Chapter 4 _____________________________________________________ TTY Nonvolatile Setups
VAISALA______________________________________________________________________ 137
normal AFC parameters (minimum slew, maximum slew, feedback slope)
all resume working properly. The algorithm operates as follows:
- Whenever AFC correction is being applied, the RVP900 calculates
how long it would take to reach the desired IF frequency at the present
rate of change. For example, if we are 1MHz away from the desired
IF frequency, and the measured rate of change of the IF burst
frequency is 20 KHz/sec, then it will be 50 seconds until the loop
reaches equilibrium.
- Whenever the AFC loop is in Track–Mode, but the time to
equilibrium is greater than two minutes, then the "Minimum Slew"
parameter will be slowly increased. The idea is to gradually increase
the starting motor drive whenever it appears that the IF frequency is
not actually converging toward the correct value, that is, the motor is
stuck.
- As soon as the frequency is observed to begin changing, such that the
desired IF would be reached in less than two minutes, then the
"Minimum Slew" parameter is immediately put back to its correct
setup value. The loop then continues to run properly using its normal
setup values.
Manual Frequency Control (MFC) operates unchanged in both of the AFC
servo modes. Whenever MFC is enabled in the Ps command, it always has
the effect of directly controlling the output voltage of the AFC D/A
converter. The MFC mode can be useful when testing the motor response
under different drive levels, and when determining the correct value for the
minimum slew request.
4.2.7 M+ — Debug Options
A collection of debugging options has been added to the RVP900 to help
users with the development and debugging of their applications code. For
the most part, these options should remain disabled during normal radar
operation. These questions are included so that the RVP900 can be placed
into unusual, and perhaps occasionally useful, operating states.
Noise level for simulated data: -50.0 dB
This is the noise level that is assumed when simulated "I" and "Q" data are
injected into the RVP900 via the LSIMUL command. The noise level is
measured relative to the power of a full–scale complex (I,Q) sinusoid, and
matches the levels shown on the slide pots of the ASCOPE digital signal
simulator.
Limits: –100dB to 0dB
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