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This letter presents a novel multiband rectenna for the ambient wireless energy harvesting of an autonomous internet of thing (IoT) sensor. A bow-tie antenna with slits is proposed to obtain four frequency bands at 840 MHz, 1.86, 2.1, and 2.45 GHz, respectively. Furthermore, a multiband rectifying circuit combined of four single ring-loop rectifiers is designed with high conversion efficiency. Finally, a power management circuit with storing and converting the harvested voltage is proposed for smoothing dc output voltage. The energy harvester can be used in practical wireless sensor applications.

The free-positioning wireless power transfer (WPT) system has drawn attention in recent years. Traditionally, a WPT system can transfer energy in one or two directions on the same plane, but it leads the restrictions of angle and axis misalignment between a transmitter and a receiver coil. In this paper, we propose a free-positioning WPT system using a three-dimensional cubic-shaped transmitting coil for portable device charging. A small receiving coil is placed inside the transmitter to achieve the transferred energy through the magnetic resonant coupling. In addition, the equivalent circuit and the mutual inductance between the Tx and Rx coils are analyzed. Finally, a practical experiment is implemented to verify the transfer performance, which can reach up to about 50% power transfer efficiency. The proposed system can charge in spatial freedom.

In this work, we propose a novel Wi – Fi blocking window based on metamaterial microwave band – stop filter. Made of glass and fluorine – doped tin oxide (FTO), the proposed window is transparent for visible light, allows other RF waves to go though significantly while completely blocks the Wi – Fi signal. With such property, this window can be used for confidential purpose.

Wireless power transfer presents a robust method to provide a safe and convenient solution for powering biomedical implants. The implanted device is necessarily minimized conducive to the transfer efficiency degradation. This paper presents a wireless power transfer for retinal prosthesis using an artificial intelligent algorithm to optimize the power transfer efficiency with the minimizing implanted device dimension. A novel transmitter is designed based on the conformal strongly coupled magnetic resonator, which is proposed to attach to the glasses lens. An implanted receiver is optimized to obtain the highest efficiency with the minimal dimension of 9.7 x 9.7 x 1.9 mm3. The WPT system achieves approximately 17.5 % at the operating ISM frequency band of 433 MHz and a distance between transmitter and receiver of 20 mm.

Midfield wireless power transfer has been proven as a solution for biomedical micro-implant that can operate at nearly any location in the body. Some previous experiments using an external patterned structure as optimal source demonstrated magnetic and current density focusing characteristic on multilayers tissue, therefore, significantly enhancing efficiency for wireless powering to miniature receivers than conventional inductively coupled coils. This paper proposed a novel compact and simple source transmitter while conserving convergence effect on human tissue.

This paper presents a novel wideband element antenna for base station application covering all frequency bands for existing cellular system from 1.65 to 2.93 GHz. The proposed antenna element has a stable gain of 8.7 ± 0.8 dBi over the entire frequency range. The horizontal beamwidth is at least 60 degrees. The performance of this antenna element is satisfied all requirements for expected wideband base station antennas. The antenna element based on magneto-electric (ME) dipoles consists of two double-bowtie shaped dipoles for two polarizations of ±45 degrees. The feeding baluns for the two dipoles have step-changed width to obtain better impedance matching, and they are simply designed for mass production. Besides, the radiators of the dipoles are double- bowtie shaped to enhance the impedance bandwidth.

A reflectarray antenna of 441 unit-cells with dimensions of 112.5 mm x 112.5 mm is proposed in this paper. The unit-cell consists of a cross and a square ring. The reflectarray is illuminated by a horn antenna at the center-feed and 25 degrees offset-feed with the 3 GHz bandwidth (from 26.5 GHz to 29.5 GHz) for N257 band/5G. The shadow area of the reflectarray antenna is improved by the 25 degrees offset-fed structure with a peak gain of 26.4 dBi satisfied with the 5G base station antenna requirement.

In this paper, a wide – angle rectenna based on metamaterial absorber is proposed. By using the absorbing surface consists of multiple periodically arranged unit cells, the proposed ambient RF energy harvesting device can power sufficient DC power for a wireless sensor from the ambient RF sources in environment. The rectifiers employed in this rectenna system are optimized to have a RF-DC conversion efficiency of 38% and 50% at very low input power of -10 dBm and -5 dBm, respectively. The symmetric unit cells are designed to yield a high absorptivity at wide incident angle in both H plane and E plane and by attaching two rectifiers for each one of them, the device is able to achieve a wide – angle dual – polarized operation up to 140 degrees. Numerical simulations are conducted to validate the design while a comparison to previously introduced rectennas is also provided to elucidate the advantages of the ambient RF energy harvesting system in this work.

A novel wireless sensor network node (WSNN) is presented in this paper where the solar energy harvester system is used as an autonomous power solution for endless battery lifetime. In this sensor node, the meander-line Inverted-F-Antenna (MIFA) is proposed and integrated in a single-CC2650 chip of Texas Instrument. The simple structure, low cost, compact size, high efficiency and low power consumption are advantages of this single-chip WSNN. The experimental results show that MIFA antenna is promising solution to enhance communication performance in WSN. In addition, the investigated single-chip WSNN with multi-wireless technologies including Bluetooth Low Energy and Zigbee as well as 6LowPAN is an attractive device for internet of thing (IoT) applications.

Metamaterial absorbers with excellent absorption properties and real-time tunability are desirable for practical applications. In this paper, we design and numerically investigate a polarization insensitive wide-angle metamaterial absorber with tunable absorption strength formed by finite-length symmetric metallic plates and graphene sheet. This structure achieves a near perfect absorption, and remains highly absorptive with wide incident-angle, higher than 80% at 60o for TE mode and around 90% at 70o for TM mode. Absorption strength can be varied between 97% and 52% by controlling the Fermi energy of graphene while the operating frequency remains relatively stable. Also without the presence of a ground plane as in other conventional absorbers, waves outside of the absorption band are allowed to travel through. The absorbing principle and absorption tunability mechanism are elucidated using effective medium analysis and finite integration simulations.

This paper presents a novel dual-band rectenna for RF energy harvesting system. This rectenna is created from a dual-band antenna and a dual-band rectifier which operates at GSM bands (900 MHz and 1800 MHz). The printed monopole antenna is miniaturized by two meander-lines. The received signal from the receiving antenna is rectified by a voltage double using Schottky diode SMS-7630. The rectifier is optimized for low input power level of -20dBm using harmonic balance. Prototype is designed and fabricated. The simulation is validated by measurement with power conversion efficiency of 20% and 40.8% (in measurement) at the input power level of -20dBm. The proposed rectenna has output voltage from 183-415 mV. From the measured results, this rectenna provides the possibility to harvest the ambient electromagnetic energy for powering low-power electronic devices.

Beamforming and the direction of arrival (DOA) estimation for the massive multi-input multi-output (MIMO) play a significant role in the fifth-generation (5G) cellular networks. Several existing DOA and beamforming algorithms are validated for the MIMO antenna system in 5G gNodeB. The proposed non-blind adaptive beamforming algorithm using Recursive least squares Dolph Chebyshev (RLS-DC) with Uniformly spaced Linear Array (ULA) of 32 elements is presented in this paper. The sidelobe level is suppressed from -14 dB to -30 dB while steering area from -60o to +60o is obtained.

A new broadband high gain planar dielectric rod SIW antenna is proposed in this paper. SIW transmission line structure is applied to minimize transmission losses and Vivaldi structure is used to achieve a wide bandwidth. The proposed antenna has the high gain property (9–13 dBi) within the wide bandwidth of 73% from 24 GHz to 50 GHz.

In this work, we theoretically investigate the multilayer absorber with metal/ dielectric/metal functional layers. The model is tested by the numerical simulations, yielding agreeable results with analytical calculations for the number of layers up to 40. From that model, an approach to achieve wideband absorption is deduced: by either adding more layer or arranging adjacent unit cells close to each other. The validity of this method is verified with simulations in which a 40-layer structure obtains near perfect absorption at 0.69 THz and maintain its absorption strength higher than 90% in a 0.12-THz bandwidth. Compared to common pyramid-like multilayer absorbers, our proposal can also achieve a bandwidth enhancement while having clear advantages in fabrication simplicity.

A novel wideband circularly polarized antenna array using sequential rotation feeding network is presented in this paper. The proposed antenna array has a relative bandwidth of 38.7% at frequencies from 5.05 GHz to 7.45 GHz with a highest gain of 12 dBi at 6 GHz. A corresponding left-handed metamaterial is designed in order to increase antenna gain without significantly affecting its polarization characteristics. The wideband circularly polarized antenna with 2.4 GHz of bandwidth is a promising solution for wireless communication system such as tracking or wireless energy harvesting from Wi-Fi signal based on IEEE 802.11ac standard or future 5G cellular. A potential application of this antenna as a receiving antenna for RF-DC device to obtain DC power for a wireless sensor node from Wi-Fi signal is shown.

A microstrip antenna with wideband, high gain, high efficiency and circular polarization is desirable for wireless applications. A simple way to obtain wideband and circular polarization of a novel three-dimensional dipole antenna array (TDAA) is presented in this paper. This proposed microstrip antenna has a wideband from 4.3 GHz to 7.1 GHz, circular polarization in two bands: from 5.5 GHz to 6.2 GHz and from 6.35 GHz to 6.8 GHz with the maximum gain of 10 dBi. A prototype with dimension of 50×50×22 mm3 has been designed, fabricated and tested; it is suitable to operate in Wifi based on 802.11 ac, WiMAX, and Public Safety bands. Two applications including tracking and RF energy harvesting systems demonstrate the advantage of this proposed antenna.

This paper presents a novel dual-band rectenna for RF energy harvesting system. This rectenna is created from a dual-band antenna and a dual-band rectifier which operates at GSM bands (900 MHz and 1800 MHz). The printed monopole antenna is miniaturized by two meander-lines. The received signal from the receiving antenna is rectified by a voltage doubler using Schottky diode SMS-7630. The rectifier is optimized for low input power level of −20dBm using harmonic balance. Prototype is designed and fabricated. The simulation is validated by measurement with power conversion efficiency of 20% and 40.8% (in measurement) at the input power level of −20dBm. The proposed rectenna has output voltage from 183–415 mV. From the measured results, this rectenna provides the possibility to harvest the ambient electromagnetic energy for powering low-power electronic devices.

In this paper, we introduced a methodology to design a microstrip MTMs and a high gain antenna. A new structure of MTM in the range of 5.7–6.1 GHz is presented. Using this structure the gain of the patch antenna is increased 3dB, from 6.5 dB to 9.6 dB. We also have used this DNG metamaterials for the gain enhancement of an array of 4 patch antennas from 12.5 dB to 15.3 dB while the circular polarization is maintained. The authors wish to thank K. Belmkaddem (CEA-LETI) for his help for the measurements.