User's Manual Part 2

Plot–Assisted Setups
RVP8 User’s Manual
April 2003
4–23
4.6 Pr — Plot Receiver Waveforms
The “Pb” and “Ps” commands described in the previous sections have been used to analyze the
signal that is applied to the “Burst-In” connector of the RVP8/IFD receiver module. The task
that remains is to checkout the actual received signal that is connected to “IF-In”. The goal is to
verify that the received signal is clean and appropriately scaled, and that nearby targets can be
seen clearly. The “Pr” command is used to make these measurements.
4.6.1 Interpreting the Receiver Waveform Plots
An example of a plot from the Pr command is shown in Figure 4–6. The horizontal axis
represents time (range) starting from a selectable offset and spanning a selectable interval. The
data are acquired from a single transmitted pulse, are are plotted both as raw IF samples and as
the LOG of the detected power using the FIR filter for the current pulsewidth.
Figure 4–6: Example of Combined IF Sample and LOG Plot
The IF samples are plotted on a linear scale as signed quantities, with zero appearing at the
center line of the scope. Any DC offset that may be present in the A/D converter is not
removed, and will be seen as a shift in the baseline at higher zoom levels. For example, the
converter’s worst case DC offset of 10mv would appear as a 91-count offset in the 12-bit range
spanning –2048 to +2047. At the x32 or higher zoom scales, this offset would peg the sample
plot off scale. Typically the DC offset will be much less than this worst case value; but the
RVP8 preserves the DC term in the Pr sample plot so that its presence is not forgotten.
The “AC” amplitude of the IF samples will increase wherever targets are present. On top of
these samples is drawn the detected power on a logarithmic scale. Each horizontal line
represents a 10dB change in power. The graph is scaled so that the LOG power reaches the top
display line when the samples occupy the full amplitude span. Using Figure 4–6 as an example,