Alpha-Beta Tracker
The Alpha-Beta tracker is shown in the figure below, along with the open loop transfer function G(S) of the continuous equivalent circuit. At sample intervals, T, a height error is measured and applied with scaling to a rate integrator and a position integrator. In the SEASAT-A altimeter the integrators will become digital accumulators. The output of the rate integrator, which is height rate, is applied along with the error signal (scaled by alpha) to the position integrator whose output is the smoothed estimate of height. In the absence of an error signal, the output of the rate integrator will cause the position integrator to ramp up or down, corresponding to the last value of rate. This is characteristic of the Type II servo - the ability to follow a constant rate input without error, or lag.

This excerpt and diagram taken from (MacArthur 1978).


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