RBM (Head-to-Tail) v.s. CRBM

Many jammers use range bin masking (RBM) techniques but few actually generate truly coherent range bin masking (CRBM).  In fact prediction is the only reliable method of ensuring coherency for long PRI and/or short pulses - this is the true test for a bin masking technique.

Most RBM techniques are generated by replaying copies of the radar pulse in a head-to-tail fashion.  The first clip shows that the downrange copies (i.e. those to the right of the detected video) are being generated consistently in the same spot from PRI to PRI as desired.  Unfortunately, due to accumulating timing errors, the uprange copies appear at different ranges from PRI to PRI.  This leads to a loss of coherency, a loss of integration in the radar receiver and results in reduced effectiveness.  This clip also shows what happens when the jammer's detected video is blanked for a few PRI.  The accumulating time errors result in total loss of coherency for the blanking interval.

Coherent range bin masking (CRBM), when generated by a PRI predictor, ensures that the copies of the radar pulses are placed in the correct locations for EACH PRI.  The second clip clearly shows the level of improvement in coherency that results.  As in the first clip, the detected video is blanked for a few PRI to show the effects.  Due to prediction, the timing errors are minimized and a coherent ECM continues to be generated even with the
receiver blanking applied.

In each of the videos, the top (yellow) trace of the oscilloscope shows the video signal input to the PRED.  The bottom (blue) trace shows the output of the PRED which can be used as the DRFM_Read strobe or to modulate a VCO.

click here to begin the head-to-tail video  

click here to begin the CRBM video