Tsutomu Mitsui

Experimental Evaluation of Estimating Living-Body Direction Using Array Antenna for Multipath Environment

In this letter, we introduce a method that uses the radar system to observe the waves reflected from the target with the single-input-multiple-output (SIMO) array configuration to estimate living-body directions in a multipath environment for applications such as elderly monitoring. Directions of living body are estimated by the MUltiple SIgnal Classification (MUSIC) method, where the Fourier transformed channel matrix is used. Our use of the 2.4-GHz band allows greater miniaturization of the antenna than is possible with the low-frequency band used by conventional systems. Also, this method can be used in multipath-rich environments such as indoors. The experiments are carried out in a specific indoor environment as a demonstration, and the SIMO channel is measured with various subject numbers and positions. The results indicate that the proposed method can estimate living-body directions with high accuracy even in multipath environments.

Improvement of channel capacity on MIMO antenna systems with antenna pattern selection

Although MIMO (multi-input multi-output) has attracted attention as an efficient communication technology for high frequency use, the channel capacity of MIMO systems depends primarily on radio propagation. Therefore, development of a MIMO antenna system that can obtain high channel capacity in a variety of propagation environments is important. This paper focuses on antenna pattern selection (APS system) by providing multiple directional patterns that can be switched to each antenna element of the receiver according to the propagation environment.

Performance Evaluation of Downlink Multi-Beam Massive MIMO with Simple Transmission Scheme at Both Base and Terminal Stations

Multi-beam massive multiple-input–multiple-output (MIMO) configurations that utilize high-power beam selection in the analog parts and blind algorithms such as the constant modulus algorithm (CMA), which do not require channel state information (CSI), in the digital parts, have been proposed in the literature to improve the transmission rates and efficiency. In this paper, we evaluate the transmission performance in the downlink, with simple control at the base station (BS) and user terminal (UTs), for massive MIMO transmissions. Through computer simulations, it is shown that the analog multi-beam selection at the BS and the application of CMA at the UT with two antennas can effectively realize transmissions with high-order modulation schemes. In addition, the weight update switching by the CMA is proposed in order to obtain fast and stable performance with a realistic data size.

Fast estimation algorithm for living body radar

The authors have proposed a direction estimation method of the living-body using array antenna in multi-path environment. However, this method has a problem that takes time as several tens of seconds. In this paper, we present a fast algorithm for estimating living-body direction. The experiment showed that the proposed method works well in estimating living-body direction with high accuracy in multi-path environment even when the observation time is less than conventional method.

Antenna Array Calibration for Living-Body Radar

This letter introduces an antenna array calibration method that uses the channel response with known subject direction so as to accurately estimate living-body directions in multipath environments for elderly monitoring. Said calibration is extracted from the known living-body direction information using the Fourier transformed channel matrix. An experiment shows that the proposed method offers successful antenna array calibration even in indoor environments. Living-body directions are successfully estimated within acceptable error proving that the proposed method is effective in calibrating living-body radars.

3-Beam Switched by quarter-wave shorted patch array antenna

The quarter-wave shorted patch antenna with two parasitic elements having switch elements was proposed to control the beam profile by a simple structure. This antenna has the feature to change the radiation pattern to three directions using only four switch elements. The fabrication of the antenna using switch elements and the measurement will be left for future problem.