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

This letter presents the design of an asymmetrical Ka -band single-pole double-throw (SPDT) switch, based on two integrated hybrid couplers. The principle of operation of this switch and its two asymmetrical receiving (Rx) and transmitting (Tx) states are detailed. The circuit theory is supported by the implementation of a demonstrator using an advanced integrated technology: 65-nm substrate on insulator (SOI) CMOS from STMicroelectronics . To the author’s best knowledge, it is the first implementation of such topology using an integrated CMOS technology. The demonstrator is designed considering a system-level tradeoff between the two states, in order to implement 28-GHz duplexers for 5G front-end modules (FEMs). The Rx state exhibits 1.9 dB of insertion loss, 24 dB of isolation and a 1 dB input compression point of 17.5 dBm, whereas the Tx state has 2.9 dB and 35 dB of insertion loss and isolation, respectively. Besides, the gain compression in the Tx state is lower than 0.3 dB, considering an input power of 18 dBm.

An Integrated 65-nm CMOS SOI Ka -Band Asymmetrical Single-Pole Double-Throw Switch Based on Hybrid Couplers

In this paper, the interconnection between two sections of Air-Filled Substrate Integrated Waveguide (AFSIW) transmission line is presented AFSIW is of high interest for high performance and low-cost millimeter wave applications It is based on multilayer Printed Circuit Board (PCB) process For system prototyping and assembly, it is common to interconnect components and sub-circuits However, to comply with stringent specifications, especially for space and aeronautical applications, connectors must be avoided as they directly impact the cost, the size and the loss Also, transition from AFSIW to conventional transmission lines to implement conventional interconnect solutions will not be optimal in term of loss, size and power handling Instead, in this paper, a direct interconnect between two AFSIW sections is studied An experimental demonstration of the proposed interconnection shows a 029 dB insertion loss

Air-Filled SIW interconnections for high performance millimeter-wave circuit and system prototyping and assembly

This paper reports a high voltage standing wave ratio (VSWR) impedance tuner with two independent slugs, which slide along a low-loss coaxial line. Impedance tuner are instruments used for characterizing performances of active microwave components and systems, and more particularly for load-pull and source-pull measurement of transistors, power or low noise amplifiers. After presenting the proposed tuner principle, a demonstrator based on a 3.5 mm coaxial line and designed to operate at microwave frequencies from 2 to 18 GHz is introduced. Then, its performances are measured and compared to simulation results. Finally, overall performances are compared to other currently commercialized impedance tuner technologies. Depending on the targeted frequency band, different slugs can be used to obtain an optimal VSWR. Slugs typically offers a 200∶1 VSWR. Their dimensions can be optimized in order to achieve very high VSWR in excess of 300∶1. The demonstrated tuner is very compact and achieve a minimum repeatability of −40 dB.

Early demonstration of a high VSWR microwave coaxial programmable impedance tuner with coaxial slugs

A concept of simultaneous electric and magnetic two-dimensional (2-D) tuning of cavity resonator based on substrate integrated waveguide (SIW) technology is presented and demonstrated. For a dominant TE 101 mode SIW cavity resonator, magnetic tuning is achieved by loading a YIG ferrite slab and electric tuning is achieved by placing a varactor diode and capacitors in the cavity. Considering only electric tuning using varactor diodes 1.3% of total tuning range is measured, while for simultaneous electric and magnetic tuning it is 7.9% with unloaded Q-factor better than 130. Using 0.05–0.1 pF of surface mount capacitor a total tuning range of 20% is experimentally achieved. Transmission line theory is used to derive a theoretical 2-D tuned resonant frequency curve, which depicts the variation of cavity resonant frequency with external applied magnetic fields and the capacitance values. The designed dual E- and H-field tunable cavity resonator is cost effective and can be applied in frequency-agile microwave systems.

Simultaneous electric and magnetic two-dimensional tuning of substrate integrated waveguide cavity resonator

In this paper, an ultra-compact transformer-based integrated quadrature hybrid coupler is presented. Its design, taking advantage of the transformer distributed parasitic capacitances to minimize lumped capacitors, achieves low insertion loss and high compactness. For demonstration purposes, a prototype, operating at Ku-band and based on the 130 nm BiCMOS technology from STMicroelectronics, has been fabricated. Theoretical, simulated and experimental results are reported. The demonstrated integrated coupler occupies an area as small as 0.0014 mm2. In the 17.3 to 20.2 GHz frequency range (15.5% relative bandwidth) used for SATCOM applications, an insertion loss and a phase imbalance of better than 0.4 dB and 2° are experimentally obtained, respectively, with an amplitude imbalance of less than 1 dB.

Anthony Ghiotto

Papers

An Integrated 65-nm CMOS SOI Ka -Band Asymmetrical Single-Pole Double-Throw Switch Based on Hybrid Couplers

Air-Filled SIW interconnections for high performance millimeter-wave circuit and system prototyping and assembly

Early demonstration of a high VSWR microwave coaxial programmable impedance tuner with coaxial slugs

Simultaneous electric and magnetic two-dimensional tuning of substrate integrated waveguide cavity resonator

Ultra-Compact Low-Loss Integrated Transformer-Based Ku-Band Quadrature Hybrid Coupler