Helin Yang

A novel application of frequency selective surface in dual-band WLAN antenna

In this paper, combined elements method is introduced to achieve dual stop-band frequency selective surface (FSS). Later, a dual-band WLAN antenna is designed and the centre frequency is at 2.4GHz and 5.4GHz which accord with the FSS in this paper. We use FSS as dual-band WLAN antennas reflection plan to improve the performance of antenna. The analysis and results of antenna and FSS are given. The results show that antennas gain can be improved after the FSS is placed as the reflection plane. This is a new research area which have great prospect in the design of antenna combined with FSS.

A broadband bow-tie antenna used in UHF with metal reflection plane

There are many kinds of antennas used in UWB system. Double-side printed bow-tie antenna is one of them which has the advantages of light weight, planar structure, low cost and broad bandwidth. In this paper, a double-side printed bow-tie antenna used in UHF band is proposed first. Then a metal reflection plane is added on the back of this antenna to increase its gain and inhibit backward radiation. Return loss of -10dB or better is located in the band of 0.95-2.7 GHz and the relative bandwidth is 95.9%. They have the similar VSWR quality. Besides, the reflection plane has a strong influence on radiation pattern and antenna gain. Gain in dB of former antenna has been raised from around 2.5dB to 7.5dB due to the metal reflection plane. Hence, it has a great prospect in the application of double-side printed bow-tie antenna with metal reflection plane.

Near-field EM scattering by coated objects with Left-Handed Materials

Based on the physical optics (PO) and the principle of impedance boundary condition ( IBC ) with Left-Handed Materials, a numerical method is described to analyze the near-field EM scattering from targets coated with medium. For typical targets such as a metal plate covered with radar absorbing materials (RAM) in far field and a missile coated with RAM having Left-Handed Materials in near field, the EM scattering values are obtained and discussed.

Polarization-insensitive planar left-handed metamaterials

In this paper, we propose a new kind of four-fold symmetric planar left-handed metamaterial (LHM) which consists of a cross and a ring. The results demonstrate that the left-handed metamaterial has a pass band at around 12.79GHz. Negative refractive index realizes with both negative permittivity and negative permeability over the same frequency. Also S-parameter retrieval method is used to extract effective permittivity, permeability and refractive index. Refractive index below zero extends from frequency of 12.43GHz to 13.64GHz. At last, transmission properties with different polarizations of incident EM waves are discussed which verify the polarization-insensitive left-handed metamaterial.

Band-pass filter using dual magnetic resonances

Recently, there has been great interest in using the metamaterial resonators as constituent particles for the design of band-pass and band-reject filters. In this paper, a dual-band band-pass filter using loop split ring resonator with dual magnetic resonances is proposed. The single loop split ring is made of simple conducting strip with winding geometry. Simulated transmission and phase properties predict that there are two magnetic resonances near 8.4GHz and 9.2GHz. Dual bands of negative permeability are verified using the retrieval procedure. Then, the filter is designed by combination with periodically loop split rings and narrow short connecting wires which is based on coplanar waveguide (CPW) structure. The short connecting wires make the structure have negative effective permittivity with broad frequency range. Combined with the negative permeability loop split ring etched on the back of the CPW, two pass bands appear near 8.2GHz and 9.2GHz. Since rings are much smaller than signal wavelength at resonance and can be easily tuned, it has great prospects in application based on left-handed property.

The simulation research of manipulating electromagnetic wave polarizations by metamaterial

A new metamaterial polarization transformer is designed in our paper, which is a sandwich structure. There are three metal layers and two dielectric layers in it. The top and bottom layer is SRR structure, and the middle layer is a metal cross-shape structure. We give the simulated results of this model. It reaches a near-complete cross polarization conversion at 11.03 GHz, and the polarization conversion ratio is 96.6%. Then the internal physical mechanism is analyzed through the current and electric field distribution figures. The enantiomeric pattern and sandwich coupling structure help us to manipulate the electromagnetic wave polarizations. In addition, we load the lumped elements on the gaps of SRRs to control the polarization characteristic. And we find the impact of resistor is very big. Using this feature, we can manipulate the electromagnetic wave polarizations more flexibly.

Analysis of near-field scattering by targets on rough sea surface

Based on the method of physical optics (PO) and the method of ray tracing (RT), we analyzed the near-field primary scattering of the panels, the near-field secondary scattering between the facets, the near-field composite scattering between facets and rough sea surface. Simultaneously, we calculated the near-field and far-field scattering versus incident angles by a dihedral made of two orthogonal plates and a ship model, respectively, and then discussed the characteristics of the near-field and far-field scattering. The near-field composite scattering between the ship model and sinusoidal composed surface were calculated and analyzed.