Kazumasa Taira

Polarization dependence of multipath propagation and high-speed transmission characteristics of indoor millimeter-wave channel at 60 GHz

Measurements of polarization dependence of multipath-propagation characteristics were conducted at 60 GHz in a room within a modern office building. Delay profiles were measured using a swept frequency method with a high time-delay resolution of 2 ns. Directions of arrival of the multipath components reflected from walls were analyzed by rotating a narrow-beam receiving antenna with an angular resolution of 5 degrees. Results of this experiment showed that multipath delayed waves due to wall reflection can be effectively suppressed by employing circular polarization instead of linear polarization. Based on this experimental result, a computer simulation was made to clarify the polarization dependence of the high-speed transmission characteristics of an indoor communications system operating at 60 GHz. >

Multipath measurement at 60 GHz for indoor wireless communication systems

Measurements of multipath-propagation characteristics were conducted at 60 GHz in a room within in a modern office building. Delay profiles were measured by a swept frequency method with a high time-delay resolution of 2 ns. Direction-of-arrivals of the multipath components reflected from walls analyzed by rotating a narrow-beam receiving antenna with an angular resolution of 5 degrees. As a result of this experiment, it was found that multipath delayed waves due to wall reflections can be effectively suppressed by employing circular polarization instead of linear polarization. Based on this experimental result, a computer simulation was made to make clear the polarization dependence of the high-speed transmission characteristics of a indoor communications system operating at 60 GHz.<<ETX>>

Reconstruction of Printed Image Using Electromagnetic Disturbance from Laser Printer

The electromagnetic disturbance that leaks from ICT (information and communications technology) equipment might contain important information. Our measurements show that the information hidden inside of the electromagnetic disturbance can be monitored. First, we measured the level of the electromagnetic disturbance that leaks from laser printers and collected the waveform in the time domain. Then, we reconstructed the printed image from the data. As a result of our measurements, we found that at points 200 cm away or beyond it is difficult to reconstruct the printed image, and therefore the threat to electromagnetic security is not significant.

Measurement of spatiotemporal propagation characteristics in urban microcellular environment

The spatiotemporal characteristics of line-of-sight and non line-of-sight propagation cases are measured on a street in the central Tokyo area. The results indicate that most arrival signals in the line-of-sight case propagate along the road and are assumed to be approximated by the ray model. The results in the non line-of-sight case indicate that most arrival signals propagate along the road and are scattered around the nearest crossing, and then arrive at the shadowed area.

Estimation of Multiple Coherent Source Locations by Using SPM Method Combined with Signal Subspace Fitting Technique

A visualization method of coherent source locations based on the Sampled Pattern Matching (SPM) method is described. Modified SPM method is proposed to improve the S/N, in which the measurement of the electric field distribution is repeated in appropriate time duration and eigenvalue decomposition of the covariance matrix is introduced. A combination of the modified SPM method with the Weighted Subspace Fitting (WSF) method is also proposed to estimate accurate source locations. A calibration technique by using a reference antenna to compensate the complex pattern of the receiving antenna is proposed. Experimental investigation to estimate source location for one dipole antenna and two dipole antennas is also made to demonstrate the validity of the proposed method.

Estimation of Short Range Multiple Coherent Source Location by Using MUSIC Algorithm

An estimation method of source location of undesired electromagnetic wave from electronic devices by using the MUSIC algorithm is proposed. The MUSIC algorihm can estimate the direction of arrival accurately however, the estimation error is large in the case of short range multiple coherent sources. In order to overcome this problem, a method to improve the estimation accuracy is presented. Experimental results show that the proposed method can reduce the maximum estimation error from 7 cm of the conventional method to 2 cm.