Satoshi Hori

Classification and characterization of wireless power transfer systems of resonance method based on equivalent circuit derived from even- and odd mode reactance functions

Wireless connections by resonance method are promising for mobile and contactless power transfer, but the essential properties remain to be completely elucidated. This paper treats basic systems consisting of two equal lossless antennas of closed path type or open path type. Resonance and anti-resonance frequencies for even- and odd mode excitations are used to formulate the reactance functions and the image impedance of the system, from which a simple but accurate equivalent circuit with five different LC elements is derived. High image impedance frequency band is found to exist, which would broaden the possible applications.

Implementation of Joint Pre-FFT Adaptive Array Antenna and Post-FFT Space Diversity Combining for Mobile ISDB-T Receiver

In our application targeted here, four on-glass antenna elements are set in an automobile to improve the reception quality of mobile ISDB-T receiver. With regard to the directional characteristics of each antenna, we propose and implement a joint Pre-FFT adaptive array antenna and Post-FFT space diversity combining (AAA-SDC) scheme for mobile ISDB-T receiver. By applying a joint hardware and software approach, a flexible platform is realized in which several system configuration schemes can be supported; the receiver can be reconfigured on the fly. Simulation results show that the AAA-SDC scheme drastically improves the performance of mobile ISDB-T receiver, especially in the region of large Doppler shift. The experimental results from a field test also confirm that the proposed AAA-SDC scheme successfully achieves an outstanding reception rate up to 100% while moving at the speed of 80km/h.

Transmission properties of dual-band loop slot Frequency Selective Surfaces on plastic board

Dual-band Frequency Selective Surfaces (FSSs) that have a transmitting property at 1.5GHz and 5.8GHz are fulfilled by arranging two different loops in one period and by using a fractal loop slot. In the model with two different loops, close arrangement of inner loops operates over broad bandwidth at higher resonant frequency. On the other hand, the fractal loop achieves both double resonance and size reduction of the period. To confirm these results, the measurement system is developed and the measured scattering coefficients of an ordinary square loop slot FSS are compared with the simulation S11. The performances of the developed FSSs are evaluated by simulation and measurement.

Joint Hardware-Software Implementation of Adaptive Array Antenna for ISDB-T Reception

In this paper, an adaptive array antenna is implemented to enhance the performance of digital TV ISDB-T reception. Issues of realizing the proposed array antenna and its implementation by a joint hardware-software solution are also presented in this paper. Instead of using known reference signals, the proposed method utilizes the GI (Guard Interval) and a periodic property of OFDM signal as a constraint to realize MRC (Maximum Ratio Combining) and SMI (Sample Matrix Inversion) adaptive beam-forming algorithms. Experimental results show that the proposed system drastically improves the quality of reception. Moreover, the proposed system can achieve excellent performance under the conditions of strong interferences.

Experimental study of adaptive array antenna system for ISDB-T high speed mobile reception

In this paper, we propose the system configuration in consideration of antenna directivity when four antennas are mounted on a vehicle and we experimentally demonstrate that the ISDB-T reception probability is improved while the vehicle moves at high speed.

Miniaturization of period of dual-band frequency selective surface by using C-shaped ring slots

For shielding various communication equipments, it is advantageous to miniaturize the size of period of FSS. To decrease the size of the period of dual-band FSS for LTE, Bluetooth and Wi-Fi, C-shaped ring slots are proposed. As a result of the electromagnetic simulation, the proposed model achieves 43.2% miniaturization of the FSS period even with the comparable property as the conventional ring slots.

Wireless resonance connection employing a single resonator between transmitting and receiving electrically small non-resonant antennas

Wireless sympathetic connection systems are proposed which employ a single resonator located between two electrically small non-resonant antennas. Symmetric configurations consisting of two equal transmitting and receiving antennas and a resonator are characterized by the equivalent reactive circuits with two inductors and one capacitor in the case of closed path type antennas and with two capacitors and one inductor in the case of open path type antennas. The equivalent circuit constants are identified by the series and parallel resonance frequencies for the even mode excitation and by the low frequency inductance or capacitance for the odd mode excitation. The power transfer efficiency evaluated by the equivalent circuit analysis agrees well with the full wave analysis result, and is 100 percent when the port impedances are matched to the image impedance and the structures are assumed to be lossless. Asymmetric cases of unequal transmitting and receiving antennas are treated, and the theory is applied to the simplified design of HF-RFID systems, where the reader/writer port impedance is 50Ω and the tag port impedance is 3 KΩ. The power transfer efficiency is evaluated in case the antennas and the resonator are made of cupper. It keeps the efficiency larger than -10 dB when the tag antenna moves from the home position by 15 cm horizontally or vertically.

Design of LF-WPT systems of sympathetic connection employing non-resonant grounded antennas and external circuits which emulate the systems employing self-resonant electrically small antennas

A design method of WPT systems for use in EV wireless charging is developed. The proposed loops and the external circuit configurations are in the form of equivalent circuit for WPT systems with self-resonant antennas, and the explicit design formulae for the external capacitors and inductors are given in terms of the magnetic coupling coefficient k between two coils, working frequency f0 and the port impedances R0. Aggressive targets are set, such as smaller loops, longer spacing between loops, lighter systems weight, and so on. k and the Qs of the coils and the external circuit are the key parameters determining the obtainable power transfer efficiency. Higher magnetic coupling coefficient is possible by employing thicker conducting pipes for making coils. A design example for a system in 150kHz band with rectangular loops with side-length less than 40cm, loops separation 19cm, transmitor or receiver weight less than 5 kg including ground plates, is tested by simulation and experiment. The usefulness of the design theory has been verified, and the directions towards the future efforts are described.

Effects of noise in near field object position estimation using array antenna

This paper shows the effects of noise on estimation accuracy in an object position estimation method using hyperbolas obtained from phase difference between elements of array antenna. It is shown that the contribution of antenna elements located at array ends to the position estimation is depend on the noise. It is shown that all antenna elements contributes effectively in case of the noise sufficiently small compared to the radiation power.