Figure 2-27.—WSR-88D antenna, pedestal, and radome.
TRANSMITTER.— The transmitter is an
amplifier that generates high-powered pulses which
are then radiated by the antenna. By producing nearly
triple the power of earlier radars, the transmitter is the
driving force behind the WSR-88D sensitivity. The
transmitter has an operating frequency range of 2,700
to 3,000 MHz (2.7 to 3.0 GHz).
RECEIVER.—Backscattered energy generally
travels many miles before returning at a fraction of its
original strength. This makes it difficult to interpret.
Much like a stethoscope helps a doctor hear sounds
from deep within your chest, the receiver boosts signal
strength of backscattered energy to levels at which the
radar can extract crucial target information. Amplified
energy is then routed to the signal processor.
SIGNAL PROCESSOR.—The signal processor
is the first of four computers within the WSR-88D to
encounter radar data. Here, data coming from the
receiver is digitized, and contaminants, such as range
folding and ground clutter, are reduced or eliminated.
This preprocessing converts raw (analog) data into a
digitized "base data" format.
RDA Special Processes
The significance of range folding and ground
clutter were discussed earlier in this chapter. Two
special features of the RDA signal processor include a
range unfolding process and a ground clutter filtering
process.
RANGE UNFOLDING.—The process of
cleaning up range folded data must begin by
comparing each echo to previous scans. If continuity
exists for an echo, the target is considered real and the
test is terminated. However, if an echo has
mysteriously appeared with no prior history, a
secondary test is performed. In such cases, the signal
processor compares mystery echoes to energy received
from beyond the radar’s displayable range. Through
pattern matching, it determines the likelihood of each
target’s true existence, or the probability that such
targets are a result of range folded data. If range folding
is confirmed, false echoes are removed from products.
If the processor is unsure, suspect areas are shaded
purple. This purple area is easily recognized and alerts
you to the possibility of range folding. When
preprocessing is complete, data is transmitted to the
RPG.
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