A compact substrate integrated waveguide (SIW) with open complementary split‐ring resonators (OCSRRs) loaded on the waveguide surface is proposed. The OCSRRs can be interpreted in terms of electric dipoles and they are good candidates to behave as electric scatterers. By loading OCSRRs on the waveguide surface, a forward‐wave pass‐band propagating below the waveguide cutoff frequency is generated. The resonance frequency of the OCSRRs is approximately half of the resonance frequency of the complementary split ring resonator (CSRR). Therefore, the electrical size of this particle is larger than the CSRRs and the OCSRRs are more appropriate for the SIW miniaturization. A bandpass response with a sharp rejection frequency band is obtained by properly manipulating the structure of the elements. By changing the orientation of the OCSRRs, two types of unit cell are proposed. Moreover, by resizing the OCSRRs, resonance frequency can be easily moved and the bandwidth can be tuned by the coupling between two OCSRRs. Compared with some other reported bandpass filters (BPFs) with SIW technique, the presented BPF has great improvements on size reduction and selectivity. To verify the methodology, two filters with center frequency of 5.5 GHz are designed and measured. The measured results are in good agreement with the simulated ones. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:674–682, 2016.

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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.

A novel super compact filter based on half-mode substrate-integrated waveguide (HMSIW) technology loaded by the modified complementary split-ring resonator (MCSRR) is proposed. The working principle of the proposed filter is based on the evanescent-mode propagation technique. According to this technique, by loading the complementary split-ring resonator (CSRR) on the metal surface of the substrateintegrated waveguide (SIW) structure, an additional passband below the SIW cutoff frequency can be obtained. In order to miniaturize the physical size of the conventional CSRR, a new method is introduced. In the proposed MCSRR unit-cell, the meander slots are carved inside all of the interior space of the ring. Accordingly, the length of the slot is increased which leads to an increase in the inductor and capacitor of the proposed structure without occupying the extra space. Therefore, the electrical size of the proposed MCSRR unit-cell is reduced. Consequently, the resonance frequency of the proposed MCSRR unit-cell is decreased compared to the conventional CSRR with the same sizes. Namely, the lower resonance frequencies can be achieved by using this technique without increasing the size of the unit-cell. In order to confirm the miniaturization technique, two HMSIW filters loaded by the proposed MCSRR unit-cell are designed, fabricated, and experimental verifications are provided. The results show that a miniaturization about 67% is achieved. K E Y W O R D Sband-pass filter, half-mode substrate-integrated waveguide, miniaturization, modified complementary split-ring resonators