Vaisala RVP900 User Manual

Chapter 2 _______________________________________________ Introduction and Specifications
VAISALA_______________________________________________________________________ 49
The technique requires that the phase of each pulse be random. Digital
phase correction is then applied in the processor for the first and second
trips. The critical step is the adaptive filter, which removes the echo of the
other trip to increase the SNR. Magnetron radars have a naturally random
phase. For Klystron radars, a digitally controlled precision IF phase shifter
is required. The RVP900 provides an 8-bit RS422 output for the phase
shifter.
2.9.5 Polarization Mode Processing
Polarization processing uses a time domain autocorrelation approach to
calculate the various parameters of the polarization co-variance matrix,
that is, Z
dr
, LDR, PhiDP, RhoHV, PhiDP (K
dp
), etc. In addition, the
standard moments T, V, Z, and W are also calculated. Which parameters
are available, and which algorithms are used to calculate them, depends on
the type of polarization radar, for example, single channel switching,
STAR, or dual channel switching. Vaisala is licensed by US National
Severe Storms Laboratory (NSSL) to use the STAR hardware and
processing techniques and algorithms.
Polarization measurements require special calibration of the Z
dr
and LDR
offsets. The use of a clutter filter for the polarization variables can
sometimes bias the derived parameters. Because of this, the user decides
whether or not to use filtered or unfiltered time series.
2.9.6 Output Data
The RVP900 output data for standard moment calculations consist of mean
radial velocity (V), Spectrum Width (W), Corrected Reflectivity (Z or
dBZ), and Uncorrected Reflectivity (T or dBT). Other data outputs include
I/Q time series, DFT/FFT power spectrum points, and polarization
parameters. The output can be made in either 8-bit or 16-bit format. An
8-bit format is preferred over a 16-bit format for most applications, since
the accuracy is more than adequate for an operational radar system, and the
data communications are reduced by 50%. A 16-bit format is sometimes
used by research customers for data archive purposes. Time series and
DFT are always 16-bit formats. All data formats are documented in
Chapter 7, Host Computer Commands, on page 255.
A standard output is the I/Q time series on gigabit network (1000 BaseT).
These are sent through UDP broadcast to an I/Q archiving system or even
a completely independent parallel processing system.

Vaisala RVP900 Specifications

General

Brand	Vaisala
Model	RVP900
Category	Receiver
Language	English