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In this paper, we present the design of a low-profile antenna consisting of two orthogonal parasitic meandered monopoles excited by the near-filed coupling with a feeding bow-tie. The two parasitic radiators and the driven element are placed on two different faces of the same dielectric substrate and a coaxial probe excites the bow-tie through a metallic ground plane. In this way, the antenna has compact dimensions of 21 x 10.5 x 1.6 mm³ (λ0/6 x λ0/12 x λ0/75, excluding the ground plane) and exhibits a good impedance matching in the 2.4-2.485 GHz Wi-Fi band with an overall efficiency around 50%. [ABSTRACT FROM AUTHOR]

In this paper, we present the design of a low-profile antenna consisting of two orthogonal parasitic meandered monopoles excited by the near-filed coupling with a feeding bow-tie. The two parasitic radiators and the driven element are placed on two different faces of the same dielectric substrate and a coaxial probe excites the bow-tie through a metallic ground plane. In this way, the antenna has compact dimensions of 21 x 10.5 x 1.6mm3 (λ0/6 x λ0/12 x λ0/75, excluding the ground plane) and exhibits a good impedance matching in the 2.4--2.485 GHz Wi-Fi band with an overall efficiency around 50%. [ABSTRACT FROM AUTHOR]

Recently, we have presented a novel approach to design metamaterial-inspired notch filters that can be integrated within horn antennas of receiving systems to mitigate the effects of narrowband interfering signals. The filter module consists of a single Split Ring Resonator (SRR), whose rejection band needs to be matched to the bandwidth of the particular interfering signal we want to suppress. Extending our previous work, we show here how it is possible to control the bandwidth of such a filtering module by using different metamaterial-inspired resonators. In particular, we show that, while a reduction of the rejection band can be easily obtained by increasing the miniaturization rate of the resonator, the enlargement of the rejection band cannot be obtained in the same way by simply reducing the resonator quality factor. We show that a solution of the latter problem can be worked out by applying the "critical coupling" concept and considering the filtering module to be made of two equal SRRs with a proper optimal separation. The effectiveness of the approach is demonstrated trough proper full-wave simulations and experiments on a fabricated prototype. The proposed technique, used here to design a filtering module for a specific radiating system, has a more general relevance and can be applied to all cases where the operation bandwidth of a component is limited by the resonant nature of a single metamaterial-inspired particle. [ABSTRACT FROM AUTHOR]

The recent extension of the orbital angular momentum (OAM) concept from optical to microwave frequencies has led some researchers to explore how well established antenna techniques can be used to radiate a non-zero OAM electromagnetic field. In this frame, the aim of the present paper is to propose a new approach to generate a non-zero OAM field through a single patch antenna. Using the cavity model, we first analyze the radiated field by a standard circular patch and show that a circular polarized (CP) TMnm mode excited by using two coaxial cables generates an electromagnetic field with an OAM of order ± (n-1). Then, in order to obtain a simpler structure with a single feed, we design an elliptical patch antenna working on the right-handed (RH) CP TM21 mode. Using full-wave simulations and experiments on a fabricated prototype, we show that the proposed antenna effectively radiates an electromagnetic field with a first order OAM. Such results prove that properly designed patch antennas can be used as compact and low-cost generators of electromagnetic fields carrying OAM. [ABSTRACT FROM AUTHOR]