Vaisala RVP900, User Manual, Page: 470 / 484

DAFC
Digital Automatic Frequency Control.
DFT
Discrete Fourier Transforms
Doppler spectrum width
The standard deviation of the Doppler spectrum in m/s. The spectrum width is a
measure of the shear and turbulence in the radar pulse volume at a given range. See
also
Doppler velocity spectrum (page 468) .
Doppler velocity (v)
Reflectivity-weighted average velocity of targets in the pulse volume. Determined by
phase measurements from a large number of successive pulses. It is assumed that
raindrops and other particles are advected with the wind and have no own motion
except their falling velocity. Also called radial velocity.
Doppler velocity spectrum
The spectrum of the power returned as a function of the Doppler velocity (towards or
away from the radar). The mean of the Doppler velocity spectrum is the mean velocity
computed by the signal processor. The standard deviation of the Doppler spectrum is
the spectrum width (in m/s).
double conversion
Received signal frequency is down-converted in two steps; first to higher intermediate
frequency (IF1) and then to final intermediate frequency (IF2).
dual conversion
See double conversion (page 468) .
dual polarization
Property of dual pol radars. Dual pol radars (also known as polarimetric radars) can
transmit both horizontally (H) and vertically (V) polarized microwaves. In olden days
this happened alternating with a high-speed switch, nowadays simultaneous dual pol
is preferred. Comparing of H and V gives information on hydrometeors.
elevation
The vertical pointing angle of the antenna. 0° is horizontal, 90° is vertical.
ENR
Excess Noise Ratio.
FFT
An RVP signal processing mode based on Fast Fourier Transform. See also PPP
(page 470) .
FIR
finite impulse response
FPGA
field programmable gate array
gain
The measurement of a device's ability to amplify incoming signals.
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