Zhizhang Chen

• Ph.D., Fellow of IEEE,CAE and EIC
• Professor at Dalhousie University

An optically transparent antenna (OTA) based on a grating metamaterial is proposed for launching high-gain millimeter-wave radiation on glasses. This design incorporates a glass-based dielectric image line with a grating made of a transparent conductive film (TCF), which provides an effective near-zero-index response through the precise manipulatio...

The interactions of medical devices within the body area network (BAN) have significantly alleviated the pressure on healthcare resources attributed to an aging society. However, the low-power, high-reliability wireless communications among these devices are susceptible to the influence of the human body. This paper exploits the capacitive effects...

Measurement and computation are indispensable fundamental tools in the antennas and propagation community. Over the past decades, measurement and computational techniques have evolved and advanced significantly, leading to success in many electromagnetic modeling, simulation, or performance evaluation tasks.

ElectricalImpedance Myography (EIM) is an innovative, non-invasive technique offering a convenient means of localized exogenous electrophysiological recording. By measuring muscle impedance parameters, this method characterizes the physiological state of muscles, functioning as a biomarker for muscle contractility, injuries, and the progression of...

Semantic communication, by the extraction of essential semantic information from source data, reduces data volume and enhances transmission efficiency, making it increasingly popular among candidate technologies in 6G. In this letter, a covert transmission scheme for text semantic communications is proposed, where a transmitter attempts to send tex...

Different from the reflective approach of the carpet cloak designed to conceal surface irregularities on highly reflective surfaces, the transmission invisibility cloak, often capable of achieving perfect invisibility, operates within a transmission geometry. In this configuration, the cloaking mechanism ensures that an object neither reflects nor...

Ensuring a low cross-polarization level (CPL) is imperative in the design of antennas with a low sidelobe level (SLL). This paper introduces an innovative approach for designing wideband, high-gain, low-sidelobe, and low-cross-polarization reflectarray (RA) and transmitarray (TA) antennas. The methodology leverages a groundbreaking metasurface endo...

This paper presents a visualized approach to efficiently designing an antenna decoupling network constructed by cascaded coupled transmission lines (CTLs). The cascaded CTL architecture is explored to decouple tightly-packed antenna pairs with extremely small feed point spacing, circumventing the narrow bandwidth and loss issues associated with res...

In this paper, we introduce a novel design for a high-gain, low-profile quad-feed folded transmitarray antenna (FTA) to enable a more compact system. The proposed antenna system consists of a transmitarray, a reflectarray, and four identical planar microstrip U-slot patch antennas placed on the same surface of the reflectarray with an adjacent dist...

This paper considers covert communications in the context of unmanned aerial vehicle (UAV) networks, where a UAV is employed as a base station to transmit covert data to a legitimate ground user, while ensuring that the data transmission cannot be detected by a warden. Aiming at maximizing the legitimate user’s average effective covert throughput (...

The stable vehicular space-air-ground integrated network (SAGIN) requires high-gain multi-beam/beam-steering antenna systems. In this paper, we propose a compact high-gain wideband circularly-polarized (CP) beam-steering antenna with novel rotatable phase-gradient metasurface (PGM) transmitarrays for the SAGIN. It consists of a novel substrate-inte...

Localizing and reconstructing interference sources is crucial in applications such as electromagnetic interference. While the electromagnetic time-reversal (TR) method has been proposed for source localization, there is limited experimental validation for TR source reconstructions. This letter presents a theoretical analysis and experiments that va...

This paper presents a novel millimeter-wave radar-based continuous motion detection approach called mmCMD for the long-term care of the elderly. The proposed mmCMD visualizes the micro-Doppler signatures of continuous motions generated from millimeter radar as images, which are then analyzed by an object detection network for continuous motion dete...

We propose two simple and effective spiking neuron models to improve the response time of the conventional spiking neural network. The proposed neuron models adaptively tune the presynaptic input current depending on the input received from its presynapses and subsequent neuron firing events. We analyze and derive the firing activity homeostatic co...

A compact ultra‐high frequency radio frequency identification tag antenna loaded with a pair of rectangular coupling rings for two‐side anti‐metal performance is proposed. It evolves from a planar inverted‐F antenna and has the same upper and lower structures. A pair of coupling rings is symmetrically loaded on the inner sides of the upper and lowe...

Intrabody communication (IBC) is a promising approach for realizing information transmission among various wearable or implantable devices within bodyNET. The existing IBC studies are limited to the local or abstract geometric channel model, which is limited to providing efficient channel characteristics for the various transmitting scenarios. The...

Optical metasurfaces are researched more and more intensively for the possible realization of lightweight and compact optical devices with novel functionalities. In this paper, a new beam-steering system based on double metasurface lenses (metalenses) is proposed and developed. The proposed system is lightweight, small volume, low cost, and easy to...

Presents the MTTS Field Theory and Computational EM Committee: Report for 2021.

The multi‐beam reflectarray and transmitarray (TA) antennas are new antennas that can have wide angular coverage. However, they are generally of large profiles. To address the issue, this article proposes a folded TA antenna of high gain and low profile that can produce circularly polarized (CP) multi‐beams. It consists of a main‐reflector, a TA, a...

We propose two simple and effective spiking neuron models to improve the response time of the conventional spiking neural network. The proposed neuron models adaptively tune the presynaptic input current depending on the input received from its presynapses and subsequent neuron firing events. We analyze and derive the firing activity homeostatic co...

Intelligent reflecting surfaces (IRSs) have been proposed as a promising technology to enhance signal transmissions in high-frequency bands. Up to now, the research on the performance of large networks with IRSs is still in its infancy. In this paper, we study a Poisson bipolar network with line segment blockages and reflectors. By deriving the pro...

The conventional phase-locked loops or frequency-locked loops should take time to calibrate the oscillator’s resonant frequency in a super-regenerative receiver (SRR) and severely disrupts the receiver’s operations. This paper proposes a novel intermittent frequency locked loop (IFLL) as a frequency synthesizer to continuously maintain the resonant...

In galvanic coupling conductive intracardiac communication(GCCIC) of the leadless pacemakers, the electrical signal transmitted directly through the myocardium and blood is inevitably affected by the cardiac cycle. Established studies focused more on the effect of the myocardium. However, our preliminary in-vitro experiments suggested that blood vo...

Partially reflecting surface (PRS) resonant antennas have attracted significant attention for the past two decades. However, how to improve their peak gain is still a challenge. This article proposes a nonresonant PRS antenna that does not require the conventional resonant condition that limits design flexibility and peak gain. It consists of a PRS...

In our previous study, we introduced the concept of electromagnetic kurtosis and incorporated it into the electromagnetic time-reversal process for source reconstruction. In this paper, we extend the idea and propose the space and time kurtoses methods. The temporal distribution of the space kurtosis identifies the source excitation time instant, w...

Optical metasurfaces are researched more and more intensively for the possible realization of lightweight and compact optical devices with novel functionalities. In this paper, a new beam-steering system based on double metasurface lenses (metalenses) is proposed and developed. The proposed system is lightweight, small volume, low cost, and easy to...

This article proposes convex optimization of mutual inductance between multiantiparallel coils (MACs) for distance-insensitive wireless charging of air–ground robots. In order to reduce optimization costs, the proposed optimization method is developed by hybridizing analytical and numerical models. First, it is shown that the commonly used analytic...

Counting the number of people and estimating their walking speeds are essential in crowd control and flow. In this work, we propose a system that uses prevalent Wi-Fi signals to identify the number of people entering and leaving a room through a door. It selects the best subcarrier of Wi-Fi signals and applies the Hampel filter to remove outlier in...

The time-reversal technique has been developed to solve inverse problems and to reconstruct sources. However, much work on the topic so far has not considered the determination of source excitation time instants, which is a crucial step towards practical applications of the time-reversal method. In this paper, we introduce the concept of kurtosis i...

Near-field-based imaging methods have been widely used to construct images of complex objects. A large number of near-field samples are needed to obtain an accurate image, resulting in high implementation expenditures. By utilizing the fact that the electric field varies fast near strong sources, this paper proposes an adaptive sampling strategy to...

A compact quadrangular prism-shaped slot helix antenna with wide axial ratio (AR) bandwidth using a spiral microstrip coupling feedline is presented. The proposed antenna is constructed with FR4 substrate copper-clad plate with four slots symmetrically etched on the substrate exterior surface and a spiral microstrip coupling feedline printed on the...

Equivalent models of antennas are useful for fast simulation of vehicle to everything (V2X) communication. Existing antenna equivalent models are inflexible because they assume rectangular antenna contour. This paper presents a hybrid equivalent surface-edge current model to overcome the limitation of existing equivalent models. Based on Huygens’ p...

In this communication, the recursive convolutional complex frequency shifted perfectly matched layer (CFS-PML) absorbing boundary condition (ABC) is developed for the wave-equation based meshless method. The numerical results show that the proposed CFS-PML can achieve an excellent absorption performance with the reflections less than -52.5 dB when...

Electromagnetic inverse problems have been traditionally solved in frequency domain. The time-reversal method has been developed to offer an alternative approach in time domain with natural time stepping computations. However, in its applications to electromagnetic source reconstruction, much work so far has not considered possible different excita...

Misalignments between the transmitting and receiving coils of a wireless power system can significantly reduce power transfer efficiency (PTE). In this paper, we propose a novel magnetically coupled resonant wireless power transfer (MCR-WPT) system with good misalignment tolerance for wireless charging applications. Specifically, we employ three in...

In this letter, we propose a new time-domain meshless method without discretization in time based on eigenexpansions of numerical solutions. As a result, numerical time-stepping is not required, and its associated errors are eliminated. Analytical solutions of the radial point interpolation meshless (RPIM) method are derived, and the solutions beco...

An intermittent frequency synthesizer for fast duty-cycled receivers is presented in this paper. Different from state-of-art techniques which try to eliminate the initial phase error that degrades the intermittent frequency detection, a new frequency detector is proposed to maintain an accurate frequency detection regardless of the initial phase er...

List the guest editors for the guest editorial in this issue of the publication.

An array can be synthesized by first optimizing a relevant continuous aperture (CA) and then transform it to the array; this paper presents a skeletonization-scheme-based method for such a transformation. Firstly, the continuous aperture source (CAS) integral is analyzed and it is shown that the uniform discretization of the integral requires a lar...

In the design of smart antenna, switched beam technology is widely used to increase communication capacity and reduce electromagnetic interference. This paper presents a switched-beam antenna array for three-channel multiple-input multiple-output (MIMO) wireless local area network (WLAN) operating in 2.4/5.8 GHz. In the proposed array, there are tw...

This manuscript deals with the design of a metamaterial-based surface structure for high efficiency wireless power harvesting or collection. Differently from the previously presented structures which require the use of thicker and low-loss (and for this reason high cost) dielectric substrates, the presented work employs a dual-layer structure with...

Radio frequency (RF) source reconstruction is useful for RF radiation analysis and interference diagnosis in Internet of Things. Near field (NF) sampling is a critical step of RF source reconstruction. Accurate RF source reconstruction usually requires a large number of NF samples, which results in tremendous effort of NF sampling. This paper prese...

Research and development of wireless power transfer (WPT) systems has attracted much attention in recent years for their potential widespread applications. One of the much desirable features of a WPT system is load-independence. In this letter, we propose the insertion of a simple T-type network into a multi-receiver WPT magnetically coupled resona...

Equivalent modeling is widely used to predict the EMI (electromagnetic interference) of high speed circuits (HSC). This paper presents three sparse source equivalent models (SEM) which can accurately model the radiated emission of HSC. The SEM based on the equivalence principle and the uniform theory of diffraction (UTD) is proposed first. In order...

Electrical Modeling of vehicular antennas is required for design of modern vehicle-to-everything communication networks. However, full-wave modeling and the existing equivalent source methods still ask for long computation time. To address this issue, a fast simulation method is proposed in this paper: a sparse equivalent source model is developed...

A 2 × 2 circularly polarized (CP) sequential rotation microstrip patch antenna array with high gain for long-range ultra-high frequency (UHF) radio frequency identification (RFID) communication is proposed in this paper. In order to meet the operational frequency band requirement of 840–960 MHz and, at the same time, achieve enhanced broadside gain...

A novel unconditionally stable one-step leapfrog alternating–direction-implicit finite-difference time-domain (Leapfrog ADI-FDTD) is developed for modeling dispersive media. In contrast to previous approaches, the proposed method uses a vector fitting technique to incorporate various types of dispersive media through electric polarization terms gov...

Transmission lines (TLs) on a ground plane are one of the main radiators in printed circuit boards. This paper presents a sparse source model to predict radiation of the TLs on a ground plane. Because the current sources distribute sparsely or coherently in space, a sparse source model is developed so that the equivalent radiation sources can be re...

To numerically model open-domain structures and radiation problems, absorbing boundary condition (ABC) have to be applied to emulate infinite open space. In this letter, the split-field perfectly matched layer (PML) ABC is developed and presented for the unconditionally stable node-based locally one-dimensional (LOD) radial point interpolation mesh...

The equivalent sources reconstructed from near field has been used to predict the radiation characteristic in equivalent modeling of electromagnetic compatibility. In most existing source reconstruction methods, the ground plane of original radiator was assumed to be infinitely large. It means that the diffraction of ground plane edges is ignored,...