Wireless charging is a technology of transmitting power through an air gap to electrical devices for the purpose of energy replenishment. The recent progress in wireless charging techniques and development of commercial products have provided a promising alternative way to address the energy bottleneck of conventionally portable battery-powered devices. However, the incorporation of wireless charging into the existing wireless communication systems also brings along a series of challenging issues with regard to implementation, scheduling, and power management. In this paper, we present a comprehensive overview of wireless charging techniques, the developments in technical standards, and their recent advances in network applications. In particular, with regard to network applications, we review the static charger scheduling strategies, mobile charger dispatch strategies and wireless charger deployment strategies. Additionally, we discuss open issues and challenges in implementing wireless charging technologies. Finally, we envision some practical future network applications of wireless charging.

Wireless Charging Technologies: Fundamentals, Standards, and Network Applications

We propose a compact planar ultrawideband (UWB) antenna with 3.4/5.5 GHz dual band-notched characteristics. The antenna consists of a beveled rectangular metal patch and a 50 Omega coplanar waveguide (CPW) transmission line. By etching two nested C-shaped slots in the patch, band-rejected filtering properties in the WiMAX/WLAN bands are achieved. The proposed antenna is successfully simulated, designed, and measured showing broadband matched impedance, stable radiation patterns and constant gain. An equivalent circuit model of the proposed antenna is presented to discuss the mechanism of the dual band-notched UWB antenna. A UWB antenna and a single band-notched one are also provided for references.

A Compact Ultrawideband Antenna With 3.4/5.5 GHz Dual Band-Notched Characteristics

This paper presents a novel broadband rectenna for ambient wireless energy harvesting over the frequency band from 1.8 to 2.5 GHz. First of all, the characteristics of the ambient radio-frequency energy are studied. The results are then used to aid the design of a new rectenna. A novel two-branch impedance matching circuit is introduced to enhance the performance and efficiency of the rectenna at a relatively low ambient input power level. A novel broadband dual-polarized cross-dipole antenna is proposed which has embedded harmonic rejection property and can reject the second and third harmonics to further improve the rectenna efficiency. The measured power sensitivity of this design is down to $- {\bf 35}\;{\bf dBm}$ and the conversion efficiency reaches 55% when the input power to the rectifier is $- {\bf 10}\;{\bf dBm}$ . It is demonstrated that the output power from the proposed rectenna is higher than the other published designs with a similar antenna size under the same ambient condition. The proposed broadband rectenna could be used to power many low-power electronic devices and sensors and found a range of potential applications.

A High-Efficiency Broadband Rectenna for Ambient Wireless Energy Harvesting

Reactive matching is extended to wide bandwidths using the impedance property of LC-ladder filters. In this paper, we present a systematic method to design wideband low-noise amplifiers. An SiGe amplifier with on-chip matching network spanning 3-10 GHz delivers 21-dB peak gain, 2.5-dB noise figure, and -1-dBm input IP3 at 5 GHz, with a 10-mA bias current.

A 3-10-Ghz low-noise amplifier with wideband LC-ladder matching network

With the development of wireless communication technology, the need for bandwidth is increasing continuously, and the growing need makes wireless spectrum resources more and more scarce. Cognitive radio (CR) has been identified as a promising solution for the spectrum scarcity, and its core idea is the dynamic spectrum access. It can dynamically utilize the idle spectrum without affecting the rights of primary users, so that multiple services or users can share a part of the spectrum, thus achieving the goal of avoiding the high cost of spectrum resetting and improving the utilization of spectrum resources. In order to meet the critical requirements of the fifth generation (5G) mobile network, especially the Wider-Coverage , Massive-Capacity , Massive-Connectivity , and Low-Latency four application scenarios, the spectrum range used in 5G will be further expanded into the full spectrum era, possibly from 1 GHz to 100 GHz. In this paper, we conduct a comprehensive survey of CR technology and focus on the current significant research progress in the full spectrum sharing towards the four scenarios. In addition, the key enabling technologies that may be closely related to the study of 5G in the near future are presented in terms of full-duplex spectrum sensing, spectrum-database based spectrum sensing, auction based spectrum allocation, carrier aggregation based spectrum access. Subsequently, other issues that play a positive role for the development research and practical application of CR, such as common control channel, energy harvesting, non-orthogonal multiple access, and CR based aeronautical communication are discussed. The comprehensive overview provided by this survey is expected to help researchers develop CR technology in the field of 5G further.

Full Spectrum Sharing in Cognitive Radio Networks Toward 5G: A Survey

A cavity-backed slot antenna based on air-filled substrate integrated waveguide (AFSIW) with the technology of multilayer printed circuit board (PCB) is proposed for the 5th generation (5G) mobile communication system at 28 GHz for the first time. The whole antenna is made of five layers and its size is $10\ \text{mm} \times 9\ \text{mm}$ . The top and bottom layers are Rogers RT6002 and the medium layer is based on an air-filled substrate integrated waveguide. According to simulation results, compared with the antenna which has the same structure but based on a substrate integrated waveguide (DFSIW), the antenna proposed in this paper increases the gain by 5.8 dB (4.8 dB), the total efficiency by 92.0% (69.7%) and the bandwidth by 990 MHz (207 MHz).

Air-Filled Substrate Integrated Waveguide (AFSIW) Cavity-Backed Slot Antenna for 5G Applications

In this paper, a Ka-band Schwinger coupler based on Substrate Integrated Waveguide (SIW) and using LEGO-like interconnected PCB building blocks is proposed for the first time. This reversed phased coupler is composed of two interconnected SIW printed circuit boards (PCBs) coupled through slots spaced by a quarter wavelength. For demonstration purposes a prototype is fabricated. The measured results are in good agreement with simulations. The demonstrated coupler operates from 30 to 38 GHz. A week coupling of 20 dB (±1 dB) is achieved with an isolation and return loss better than -25 dB. The proposed geometry represents one of the key components for future 3-dimensionnal System on Substrate (SoS). Finally, for system development and repair purposes, the demonstrated coupler is proposed for SIW circuit probing.

Schwinger coupler for substrate integrated circuits and systems

A low-cost frequency modulated feedback-loop oscillator for high-power microwave transmitter on the basis of a Ferrite Loaded Substrate Integrated Waveguide (FLSIW) cavity is proposed and demonstrated for the first time. The proposed structure is low-cost as its fabrication involves standard PCB process and the integration of high-power handling ferrite allowing the combination of an oscillator and high-power amplifier within a single device. With the application of an external magnetic bias, the resonant frequency of the FLSIW cavity is controlled to adjust the feedback-loop oscillation conditions and tune the oscillator frequency. It is also demonstrated that, by applying an alternating magnetic bias, the output signal of the oscillator can be modulated. The validation of the proposed oscillator consists of a multilayer and single layer X-band prototype. The fabricated multilayer component is based on a four ferrite slab loaded SIW cavity achieving a 16% frequency tuning. The oscillator with a frequency tuning range of 210 MHz centered at 11.91 GHz with a fairly constant output power and a phase noise of 90 dBc/Hz at 100 kHz offset is demonstrated. The single layer prototype is controlled by a double winded electromagnet to achieve both frequency tuning and modulation. A 10 kHz frequency modulation is demonstrated. This type of oscillator is suitable for low-cost highpower microwave transmitter for possible use in FMCW radar.

Low-cost frequency modulated ferrite loaded SIW oscillator for high-power microwave transmitter

This paper presents the design, implementation and characterizations of a Ka-Band [17.3 - 20.2 GHz] linearized channel amplifier (LCAMP) for space Travelling Wave Tube Amplifier (TWTA). The 130nm SiGe BiCMOS technology from ST Microelectronics (BiCMOS9MW) has been used. It validates the feasibility of a LCAMP and all its constitutive building blocks in silicon technologies at such high frequencies with high linearity requirements, hence allowing to consider a drastic mass, footprint and cost reduction of such equipment.

Feasibility Demonstration of a Ka-Band Linearized Channel Amplifier in Silicon Technology for Space Applications

To authors' knowledge, this paper presents the first silicon integrated PA intended for ultra-wideband (UWB) location tracking application in emergency and disaster situations (LAES). In the allocated 3.4 to 4.8 GHz frequency band, the proposed 65 nm CMOS PA provides a 1 dB compression output power and maximum power added efficiency of 17.4 ±0.5 dBm and 24.6 ±2.5 %, respectively, for a supply voltage of Vdd = 4 V. In addition, in the frequency range of interest, it achieves an excellent group delay variation and gain flatness of 75.2 ±15.05 ps and 13.65 ±0.25 dB, respectively. The proposed UWB PA provides the lowest group delay and gain variation, with the highest output power level reported so far.

Anthony Ghiotto

Papers

Air-Filled Substrate Integrated Waveguide (AFSIW) Cavity-Backed Slot Antenna for 5G Applications

Schwinger coupler for substrate integrated circuits and systems

Low-cost frequency modulated ferrite loaded SIW oscillator for high-power microwave transmitter

Feasibility Demonstration of a Ka-Band Linearized Channel Amplifier in Silicon Technology for Space Applications

3.4 to 4.8 GHz 65 nm CMOS power amplifier for ultra wideband location tracking application in emergency and disaster situations