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Introduction
PRI prediction
enables a jammer to generate up-range false targets even
when an emitter makes use of staggered PRI patterns. Some
ECM systems employ PRI trackers; this isn’t the same thing
as PRI prediction – although PRI tracking part of the
prediction algorithms, it is only one aspect of PRI
prediction. The enhanced prediction algorithms offer
improved performance when the system is operated in
environments containing either extra or dropped pulses.
Prediction also allows for a variety of new features
including look-through generation, additional ECM
techniques, ECM timesharing among multiple emitters,
real-time pulse train de-interleaving and fast
re-acquisition of recently tracked patterns.
Previous MCCM
PRI Predictors such as the PRED-5A were designed to make use
of RF tag information provided by the host system to help in
the de-interleaving process. Many ECM systems do not
contain frequency measurement devices such as IFM or DFD’s.
This makes the job of a PRI predictor much more difficult as
the only information available for de-interleaving is time
domain measurements. MC Countermeasures Inc. has developed
a set of unique algorithms, incorporating both hardware and
software elements, that are optimized for the tasks of
de-interleaving and predicting complex PRI patterns when no
RF information is available.
The basic
architecture of the PRED in this configuration is
quite similar to the multi-channel PRED-5A. The detected
video signal is passed through a “Video Pre-processing”
block that where the hardware-based de-interleaving
functions are implemented. PRI measurements are made and
the MAP (Multiple Adaptive Processes) acquisition algorithms
are applied in order to acquire the PRI patterns. Once the
patterns are acquired they are assigned to one of the track
channels – there are six channels for tracking staggered PRI
patterns and an additional channel dedicated to constant PRI
patterns. The control logic implements a timeshare
function, look-throughs and generates an up-range strobe
output that can be used to pre-trigger the host systems
techniques generator.
The PRED PRI
Predictor can be used in several modes. Using simple
commands from the host ECM system, The PRED can be
programmed to:
-
select a
single emitter for jamming in a multi-emitter
environment,
-
select
multiple-emitters for simultaneous time-shared ECM
(controlled by the PRED), or
-
select and
jam all emitters detected on a time-shared basis.
This example
shows how the PRED can be used to isolate a single emitter
(characterized by a 5-element, 25-position staggered PRI
pattern) from a multi-emitter environment and then generate
appropriate signals that will:
-
Control a
DRFM to write ONLY pulses from that emitter into memory
-
Control a
DRFM or TG to generate up-range false targets for that
emitter
-
Control the
system to look through the jamming in a periodic fashion
in order to refresh the DRFM contents and to ensure that
the signal is still present.
The PRED has been programmed
to:
-
acquire the
5-element/25-position PRI pattern in 2 frames (ie 50
pulses)
-
verify
tracks upon (fast) re-acquisition using only 5 PRI
-
generate
look-through commands one out of every 8 pulses
-
Continue
generating Expected_Video pulses for 5
pulses after a loss of signal
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