Define pulse width control and PRT Limits (PWINFO)
RVP10 can control the radar transmitter's pulse width and corresponding receiver bandwidth.
There are 16 pulse/bandwidth codes, numbered
0 ... 15. The association between codes and pulse widths
is determined by the needs and capabilities of each radar. In some cases, code
0 can represent 0.25 microsecond pulse width, and in other cases it can
represent 2.0 microseconds, and some radars may use all sixteen codes while others provide
fewer options.
The PWINFO command defines what happens for each pulse width code. SETPWF defines selects which code is used.
The PWINFO
command loads four codes at a time according to the UpperPW bits:
00 loads codes 0 ... 3,
01 loads codes 4 ... 7, and so on.
RVP10 drives four TTL output lines
(PWBW0 – 3) which control the radar pulse/bandwidth hardware. Typically
this control is through relays or solid-state switches in the transmitter and receiver. The
user decides what state the four lines assume for each pulse width code 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.
For each pulse width there is a corresponding
minimum trigger PRT permitted. This bound limits the transmitter duty cycle to a safe value
under all conditions. PWINFO sets up these minimum PRTs using
words 2 ... 5 following the command. The maximum frequency
of the internal trigger generator is then constrained at each pulse width to the indicated
rate. This protection applies at all times, that is, during noise sampling, during ray
processing, and during the standby time between rays. The default PRT bounds are 2000, 1000,
750, and 500 Hertz (Inputs of 3000, 6000, 8000, and 12000). If your radar does not use all of
the pulse width codes, it is still a good idea to set the unused PRT limits to reasonable
values. This way protection is still provided if that SETPWF accidentally
selects one of the unused states. If the internal trigger generator is not being used, then
the PRT limits no longer affect the trigger rate and transmitter protection becomes the
responsibility of the user hardware.
 | You can turn off the pulse/bandwidth mechanism by setting the bit patterns and PRT limits all to the same value. |
The PWINFO command can be disabled (for transmitter safety), so that PRT limits cannot accidentally be changed by the host computer. When this is done, RVP10 still reads the five input words, but no changes are made to the pulse width and PRT information. The command I/O behaves the same way, whether enabled or disabled.
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
---------------------------------------------------------------
| | | | | | | | | | | | | | | | |
| |UpperPW| | 0 1 1 1 1 | Command
|-----------------------|---|---|------------|-------------------| 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
---------------------------------------------------------------
| | | | | | | | | | | | | | | | |
| Bits for PW 3 | Bits for PW 2 | Bits for PW 1 | Bits for PW 0 | Input 1
|---------------|---------------|----------------|---------------|
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
---------------------------------------------------------------
| | | | | | | | | | | | | | | | |
| Min Trig Period (0.16667usec Increments) for Pulse Width 0 | Input 2
|----------------------------------------------------------------|
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
---------------------------------------------------------------
| | | | | | | | | | | | | | | | |
| Min Trig Period (0.16667usec Increments) for Pulse Width 1 | Input 3
|----------------------------------------------------------------|
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
---------------------------------------------------------------
| | | | | | | | | | | | | | | | |
| Min Trig Period (0.16667usec Increments) for Pulse Width 2 | Input 4
|----------------------------------------------------------------|
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
---------------------------------------------------------------
| | | | | | | | | | | | | | | | |
| Min Trig Period (0.16667usec Increments) for Pulse Width 3 | Input 5
|----------------------------------------------------------------|