Beam direction of the difference pattern in a monopulse phased array antenna

Abstract

The beam direction of a monopulse phased array antenna can be changed rapidly by controlling the phase shifters, which is useful in detecting the direction of arrival of radio waves. In monopulse tracking, the null point of the difference pattern is used as the reference for direction determination. However, errors of phase setting, including the quantization error of the phase shifters, give rise to the problem of null shift, that is, the null point shifts from the set direction. This study examines the relation between the phase setting error and the null shift from the statistical point of view and expresses the relation between the two in a simple formula. In the general evaluation function, the position of the element antenna and the excitation amplitude are used as the parameters. Then, an expression is derived by approximating the amplitude distribution over the antenna aperture as a quadratic function, with the result that the evaluation function can be derived without defining the element position. The effectiveness of these expressions is verified by numerical calculation examples. In addition, the minimum change of the beam direction, which determines the angular measurement accuracy of the monopulse phased array antenna, depends on the phase setting accuracy of the digital phase shifters and on the accuracy of the operation unit that calculates the phase to be set in the phase shifters. The accuracies (expressed as numbers of bits) required by the phase shifters and the operation unit so that they can produce the minimum change of the beam direction are investigated, and a simple formula is obtained. In order to verify the results of these investigations, experimental results and numerical calculations are presented. © 2000 Scripta Technica, Electron Comm Jpn Pt 1, 84(1): 68–76, 2001

Development of bread board model for microwave power transmission experiment from space to ground using small scientific satellite

“…Direction error (σ θ ) expressed as follows: [5] [6] (1) (2) where N is number of elements, σ is phase error, λ is wave length, D is diameter of the antenna, θ 0 is the beam direction, respectively. We adopted a 6 bits digital phase shifter, so phase error of LSB=5.625 deg.…”