The range is supplied directly in kilometers up to a maximum of 992 km. The trigger rate,
resulting from a given input, is 6 MHz divided by the input value, that is, the input value is
the trigger period in 0.1667 μsec increments. Note that the given rate is bounded against the
minimum PRT allowed for the current radar pulse width.
The SNOISE command bounds the requested starting range of the noise sampling interval.
This is to make sure the noise samples fit within the specified PRT, and within the range
mask hardware RAM. RVP900 sets an error bit when an improper range is requested.
Reissue the SNOISE command periodically to compensate for drift in the RF and A/D
systems.
The noise levels must be measured for the RVP900 to properly process data. This can be
done by issuing the SNOISE at least once after power-up, or by setting the correct values
for the power-up noise levels with the Mt setup command (see 5.2.6 Mt<n> — Triggers for
Pulsewidth n (page 116)). RVP900 does not automatically take a noise sample as part of its
initialization procedure.
The measured
osets are stored internally for all subsequent uses in RVP900. The oset
values may be inspected through the GPARM command, as may the current range and rate
values themselves. When the range or rate are changed, the user must make sure that the
new trigger rate allows at least 32 km following the new noise range. If this requirement is
not met, or if other failures are detected during the noise measurement, appropriate bits are
set in theGPARM latched status word. This word should generally be checked after SNOISE
to make sure that everything worked properly.
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
---------------------------------------------------------------
| | | | | | | | | | | | | | | | |
| | Action |Rat|Rng| | 0 0 1 0 1 | Command
|--------------|-----------|---|---|--------|-------------------|
Rng
If 1, the range in input word 1 is taken as the starting noise range for this and all
subsequent SNOISE calls.
Rat
If 1, the trigger rate in input word 2 is taken as the noise rate for this and all
subsequent SNOISE calls.
Action
Specifies what action is carried out by the command.
0
Compute a new noise sample based on the present IFD input signals.
1
Do not compute a noise sample, but rather, read new noise values from the host
computer and use them for subsequent processing. Four additional input words
supply the noise information, and GPARM words 6, 9, and 44 .. 50 are changed to
reflect the new noise settings.
If the current transmit pulse is a hybrid pulse, and XARGS arguments are supplied,
then the additional arguments set the noise level for the second pulse.
Chapter 8 – Host Computer Commands
253
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