Masahiro Hanazawa

Acute Ocular Injuries Caused By 60-ghz Millimeter-wave Exposure

The goal of this study was to examine the clinical course of 60-GHz millimeter-wave induced damages to the rabbit eye and to report experimental conditions that allow reproducible induction of these injuries. The eyes of pigmented rabbits (total number was 40) were irradiated with 60-GHz millimeter-waves using either a horn antenna or one of two lens antennas (6 and 9 mm diameter; ϕ6, ϕ9) Morphological changes were assessed by slit-lamp microscopy. Additional assessments included corneal fluorescein staining, iris fluorescein angiography, and lens epithelium light microscopy. Under the standardized eye-antenna positioning, the three antennas caused varying damages to the eyelids or eyeglobes. The most reproducible injuries without concurrent eyelid edema and corneal desiccation were achieved using the ϕ6 lens antenna: irradiation for 6 min led to an elevation of the corneal surface temperature (reaching 54.2 ± 0.9°C) plus corneal edema and epithelial cell loss. Furthermore, mitotic cells appeared in the pupillary area of the lens epithelium. Anterior uveitis also occurred resulting in acute miosis (from 6.6 ± 1.4 to 2.2 ± 1.4 mm), an increase in flares (from 6.7 ± 0.9 to 334.3 ± 130.8 photons per second), and iris vasodilation or vessel leakage. These findings indicate that the three types of millimeter-wave antennas can cause thermal injuries of varying types and levels. The thermal effects induced by millimeter-waves can apparently penetrate below the surface of the eye.

Measurement of complex permittivity of liquid at V band

It is well known that a dielectric constant is essential and has frequency dispersion. So, great numbers of dielectric constant measurement methods have been studied at many frequency bands. Recently, commercial frequency bands have shifted to higher frequency regions. There have been strong demands for a dielectric constant measurement method of a liquid in the millimeters wave region. For that purpose, we gave attention to a free space method, using a lens antenna and measured dielectric constants of ethanol at V band as an example. These results were in good agreement with values measured by a probe method. It was confirmed that the method is effective in permittivity measurement of a liquid in the millimeter wave band.

Design of rectenna array panel taking into account mutual coupling for RF energy harvesting

A study of a rectenna (rectifying anntena) array on a 1×1-m substrate for RF energy harvesting is presented. Square loop antennas are laid out on the given substrate size assuming to harvest 500-MHz Digital TV radio waves. The optimum number of elements is determined from the obtainable DC power and its angle characteristics taking into account mutual coupling between antenna elements and the non-linear RF-to-DC conversion efficiency of the rectifier. Mutual coupling effects can be exploited to control the angle characteristics to some extent. In this particular consideration, a 4×3 rectenna array was optimum in the harvesting of 500-MHz radio waves from a broad angle range in the horizontal dimension.

The Measurements of the Complex Permittivities of Blood Samples in Quasi-Millimeter and Millimeter Wave Bands

We measured the complex permittivities of whole blood and blood plasma in quasi millimeter and millimeter wave bands using a coaxial probe method. The validity of these measurements was confirmed by comparing with those of a different measurement method, i.e., a dielectric tube method. It is shown that the complex permittivities of the blood samples are similar to those of water in quasi millimeter and millimeter wave bands. Furthermore, the temperature dependences of the complex permittivities of the samples were measured.

High Performances of X-Band Wave Absorber for TE and TM Polarizations using Transparent Resistive Film

An X-band transparent wave absorber for TE and TM wave polarizations is examined theoretically and experimentally. In the case of both polarizations, the absorption of 20dB or more was obtained at the frequency ranging from 8.5 to 11.5 GHz, and the incident angle between 0 and 40 degrees under the target frequency of 10 GHz and the target incident angel of 20 degrees. The optical transmittivities of the presented wave absorber of about 80% or more was also obtained, as expected.

An X-band transparent wave absorber using an ITO resistive-film for oblique incident wave

Performances of a presented X-band transparent wave absorber for an oblique incidence are clarified theoretically and experimentally. In the case of TE-polarization, the absorption of 20dB or more was obtained at the frequency between 9.1 and 10.5 GHz, and the incident angle between 0 and 40 degrees under the target frequency of 10GHz and the target incident angel of 20 degrees. In the case of TM-polarisation, on the other hand, the absorption of 20dB or more was also obtained at the frequency between 9.5 and 11.0 GHz, and the incident angle between 0 and 30 degrees. The optical transmittivities of our absorber of about 80 % or more was also obtained.