Conical scanning

Some older target tracking radars use the Minimumpeilung to determine the target direction. In English, this type of tracking called " conical scan". The first radar, which worked with this method was the Würzburg D.

This antenna pattern is produced by a rapid rotation of the radiator in the antenna. So that the antenna pattern to rotate about the geometrical axis of the linear antenna. In the optical direction of the antenna itself now forms a funnel-shaped signal minimum.

The aim therefore is always located on the side edge of the antenna pattern, which at this point has a pretty good slope, ie a relatively large signal level change takes place even at the smallest angle changes.

Compared with a simple direction finding, this method has the advantage that when the aircraft leaves the antenna main direction, then the direction is considered and a tracking of the antenna is facilitated.

If the target is exactly on the central axis, then a relatively constant, but very little response is always received. But if the target is also just a little of this axis, then change the level during a antenna beam rotation. The target is located, for example, too far left, then the echo signal will show a maximum when the rotary motor of the antenna feed points to the left and when he points to the right, then a minimum is received. Thus, if the target moves from the minimum slightly to the left, then evaluates a computer or an analog tracking system this information and generates control signals for the servo mechanism of the antenna, which is now also moved slightly to the left, to again receive a constant level of the echo signal will. In this way the direction is determined goal in lateral and vertical angles always automatically and very precisely.

Source

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