Search

This article describes a 5.8-GHz band highly efficient 1-W rectenna that consists of a bridge diode, directly connected to a short-stub-connected high-impedance dipole antenna, with a designed antenna resistance of $580~\Omega $ . The proposed antenna topology realizes circuit functionalities of impedance transform, impedance matching, harmonic reaction, and dc blocking while maintaining a high antenna radiation efficiency. Lossy circuit components between the antenna radiator and the bridge diode can be eliminated for a highly efficient rectification. In experimental investigations, the measured rectification efficiency of the 5.8-GHz band rectifier is 92.8% at an input power of 1 W, and the estimated antenna radiation efficiency from the measured antenna gain is 96.9%, including loss due to circuit functionalities and interconnection. With lesser additional losses, the proposed antenna can be integrated with circuit functionalities to achieve a highly efficient rectenna. The measured rectification efficiency is almost the same as the fundamental limitation restricted by the rectifier diodes’ performance.

Multi-mode excitation with complementary resonance for radiation resonance is useful for broadbanding of electrically small antennas. Bandwidth of a small antenna with series resonance such as short dipole, small helical and meander line antennas can be expanded by using no-radiation parallel resonance. Another antenna type with parallel resonance like a microstrip antenna (MSA) is also able to get wideband characteristics using series resonance. We have studied compact broadband small antennas with multi-mode excitation and evaluated them in the view point of practical use. In the paper, we will show evaluation results of a miniaturizing factor, product of bandwidth and radiation efficiency ( Bη product), for practical inverted-L antenna (ILA) and MSA.

In recent years, small antennas have been developed for portable devices such as smartphones and tablet PC devices. As the development of electronic devices progresses toward IoT, miniaturization of antennas with high performance are required rapidly. Sharing of a terminal for multiple frequencies is demanded to use several wireless systems. In this project, we study on a J-type antenna that enables dual frequency sharing and conduct research on miniaturization. After simulations of fundamental J-type antennas were examined to understand the principle of dual frequency sharing, miniaturization of the J-type antenna was conducted with meander elements. In this report, we research the miniaturization of the J-type antenna for the purpose of sharing in the 5G frequency bands. After the dual-band J-type meander antenna is simulated, characteristics of the antenna are clarified in measurement.

Gain enhancement of a microstrip antenna (MSA) set on the surface of a human body is investigated. Antenna characteristics based on the distance between the ground plane of the antenna and the surface of a human phantom are simulated, and measurements with a human subject are examined. In order to obtain maximum gain of the MSA, different sizes of the ground plane are used. The effect of gain enhancement of MSA close to the human body is discussed by comparing the numerical simulation with measurement results.

In this paper, the high sensitive 2.4 GHz band rectenna with direct matching topology is described. The rectenna is consisting of the inductive planar 3-strip folded dipole antenna with 10 $\mathrm{k}\Omega$ impedance and the SOI-CMOS rectifier IC. The rectifier IC is fabricated on Global Foundries 40 nm SOI-CMOS for improvement of the rectification efficiency in $\mu \mathrm{W}$ region. Furthermore, the inductive planar 3-strip folded dipole antenna is proposed to be combined with the rectifier IC with capacitive admittance for direct impedance matching. The developed rectenna achieves the rectification efficiency of 14.7 % at the input power of -30 dBm.

This paper proposes a new circuit model for E-shaped patch antennas (ESPA) using the multiconductor transmission line mode theory (the modal theory). First, radiation and transmission line modes generated on the ESPA are described, and an equivalent circuit is derived from the modal theory. The equivalent circuit is analyzed in detail to obtain wideband and multiband characteristics. For wideband ESPAs, the theoretical maximum bandwidth is derived under VSWR criterion. Dual-band ESPA is also discussed theoretically. Finally, impedance characteristics obtained by the circuit model are compared with full-wave electromagnetic simulations and measurements.

A meta-surface inspired antenna (MACKEY) has been proposed, which works not only infree space but also on a metal plate. A MACKEY parallel arrangement model will be proposed in which an original MACKEY (WiFi 2 GHz band) and a MACKEY wide-band type (WiFi 5 GHz band) arearranged in parallel. Then, a MACKEY type T will be proposed, where one of the two grids of an original Mackey and that of a wide-band type are shared.

A microstrip antenna using a stub excitation under the patch is investigated to obtain broadband characteristics. A stub with a line composed of three kinds of characteristic impedance is employed for broadbanding. We design a broadband microstrip antenna using the stub and evaluate bandwidth - efficiency product $(\pmb{B}\eta)$ of a prototype antenna compared with the theoretical limitation.

High-impedance folded dipole antennas (FDAs) consisting of three conductors are designed in order to improve rectification efficiency of energy harvesters. FDAs with $\mathbf{10k}\Omega$ -impedance designed for three terrestrial systems of DTV, cellular and Wi-Fi.

Meta-surface inspired antenna (called MACKEY) which works not only in free space but also on metal plates, was proposed. In this paper, a dual-band MACKEY device, in which the position of the dipole antenna is changed from the center of the substrate, is proposed. Additionally, the conditions for controlling the resonance frequencies are clarified.

We have proposed an open terminated folded inverted-L antenna (FILA) with slits. In order to miniaturize the FILA, several slits are employed on the substrate surface. Folded structure is used for broadbanding. Design of the FILA to achieve broadband characteristics is shown. Simulation and measurement are implemented, and comparison of the results are evaluated. Finally, we calculate the product of bandwidth and radiation efficiency (Bη product) and evaluate it of the FILA compared with the theoretical limitation.

We have studied a high impedance antenna in order to improve the rectifier efficiency for energy harvesting applications. Folded dipole antenna (FDA) with high impedance of over 10 kΩ is proposed. To obtain higher impedance stepup ratio compared with the conventional FDA, an FDA consisting with three strip conductors is investigated. Impedance stepup ratio is calculated and the results in theory, simulation and measurement are compared.

This paper provides a dual-band / wideband MACKEY with a dipole element setting at the offset position away from the center (MACKEY type O) will be proposed.

In this paper, aberration theory will be introduced to estimate the frequency characteristics of reflectarrays. By introducing aberration theory, the mechanisms of the frequency characteristics of the beam squint and the phase errors on the aperture will be qualitatively clarified. The validity will be quantitatively verified by simulations.

We demonstrated the high efficiency on the rectenna which is composed of the high impedance antenna and the optimized gate controlled diode (GCD), for RF energy harvesting. It was clearly shown that the high impedance and the cancelation of the parasitic capacitance (Cj) of the diode improve the rectification efficiency, by using the fabricated transmission line module. The rectification efficiency of 15% at input power of −15dBm around 500MHz was obtained with the first demonstration of the fabricated rectenna which is composed of the 1.6k Ω folded dipole antenna, the Cj canceler, and the optimized GCD.

This paper provides a MACKEY-E with E shape radiator that has dual band characteristics and works not only in free space but also on a metal plate.

A small antenna MACKEY (Metamaterial Antenna Chip developed by KIT EOE LaboratorY) consists of substrates that are metal plate loaded capacitance grids using AMC (Artificial Magnetic Conductor) substrate and dipole antenna is showing a characteristic distribution from the principle of operation, it is possible to be installed on a metal plate without affecting the characteristics of impedance and radiation in prior studies. In this report, the results of numerical analysis by FEM about the E shape model is shown. From the results, a feasibility study on the dual band MACKEY is presented.

In this paper, the 500MHz band low power rectenna with high sensitivity characteristic is described. The rectenna is consisting of the folded dipole antenna with a 1.6kΩ impedance and the Cockcroft-Walton type rectifier for improvement of the rectification efficiency and the output dc voltage. Furthermore an L-Type LPF is added to reduce the negative influence due to the junction capacitance of the SBD. The developed rectennas (stage number: 1, 2) achieve the rectification efficiency of 48.9 % (stage number: 1) and 43.1 % (stage number: 2) at −15dBm of the input power. In addition to above, the top level efficiency of 8.7 % (stage number:1) at the input power of −30dBm can be achieved. In the Tokyo are, the output dc voltage of 0.22 V can be measured at the 25 km point from the antenna tower.

Autonomous systems are important for realization of the sensor network. The RF energy harvesting is one candidate of the power source for the systems. It extracts the electric power from the electromagnetic waves which exist environmentally [1]. We have chosen the wave of the Digital Terrestrial Television (DTTV) which frequency is around 500MHz, because the covered area and the expected power will become large, compared with others, e.g. the Wi-Fi and the cellular phone [2]. Although the DTTV is chosen, the expected received power is around or below the micro watts when the covered area is intended to be enlarged. Therefore, the most important issue of the RF energy harvesting is the high efficiency rectification on such ultralow input power level [1].

This paper provides an AMC inspired small antenna MACKEY that can be installed regardless of the presence of a surrounding metal.

In this paper, analysis on the linearity of the balanced diode mixer driven by the square wave LO is described For the objective, the circuit analysis based on the diode model with the ideal switch and the resistor is indicated and the derived formula clarifies the linear operation under some conditions. Furthermore the normalized output powers and the third order distortion of the mixer are demonstrated with the square wave LO and the sinusoidal LO. This analytical result and experiments confirm the high linear characteristics of the balanced diode mixer driven by the square wave LO.

A card-type folded dipole antenna with high impedance and wideband characteristics was investigated for energy-harvesting applications. An impedance of more than 2000 O was realized by the high-impedance step-up ratio of the folded structure. A prototype of the antenna was designed with an EM simulator, and the simulated and measured results were compared. The measured results agreed with the simulated results, and the measured bandwidth was 4.5% of that corresponding to the four channels of digital TV broadcasting waves.

We have investigated a folded inverted-L antenna (FILA) and introduced equations with respect to the limitation of the theoretical bandwidth. The miniaturization of the conventional FILA was not sufficient because the FILA consists of a substrate perpendicular to the ground plane. In this paper, we study two different types of FILAs in order to miniaturize the antenna. The miniaturization ratios of the FILAs with the efficiency bandwidth product (Bη product) are estimated. As a result, a 15.3% improvement in the Bη product was obtained over the conventional FILA.

Various domestic appliances have become wireless, and it is necessary to establish a design theory for a small antenna. In this report, we suggest a model that has a dipole antenna unified with an AMC (Artificial Magnetic Conductor) substrate, and we show that the AMC substrate becomes a wide-plate dipole and operates as a radiation element.

High-impedance wideband folded dipole antennas (FDAs) are proposed for energy harvesting applications in order to obtain high rectification efficiency. Design method of the FDA is discussed based on an equivalent circuit, and condition of high-impedance wideband characteristics is expressed with equations. As design examples, straight-type and card-type FDAs are described for the digital TV broadcasting waves in Japan.

A new method of increasing the bandwidth of normal-mode helical antennas (NMHA) is proposed. The antenna has length of around 0.1 of the target wavelength, and consists of a helix constructed with two flat wire strips. The method exploits the two current modes of the two-wire design to obtain wideband response. Based on an analysis of the equivalent circuits of the two modes and subsequent optimization of design parameters, a final two-strip NMHA design is proposed that is demonstrated to have a bandwidth of 12% in the 760-MHz band at a voltage standing wave ratio of less than 2.

In this study, the dual band characteristics of the capacitance-grid (CG)-type Artificial Magnetic Conductor (AMC) substrate are presented, it is shown that the substrate works as an AMC substrate at the dual bands separated three times.

A high-impedance wideband folded dipole antenna (FDA) has been designed for energy harvesting applications. High impedance is necessary for producing high efficiency rectennas. An impedance of over 300 Ω can be achieved by FDAs due to the impedance step-up function. The wideband design is introduced theoretically using an equivalent circuit for the FDA. A bandwidth over 20% with a characteristic impedance of 350 Ω was achieved. Measurements of the fabricated antenna are compared with the results of simulations and the high-impedance wideband design is verified.

In this study, we propose a polarization conversion reflector using a metal-plate-loaded meander line and determine the reflector's axial ratio characteristics with a numerical analysis involving the method of moments. A relative bandwidth greater than 90% is obtained.

In this paper, we propose a high efficiency and low-side-lobe reflectarray antenna by taking into account the grating lobe between the frequency selective reflector and the metal plate. Then, we verify the validity of the design by simulation and measurement.

We analyze a solution of the heat equation for second harmonic generation (SHG) with a focused Gaussian beam and simulate the temperature rise in SHG materials as a function of the second harmonic power and the focusing conditions. We also propose a quantitative value of the heat removal performance of SHG devices, referred to as the effective heat capacity Cα in phase matched calorimetry. We demonstrate the inverse relation between Cα and the focusing parameter ξ, and propose the universal quantity of the product of Cα and ξ for characterizing the thermal property of SHG devices. Finally, we discuss the strategy to manage thermal dephasing in SHG using the results from simulations.

This paper describes the high efficient bridge rectifier topology and its implementations in 100MHz and 2.4GHz bands. The rectifier topology realizes full-wave-rectification without large sized filters used in single-shunt type rectifiers. By employing the topology, further downsizing and integration can be achieved easily. High impedance operation with impedance transformer or the high-impedance antenna is employed to improve the rectification efficiency. Also formulas of the rectification efficiency on the proposed topology are described in the paper for clarification of effectiveness. Experimental investigations demonstrate confirmation of the derived formulas. Also 94% efficiency of the 100MHz band rectifier and 80% efficiency of the 2.4GHz rectenna are achieved. These values are the top-level performance with the commercial-based Si-SBD. Also the size of the 2.4GHz band rectifier is 4.5mm × 4.8mm that is the smallest implementation than the past works.

Gate controlled diodes (GCD) and rectifiers using the GCD with the different threshold voltage (Vt) of the MOS by the ion-implantation were fabricated with 0.18um CMOS technology. The DC characterization of the GCD revealed that the turn on voltage of the GCD is reduced and becomes lower than the Schottky Barrier Diode (SBD) when the Vt of the MOS is reduced and there exist the bulk leakage pass of the MOS on the reverse leakage current of the 0.18um GCD. It was also clarified that the parasitic capacitance of the GCD will be lower than the SBD. From simulations and measurements of the rectifier, it was found out for the first time that the rectification efficiency of the rectifier using the GCD has a peak value when changing the Vt of MOS in the GCD, and the rectification efficiency of the rectifier using the GCD with the near zero Vt of the MOS overcomes the rectifier' using the specially designed SBD for the small signal applications, on the ultralow power input of the RF energy harvesting.