Product specifications

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Digital filter nulling
The gated and filtered pulsed IF signal is digitized and sent to DSP for IF
filtering. The remaining pulse spectrum is filtered using custom IF filter
nulls leaving only the center spectral component to analyze. The spacing
between the nulls depends on the IF filter bandwidth, which is adjusted to
align with the PRF. Figure 21 illustrates the effects of digital filter nulling. In
this example, the PRI is adjusted to 1.767 ms to align with the standard 500
Hz IF filter nulls to demonstrate the nulling effects. In actual narrowband
pulse applications the custom IF filter is created to align an arbitrary PRF.
The center spectrum is -75.15 dBm at 5 GHz as indicated with marker 1 in the
top window. Other pulse spectral components are at the same power level as
the center spectrum (marker 2 through 5 in the top window). After the pulsed
IF signal goes through the digital filter, the undesired spectral components
decrease by about 60 to 70 dB (marker 2 through 5 in the bottom window),
while the signal level of the center spectrum is nearly unchanged.
Figure 21. Filter nulling is used to reject undesired pulse spectrum