Vaisala RVP900 - Figure 22 Recommended Receiving Circuit for the Coax Uplink; Figure 23 Timing Diagram of the IFD Coax Uplink

Max913
or equiv.
Received
TTL
Signal
+5V
GND
GND
Coax
Uplink
Input
Figure 22 Recommended Receiving Circuit for the Coax Uplink
The uplink signal shown in the following figure is periodic at the radar pulse repetition
frequency, and conveys two distinct information types to the IFDR. The signal is normally
low (to minimize driver and termination power), but begins a transition sequence at the
beginning of each transmitted pulse.
1 2 3 4 5 6 7 8 9 10...
Figure 23 Timing Diagram of the IFD Coax Uplink
The first part of each pulse sequence is a variable length burst window that is centered on
the transmitted pulse and has a duration Ʈ
burst
approximately 800 nanoseconds greater
than the length of the current FIR matched
filter. The burst window defines the interval of
time during which the IFDR transmits digitized burst pulse samples, rather than digitized IF
samples, on its downlink. The exact placement and width of the burst window depends on
the chosen trigger timing and digital
filter specifications, usually through the Pb and Ps plot
setup commands.
After the burst window, there is a fixed-length sequence of 25 serial data bits that convey
information from the IFDR. The following table shows the interpretation of the serial data
bits.
Chapter 4 – RVP Hardware
81