Figure 1: Pedestal head with slew ring and two redundant drive motors
(Courtesy of Easat Ltd.)
In radar, the pedestal is an assembly of the antenna array. It is sometimes called a turntable and is a device for supporting and positioning the antenna. Typically, the pedestal allows the azimuth and elevation angles of the antenna to be controlled separately or in a coordinated way to permit different methods of scanning to ensure complete scanning of the space with the antenna pattern.
In a pedestal of the radar there are the following assemblies, which are partly duplicated for redundancy reasons:
- a powerful electric motor, which rotates the upper part of the pedestal via a slew ring (in principle via a gear wheel, where the teeth are mounted inside);
- an encoder, that transmits the current position of the antennas alignment to the radar electronics;
- a slipring-unit for powering the rotating part of the pedestal and the antenna and for transmitting control signals;
- for passive antennas: a rotating joint for transmission of the transmitting power and the echo signals.
Figure 2: Pedestal with the slipring unit and the two redundant driver motors of the ATC-radar STAR 2000.