User manual

Code: ENIGMA III User Manual
Edition: 1 Revision: 4
Date: 19/12/2008
Page: 51/97
Here ENIGMA measured a power difference of 20.3 dB. The next step is to set this value:
set PowerDiffH 20.3
Now issue the getadcdiff command again.
getadcdiff
getadcdiff errormsg=null phaseDiffH=123.7 phaseDiffV=0
powerDiffH=0.013 powerDiffV=0
You see that the power difference now is effectively calibrated to 0 (with a very small residual error).
Now you can calibrate the phase difference by issuing:
set PhaseDiffH 123.7
Remark: Important is that you need to calibrate the power difference first, then measure again
and calibrate the phase difference.
In case of a dual polarization system (with two extended dynamic channels) proceed in the same way for
the vertical channel. This option is only available with the ENIGMA IFD+.
6.6 IF signal processing
6.6.1 Matched filter
The matched filter is implemented as FIR filter in the IFD. For coherent on receive radars (Magnetron,
non coded pulse) the matched filter is a digital bandpass filter centered at the (folded if undersampling)
IF frequency with a bandwidth corresponding to the pulse width:
Example:
● IF frequency 60MHz
● Sampling frequency 76.8MHz (undersampling)
● 1µs pulsewidth
The bandpass filter should be centered at 16.8Mhz and have a bandwidth of 1MHz. The stopband
attenuation should be as high as possible. Please refer to the 'Digital IF User Manual' for further details.
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