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

The growing interest in the Radio Frequency Identification (RFID) technology is giving rise to new applications, in particular for the identification of metallic objects. This interest has initiated the development of new designs for RFID tag antenna. This paper presents a UHF miniaturized patch antenna aimed at this application. The patch antenna is fed by a balanced feed to avoid a cross-layered construction and matched with a stub. Its miniaturization is achieved by inserting a u-shaped slot in the radiating patch.

Miniaturized patch antenna for the Radio Frequency Identification of metallic objects

This letter reports a broadband transition from dielectric-filled substrate integrated waveguide (DFSIW) to half mode air-filled substrate integrated waveguide (HM-AFSIW). The HM-AFSIW, demonstrated for the first time, is based on a multilayer printed circuit board (PCB) topology. Its fabrication involves three layers. The top and bottom substrates can make use of a low-cost standard substrate such as FR4. For our demonstration purpose, a back-to-back transition implementing a 10 mm-long HM-AFSIW operating over the entire $Ka$ -band is fabricated. It achieves measured return loss of better than $-$ 15.9 dB and insertion loss of 0.79 $\pm$ 0.25 dB (0.3 $\pm$ 0.15 dB for the transition) from 26 to 40 GHz. This transition is of interest for interconnecting dielectric-loss-free components based on HM-AFSIW including, for example, leaky wave antennas.

Broadband Dielectric-to-Half-Mode Air-Filled Substrate Integrated Waveguide Transition

In this paper, air-filled Substrate Integrated Waveguide (SIW) is proposed and demonstrated for the first time at U-band This low-loss transmission line is developed on a low-cost multilayer Printed Circuit Board (PCB) process The top and bottom layers may make use of an extremely low-cost standard substrate such as FR-4 on which base-band or digital circuits can be designed so to obtain a very compact, high performance, low-cost and self-packaged integrated system For measurement purposes, an optimized-length dielectric- to air-filled SIW transition operating at U-band with 021 ±0055 dB insertion loss is developed The measured insertion loss of an air-filled SIW of interest at U-band is 0122 ±0122 dB/cm compared to 04 ±013 dB/cm for its dielectric-filled counterpart Furthermore, an air-filled SIW phase shifter is reported for the first time It achieves a measured 015 ±014 dB transmission loss at U-band The proposed air-filled SIW transmission line and phase shifter are of particular interest for high performance and low-cost millimeter-wave circuits and systems

Air-filled SIW transmission line and phase shifter for high-performance and low-cost U-Band integrated circuits and systems

A compact and low cost substrate integrated waveguide (SIW) cavity and bandpass filter using Surface Mount (SM) shorting stubs is proposed in this paper. These cavity and filter allows a drastically reduction in Printed Circuit Board (PCB) footprint. They are compact and also low cost as there fabrication involves standard PCB process and SM technologies. For demonstration purpose, one cavity and one 7th order bandpass filter were designed and fabricated over Ka-band. The cavity is designed at the center frequency of 34 GHz. It achieves an unloaded Qu factor of 201 with a footprint of only 1.9 × 6.3 mm2 compared to 5.38 × 6.3 mm for a planar cavity. Then, a 7th order filter is designed at the center frequency of 34.5 GHz. It provides a sharp frequency selectivity using arranged transmission-zeros and achieves a bandwidth of 1 GHz with an insertion loss of better than 2.9 dB with a footprint of only 11.2 × 6.3 mm2. The experimental prototypes achieve good performances. They potentially have many applications in microwave and millimeter wave devices, circuits and systems.

Compact and low cost substrate integrated waveguide cavity and bandpass filter using surface mount shorting stubs

In this paper, a 64QAM and OFDM capable CMOS transceiver designed for wireless communications in the 60 GHz band is used in combination of a plastic waveguide to realize a 4m link. The plastic waveguide is made of Teflon (PFTE) and features an innovative design enhancing confinement and propagation robustness compared to literature. The first QPSK communication over plastic waveguide is then demonstrated at a rate of 4 Gb/s. It was even possible to perform 64QAM (12 Gb/s) by using scope direct demodulation instead of the receiver chip. Preliminary results also indicate that OFDM communication is possible as well, further highlighting the versatility of plastic waveguides and paving the way to reconfigurable wireless / wireline use cases.

Anthony Ghiotto

Papers

Miniaturized patch antenna for the Radio Frequency Identification of metallic objects

Broadband Dielectric-to-Half-Mode Air-Filled Substrate Integrated Waveguide Transition

Air-filled SIW transmission line and phase shifter for high-performance and low-cost U-Band integrated circuits and systems

Compact and low cost substrate integrated waveguide cavity and bandpass filter using surface mount shorting stubs

A 12 Gb/s 64QAM and OFDM compatible millimeter-wave communication link using a novel plastic waveguide design