Chapter 7 __________________________________________________ Host Computer Commands
VAISALA______________________________________________________________________ 289
When Power Spectrum output is selected, the spectrum size is chosen as
the largest power of two (N2) that is less than or equal to the current sample
size (N). When the sample size is not a power of two, a smaller spectrum
is computed that by averaging the spectra from the first N2 and the last N2
points. The data format is one word/bin/pulse, in the same order as for time
series output. Each word gives the spectral power in hundredths of dB,
with zero representing the level that would result from the strongest
possible input signal (P
MAX
). Thus, the spectral output terms are almost
always negative.
The time series that are output by the RVP900 are the filtered versions of
the raw data, when available. If a non-zero time-domain clutter filter is
selected at a bin, then the I and Q data for that bin show the effects of the
filter. Whenever you need to observe the raw samples, make sure that no
clutter filters are being applied.
In pulse pair time series mode with dual receivers, selecting (H+V) will
produce data in one of two formats according to the "Sum H+V Time
Series" question in the Mp setup section:
- Answering "Yes" results in summed time series from both channels,
but spectra from the DSP will be the averaged spectra from each
channel individually. This allows the IRIS ascope utility to display
either the spectrum-of-sum or sum-of-spectra according to whether
the "Spectra from DSP" button is pressed in the Processing/Gen-Setup
window.
- Answering "No" still produces the usual (BxN) time series output
samples, except that the first half of these samples will be the first half
of the "H" data in their normal order. This will be followed by a zero
sample if (BxN) is odd; followed by the first half of the "V" data, also
in their normal order.
- In other words, only the first halves of the individual "H" and "V"
sample arrays are output by the RVP900. As an example, if you select
25 bins and 100 pulses, then the output data will consist of 1250 "H"
samples (from all bins in the first 50 pulses), followed by 1250 "V"
samples from the exact same set of bins and pulses. This is the more
useful option when custom algorithms are being run on the data from
the two separate receivers.
When the number of output words is large there is a possibility that the
internal buffering within the RVP900 may overflow and data may be lost.
Due to internal memory limitations, the product (BxN) must be less than
12000. A bit in the latched status word (see Section 7.9 Get Processor
Parameters (GPARM) on page 290) indicates when time series overflows
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