User's Manual Part 2
Host Computer Commands
RVP8 User’s Manual
May 2003
6–19
The Command word format for Time Series Mode is:
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
| | | | | | | | | | | | | | | | |
| TSOUT | Spec Type |Unfold | | 1 1 | 0 0 1 1 0 | Command
|_______|_______________|_______|___|_______|___________________|
TSOUT Selects type of data to be output.
00 : 8-bit Time Series 01 : Power Spectrum
10 : 16-bit Time Series 11 : Unused
When the TSOUT bits select “Power Spectrum” then, depending on the current major mode, a
further choice may be needed to select one of several spectral view points. For the Random
Phase major mode the possible values of “Spec Type” are:
0: Raw First Trip 4: Raw Second Trip
1: Whitened First Trip 5: Whitened Second Trip
2: Cleaned First Trip 6: Cleaned Second Trip
3: Final First Trip 7: Final Second Trip
When time series output is selected the output data consist either of (3xBxN) or (2xBxN) words,
depending on the output format, where B is the number of bins in the current range mask, and N
is the number of pulses per ray. Data samples for each bin of pulse #1 are output first, followed
by those for each bin of pulse #2, etc. up to pulse #N. In other words, the data are output in the
same time-order that they were acquired.
In the floating point format, three words are used for each bin:
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
| | | | | | | | | | | | | | | | |
| Exponent | S | Mantissa | (I)
|___________________|___|_______________________________________|
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
| | | | | | | | | | | | | | | | |
| Exponent | S | Mantissa | (Q)
|___________________|___|_______________________________________|
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
| | | | | | | | | | | | | | | | |
| 0 0 0 0 | Log of Power in Sample | (LOG)
|_______________|_______________________________________________|
To convert the floating I and Q samples to voltages: First create a 12-bit signed integer in which
bits zero through 9 are copied from the Mantissa field, and bits ten and eleven are either 01 or 10
depending on whether S is 0 or 1. Then, multiply this number by 2**(exponent–40), where the
exponent field is interpreted as an unsigned 5-bit integer. Finally multiply by the maximum
voltage. The resulting value has 12-bits of precision and a dynamic range of approximately
190dB. The large dynamic range is necessary to cover the full range of data. In summary:
Voltage V
MAX
(Sign, Mantissa) 2
Exponent40
Note that the resulting voltage span is actually 4 V
MAX
. The extra factor of four is built into
the format so that transient excursions above the full scale input voltage can still be encoded
properly. These may arise for time series data that have been processed by an IIR clutter filter.