Vaisala RVP900

Chapter 4 _____________________________________________________ TTY Nonvolatile Setups
VAISALA______________________________________________________________________ 121
The "Maximum instantaneous 'PRF'" question allows you to configure the
maximum instantaneous rate at which triggers are allowed to occur, that is,
the reciprocal of the minimum time between any two adjacent triggers.
This parameter is included so that you can limit the maximum DPRT
trigger rate individually for each pulsewidth. Note that the maximum
instantaneous PRF can not be set lower than the maximum number of
pulses per second.
PRF limits: 50 Hz to 20000 Hz
External pretrigger delay to range zero: 3.00 usec
Range Zero is time at which the signal from a target at zero range would
appear at the radar receiver outputs. This parameter adjusts the delay from
the active edge of the external trigger to range zero. It is important that this
delay be correct when the RVP900 is operating with an external trigger,
since the zero range point is a fixed time offset from that trigger. When the
transmitter is driven from the internal trigger signals, those signals
themselves are adjusted (see Burst Pulse alignment procedures) to
accomplish the alignment of range zero.
Limits: 0.1 µsec to 1000 µsec
Range mask spacing: 125.00 meters
The range resolution of the RVP900 is determined by the decimation factor
of the digital matched FIR filter that computes "I" and "Q". This
decimation factor is the ratio of the filter's input and output data rates, that
is, the output rate is some integer divisor of the IFDR Acquisition Clock
(see Section 4.2.1 Mc — Top Level Configuration on page 104).
The ranges that are selected by the bit mask in the LRMSK command are
spaced according to the range resolution that is chosen here. Also, the
upper limit on the impulse response length of the matched FIR filter (see
below) is constrained by the range resolution. If you choose a range
resolution that can not be computed at the present filter length, then a
message of the form: "Warning: Impulse response shortened from 72 to 42
taps" appears.
Limits: 10 m to 1000 m (exact limits depend on other Rx setup values)
Tx Intermediate Frequency: 30.0000 MHz
Rx Intermediate Frequency: 30.0000 MHz
The radar intermediate frequency can be selected separately for each pulse
width, so that different width pulses could occupy different frequency
bands if desired.