Yansheng Jiang

Dual-band polarization angle independent 90° polarization rotator using twisted electric-field-coupled resonators

A bilayered chiral metamaterial is proposed to realize a dual band polarization angle insensitive 90° polarization rotator. The unit cell of the chiral metamaterial is composed by twisted electric field coupled resonators in four-fold rotation symmetry. The simulation and measured results show that this device can work in dual band with an extremely low loss and polarization conversion ratio of more than 99%. The study of the current and electric fields distribution indicates that the cross-polarization transmission is due to both the electric coupling and the magnetic coupling.

Gradient Metasurface With Both Polarization-Controlled Directional Surface Wave Coupling and Anomalous Reflection

A gradient metasurface is proposed to obtain both surface wave coupling and anomalous reflection. The unit cell of the gradient metasurface is composed by six electric field coupled resonators in different rotation angle, which provides a phase gradient. The simulation and measured results show that this gradient metasurface can work at 7.8 GHz as a surface wave coupler and at 10.288 GHz providing a phenomenon of anomalous reflection. At the two frequencies, the direction of the reflection is polarization-controlled, and the efficiencies are polarization-invariant. At left-handed polarization incidence, the direction of the coupled surface wave and the anomalous reflection are opposite to the situation at right-handed polarization incidence.

Design of a Circular Polarized Horn Antenna with an Anisotropic Metamaterial Slab

Abstract In this paper, a novel design of a circular polarized horn antenna is presented. An anisotropic metamaterial slab with metal periodic structures printed on a substrate is designed and its constitutive parameters and S parameters are analyzed. It shows that the metamaterial is anisotropic and can turn a linearly polarized wave to a circular polarized one. Then a novel horn antenna composed of a conventional rectangular horn antenna and the metamaterial slab is fabricated and measured. The results show that the novel horn antenna radiates a left handed circular polarized wave with an axis ratio below 3 dB at 16 GHz, and its gain and radiation pattern are the same as those of the conventional rectangular horn antenna.

Estimation of Echo Amplitude and Time Delay for OFDM-Based Ground-Penetrating Radar

The orthogonal frequency division multiplexing (OFDM) based ground-penetrating radar (GPR) has been proven to have many advantages. The estimation of amplitudes and time delays of interface echoes is significant particularly in GPR systems for pavement profiling. For the recently developed OFDM-based GPR systems, this letter proposes an algorithm for precisely estimating the echo amplitudes and time delays. We estimate the propagation channel in frequency domain and transform the resulted channel frequency response to time domain. Considering the reduction of the channel impulse response (CIR) leakage caused by IFFT, a windowing method is applied before the IFFT. The challenge is that the general windowing method leads to resolution decrease and peak value losses for the windowed CIR, which contains the echo amplitude and time delay information. We design a window that causes very little echo amplitude loss and improves the estimation resolution. In this way, the echo amplitudes and time delays can be obtained from the largest few extreme values of the windowed CIR. The algorithm performs a low complexity, and the simulation results show that the estimation errors for both amplitudes and time delays are small with the range resolution improved.

A design of dual-band 90° polarization rotator using twisted electric-field-coupled resonators

In this paper, a dual band polarization angle insensitive 90° polarization rotator using chiral metamaterial is proposed. The chiral metamaterial unite cell is composed by twisted electric-field-coupled (ELC) resonators in four-fold rotation symmetry. Thus it has the same response to the waves with arbitrary polarization angle. The simulation results show that it can works at 13.27GHz and 17.12GHz with the efficiency more than 90%.

Design of a Five-Band Internal Antenna for Handsets

Abstract A novel compact five-band internal handset antenna covering LTE (746–806 MHz), GSM850 (824–894 MHz), GSM900 (890–960 MHz), DCS (1710–1880 MHz) and PCS (1850–1990 MHz) bands is presented. To enhance the bandwidths of the proposed antenna both at the low frequency band and high frequency band, a rectangular slot with a proper size is removed in the ground plane at an appropriate location. Both the simulated results and measured results show that reasonable radiation patterns and antenna gains for each frequency band are achieved.

Design of OFDM Signal with Good Autocorrelation for Ground Penetrating Radar

Abstract Orthogonal frequency division multiplexing (OFDM)-based ground penetrating radar (GPR) has been proved to have a number of advantages. To improve the performance of a GPR system, time domain non-periodic autocorrelation (AC) of the transmitted OFDM signal should be designed to have similar shape to an ideal pulse. Challenge in OFDM signal design for GPR is that there is little pertinent literature and the design should be different from that in communication and air radar fields. In this paper, we propose a design scheme of OFDM signal with good AC for GPR. We divide the AC into main lobe and side lobe with proving that the main lobe is dominated with the functionality of the modulating amplitudes while the side lobe’s main function is modulating phases. Thus, modulating amplitudes and phases can be designed, respectively. Performance of this proposed approach is demonstrated by numerical examples. The results show that the designed OFDM signal yields a better AC and fewer false alarms for GPR systems.

Multi band polarization converter based on anisotropic metasurface

In this paper, a multi-band polarization converter using anisotropic metaurface is proposed. The unite cell of the anisotropic metaurface is mediated by electric-field-coupled (ELC) resonator. The proposed metasurface can converts the linearly polarized waves to its cross polarization at 7.83GHz and 10.22GHz. Whats more, the designed metasurface can convert the linearly polarized waves to left handed circularly polarized waves at 7.76GHz and 10.54GHz, and convert the linearly polarized waves to right handed circularly polarized waves at 7.91GHz and 9.94GHz. The polarization conversion ratio (PCR) at 7.83GHz and 10.22GHz are more than 96%. The axial ratio at 7.76GHz, 7.91GHz, 9.94GHz and 10.54GHz are smaller than 1dB.

A design of OFDM signal for ground penetrating radar

This paper discusses a flexible OFDM signal design for ground penetrating radar. First, the subcarriers are modulated by values of desired spectrum sequence; secondly, according to different sizes and depths of targets, the desired GPR signal spectrum is adaptively estimated using some priori knowledge of target information. The simulating results show the proposed signal design scheme for GPR performs well in detection of both thin and deep layer targets.

GPR imaging algorithm of targets located in layered mediums based on CS

Previous studies in compressive sensing (CS) based subsurface imaging methods depended on two important assumptions; namely, that the imaging scene is modeled as a single homogeneous medium and that the relative permittivity of background environment is known. However, these assumptions are not always valid for the practical application of underground imaging with ground penetrating radar (GPR). To this end, a new GPR imaging algorithm based on CS is proposed in this paper. The algorithm attempts to image the point like targets located in unknown layered mediums subsurface. A 2-D underground objective vector firstly obtained includes both unknown layered mediums vector and unknown targets vector. Then the scattering and imaging model is formed by the ray-based simulation methods. This model is designed under the framework of CS theory. Finally, the GPR data can be reconstructed from an extended dictionary by solving a convex l1 minimization problem. Experimental results of GPR simulation data validate the effectiveness of the proposed algorithm.