User manual

Code: ENIGMA III User Manual
Edition: 1 Revision: 4
Date: 19/12/2008
Page: 13/97
When using the frequency domain filtering (FFT and DFT mode) Interpolation or Dual Slope
Interpolation should be used. These filters do not affect weather targets overlapped by clutter
● Set CCOR threshold to –30 dB.
● Select Clutter Micro Suppression Threshold (30-40dB) if you are using range sampling
● Select IQ clutter filter to IQ3.
● Select NOISE | CCOR for CZ threshold flags.
● Click on Apply in the extended SDP settings.
With this parameter settings, clutter will be thresholded (= rejected), when the calculated clutter power is
less than the CCOR threshold level otherwise the measured clutter power is subtracted from the echo. If
you can identify a strong clutter target in the closer area of the radar, observe the difference in the
uncorrected and corrected reflectivity A-Scope.
The results when using Pulse Pair Processing (PPP) or one of the frequency domain processing modes
(FFT or DFT)will be different. The main difference is that the time domain filtering used by PPP is not
adaptive. It will always subtract the power measured at zero velocity. Regardless if there is clutter
present. As an side effect weather at zero (radial-) velocity will also be attenuated. The clutter filter used
by the frequency domain processing modes are adaptive. The filter will adapt to the spectrum (both in
attenuation and width).
Remark: As the frequency domain filters (Interpolation and Dual Slope Interpolation) adapt to the
signal it is not necessary to keep them as small as possible (As would be necessary with the
classical time domain filtering). IQ5 is a good starting value for frequency domain
processing.
Remark: The clutter filter for Pulse Pair Processing should be as small as possible and should be
switched off for higher (clutter free) elevations. A good value for time domain filtering
would be IQ3.
Parameter: ClutterFilter and MaxFilterRange
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