Vaisala RVP900 - Time Series and Doppler Power Spectrum Example; Table 48 Supported Time Series Processing Modes

Table 48 Supported Time Series Processing Modes
Mode Description
DFT/FFT Mode A frequency domain approach that is used for most operational processing
applications.
There are a variety of clutter filtering options, including the Gaussian Model
Adaptive Processing (GMAP) algorithms.
Random Phase Mode
(RPHASE)
A frequency domain approach similar to the DFT/FFT, except that filtering and
extraction of both the first and second trip echoes is supported.
Pulse Pair Processing
(PPP) mode
Within PPP it is possible to first enter the frequency domain to perform spectrum
based clutter filtering.
The fixed and adaptive width clutter filters including the Gaussian Model Adaptive
Processing (GMAP) are available with dual polarization processing. Both of these
clutter filters perform interpolation across the spectrum after ground clutter
spectrum points are removed. Time domain 5-pole IIR filtering with 40 and 50 dB
rejection are also available in PPP mode, but Vaisala recommends frequency-based
filtering.
Batch Mode A small batch of low PRF pulses is transmitted (for example, for 0.1° of scanning)
followed by a large batch of higher PRF pulses (for example, for 0.9° of scanning)
to determine which ranges are likely contaminated by second trip echo. This was
developed to support a US WSR88D legacy requirement.
7.3.1 Time Series and Doppler Power Spectrum Example
The following figure shows the components of the Doppler spectrum, that is, white noise,
weather signal, and ground clutter. Other target types such as sea clutter, birds, insects,
aircraft, surface
trac, second trip echo, and so on may also be present.
• The top part shows the I and Q values for a simulated time series using the Ascope
utility.
• The bottom part shows an example of a Doppler power spectrum for the time series
shown in the upper part of the
figure.
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