Junya Muramatsu

Mutual coupling reduction between two dipole antennas with parasitic elements composed of composite right-/left-handed transmission lines

In this study, a composite right-/left-handed transmission line (CRLH TL) is used as a parasitic element. It is shown that a right-handed (RH) dipole antenna with the CRLH parasitic element has band rejection characteristics. Moreover, transmission characteristics and electric field distribution confirm that mutual coupling between the two dipole antennas can be reduced by using CRLH parasitic elements between the two antennas.

Prediction of Line-of-Sight Propagation Loss in Inter-Vehicle Communication Environments

This paper presents a prediction formula of propagation loss for low antenna height scenarios on a line-of-sight (LOS) straight-line road having an intersection, for modeling the propagation loss characteristic in inter-vehicle communications (IVCs). The regression analysis is applied to the propagation loss data generated by computer simulation based on the geometrical optics theory, and the regression formula is established as a dual-slope model having variables of propagation distance, frequency, road width, and antenna height. In this analysis, the position of breakpoint is determined so that the RMS error of the regression becomes the smallest on both slope regions because its position is an important factor for good prediction accuracy. Furthermore, the comparison between predicted and measured propagation losses is performed in 2 GHz and 5 GHz bands, and the effectiveness of the prediction formula is confirmed by evaluating the prediction errors.

The pattern-controllable novel small antenna with CRLH parasitic element

The pattern-controllable novel small antenna with CRLH-PE has been proposed. The distance between the radiator and the parasitic element of the proposed antenna is 1/20 of wave length. The directivity in arbitrary direction is obtained by resonation of an appropriate PTLH-PE in the usable frequency band of the dipole antenna. The minimization of the radiator is future study.

Non-Linear Numerical Expression of Surge Voltage for Electromagnetic Clutch

In this paper, we propose a numerical method for accurately predicting the surge voltage generated in an electromagnetic (EM) clutch, which is the inductive load of a vehicular air conditioner compressor. The EM clutch is expressed by a 2-D transient response model that considers eddy currents and the non-linear magnetization characteristics of the clutch materials. We found that the surge voltage can be calculated exactly using this model. The calculation result differed from the measured value by <;5%.

Proposal of Electromagnetic Clutch Structure to Suppress Surge Voltage

A new structure for a vehicular electromagnetic (EM) clutch is proposed here that suppresses the surge voltage generated by turning off the ignition switch of a vehicle. Through the theoretical consideration of the EM field, it is found that a larger eddy current in the EM clutch would be able to suppress the surge voltage because it causes a small time change in the magnetic flux passing through the coil. Therefore, the proposed structure has a metal layer with low resistivity surrounding the clutch coil and located between the coil and the coil housing. Numerical calculation of the EM field and electrical circuit, which expresses the measured time-series surge voltage well, shows the suppression effect of the surge voltage with the proposed structure. Therefore, the structure is verified to be useful for suppressing the surge voltage.

Low-profile radiation pattern controllable antenna using composite right/left-handed parasitic element

Recently, a vehicle is crowded with communication systems. There are few places for installing new system antennas. Furthermore, mutual interference problems occur in systems which use adjoining band. To solve these problems, band rejection and mutual coupling reduction characteristics of the composite right/left-handed parasitic element (CRLH-PE) have been reported [1]. The value of the series capacitance composed of the CRLH-PE changes currents phase relationship between the radiation element and CRLH-PE. As a result, CRLH-PE works as director and reflector. Using this concept, the radiation-pattern controllable antenna has been realized [2]. The configuration of the PCA is half-wavelength dipole antenna with ladder-shaped CRLH-PE. From a practical point of view, the high-profile dipole type antenna is not appropriate to install on the ceiling. Therefore, the low-profile planar type antenna is required.

Trench Structure to Suppress Magnetic Field Leakage From an Aperture in a Metallic Enclosure

In hybrid vehicles, power converters such as inverters and dc–dc converters are installed in the power control unit (PCU). A strong current flows through the inductor of the output filter of the power converter, which causes electromagnetic interference in AM radios and other electrical equipment due to low-frequency noise. In this letter, we attempt to clarify the mechanism of low-frequency magnetic field leakage from the aperture of a simplified metallic enclosure representing a real PCU enclosure. A novel structure is herein proposed that suppresses leakage of the magnetic field by controlling the flow of eddy currents around the aperture. The proposed enclosure is manufactured, and its shielding factor is measured. The shielding factor of the proposed enclosure is confirmed to correspond approximately with that of an enclosure without an aperture.

Experimental verification of proposed electromagnetic clutch structure for surge voltage suppression

Based on experimental time-series data, a new electromagnetic clutch structure is verified to be useful for surge voltage suppression, providing a reduction in the surge voltage of approximately 50%, in its trial production. The new structure has a metal layer with low resistivity surrounding the clutch coil, which is located between the clutch coil and the coil housing. First, we optimized the structure in order to maximize the surge voltage suppression effect. We then fabricated the optimized structure and experimentally confirmed that the surge voltage of the proposed structure is much lower than that of the conventional structure.

Path-loss measurement system for design of in-vehicle short range communication

A compact path-loss measurement system for design of in-vehicle short range communication is proposed. The system is composed of sensor network modules for data transmission and a transceiver for the sounding signal. The channel is measured in an engine compartment of a hybrid vehicle using the developed system. As a result, it is clarified that the engine compartment has a severe fading channel.