Vaisala RVP900 - Ray Synchronization on Angle Boundaries; Clutter Filtering Approaches; Table 50 Clutter Filtering in Major Modes

7.3.4 Ray Synchronization on Angle Boundaries
The exact number of samples (M) that is used for each time average is usually set when
setting up the operating parameters of RVP900.
The exact value of M that is used for each time average is generally the sample size that is
selected by the SOPRM command.
However, when the RVP900 is aligning its processed rays to AZ/EL angle boundaries, the
actual number of pulses used may be limited by the number that fit within each ray’s
angular limits at the current antenna scan rate. So the antenna scan rate may limit the
number of samples averaged. The number of samples will never be greater than the set
sample size, even if the antenna is scanning at low angular speed that would allow more
samples.
For example, if RVP900 is operating at 1 KHz PRF, 20-deg/sec scan rate, 1° ray
synchronization, and a sample size of 80. Then, if the LSYNC Dyn bit is set, rays consist of a
full 80-pulses ending at each angle and extending back 30-pulses into the previous angle
sector.
However, when Dyn is clear, there are 50 pulses used for each ray (not 80) and those pulses
exactly
fill the scanning angle sector.
More Information
‣
Setup Operating Parameters (SOPRM) (page 239)
‣
Load Antenna Synchronization Table (LSYNC) (page 297)
7.3.5
Clutter Filtering Approaches
The following table shows how each major mode implements clutter filtering.
Table 50 Clutter Filtering in Major Modes
Mode Clutter Filtering
FFT Major Mode Uses frequency domain clutter filters, including GMAP. The power
spectra are restored by interpolating across the gap of removed
spectral points.
PPP Mode Used only for dual polarization.
For eciency, PPP computations are performed using DFT techniques
that are algebraically equivalent to the traditional time-domain
algorithms. The fixed width and variable width spectral clutter filters
can be used in PPP mode; however, the power spectra and the spectra
of cross- correlations are not interpolated.
Random Phase Mode Uses frequency domain clutter filters, including GMAP. The power
spectra are restored by interpolating across the gap of removed
spectral points.
Batch Mode Uses a simple DC removal for the small batch clutter filter. The high
PRF large batch is then processed using frequency domain clutter
filters, including GMAP. The power spectra are restored by
interpolating across the gap of removed spectral points.
Chapter 7 – Processing Algorithms
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