Chapter 2 _______________________________________________ Introduction and Specifications
VAISALA_______________________________________________________________________ 27
2.6 RVP901 IFDR
0916-005
Figure 5 RVP901 IFDR IF Digital Receiver
The 16-bit IFDR is a sealed unit for optimum low-noise performance. The
unit is carefully grounded and shielded to make the cleanest possible
digital capture of the input IF signal. Because of this, the IFDR achieves
the theoretical minimum noise level for the A/D convertors.
The possible inputs to the IFDR are:
- IF video signals—There are four A/D convertors used for received
waveforms. Single polarization radars receive on ADC-A input. For
dual-polarization radars, ADC-A is used for the primary polarization
(usually H) and ADC-B for the secondary (usually V). The extra
channels allow very wide dynamic range (WDR) applications for
single and dual-polarization radars.
- The IF burst pulse sample for magnetron or IF COHO for Klystron is
received over ADC-E.
- Optional reference clock for system synchronization. For a Klystron
system, the COHO can be input. Magnetron systems do not require
this signal.
- Trigger input or output is available on two 5 V 50 driver/receivers.
All of these inputs are on SMA connectors. The IF signal input is made
immediately after the STALO mixing/sideband filtering step of the
receiver, where a traditional log receiver would normally be installed. The
required signal level for both the IF signal and burst is +8 dBm for the
strongest expected input signal. A fixed attenuator or IF amplifier can be
used to adjust the signal level to be in this range.
Digitizing is performed for both the IF signal and burst/COHO channels
from a user-selectable range of 50 to 100 MHz at 16-bits resolution. This
provides 92 dB to 105 dB of dynamic range (depending on pulse width)
without using complex AGC, dual A/D ranging, or down mixing to a lower
IF frequency. The five individual A/D convertors are time synced within 1
nanoseconds. This ensures sampling in multiple channels is of the nearly
equivalent targets.
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