Search

Crosshole borehole radar measurement is needed to compensate the antenna transfer functions in polarimetric single-hole radar measurement with combinations of a dipole antenna and a cylindrical conducting slot antenna. This paper presents a method to estimate the antenna transfer functions from the single-hole measurement alone. A small dipole model in a homogeneous medium is used to approximate the relationship between the direct coupling wave in the single-hole measurement and the direct wave in crosshole measurement (antenna transfer function). We show that the far field crosshole signal approximately has the same frequency dependency as the time derivative of the direct coupling signal measured via single-hole measurement. We experimentally demonstrate that the measured far field waveforms have good agreement with the time derivative of the measured direct coupling waveform for dipole–dipole and slot–slot arrangements with an antenna separation of 1.6 m. © 2000 Scripta Technica, Electron Comm Jpn Pt 1, 83(11): 11–21, 2000 [ABSTRACT FROM AUTHOR]

A borehole radar is one form of ground penetrating radar which can be used in deep boreholes. We have been developing a directional borehole radar system with a conformal array antenna on a conducting cylinder. In this paper, we propose a 2-D MUSIC algorithm for the circular array of a directional borehole radar, which can be used to estimate the 2-D source location in a plane containing the array. A decorrelation technique is employed and we derive an algorithm which can determine the locations of two coherent sources. Experimental results obtained with the borehole radar show that this algorithm can accurately estimate parameters with a circular array having a radius of 0.03 m, which is much less than the signal wavelength of 0.8 m. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 1, 80(6): 69–77, 1997 [ABSTRACT FROM AUTHOR]

Unwanted electromagnetic waves radiated from equipment making use of electromagnetic energy create numerous societal problems. The prevention of these problems has been studied extensively. In this paper, a method for estimating the location of the unwanted electromagnetic waves is studied. Since it is difficult to make the antenna aperture large especially at low frequencies, a search for electromagnetic wave source via a synthetic aperture technique is proposed. In the estimated electromagnetic source distribution by this method, images similar to the antenna sidelobes appear. It is demonstrated by computer simulation that the images can be suppressed by use of the synthetic aperture method with subarrays or use of Mill's cross method. Discrepancies between the true source location and the estimated location have been found in regard to the synthetic aperture length and the geometrical relationship with respect to the aperture center. It has been found that the antenna configuration with the synthetic aperture length of 10 λ can estimate an electromagnetic wave source within 10 λ square with accuracy of less than 1/4 λ square. Therefore this method is sufficiently practical if the location of the source is restricted somewhat. [ABSTRACT FROM AUTHOR]

It has been brought to the attention of the publisher that an error appeared in the citation of the original Japanese publication of the above article. It should read as follows: Translated from Denshi Joho Tsushin Gakkai Ronbunshi Vol. 79-B-II. No. 9, September 1996, pp. 574–582. We apologize for any inconvenience this may have caused the authors. [ABSTRACT FROM AUTHOR]