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

In this paper Koch fractal antennas for bi-band operations at UHF frequencies (868MHz and 2.45GHz) are analyzed. In particular, two modified models of Koch fractal dipoles are compared to the standard bi-band Koch fractal dipole antenna. The goal is to reduce the size of the fractal antenna while still providing good gain and allow operation at multi-frequencies. A size reduction of 8% with respect to the standard Koch antenna is obtained, by using a new set of fractal antenna. The standard and the modified fractal Koch antennas are printed on glass-epoxy FR-4 substrate having a thickness of 1.6 mm and a relative permittivity of 4.4. The return loss parameter and radiation properties of the fabricated antennas are measured and compared with simulation results.

New bi-band fractal antennas

In this paper, the design and measurement of the requirement standards of the IEC610004-21, over a compact electromagnetic reverberation chamber are presented. Although the immunity tests may be made in an anechoic chamber, it's more laborious, takes a longer operation time, needs a high power amplifier and present a high cost experiment. On the other hand, a reverberation chamber is presented as a low cost measurement site which simultaneously provides all kind of emission polarization, increasing the tests speed.

Compact electromagnetic reverberation chamber design and construction

A novel technic of on-antenna power combining based on a quadruple-fed off-centered aperture-coupled microstrip patch antenna (ACMPA) is proposed in this paper. Four driving signals are combined into two off-centered apertures electrically coupled to a radiating patch antenna. As a result, higher efficiency and improved transmitted power are achieved by removing lossy power-combiner either implemented on printed circuit board (PCB) or on monolithic microwave integrated circuit (MMIC). Moreover, compared to a dual-polarized centered aperture-coupled microstrip patch antenna, this type of feeding reduces the cross-polarization level as each slot is separated. As a proof of concept, the passive and active versions of the antenna are designed and fabricated at 2.45 GHz. For comparison purpose, the single-ended off-centered aperture-coupled passive and active versions are also fabricated. The results show +5.6 dB of transmitting power compared to the single-ended active version, demonstrating the on-antenna power combining capacity of this type of antenna while keeping a symmetrical radiation pattern and very good cross-polarization levels.

Quadruple-fed Aperture-coupled Microstrip Patch Antenna for On-antenna Power Combining

This paper reports a circularly polarized cross-slot coupled elliptical patch antenna for implementation in a new radio-frequency identification and localization system currently under development. The radio-frequency localization system in this work is composed of a reader and a semiactive tag (a battery feeds the tag to increase its reading range but the backscattering modulation principle is used to decrease its power consumption). The overall system is designed in the ISM frequency band of 5.8 GHz. This frequency band is a good compromise that permits a large bandwidth and a good range for use in a local positioning system (∼10 m). This antenna is to be used by the reader as its radiation pattern is semispherical. It provides the circular polarization required by the targeted application to allow the tag identification within any physical position. The antenna bandwidth and axial ratio were enhanced using a proper design and a cross-slot feeding of the patch. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 336–339, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22136

Cross Slot Coupled Elliptical Patch Antenna Circularly Polarized for Localization

In this paper the Koch fractal antenna at UHF frequency will be analyzed In particular, a new technique proposed to adapt the input impedance of the Koch model to be matching with the impedance of the RFID chip It is important to remark that the proposed technique conserves the same special form of the bi-band Koch dipole model The Bi-band fractal antenna with input impedance 50 ohms is compared to the new design proposed to be used as a tag RFID Fractal antennas can obtain both input impedance and radiation pattern similar to a longer antenna, yet take less special area due to the many contours of shape The fractal antennas (with input impedance equal to 50 ohms) are printed on glass-epoxy FR-4 substrate of thickness 16 mm and relative permittivity 44 Fractal antennas are a fairly new research area and are likely to have a promising future in RFID applications

Anthony Ghiotto

Papers

New bi-band fractal antennas

Compact electromagnetic reverberation chamber design and construction

Quadruple-fed Aperture-coupled Microstrip Patch Antenna for On-antenna Power Combining

Cross Slot Coupled Elliptical Patch Antenna Circularly Polarized for Localization

Bi-band fractal antenna design for RFID applications at UHF