AFC
You can independently choose a sub-interval of burst pulse samples that are used by the
AFC frequency estimator.
The AFC feedback loop is not constrained to use the same set of samples that are chosen for
the FIR filter window. The FIR window typically is longer than the transmitted pulse, and
thus, the samples contributing to the frequency estimate includes the leading and trailing
edges of the pulse. These edges tend to have severe chirps and sidebands, compared to the
more pure center portion of the pulse.
The AFC frequency estimate (which is power weighted) could be misled by these edges and
might not tune to the optimum center frequency if they were included.
Triggers
The lower portion of the plot shows the triggers output by RVP900. The number of triggers
plotted match the number of
user-defined output triggers set in the Mt menu, with
Trigger #1 at the top. They are drawn in their correct polarity and timing relative to each
other, and relative to the burst sample window. The sample window is always drawn in the
center of the overall time span. Depending on the PlotSpan and location of the trigger
edges, triggers that do not vary within the plotted time span appear as
flat lines.
RVP900
defines Range Zero to occur at the center of the burst sample window. This also
defines the zero reference point for the starting times of the six programmable triggers. For
example, a trigger whose starting time is zero is plotted with its leading edge in the exact
horizontal center of the display. Knowing this convention makes the absolute value of the
trigger start times more meaningful.
6.5.2
Pb Subcommands
The list of subcommands is printed on the TTY:
Available Subcommands within 'Pb':
I/i Impulse response length Up/Dn
A/a & S/s Aperture & Start of AFC window
L/l & R/r Shift triggers left/right
T/t Plot time span Up/Dn
Z/z Amplitude zoom
> and < Start/Stop logging to rvp9-pb.log
% Toggle between IF input channels
B/b BP Tracking On/Off (temporary)
+ Hunt for missing burst
- Single Step
These subcommands change the matched filter's impulse response length, shift the radar
triggers, and alter the format of the display.
RVP900 User Guide M211322EN-J
134
To Next Page
Loading...