A four-way filtering power divider (PD) based on a substrate-integrated waveguide (SIW) is presented. This structure is composed of two layers of the dielectric substrate. The eighth-mode SIW (EMSIW) technique is used to make four cavities in the upper substrate. In addition, an SIW cavity is provided in the lower substrate. To achieve an efficient transition between the two layers, four rectangular slots are etched on the middle metal planes. A circular slot is etched on the top metal layer of the EMSIW cavities to suppress the higher operating modes. To prove the validity, a four-way PD with a second-order bandpass filtering response is designed and fabricated. The measured results show that the PD achieves an insertion loss of 1.3 dB at 3.5 GHz, a return loss of higher than 17 dB, a 3-dB fractional bandwidth of 7.75%, and an out-of-band rejection of greater than 26 dB from 3.92 to 16.5 GHz. The results show that this PD has the advantages of compact size, high selectivity, and ultrawide out-of-band rejection.

A miniaturised equal/unequal substrate integrated waveguide power divider with bandpass filtering response loaded by complementary split‐ring resonators (CSRRs) is proposed. The proposed structure is based on the theory of evanescent mode propagation. The use of the CSRRs enables the filtering function of the power divider and is able to reduce its size. By changing the orientations of the CSRRs, the equal/unequal power dividers are achieved. In the unequal power divider, the power ratio can be arbitrarily controlled by carefully tuning the parameters of the CSRRs and locations of the output ports. Three miniaturised filtering power divider samples with power division ratios of 1:1, 1:4 and 1:8 are fabricated and tested. These designs resonate at the frequency of 5.8 GHz covering WLAN. The sizes of the proposed power dividers (1:1, 1:4 and 1:8) are only 0.37 × 0.21λ _g ² , 0.3 × 0.16λ _g ² and 0.3 × 0.15λ _g ² , respectively.

This paper presents a C-band filtering power divider (FPD) based on a hybrid of spoof surface plasmon polariton (SSPP) and half-mode substrate integrated waveguide (HMSIW). The proposed hybrid circuit is designed by etching subwavelength corrugated grooves in the HMSIW upper wall and has both characteristics of the SSPP and HMSIW structures. It can create the bandpass response and reduce both transverse and longitudinal dimensions of the substrate integrated waveguide structure by nearly 50%. The dispersion and transmission characteristics of the proposed HMSIW-SSPP transmission line are analyzed. The lower and upper edges of the passband can be adjusted independently by tuning the dimensions of the HMSIW and SSPP structures. The presented FPD is fabricated and measured to validate the proposed design procedure. The simulated and measured results are in good agreement. The measured results show that the proposed circuit achieves a bandwidth of 66% from 4 to 8 GHz with better than 10.5 dB return loss and a minimum insertion loss of 1.05 dB.