Takanobu Tabata

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.

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.

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.

Design of spiral-slot frequency selective surfaces for shielding from noises of wireless power transfer

A spiral-slot Frequency Selective Surface (FSS) is applied to a Wireless Power Transfer (WPT) system in 12MHz band. To reduce the physical size of FSS, single spiral-slot configuration is designed. As a result of the simulation of the designed WPT system with FSS, transmission efficiency higher than 80% is obtained, while interference can be stopped in other frequency band.

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.