embedded in the closed dual-mode FSIW to achieve the quadruple-mode resonator with reduced size. In addition, the CIN containing two interdigital capacitors is embedded in two hybrid resonators, which greatly improves the isolation of output ports as well as further effectively reduces the size of the FPD. In final, a prototype with 3-dB fractional bandwidth of 15.2% is designed and fabricated at 4.98 GHz (
$f_{0}$
), and its insertion loss is 1.47 dB. The isolation and upper-stopband rejection are better than 25.2 dB, and 20 dB extended to
$1.97f_{0}$
, respectively. It occupies only 0.26
$\lambda_{g}^{2}$
, where
$\lambda_{g}$
is the guided wavelength at
$f_{0}$
.