Vaisala RVP900 - Random Phase Second Trip Processing; Figure 50 Example of Dual PRF Trigger Waveforms

Note that there are a number of low probability pulses. The exact details of the sample sizes
and the trigger hold o time can make the low probability pulses appear to come and go
randomly. This is normal, and is no cause for alarm.
47.0%
47.3%
1.0%
1.0%
1.0%
1.3%
1.3%
SCOPE
100% 50% 50% 49% 2.3% 48.6% 48% 2.3% 2.3% 94.3% 2.3% 2.3%
Figure 50 Example of Dual PRF Trigger Waveforms
7.9
Random Phase Second Trip
Processing
Second trip echoes can be a serious problem for applications when the radar is operated at
high PRF (for example, >500 Hz). Second trip echoes are caused by the range aliasing of
targets. They appear as false echoes on the display, usually elongated in the radial direction.
On Klystron systems they have valid Doppler velocities. On magnetron systems, the Doppler
velocities are not valid, but the noise from the 2nd trip echoes can obscure valid
first trip
velocity information.
RVP900 has optional random phase processing for the filtering and recovery of second trip
echoes. While details of the technique are proprietary to Vaisala, we describe the general
principle and the
configuration options to optimize the algorithm performance.
The information that is used to separate the first and second trip echoes is the phase.
Magnetron Radars
For a magnetron radar, the phase of each pulse is
dierent. When 1st. and 2nd trip echoes
are received simultaneously, the phase of the first trip return is dierent from the phase of
the second trip return.
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