Vaisala RVP900 - Adjusting Burst Pulse Timing; Table 36 Pb TTY Information Lines

Table 36 Pb TTY Information Lines
Information Line Description
Zoom
Indicates the magnification (in amplitude) of the plotted samples. A zoom level of
"x1" means that a full scale A/D waveform exactly fills the height of the sample
window. Generally, the signal strength of the burst pulse is not quite this high. Use
larger zoom levels to see the weaker samples more clearly. You may zoom in
powers of two up to x128.
PlotSpan
Indicates the overall time span in microseconds of the complete scope display, from
left edge to right edge.
FIR
Indicates the length of the impulse response of the matched FIR filter, and hence,
the duration of the burst pulse sample window. The length is reported both as a
number of taps, and as a time duration in microseconds.
IF
Indicates which of the 5 IF-input sources (SMA edge connectors) is providing the
data being plotted.
Freq
Indicates the mean frequency of the burst, derived from a fourth order correlation
model. The control parameters for this model are set using the Mb command.
See 5.2.1 Mb — Burst Pulse and AFC (page 93).
Pwr
Indicates the mean power within the full window of burst samples. DC osets in the
A/D converter do not aect the computation of the power, that is, the value shown
truly represents the waveform's (Signal+Noise) energy.
DC
Indicates the nominal DC oset of the burst pulse A/D converter. This is of interest
only as a check on the integrity of the front end analog components. The value
should be in the range ± 2.0%.
Trig#1
Indicates the starting time of the first RVP900 trigger outputs. This number varies
as the L and Rsubcommands cause the triggers to slew left and right. If the radar
transmitter is directly fired by an external pretrigger, the pretrigger delay (in the
form PreDly:6.87) is printed instead.
BPT
Shows the present value of timing slew (measured in microseconds) being applied
to track the burst. The slew is 0 initially when RVP900 is first powered up, meaning
that the normal trigger start times are all being used.
6.5.4 Adjusting Burst Pulse Timing
You must calibrate the burst pulse timing separately for each pulse width. Each iteration is
independent.
1. Set up the relative timing for all used RVP900 triggers.
The trigger output lines are interchangeable, and each may be assigned to any function
within the radar system.
For example, Trigger #1 might be the transmitter pretrigger, Triggers #3 and #4
might synchronize external displays, and Triggers #2, #5, and #6 might be unused.
2. Choose an initial impulse response length of 1.5 times the transmit pulse width.
This length is
refined later when the matched filter is designed.
See 6.6 Ps — Plot Burst Spectra and AFC (page 137).
RVP900 User Guide M211322EN-J
136