receiver to be connected to the ACU, the file/program tracking works without any beacon
measurement.
8.3.1 The sat-nms Steptrack Algorithm
The principle of satellite step tracking is quite simple: For each axis, move the antenna a small
amount away from the satellite, move it a small amount to the other site and finally point the
antenna to that position where the signal is the strongest. The sat-nms ACU uses an optimized
variant of this method which lets the tracking find the best pointing ('peak') with a minimum
amount of depointing.
Within one step track cycle on one axis, the ACU does several very small steps. Using the
position and beacon level values of all steps in the cycle, the ACU calculates the peak position by
aligning the approximated antenna pattern to the measured points.
This method minimizes the impact of noise and measurement errors to the evaluated peak
position. The benefit is, that the size of depointing steps can be reduced to a very small value.
A tracking cycle consists of 2 .. 4 tests steps. With each step the antenna is moved a certain
angle increment, the beacon level is measured before and after the movement. The angle
increment is an adjustable value, expressed as a percentage of the antenna's 3dB beamwidth. A
typical value is 15% of the (half) beamwidth.
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