Toshihide Tosaka

Method for Determining Whether or Not Information is Contained in Electromagnetic Disturbance Radiated From a PC Display

To evaluate the possibility of information leakage by observing the electromagnetic disturbance radiated from a PC display, we propose an evaluation method by using a spectrum analyzer that is commonly used for electromagnetic interference measurement without reconstructing the displayed image. In this method, we measured the spectrum when the white and time-varying stripe patterns are displayed, and determined whether or not the disturbance contains the frequency component of the display pattern from the level difference. By using the patterns, we can easily evaluate the possibility of information leakage in radiated disturbance from a PC display in a wide frequency range.

Determining the relative permeability and conductivity of thin materials

In order to determine the relative permeability and conductivity of thin materials that could not be found using traditional methods, we constructed a shield box and developed a measuring system to estimate the unknown electric parameters of exotic shielding materials such as thin cloths. Thin electromagnetic shielding sheets of both nonmagnetic materials and ferromagnetic materials were used. The shielding effectiveness of the materials was measured as a function of frequency, and the results were compared with the calculated solutions for a multilayered model that was evaluated using the Sommerfeld integral that expresses near-field spherical waves by a composition of cylindrical waves. In these calculations, the relative permeability and conductivity were varied to determine the solution closest to the measured results. The least squares method was used to determine the best fitted values. Initially the nominal values of relative permeability were assumed, and the conductivity was found using the fitting technique. Then this determined value of the conductivity was assumed, and the relative permeability was found using the fitting technique. For the nonmagnetic materials, the estimated relative permeability was the same as the nominal values. For the ferromagnetic materials, the estimated relative permeability varied 0%-30% from the nominal values. For both types of materials, the estimated conductivities were 0%-9.8% different from nominal values. This research details a new method for evaluating the attenuation of interfering electromagnetic waves for thin materials.

Evaluation of Information Leakage from PC Displays Using Spectrum Analyzers

To evaluate whether electromagnetic disturbances that leak from PC displays contain information or not, we need to reconstruct the information from the measured disturbance. This requires a special receiver, and not all test houses have a special receiver. In this paper, we propose performing the evaluation with the spectrum analyzers commonly used for EMI measurement. First, we select a spectrum that containing the frequency component of the vertical sync signal using a spectrum analyzer (SA1). Then, we measure the video output of SA1 using another spectrum analyzer (SA2) and evaluate the disturbance from the frequency component of the horizontal sync signal.

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.

Estimation of electric parameters for thin shielding sheets

We suggest an estimation method of the electric parameters for thin shielding sheets. In order to evaluate our estimation method, we estimated the electric parameters for the metallic materials which have known electric parameters, and evaluated our method. For the non-magnetic materials, the estimated relative permeability was the same as the nominal values. For the ferromagnetic materials, the estimated relative permeability varied 0% to 30% from the nominal values. For both types of materials, the estimated conductivities were 0% to 9.8% different from the nominal values. Next, we apply our estimation method to shielding sheets, and we can estimate the electric parameters for items such as thin cloths

Development of a magnetic field measurement system using a tri-axial search coil

In order to measure the magnetic field noise around electric devices, we developed a measurement system using a tri-axial search coil. The crosstalk of the orthogonal search coils is less than -40 dB between the tri-axial search coil sensors. The measured magnetic sensitivity of the search coil is 10 pT//spl radic/Hz at 1 kHz.

Methods of Evaluating Information Leakage from PC Displays

To evaluate the possibility of information leakage (tapping) by observing electromagnetic disturbance radiated from a PC display, the most straightforward way is to reconstruct the displayed image from the measured signal using a special receiver. However, such a receiver is neither popular nor commercially available. Therefore, we propose two types of evaluation methods that are based on (1) the measurement of the difference in level when different images are displayed, and (2) the measurement of the frequency component of the horizontal sync signal within the electromagnetic disturbance. In both proposed methods, we only need a spectrum analyzer that is commonly used for EMI measurement.

Development of an Estimation System for the Relative Dielectric Constant of Liquid Materials

We have developed an estimation system of the electric parameters for liquid materials without a sensor connecting to the testing materials. A PC can be used for the calculation, and the calculation time is about 2 minutes. The accuracy is such that the estimated values are different from the nominal values by less than 2%.

Measurement of Shielding Effectiveness in the Microwave Frequency Range using a Dual Focus Flat Cavity

We suggested a new measurement method of SE (Shielding Effectiveness) in the microwave frequency range using a DFFC (Dual Focus Flat Cavity). TE waves are transmitted from the transmitting point to the receiving point through the testing material. The shape of the DFFC is oval and the transmitted waves are focused at the receiving point with the same phase. This method has a large dynamic range of about 100 dB. We evaluated this method at a number of frequencies by comparing the calculated value with the measured value using isotropic materials. The differences were less than 3 % at each frequency. The measurement repeatability error was less than 2 %.

Development of the Estimation System of the Equivalent Dielectric Constant of Dielectric Materials

In this research, the relative dielectric constant for the liquid materials with no contact between a sensor and the materials are estimated. SE is first measured using a shield box. Then, the shield box with a multi-layered model is modeled with Sommerfeld integral, and the electromagnetic field is calculated at the observation point. Finally, the SE is calculated to be fitted to the measured value of SE, in order to estimate the electric parameters as an inverse problem