In the phased array system, excitation amplitudes and phases based on the design are specified for each antenna element in order to synthesize desired beam scannings and radiation patterns. However, due to fluctuations of antenna and feed network characteristics, the amplitude and phase of each antenna element deviate from the desired values. To correct these deviations, the amplitude and phase of each antenna element must be accurately measured under specific operating conditions. In this paper, we employ variable phase shifters connected to the antenna elements and measure only the amplitude variation of the composite electric field of the entire array when the phase of each element is modified. The rotating element electric field vector method in which the measured amplitude variation is numerically processed for obtaining the amplitude and phase of the particular element is theoretically discussed and experimentally tested for its usefulness. The present method can be easily attained by simply adding software to the computer‐controlled phased array system.

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SEIJI MANO, TAKASHI KATAGI, AND MOT00 MIZUSAWA Abstruct-A thinning method is presented to realize the desired aperture distribution in a planar array antenna with elements fiied on an array lattice. In this method elements to be excited are determined by qnantizing cumulative weights which are calculated from the desired aperture distribution. At f i t , this method is applied to density tapering on orthogonal axes of a planar array. Radiation patterns of the planar array determined by this method are compared with those by the desired amplitude distribution, and the results show good coincidence. Next, this method is extended to density tapering on four axes, that is, orthogonal and diagonal axes of a planar array. Moreover, this method is applied to density tapering with multi-amplitude level elements in order to enhance directive gain of thinned army. Lastly, a rectangular planar array was fabricated, and its radiation patterns were measured. Measured results

This paper discusses the tracking filter that estimates the true values of the states of the target such as position and velocity by Cartesian coordinates with the target position used as the observation value of the radar. A typical example is a Kalman filter or an α‐β filter. A Kalman filter has a good tracking accuracy but a heavy computational load, whereas the α‐β filter has a light computational load and is practical, although it has a problem in tracking accuracy. If the α‐β filter with a light computational load has a tracking accuracy similar to the one for a Kalman filter, this filter becomes even more practical. Therefore, in this paper, the conditions are discussed where the α‐β filter can approximate a Kalman filter. In this paper, the radar coordinates, where the target position vector is one axis, is used for calculation of the smoothing values (estimated values of the states for target motion at the present sampling time). It is proven that the α‐β filter can approximate a Kalman filter if the angular velocity of the target and the rotation of the radar coordinates with the coordinate axis rotated with the target motion are infinitesimal and the process noise (a parameter indicating the ambiguity of the target motion model) is independent and the same between the coordinates. This result indicates that the α‐β filter can approximate a Kalman filter if the target is at a low speed, the target range is large, or the target is proceeding toward the radar in a straight line. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 1, 80(3): 67–77, 1997