Satoru Sugawara

A mm-wave tapered slot antenna with improved radiation pattern

We have proposed a new configuration of Tapered Slot Antenna (TSA) with an improved radiation pattern. The new design has a tapered section expressed by the Fermi-Dirac distribution function. At 60 GHz, the H-plane side lobe level of the antenna is 5-dB lower than that of conventional TSAs such as Linearly Tapered Slot Antennas. We also present a new technique for reducing the width of a TSA without degradation of radiation pattern.

Characteristics of a MM-wave tapered slot antenna with corrugated edges

We discuss how the radiation pattern of a reduced ground plane tapered slot antenna (TSA) is improved by varying the dimensions of a corrugated structure present at the edge of the TSA substrate. Experimental results are given that indicate that E-plane radiation patterns can be adjusted by varying the corrugation structure geometry. We also present calculated analyses of the corrugation structure using the finite-difference time-domain (FDTD) method.

Millimeter wave imaging technologies

Imaging technologies using millimeter (MM) waves offer unique measurement means in many application areas. We discuss here MM-wave focal plane imaging technologies whose resolution is limited by diffraction and also MM-wave scanning near-field microscopy whose resolution is much smaller than operating wavelength. Results of our research on both of these imaging technologies are presented.

Silicon microoptical mirrors to make close parallel beams with conventional laser diodes

We have fabricated two kinds of silicon microoptical mirrors to make optical axes of two high-power laser diodes close at an interval of 100 /spl mu/m, utilizing anisotropic etching of silicon with the self-alignment mask. One of them is a microrectangular prism mirror (MRPM). It has two orthogonal reflection mirrors, composed of polished [110] and anisotropically etched (111) planes of silicon. The other is a micro two-reflection mirror (MTRM). It has two pairs of two reflectors facing each other in parallel. The use of MTRM made the mounting process easier than that of MRPM. The use of the self-alignment mask made mirror surface smoother and it has been confirmed that full widths at half maximum (FWHM) are almost the same with and without reflections by MRPM or MTRM, respectively. It has also been shown that the etched (111) plane has the etching-condition dependence of surface roughness.

A dielectric-loaded broadband antenna with frequency-insensitive E-plane radiation pattern

In this paper, a dielectric-loaded broadband antenna with frequency-insensitive E-plane radiation pattern has been designed. The optimized antenna with a dielectric has more constant and higher gain than the antenna without a dielectric and also has low return loss over wideband. Consequently, it is found that loading a dielectric and designing antenna shape is effective to improve E-plane radiation pattern and return loss simultaneously.

Proposal of Small Broadband Antennas with Improved Return Loss and Radiation Pattern

In this paper, we propose a small broadband antenna with reduced return loss at low frequency. The proposed antenna has a new radiator shape. The characteristics of the proposed antenna are investigated. In addition, the frequency dependence of radiation pattern is examined and another small broadband antenna with improved radiation pattern and return loss is proposed

Proposal of a Radiation Pattern Varying Technique using Short-Circuited Coaxial Structure

A radiation pattern varying technique using short-circuited coaxial structure at a feed point of the antenna is proposed. Short-circuited structure makes it possible to decrease the antenna gain for short-circuited side, and increase for the opposite side. The radiation pattern variance was experimentally observed at broad bandwidth. A radiation pattern variable antenna with diode SW is also demonstrated

Diffuse optical tomography using multi-directional sources and detectors.

Diffuse optical tomography (DOT) is an advanced imaging method used to visualize the internal state of biological tissues as 3D images. However, current continuous-wave DOT requires high-density probe arrays for measurement (less than 15-mm interval) to gather enough information for 3D image reconstruction, which makes the experiment time-consuming. In this paper, we propose a novel DOT measurement system using multi-directional light sources and multi-directional photodetectors instead of high-density probe arrays. We evaluated this systems multi-directional DOT through computer simulation and a phantom experiment. From the results, we achieved DOT with less than 5-mm localization error up to a 15-mm depth with low-density probe arrays (30-mm interval), indicating that the multi-directional measurement approach allows DOT without requiring high-density measurement.