Vaisala RVP900

Chapter 6 ______________________________________________________ Processing Algorithms
VAISALA______________________________________________________________________ 241
supposed to be based on the short PRT interval. The host computer must
therefore be configured so that it can ask for these very high trigger rates.
The duration of the long PRT interval is not specified directly by the host
computer. Rather, the RVP900 "Maximum number of Pulses/Second"
setup parameter is used to compute how much delay to insert in order to
insure that the transmitter's duty cycle is not exceeded. This special
treatment applies only in DPRT mode; all other modes that have uniform
triggers continue to interpret the RVP900 trigger bound as a simple
"Maximum PRF".
Since DPRT-1 mode uses only the short pairs of pulses, it is not possible
to run the "R2" moment estimation algorithms. The RVP900 will return the
GPARM "Invalid Processor Configuration" bit if "R2" is requested in
DPRT mode. The error bit will also be returned if the number of pulses
requested (sample size) is not even. All other error conditions are the same
as FFT mode.
WARNING
Since the RVP900 "Maximum number of Pulses/Sec" is used to enforce
the duty cycle limit, it is essential that it not be overwritten by the host
computer's upper PRF limit, which typically will be much higher. To
insure this, you must make sure that the PWINFO command is disabled
in the RVP900 Mc setup menu. There is no duty cycle protection if you
do not do this.
NOTE
You may still choose to run Dual-PRF velocity unfolding within the
DPRT-1 mode. What will happen is that the short PRT will vary in the
selected 3:2, 4:3, or 5:4 ratio, but the overall duty cycle will remain
constant. The combination of Dual-PRF and DPRT-1 is tremendously
effective in extending the radar's unambiguous velocity interval.