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Osipov A.,German Aerospace Center | Kobayashi H.,Niigata University | Suzuki H.,Keycom Corporation
Asia-Pacific Microwave Conference Proceedings, APMC | Year: 2010

An improved approach to determination of radar cross section (RCS) of electrically large targets from the scattered field measured with a monostatic radar over a circle in the near-field of the targets is presented. The frequency- and azimuth-domain scattering data are used to calculate a reflectivity map (radar image) of the target, from which RCS of the target is determined. The characteristic features of the proposed version of Near-Field-to-Far-Field Transformation (NFFFT) are the use of the calibrated signal from the network analyzer as the input data in the transformation and an improved focusing operator for producing reflectivity maps. The combination of these features is expected to result in a practical and more accurate approach to the analysis of scattering properties of electrically large targets. © 2010 IEICE Institute of Electronics Informati.


Osipov A.,German Aerospace Center | Kobayashi H.,Niigata University | Suzuki H.,Keycom Corporation
IEEE Transactions on Antennas and Propagation | Year: 2013

An improved version of the near-field-to-far-field transformation (NFFFT) for determining the radar cross section (RCS) of electrically large targets from the scattered field measured with a monostatic radar over a circle in the near field of the targets is presented. The characteristic feature of the proposed NFFFT is an improved imaging operator which is derived by requiring that the integral transformations involved in the NFFFT scheme be self-consistent for every electrically small scatterer. The presented NFFFT version is expected to lead to more accurate RCS values for strongly asymmetric targets measured at smaller facilities. © 2012 IEEE.


Kobayashi H.,Niigata University | Osipov A.,German Aerospace Center | Suzuki H.,Keycom Corporation
2011 30th URSI General Assembly and Scientific Symposium, URSIGASS 2011 | Year: 2011

An improved image-based circular near-field-to-far-field transformation (NFFFT) developed recently by the authors for smaller measurement facilities and for targets with pronounced scattering centers offset from the center of the imaging area is extended to a cylindrical scanning surface. Scanning over a surface instead of a circle permits RCS estimations for targets whose size in the direction perpendicular to the measurement plane is comparable to their extension in the measurement plane. The approach consists in near-field imaging of the target, followed by integration of the image. The focusing operator, which is used to generate the image, is built in such a way so that the image of an electrically small PEC sphere is exactly the delta function. The paper describes the effect of various transformation parameters such the sampling rates in the input data and in the image domain on the quality of RCS estimations. © 2011 IEEE.


Osipov A.,German Aerospace Center | Kobayashi H.,Niigata University | Suzuki H.,Keycom Corporation
Asia-Pacific Microwave Conference Proceedings, APMC | Year: 2012

An improved version of the cylindrical near-field-to-far-field transformation (NFFFT) with computational complexity comparable to that of the circular NFFFT is described. Instead of producing a 3D radar image the proposed approach generates a 2D projection of the image on the plane, in which the radar cross section is to be determined. The imaging operator is modified so as to allow probes with directivity patterns and scanning surfaces of smaller radii. © 2012 IEEE.


Suzuki H.,Keycom Corporation | Tamukai K.,Keycom Corporation | Yoshida N.,Keycom Corporation | Ohya H.,Keycom Corporation | And 2 more authors.
Health Physics | Year: 2010

The aims of this study were to develop and improve the sensitivity of an electron spin resonance (ESR) spectrometer and to demonstrate its functionality for dosimetry in measuring ESR signals from radiation-exposed fingernails. The newly-developed spectrometer was a lightweight (22 kg) one-box ESR device with a resonator showing a Q-factor higher than that of a previous Keycom model, which is quieter, without influence from magnetic modulation, and contains a fingernail positioner. The authors obtained the best measurement result after the cavity Q-factor was increased to more than 7,200 by continuous polishing of the inner surface of the cavity using deerskin. The common mode noise of "magic T" was also successfully decreased to as low as one-half by completely tuning the arm balance. Moreover, the flatness of the modulated magnetic field was increased by as much as two-fold by changing the coil conformation. These efforts markedly decreased the noise level and extended downwardly the linear portion of dose dependence. © 2010 Health Physics Society.

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