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Vortex beams carrying orbital angular momentum are extensively studied owing to its potential to expand channel capacity of microwave and optical communication. By utilizing the Pancharatnam-Berry phase concept, an ultra-wideband single-layer metasurface is proposed to realize the conversion from incident plane waves to reflected vortex beams covering a considerable bandwidth from 6.75 to 21.85 GHz (>105%). An equivalent circuit model combined with broadband phase shift network is developed to effectively design the meta-atoms in metasurface. It is the first time to design wideband metasurfaces with the phase-based characteristics. To verify the proposed model, some deformed square loop meta-atoms are proposed to construct the metasurfaces with broadband OAM characteristic. Moreover, the vortex beams with the integer (l = −3), fractional (l = −1.5), and high-order (l = −10) OAM mode are generated respectively. Based on an OAM spectral analysis, the mode purity of the generated vortex waves is discussed in detail. The experimental results achieve a good agreement with those obtained from the simulation, thus proving the effectiveness and practicability of the proposed method.Index Terms-Orbital angular momentum (OAM), fractional OAM mode, ultra-wideband, metasurface, Pancharatnam-Berry phase (PB).

This paper presents a compilation of important review in the development of microwave filters for wideband technology used in previous years. The major research work for each year is reviewed. Several wideband filters based on the planar and non-planar circuits are compared and examined in order to propose a new topology of wideband filter using Suspended Stripline Structure (SSS). More importantly, this new proposed structure will be integrated with the Defects Ground Structure (DGS) to form an advanced hybrid system for wideband applications. This system will produce the band-pass and band-stop responses simultaneously in order to discriminate between the desired and undesired signals in the wideband spectrum. The proposed system outlined in this paper, featuring new innovation in hybrid structure as well as providing an insight of the direction of future research works. The contribution of this study is useful for applications where the reduction of physical volume is very important, while maintaining its good performance such as Ultra-Wideband (UWB), commercial radar as well as the wideband warfare receiver. As for future works, integration techniques between the UWB filter and DGS will be designed and analyzed to form an advanced new microwave device in order to produce bandpass and bandreject response in the same structure simultaneously.

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