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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