Vaisala RVP900 - Figure 31 Example of a Noisy High Resolution Pr Spectrum

The LOG points are computed at each possible oset within the raw IF samples. At the
nominal 72 MHz sampling rate the spacing between LOG samples are a mere 4.17 m. The
LOG plot gives a very detailed view of received power versus range. Of course, successive
LOG points are highly correlated because successive input data intervals dier by only one
sample point. This is why the LOG plots appear smooth compared to the instantaneous
variation of the raw IF samples.
As the starting oset of the Pr plot is decreased to range 0, you begin to see part of the
burst pulse (the second half of it) appear at the left edge of the plot. This is because the
burst data samples are multiplexed onto the same
fiber cable that carries the IF data
samples. Zero range is defined to occur at the center of the burst window; the latter half of
the burst pulse is visible when the plot begins at range 0.
Noisy High Resolution Pr Spectrum
The following figure shows a Pr display with a frequency spectrum of the received data
samples in a format that is nearly identical to the Ps display.
• The horizontal axis represents the same band of frequencies (half the sampling rate).
• The vertical axis represents power in 10 dB steps. The entire vertical axis is used so that
an overall span of 80 dB is visible.
In this example, the time span is set to 50 μsec, with a 1 m antenna attached to the IF input
so that a broad range of signals (radio stations, electrical noise, and so on) would be
detected.
Figure 31 Example of a Noisy High Resolution Pr Spectrum
Chapter 6 – Plot-assisted Setups
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