Jingfeng Chen

A method of accurate co-simulation by considering lumped port setting in EM simulator

This paper introduces a method of accurate co-simulation by considering lumped port setting in EM simulator. In this method, various equivalent circuit parameters can be obtained with different lumped port settings in EM simulator, so that the parameters of the element used for co-simulation should correspond to the particular lumped port setting in EM simulator. For verification, a resistor and a p-i-n diode are used as examples. The measured results coincide well with co-simulated results under different lumped port settings.

Perforated dielectric antenna reflectarray for OAM generation

A new type of perforated dielectric flat reflectarray for the generation of OAM-carrying radio waves is presented. The reflectarray is introduced to transform the spherical wave emanating from the feed into a vortex beam after reflection through the azimuthal variation of the effective dielectric permittivity. Through perforating the substrate with holes of various diameters, an azimuthal variation of the permittivity is obtained and the corresponding azimuthal phase-compensation creates a vortex, thus an OAM wave is generated. The reflectarray antenna works in the millimeter frequency band, and can be used to generate the OAM states of ℓ =+1.

Efficiency Improvement of Time Modulated Array With Reconfigurable Power Divider/Combiner

Time modulated array (TMA) suffers from relatively low efficiencies due to the power absorption in switches during off state. In this paper, we present the design of a novel TMA by using a reconfigurable power divider/combiner (RPDC) for improving the array’s efficiency, where the power absorbed during off state can evenly be transferred to other array elements during on state. An improved pulse sequence strategy is developed to control the radiation pattern of the TMA with RPDC. The impact of the RPDC on radiation features of the TMA is further discussed. To experimentally verify the feasibility of the proposed design, a six-element TMA with RPDC is constructed and characterized. Compared with a six-element conventional TMA with single-pole single-throw switches, the TMA with RPDC shows a significant enhancement of gain by 0.98, 1.27, and 1.65 dB when the sidelobe levels are −20, −25, and −30 dB, respectively.

Time-Modulated Arrays:A Four-Dimensional Antenna Array Controlled by Switches

With the rapid development of modern electronic technologies, antenna arrays typically operate in very complex electromagnetic environments. However, owing to the various errors such as systematic errors and random errors, conventional antenna arrays have relatively high sidelobes. Time modulated arrays (TMAs), also known as four-dimensional (4-D) antenna arrays, introduce time as an additional dimension for generating ultra-low sidelobes at fundamental component and realizing real-time beam scanning by harmonic components. Recently, the harmonic components can also be developed for various new applications including wireless communications and radar systems. In this review, we introduce comprehensively the fundamental methodologies and recent applications of TMAs. This aims to stimulate continuing efforts for the understanding of TMAs and explore their applications in various aspects. The methods mentioned in this review include three aspects: sideband radiation suppression, power efficiency of TMAs, and applications of harmonic components. These methods either improve the existing TMAs or promote the practical applications of TMAs. First, to suppress the sideband radiation, a method using non-uniform periodical modulation is introduced. The proposed method has an advantage of low computation and can be easily used for synthesizing a real-time radiation pattern according to the environmental need. Next, a TMA structure using reconfigurable power dividers/combiner is introduced to improve the power efficiency of feeding network. Finally, three applications of harmonic component including direction finding, calibration method, and space division multiple access are separately introduced to illustrate the development potential of TMAs.

A low profile CP antenna based on novel hexagon grids optimization model

In this paper, a discrete optimization to antenna based on regular hexagon grids is proposed, which avoids the point-to-point connection compared with rectangular grids optimization model. Based on the hexagon grids model, parasitic layer shape is optimized and a low profile circularly polarized antenna with stable unidirectional radiation pattern is obtained. The simulated results of the antenna demonstrate the advantages of the hexagon grids optimization model.

Wideband direction-finding based on time-modulated antenna array

A wideband direction finding method by a two-element time-modulated antenna array (TMAA) is proposed in this paper. The direction of far-field wideband source can be estimated by analyzing the harmonic characteristic of received signal after being narrow band-pass filtered. The performance such as the accuracy is obtained through Monte-Carlo simulations.