Range Parameters Description
Range mask The range mask is passed to RVP9 packed in 512 16-bit words. In each group of 16:
• The least significant bit of each packed word represents the nearest range.
• The most significant bit represents the furthest range.
According to the range bins that are selected in the mask, the signal processor
computes and stores internally a range normalization table which is later used to
convert receiver intensity levels into reflectivity levels in dBZ.
Note that LRMSK implicitly specifies the number of bins to be processed and output.
The maximum bin count is 4200, though depending on the computational intensity
of the configuration, RVP9 may be able to compute fewer bins. If the number of bins
selected in the bit mask exceeds the maximum, the trailing bins are truncated. If the
new mask does not specify any active bins, then a single bin at range 0 is forced on.
The default power-up mask selects 256 bins equally spaced by 1.0 km starting from
0 range.
Range averaging
LRMSK determines range averaging. The upper byte of the command controls how
many consecutive bins are grouped together. For example:
• 0: No averaging
For example, if 100 bits are selected in the range mask and no averaging is
elected. Then parameters are computed at those 100 ranges, and 100 bins of data
are output.
• 1: Pairs of samples are averaged
If the averaging is to 1, samples are taken at the same ranges, but pairs of bins are
averaged together and only 50 ranges would result. Note that the parameters are
averaged by summing the autocorrelations for each bin.
The individual samples that go into each average are taken according to the bits
that are set in the mask, except that they are grouped together so that only one
net bin results from the several data samples. Note that the limitation of 4200
sampled ranges applies to the bin count prior to averaging.
• 255: 256 terms are summed
The range normalization value associated with the averaged bin is computed
according to the midpoint of the first and last sample.
The command discards incompletely averaged bins. Continuing from the previous
example, if the averaging were set to 2 so that triples of samples were summed, then
only 33 bins would be output. This is because the 100- bit mask left a dangling 100th
sample. In the extreme case where there are not enough mask bits to result in even
one complete bin, the RVP900 forces the averaging to zero and turns on a single bin
at zero range.
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
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| | | | | | | | | | | | | | | | |
| Range Avg.(See Text) | | 0 0 0 0 1 | Command
| | | | |
|---------------------------------------------------------------
In the following examples, the ranges listed in Inputs 1 ... 512 assume a 125 km range bin.
RVP900 User Guide M211322EN-J
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