Ke Wu

Montreal Polytechnic · Department of Electrical Engineering

In a highly integrated analog radio-over-fiber transceiver, seamless integration of the antenna-frontend is crucial as an antenna is generally implemented on a high-κ material, which is set to highly degrade the antenna's performance. This work is concerned with the radiation behavior improvement of a planar leaky-wave antenna with an inductive par...

Providing energy to Internet of Things (IoT) apparatuses is ever more challenging. Humans are increasingly invested in the revolutionary new scenario that experts call Industry 4.0 , where billions of electronic devices are interconnected with one another. The operations of battery charging or battery replacement for these devices will soon becom...

Mixed coupling has been used in substrate integrated waveguide (SIW) filters to eliminate the transmission of spurious modes. However, the elimination only applied to the first spurious mode. Here, we propose a new mixed coupling structure that consists of slots for magnetic coupling and holes for electric coupling. Using it as the inter-coupling s...

This article investigates flexibly using mixed coupling in substrate integrated waveguide (SIW) filters to efficiently improve selectivity. To this end, a mixed coupling structure is proposed, which can be used as a universal coupling module to efficiently produce transmission zeros (TZs) in an inline/conventional SIW filter without degrading the s...

One of the fundamental problems in power amplifier (PA) design is the mismatch between the optimum loads for maximum output power and maximum efficiency. This work demonstrates that a GaN transistor of choice can reduce such mismatch when operating at the minimum input RF power required (Pin) to obtain its maximum output power. Furthermore, this w...

Metasurfaces based on periodic arrays of high- Q coils have been used as artificial lenses to boost the power transfer efficiency of magnetic induction (MI)-based power transmission systems. In conventional linear topologies, the metamaterial (MTM) focalization effect is physically limited to an extremely narrow bandwidth (BW) due to the high- Q of...

This article presents an approach to the development of band-reconfigurable tunable bandpass filters (BPFs) using a mode-switching concept. The key to realize this feature is that the first higher-order mode TE $_{201}$ can be switched to the diagonal modes TE $_{201}$ and TE $_{102}$ using tuning elements in a square waveguide cavity. A pair of...

In this work, a class of innovative waveguide couplers with polarized rotation characteristics are proposed and demonstrated for the first time. Different from all conventional waveguide couplers, the proposed couplers involve two $E$ -plane ports and two $H$ -plane ports, herein referred to as $E$ -plane and $H$ -plane (EH) waveguide coupl...

This article proposes and presents a topological receiver architecture, named virtual receiver matrix (VRM), suitable for future smart multifunction wireless systems. This concept is devised and benefits from using combinatory analog operations with multiple distributed units in a receiver matrix or array. This mechanism of receiving data through s...

This article proposes and presents an innovative approach to realizing the concurrent dual-band transmission with only a single front-end and local oscillator at radio frequency (RF). Fundamentally, the proposed concurrent dual-band front-end is based on the conventional multiport interferometric architecture for single-band operation. Nevertheless...

Continuous advances in ultralow-power electronics are a fundamental driving force of developing far-field wireless power harvesting techniques, which generally harnesses low/ambient energy in free space or dedicated wireless power from a power base station. This article reviews recent developments and technology trends in far-field (radiative) wire...

Metamaterials (MTMs) based on a periodic array of resonant coils have been shown to behave as μ-negative (MNG), enabling the focusing of magnetic flux. The phenomenon has been deployed by designers to boost the efficiency of many inductively coupled systems, such as magnetic resonance imaging, underwater and underground communications, and charging...

This paper proposes an analytical method for effectively evaluating the performances of zero-bias diode-based RF power harvesters. The method allows the accurate calculation of both the diode power conversion efficiency (PCE) and matching efficiency, while showing the wide adaptability to frequency and input power. To calculate the diode PCE accura...

It all started with a spark. Let us rewind back to 1887, in Germany. The days were getting cooler in the garden of the Technische Hochschule in Karlsruhe as Heinrich Rudolf Hertz was setting up the first-ever far-field wireless power transmission with increasingly more power [1]. He was striving to demonstrate the wireless nature of electromagnetic...

Deployment of 5G network infrastructure is a timely opportunity for millimeter-sized battery-free sensors. However, millimeter-wave (mmW) devices often suffer from high conversion loss and path loss that are heavily limiting their communication/detection distance, especially for the case of harmonic transponders based on Schottky diodes. A deep and...

This work proposes to enlarge the maximum readout distance of battery-free harmonic transponders through a careful Schottky diode selection and a consideration of low-temperature operations. Diode SMS7621 is identified to deliver lower conversion loss (CL) of harmonic transponders based on a diode selection guide. Moreover, an analytical method for...

This work summarizes an outdoor dynamic measurement of ambient radiofrequency (RF) power density in the core areas of Montreal city, which can eventually be exploited for possible battery-free Internet of Things (IoT) sensor network planning. The measurement covers a frequency range of 400 MHz to 2700 MHz. The power density along major streets, roa...

This letter introduces a simple technique to reduce cross polarization in multilayer antipodal linearly tapered slot antenna taking advantage of the slab air-filled substrate integrated waveguide (SAFSIW) topology. The operation mechanism is presented together with simulations and experimental validations. The measured results show a reflection coe...

This article introduces two-way broadband air-filled substrate integrated waveguide (AFSIW) isolated power dividers/combiners based on surface mounted absorbing materials. The proposed structures take advantage of the AFSIW multilayer feature. The absorber implementation is found highly tolerant of variations in dimensions and positioning. Three di...

In this communication, a dual-band on-chip meander-line monopole antenna is proposed and demonstrated for emerging fifth-generation (5G)-compatible Internet of Things (IoT)-served sensor nodes. The targeted 28/60 GHz compact antenna is a hybrid structure of meander-line monopole antenna and packaging substrate to both shield the antenna from its de...

Wireless Power Transfer (WPT) technology has paved the way to energize numerous sensor nodes for the Internet of Things (IoT) applications. This work theoretically and experimentally shows how a commercial multi-function sensor board can be energized by an ultra-high-frequency (UHF) multi-stage rectifier at low RF input power levels. Firstly, an an...

Battery-free devices or self-sustainable energy platforms are the foundation of the green Internet of Things (IoT) technology [1],[2]. Recycling ambient RF and wireless power in the free space offers a promising approach to energizing billions of geographically scattered but wirelessly interconnected sensing nodes or devices [3]. Typically, sensing...

This letter introduces stepped-impedance bandpass filters based on the slab air-filled substrate integrated waveguide (SAFSIW), which provides a compromise in terms of loss and footprint between substrate integrated waveguide (SIW) and air-filled SIW (AFSIW). First, the theoretical unloaded quality factor of the SAFSIW guided-wave structure is pres...

A harmonically driven bio‐radar based on the technique of a multiport interferometer (six‐port) technique is proposed and studied in order to improve the performance of vital signs monitoring. The feasibility of estimating cardiopulmonary parametric signatures by deploying a harmonic multiport interferometer radar is presented. This scheme is helpf...

A low pulling effect self-isolated harmonic active radiator operating around 28 GHz is proposed, investigated and demonstrated in this work. Thanks to the inherent self-isolation property of a feedback-loop of the proposed active radiator, a superiority of pulling effect mitigation, harmonic output and simple structure is achieved. As part of the l...

A compact transition between conductor-backed coplanar waveguide (CBCPW) and substrate integrated suspended line (SISL) is presented. Compared to the reported transitions from CBCPW to SISL, performance and compactness are improved. For demonstration purpose, a multilayer transition is designed and fabricated for operation up to 46 GHz. Experimenta...

Conversion loss performance of fully passive harmonic transponders, which is drastically affected by low power mixing operation, determines their detection ranges directly. This work presents both theoretical and experimental studies of thermal effects on the performance of fully passive harmonic transponders. For the zero bias Schottky diode-based...

In this paper, an ambient power harvester with a single diode device is proposed for simultaneously scavenging both radiofrequency (RF) and thermal energy in a mixed and cooperative manner. This cooperative harvesting process is theoretically examined through a proposed model of diode and then validated by simulation and measurement. In the propose...

In this paper, an extremely low-power and low-complexity CMOS sourceless millimeter-wave (mmW) receiver for the next-generation wireless communication and sensing systems including fifth-generation (5G) is proposed and demonstrated. It makes the use of injection-locked self-oscillating mixers (SOMs) in order to enable a direct conversion to baseban...

In this paper, we propose, investigate, and demonstrate a reconfigurable low-voltage and low-power millimeter-wave mixer in 65-nm CMOS, which can be switched as either a subharmonic mixer (SHM) or a fundamental mixer (FM) for dual-band applications. Based on a modified Gilbert mixer topology, the proposed CMOS mixer can operate at low supply voltag...

A class of self-isolated harmonic oscillator (SIHO) with a feedback-loop structure is able to significantly reduce the pulling effect without involving extra circuit complexity such as a buffer amplifier. In the first part of this paper, the operation principle of the SIHO is theoretically studied through equivalent circuit models and X-parameter t...

A novel diplexer-based fully passive transponder is presented in this paper, which targets sub-6-GHz 5G-compatible internet-of-things applications. To alleviate the antenna design restrictions of traditional transponder with two separate antennas, a new architecture has been proposed with the introduction of a diplexer, which allows transponder to...

Unlike near-field wireless power transfer based on the non-radiative inductive and magnetic resonant coupling which has already had a number of successful commercial applications, far-field radiofrequency (RF) ambient energy harvesting still trades its operation distance for a limited power density and low rectifying efficiency. Particularly, its l...

Benefiting from advantageous features of fast tuning, small size, and easy integration, the electronic impedance synthesizer (EIS) has been developed for on-wafer load-pull characterization systems, tunable matching networks, reconfigurable devices and systems, and so on. The previous designs of the EIS were mostly based on the empirical data inste...

An analytical model for the conversion loss (CL) calculation of diode-based fully passive harmonic transponders is proposed in this work. Given diode's SPICE parameters, the proposed model can accurately predict second harmonic output based on RF input power. Thus, CL can be easily obtained. Such an accurate analytical model can be applied to evalu...

The recently developed mode-selective transmission line (MSTL) is proposed and exploited as an alternative approach to accommodate the growing and future ultrafast interconnects requirements of ultralarge-scale integration for high density, speed, performance, and bandwidth (BW). A parametric study is performed to optimize the MSTL structure for hi...

An integrated cooperative harvester capable of collecting both electromagnetic [(principally radio frequency (RF)] and kinetic energy simultaneously is proposed and studied in this paper. One single substrate board is demonstrated to accommodate and integrate an electromagnetic kinetic generator, an F-shaped antenna, and a rectifying circuit, havin...

A class of longitudinally uniform transmission lines with low loss, low dispersion, and high-field confinement, called mode-selective transmission lines (MSTLs), has been proposed for ultra-broadband and ultra-fast electromagnetic signal guidance and processing. Their operation is mainly based on the concept of frequency-enabled mode selectivity. T...

With advantages of small size, light weight, and fast tuning capability, electronic impedance synthesizer (EIS) presents game-changing opportunities for industry. However, their widely acceptance is still restrained by the understanding of power-handling capacity and linearity issues. This work addresses both issues through the development of a vol...

In this paper, an on-chip dual-band rectangular slot antenna is proposed and demonstrated for a new generation of high data rate, battery free, yet active millimeter-wave identification (MMID) system, which is fully integrated on a single-CMOS die. It, therefore, does not require any external components (padless) nor the traditional packaging. The...

The so-called mode-selective transmission line or simply "MSTL" is studied theoretically and experimentally. This low-loss and low-dispersion transmission line operates with a frequency-dependent mode-switching behavior. This self-adaptive mode-selective guided-wave structure begins with the propagation of electromagnetic waves over the lower frequ...

An air-filled substrate integrated waveguide (AFSIW) slot array antenna based on multilayer PCB process is proposed. For comparison and demonstration purposes, 1 × 4 slot array antennas based on both AFSIW and conventional dielectric-filled SIW (DFSIW) operating at 30.5 GHz are designed, fabricated and measured. The exampled AFSIW 1 × 4 slot array...

A substantial reduction of substrate integrated waveguide (SIW) insertion loss can be achieved through the use of air as dielectric instead of usual dielectric material. However, air-filled SIW (AFSIW) circuits exhibit larger footprint compared with their dielectric-filled counterparts. A compact multilayer AFSIW bandpass filter is proposed to real...

In this paper, a unified method is introduced and formulated for deriving the equivalent circuit model of a guided wave structure as well as its characteristic impedance for any mode. This method is developed through the combination of a generalized multimode calibration and a full-wave simulation, and it is applicable to the fundamental mode as we...

In this work, optical properties of epitaxial CaxBa1-xNb2O6, CBN (x = 0.28) thin film based waveguides are studied at 1550 nm optical communications wavelength. CBN thin films are deposited epitaxially on MgO substrates using Pulsed Laser Deposition and characterized by prism coupling to extract the refractive index and propagation loss. It is show...