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The rotationally symmetric monopole antenna is given by a set of simultaneous equations on the rotationally symmetric surface current of a conductor, separated with respect to the variable of the envelope length on the surface of the rotationally symmetric antenna and the variable in the direction of revolution. The structnre is analyzed in detail by means of an extended moment method based on the present theory. As an application, this analysis is applied to a conical monopole antenna. Studies are performed to find body shapes providing broadband characteristics. It is found that the antennas with lengthwise cross sections approximated by straight lines, ellipses, and circles have an impedance of 50 Q over a wide frequency band. When these shapes are replaced with wire elements for analysis, 16 elements are found sufficient to approximate the characteristics of the rotationally symmetric antenna. Theoretical calculations and experimental results are compared. Agreement is excellent and the method is found useful. S

Two types of broad-band antennas are widely used for electromagnetic interference (EMI) measurements in the frequency range from 30 to 1000 MHz. Log-periodic dipole antennas (LPDA) are mainly used for the range above 300 MHz and biconical antennas for the range less than 300 MHz. These two antennas have linear polarization. However, EMI measurements can sometimes be more conveniently made with an antenna having circular polarization and so we propose an improved LPDA, which has circular polarization. This LPDA has a second array of dipoles so arranged that each dipole of the second array has a quarter-wavelength phase difference from that of the corresponding dipole of the standard LPDA array for the given radiation field. For this reason, we named it a crosselement LPDA. The cross-element LPDA does not need a broadband 90 hybrid junction to produce circular polarization. We calculated the height pattern and the frequency characteristics of the classical site attenuation (CSA) for the cross-element LPDA when used for both transmitting and receiving, as well as the antenna factor. Moreover, we calculated the normalized site attenuation (NSA) when the cross-element LPDA is used for receiving or for both transmitting and receiving.

The tracking interferometer, or the laser tracker, is a laser interferometer with a mechanism to control the laser beam direction to follow a retroreflector ("target"). Applying the multilateration principle, the target's three-dimensional position is measured. This paper proposes a novel concept of "openloop" tracking interferometer, where the laser beam is controlled toward the command target position. Its advantage is in the elimination of the automated tracking mechanism, which may significantly reduce its manufacturing cost. The paper's emphasis is on analytical evaluation of its measurement uncertainty, introduced by the elimination of automated tracking mechanism. A prototype "open-loop" tracking interferometer is developed, and its measuring performance is experimentally investigated. Metrology, Machine tool, Volumetric accuracy.

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