Vaisala RVP900

Chapter 7 __________________________________________________ Host Computer Commands
VAISALA______________________________________________________________________ 311
0916-150
7.13 Define Pulse Width Control and PRT Limits
(PWINFO)
The RVP900 is equipped to control the radar transmitter's pulse width and
corresponding receiver bandwidth. There are sixteen pulse/bandwidth
codes, numbered 0 through 15. The association between codes and pulse
widths is completely determined by the needs and capabilities of the
particular radar on hand. In some cases, the zero code might represent 0.25
microsecond pulse width, and in other cases it may represent 2.0
microseconds, and some radars may use all sixteen codes whereas others
provide fewer options from which to choose. The PWINFO command
defines what happens for each pulse width code, but does not actually
select which code is being used. The later function is performed by
SETPWF. For historical reasons, the PWINFO command loads four codes
at a time according to the UpperPW bits: 00 loads codes 0–3, 01 loads
codes 4–7, etc.
The RVP900 drives four TTL output lines (PWBW0 – 3) which are
intended to control the radar pulse/bandwidth hardware. Typically this
control is via relays or solid-state switches in the transmitter and receiver.
The user decides what state the four lines assume for each pulse width
code. This is done using word #1 following the command, which contains
four codes packed into one 16-bit word. The power-up default is to drive
output line N low for a code of N, keeping all other lines high (Input of
7BDE Hex). The flexibility in defining the output bits usually makes the
radar hardware connections very simple. For example, if pulse width
selection relied on choosing one of four relays, then each PWBWn line
could serve directly as a relay driver using the default pattern.
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
| | | | | | | | | | | | | | | | |
| | Bits for –142.22 usec | Input 2
|_______________________________________|___|___|___|___|___|___|
.
.
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
| | | | | | | | | | | | | | | | |
| | Bits for zero range | Input 1025
|_______________________________________|___|___|___|___|___|___|
.
.
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
| | | | | | | | | | | | | | | | |
| | Bits for +142.08 usec | Input 2049
|_______________________________________|___|___|___|___|___|___|