This paper presents a miniaturized tri- and quad-band power divider (PD)based on substrate integrated waveguide (SIW). By adopting different types of modified circular complementary split-ring resonators on the top surface of SIW, multiple passbands are generated propagating below the SIW cut-off frequency. The working principle is based on evanescent mode propagation that decreases the operating frequency of the PD and helps in the miniaturization of the proposed structure. The operating frequency of the proposed PD can be individually controlled by changing the dimensions of the resonator. To verify the proposed concept, a tri-band and a quad-band PD exhibiting 3 dB equal power division at 2.41/3.46/4.65 GHz and 2.42/3.78/4.74/5.8 GHz are designed using the full-wave simulator, validated through circuit model, fabricated and experimentally verified. The measured results agree well with the simulations. The proposed PDs have good performance in terms of reasonable insertion loss, isolation, minimum amplitude and phase imbalance, smaller footprint, easy fabrication and integration. The size of the fabricated prototype is 18.3 mm × 8.4 mm, which corresponds to 0.205λg × 0.094λg, λg being the guided wavelength at the first operating frequency.

This paper presents a novel asymmetric coplanar waveguide-fed quad-band hybrid antenna for wireless applications. The proposed hybrid antenna combines a conventional monopole antenna and a zeroth-order resonator antenna to perform a dual-mode operation. The first mode is generated by a slotted monopole antenna, supporting the two higher resonances at about 3.5 and 5.8 GHz. The second mode is supported by loading a composite right-/left-handed transmission line unit cell near the slotted monopole, contributing to the two lower resonances at about 1.6 and 2.5 GHz. It is printed on an FR4 substrate with the overall dimensions of 40 mm × 24 mm × 1.6 mm. Experimental results demonstrate that it can cover the global positioning system (1.57–1.59 GHz), wireless local area network (2.4–2.485, 5.15–5.35, and 5.725–5.825 GHz), and worldwide interoperability for microwave access (2.5–2.69, 3.3–3.7, and 5.25–5.85 GHz) applications with monopole-like radiation patterns and acceptable gains.

A new quad-band bandpass filter for Global System for Mobile Communications, Wireless Local Area Network, and Worldwide Interoperability for Microwave Access is designed and fabricated using the stub-loaded resonator (SLR) technology without complex fabrication process, such as via-hole or multi-layer substrate. Owing to the embedded SLR, the proposed quad-mode resonator is compact. Equivalent circuits of the proposed quad-mode resonator are analyzed in detail, and high design freedom is shown because of shifting the passband frequencies individually. Good passband selectivity and isolation of the each passband at 1.8, 2.4, 3.5, and 5.2 GHz can be well achieved due to the transmission zeros appeared near the each passband edges. Experimental results show good agreement with the simulated results.