Recovery algorithms play a key role in compressive sampling (CS). Most of current CS recovery algorithms are originally designed for one-dimensional (1D) signal, while many practical signals are twodimensional (2D). By utilizing 2D separable sampling, 2D signal recovery problem can be converted into 1D signal recovery problem so that ordinary 1D recovery algorithms, e.g. orthogonal matching pursuit (OMP), can be applied directly. However, even with 2D separable sampling, the memory usage and complexity at the decoder is still high. This paper develops a novel recovery algorithm called 2D-OMP, which is an extension of 1D-OMP. In the 2D-OMP, each atom in the dictionary is a matrix. At each iteration, the decoder projects the sample matrix onto 2D atoms to select the best matched atom, and then renews the weights for all the already selected atoms via the least squares. We show that 2D-OMP is in fact equivalent to 1D-OMP, but it reduces recovery complexity and memory usage significantly.What's more important, by utilizing the same methodology used in this paper, one can even obtain higher dimensional OMP (say 3D-OMP, etc.) with ease.

No abstract

No abstract

No abstract

A novel coplanar waveguide-fed tri-band monopole antenna with a compact radiator (10 × 23 mm 2 ) for WLAN/WiMAX applications is presented. By etching properly an inverted-L slot on the straight strip loaded with a rectangular tuning patch and further adjusting the dimensions and positions of these structures, three distinct wide bands can be achieved. The measured and simulated results show that the proposed antenna has 10 dB impedance bandwidth of 470 MHz (2.38-2.85 GHz), 360 MHz (3.36-3.72 GHz) and 890 MHz (4.98-5.87 GHz) to cover all the 2.4/5.2/5.8 GHz WLAN bands and 2.5/3.5/5.5 GHz WiMAX bands. Also, the proposed antenna produces good dipole-like radiation pattern over the covering bands.Introduction: Currently, the wireless local area network (WLAN) and the worldwide interoperability for microwave access (WiMAX) have been widely used in mobile devices. To support the WLAN and WiMAX applications in the 2.4 (2.4-2.484 GHz)/5.2 (5.15-5.35 GHz)/5.8 (5.725-5.825 GHz) and 2.5 (2.5-2.69 GHz)/3.5 (3.4-3.69 GHz)/5.5 (5.25-5.85 GHz) bands, respectively, many multiband antennas have been reported. In [1], the antenna with a dual-layer metallic structure is presented for WLAN/WiMAX applications. In [2], three types of structures are used to achieve triple band to cover the WLAN/WiMAX bands. However, these proposed antennas are complicated in structure and the resulting bandwidth is not sufficient to cover the 2.5 GHz WiMAX band. To achieve sufficiently large bandwidth to cover all the 2.4/5.2/5.8 GHz WLAN and 2.5/3.5/5.5 GHz WiMAX bands, several antennas are proposed, including a microstrip-fed rectangular monopole antenna with a large parasitic patch on the back of the substrate [3], a coplanar waveguide (CPW)-fed antenna formed by a triangular monopole and a U-shaped monopole [4], and a CPW-fed monopole antenna with two bent slots [5]. Although the antennas in [3,4] can generate two wide bands to meet the whole WLAN/ WiMAX applications, the dual wideband might cause interference with other communication systems. Moreover, the oversize of the antenna [5] is somewhat large (40 × 40 mm 2 ).In this Letter, the mode method [6] is introduced to design a novel tri-band monopole antenna covering all the 2.4/5.2/5.8 GHz WLAN and 2.5/3.5/5.5 GHz WiMAX bands. The proposed antenna has a small size of 25 × 36 mm 2 , which is smaller than the antenna proposed in [5]. Meanwhile, compared with the antennas presented in [1,2], the proposed antenna is much simpler in structure. The antenna is designed and optimised by using the electromagnetic simulation tool ANSYS HFSS 13. Details of the antenna design and the simulated and measured results are presented and discussed.

Demosaicking is a digital image process to reconstruct full color digital images from incomplete color samples from an image sensor. It is an unavoidable process for many devices incorporating camera sensor (e.g., mobile phones, tablet, and so on). In this paper, we introduce a new demosaicking algorithm based on polynomial interpolation-based demosaicking. Our method makes three contributions: calculation of error predictors, edge classification based on color differences, and a refinement stage using a weighted sum strategy. Our new predictors are generated on the basis of on the polynomial interpolation, and can be used as a sound alternative to other predictors obtained by bilinear or Laplacian interpolation. In this paper, we show how our predictors can be combined according to the proposed edge classifier. After populating three color channels, a refinement stage is applied to enhance the image quality and reduce demosaicking artifacts. Our experimental results show that the proposed method substantially improves over the existing demosaicking methods in terms of objective performance (CPSNR, S-CIELAB ΔE*, and FSIM), and visual performance.

In this paper, a dual-band dual-polarized reflectarray for generating dual beams with respect to carrying two different orbital angular momentum (OAM) topological charges operating in the C-band in horizontal polarization and in the X-band in vertical polarization is proposed, with two separate horns performing on the two proposed bands as the feeding. The proposed reflectarray consists of two band reflective element cells operating in two orthogonal directions. Owing to the two composing elements orthogonally interleaved on the reflectarray surface, the corresponding phase compensation performance in one band can be slightly affected by the elemental resonance in another band; thus, the degree of the coupling between the elements with different-band operations can be neglected, resulting in fairly independent phase compensation. In other words, the desired OAM generation reflectarray, to some extent, can be developed based on two different frequency band OAM reflectarrays at the same aperture. In addition, simulations and measurements strongly suggest the feasibility and the validity of the approach, which provides a solid foundation for the application of multi-band reflectarrays to the multi-OAM-mode generation.

In this paper, an anisotropic holographic metasurface design is proposed, fabricated, and measured, to demonstrate that it can generate multiple beams with different orbital angular momentum (OAM) modes in the radio-frequency domain. The anisotropic holographic metasurface is composed of an array of quasi-periodic square particles with a rectangular slot in the upper metallic layer covered with a dielectric ground. The classic leaky-wave theory and a microwave holography method are introduced to construct the holograms that interfere with the surface waves excited by a monopole antenna and the objective waves represented by the desired multiple beams carrying different OAM modes. Moreover, the numerical simulations and experimental results are in very good agreement, which demonstrates the excellent performance of the design and provides a method of generating multiple OAM modes simultaneously. This lays a solid foundation for a channel-multiplexing method based on OAM-mode multiplexing to expand the capacity of wireless communication systems.