User's Manual

RVP8 User’s Manual
October 2005
TTY Nonvolatile Setups
3–32
The AFC Motor/Integrator feedback loop works properly even if the motor has
become stuck in a “cold start”, i.e., after the radar has been turned off for a period of
time. The mechanical starting friction can sometimes be larger than normal, and
additional motor drive is required to break out of the stuck condition. But once the
motor begins to turn at all, then the normal AFC parameters (minimum slew,
maximum slew, feedback slope) all resume working properly. The algorithm
operates as follows:
S Whenever AFC correction is being applied, the RVP8 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 20KHz/sec, then it will be 50 seconds
until the loop reaches equilibrium.
S 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, i.e., the
motor is stuck.
S 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.
3.2.7 M+ — Debug Options
A collection of debugging options has been added to the RVP8 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 RVP8
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 RVP8 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
Simulate output rays: NO
Answering ”YES” to this question causes the RVP8 to output bands of simulated
data. The bands can occupy a selectable range interval, and span a selectable interval
of data values.