HighByte Low Byte
----------------------
| | |
| Q Sample | I Sample | First Word
| | |
----------------------
----------------------
| | |
| Zero | Log Power| Second Word
| | |
----------------------
The Log Power value is the upper 8 bits of the long format. The other numbers are
produced by the equation:
=
×
128
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 0
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 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
eects of the filter. If you must 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) produces data in one of
two formats according to the Sum H+V Time Series question in the Mp setup section:
• Yes produces summed time series from both channels, but spectra from the DSP is 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 selected in the
Processing/Gen-Setup window.
• No produces the usual (BxN) time series output samples, except that the
first half of
these samples is the first half of the H data in their normal order. This is followed by a
zero sample if (BxN) is odd; followed by the
first half of the V data, also in their normal
order.
Only the
first halves of the individual H and V sample arrays are output by RVP900. As an
example, if you select 25 bins and 100 pulses, then the output data consists 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.
Chapter 8 – Host Computer Commands
267
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