Yang Chen’s research while affiliated with Shenzhen University and other places

This paper proposed an accurate series resistance model tailored for Schottky diode‐based terahertz multipliers. Compared to the conventional electrothermal model (E‐T model) only considering thermal effects, this model comprehensively accounts for both thermal and frequency effects of the series resistor components, including the temperature‐dependent epilayer resistance (Repi) and the temperature‐frequency‐dependent spreading resistance (Rspreading). The evaluation of thermal effects relies on steady‐state thermal simulation and the corresponding electrothermal model. Notably, the frequency‐dependent spreading resistance part is derived from the fitting conductivity of doped buffer layers and extracted by auxiliary three‐dimensional electromagnetic simulations. Based on this model, a balanced 225–300 GHz frequency tripler with AlN substrate has been designed and manufactured. By introducing this model, a significant improvement in the consistency between simulated and measured results has been achieved compared to the single E‐T model, regardless of whether the input power is low (80 mW) or high (160 mW).

With the increase of graph size, it becomes difficult or even impossible to visualize graph structures clearly within the limited screen space. Consequently, it is crucial to design effective visual representations for large graphs. In this paper, we propose AdaMotif, a novel approach that can capture the essential structure patterns of large graphs and effectively reveal the overall structures via adaptive motif designs. Specifically, our approach involves partitioning a given large graph into multiple subgraphs, then clustering similar subgraphs and extracting similar structural information within each cluster. Subsequently, adaptive motifs representing each cluster are generated and utilized to replace the corresponding subgraphs, leading to a simplified visualization. Our approach aims to preserve as much information as possible from the subgraphs while simplifying the graph efficiently. Notably, our approach successfully visualizes crucial community information within a large graph. We conduct case studies and a user study using real-world graphs to validate the effectiveness of our proposed approach. The results demonstrate the capability of our approach in simplifying graphs while retaining important structural and community information.

With the increase of graph size, it becomes difficult or even impossible to visualize graph structures clearly within the limited screen space. Consequently, it is crucial to design effective visual representations for large graphs. In this paper, we propose AdaMotif, a novel approach that can capture the essential structure patterns of large graphs and effectively reveal the overall structures via adaptive motif designs. Specifically, our approach involves partitioning a given large graph into multiple subgraphs, then clustering similar subgraphs and extracting similar structural information within each cluster. Subsequently, adaptive motifs representing each cluster are generated and utilized to replace the corresponding subgraphs, leading to a simplified visualization. Our approach aims to preserve as much information as possible from the subgraphs while simplifying the graph efficiently. Notably, our approach successfully visualizes crucial community information within a large graph. We conduct case studies and a user study using real-world graphs to validate the effectiveness of our proposed approach. The results demonstrate the capability of our approach in simplifying graphs while retaining important structural and community information.

This letter presents a compact and broadband TE $_{10}$ –TE $_{20}$ mode converter for millimeter-wave and terahertz applications. The input rectangular waveguide (RWG) and output over-mode waveguide (OMWG) are in-line and orthogonal in arrangement. In this converter, the waveguide mode is converted in the short height-reduced and width-widened gradient waveguides. A simple cuboid matching structure is employed to improve bandwidth and conversion efficiency, and a bed of nails is applied to the waveguide profile to suppress electromagnetic (EM) leakage and facilitate assembly at high frequencies. For further verification, a pair of WR-4.3 band prototypes were fabricated and measured. In the range of 170–252 GHz (38.9%-bandwidth), the measured insertion loss of the back-to-back converters is found to be around 0.86 dB with the worst return loss of 14 dB except for a slight deterioration at 172 GHz. Deducting the waveguide insertion loss, the conversion efficiency is higher than 98%.

In this article, a terahertz on-chip spoof surface plasmon polaritons (SSPPs) transmission line (TL) is demonstrated and fabricated via advanced Indium Phosphide (InP) technology. A folded slot SSPPs structure can be applied and etched on the microstrip (MS) line with the characteristic impedance of 50 $\Omega$ , hoping to reduce the occupied area of the conventional SSPPs structure. Through a terahertz on-wafer test system, the proposed die prototype is measured, and the feasibility of the design is verified. Owing to the unique ability of the strong electric field confinement, the proposed SSPPs has excellent characteristics of low-crosstalk compared with MS line under the same transmission losses and footprint. The proposed SSPPs, with the benefits of compact structure and low crosstalk, provide great significance for the terahertz plasmons semiconductor-integrated circuits.

In this paper, a broadband septum circular polarizer with double inline rectangular-to-semicircular waveguide transformers is proposed, which breaks through the theoretical single-mode bandwidth. Meanwhile, a novel waveguide splitting method is utilized, i.e., the common waveguide and inline waveguide transformers are integrally manufactured. This approach avoids the air gap introduced by the traditional split-block technology, and thus solves the problems of orthogonal-modes leakage and mode resonance caused by the waveguide discontinuity. Therefore, the proposed polarizer possesses the merits of broadband, resonance-free, high consistency of orthogonal modes and low insertion loss. In the polarizer measurement, a circular to rectangular waveguide converter is designed and fabricated. The measured insertion loss of the polarizer is found to be around 0.28 dB in the frequency range of 198~260 GHz, and the in-band return loss is better than 15 dB. Moreover, the isolation of left-hand and right-hand circular polarization ports exceeds 23 dB within 206~260 GHz. The proposed polarizer has widely potential applications in millimeter-wave and terahertz devices such as broadband antennas and radial power combiners.