Miniaturized filtering rat‐race coupler based on hybrid circular substrate integrated waveguide and coplanar waveguide resonators

Abstract

In this paper, an approach to designing filtering rat‐race coupler (FRRC) with hybrid circular substrate integrated waveguide (CSIW) and coplanar waveguide (CPW) resonators is proposed. The FRRC is developed in a single CSIW cavity embedded with four CPW resonators and four feeding ports, featuring miniaturized size. The desired 0° and 180° phase characteristics of the RRC are realized by the inherent in‐phase and out‐of‐phase electromagnetic fields of the dual‐mode CSIW cavity. By properly arranging the sum, difference and other two output ports, the FRRC is exploited to achieve the desired properties of a RRC with bandpass filtering responses. In addition, transmission zeros are generated in the vicinity of the upper stopband. For validation and demonstration, a miniaturized FRRC utilizing hybrid CSIW and CPW resonators is synthesized, fabricated and experimented in a single‐layered process. Comparisons with previously state‐of‐the‐art research, the proposed FRRC prototype indicates the superiorities of miniaturized footprint, high‐quality‐factor, high‐order filtering response and enhanced out‐of‐band rejection.

Design of Filtering Magic-T with Wideband and Wide Stopband Based on HMSIW and Spoof Surface Plasmon Polaritons

“…Compared to the designs in [4,5], the proposed FMT realizes bandpass filtering response and miniaturization attributed to the bandpass characteristic and SW effect of the HMSIW-SSPP structure, and we can easily control the upper and lower cut-off frequencies of the passband by altering the structural parameters. Moreover, compared to the reported stateof-the-art FMT based on SIW technology [8][9][10][12][13][14]17], our proposed FMT exhibits the unique advantages of the wide operating bandwidth and wide stopband performance while maintaining a relatively compact size. Table 1 compares our design with other reported SIW magic-Ts and FMTs.…”

“…The experimental results are in good consistency with the simulated ones. Compared with SIW magic-Ts in [4,5] and FMTs in [8][9][10][12][13][14]17], this design achieves the superiorities of compactness, wide filtering bandwidth, wide stopband rejection, and ease to design. It could be a capable candidate for future wireless communication systems.…”

“…Moreover, using high-order resonators to meet wideband applications may lead to a large size [16]. A recent study in [17], reports an FMT based on hybrid SIW and coplanar waveguide (CPW) resonators to implement the compactness and 3rd-order filtering response, but its FBW is just 7.58%. Thus, designing a SIW FMT with compact size, wide bandwidth, and wide stopband rejection remains a challenge.…”