Using PRI Prediction to Improve ECM Effectiveness By Scott McDonald & Ken McRitchie Ottawa, Ontario,...

Using PRI Prediction to

Improve ECM Effectiveness

By

Scott McDonald & Ken McRitchie

Ottawa, Ontario, Canada

Visit us at http://www.mc-cm.com

MC Countermeasures Inc.

Sept 04 2Visit us at http://www.mc-cm.com

Overview

• Introduction• Benefits of Prediction • PRED Features• PRED Performance • Timeshare Basics• Applications• Summary


PRI Prediction

•Prediction vs Tracking

•Typical radar environments are complex– Many emitters -scanning/non-scanning

– Conventional pulse, pulse Doppler, etc.

•Focus is on DRFM-based ECM

– other applications such as VCOs also possible

– DRFM generally “single threat” device


Single Emitter

Pulse Train #1

ECM Output Down-Range Up-Range Down-Range Up-Range Down-Range Up-Range Down-Range


A Problem – Interleaved PRI Patterns

Pulse Train #1

Pulse Train #2

ECM Output Pulse Train # 1 Pulse Train # 2 Pulse Train # 1 Pulse Train # 2 Pulse Train # 1 Pulse Train # 2


DRFM Enables Uprange FT

PRI 1 FT

PRI 2 FT

PRI 3 FT

PRI 4 FT

R1

R1

R1

False Target Delay R1


PRI 1 FT

PRI 2 FT

PRI 3 FT

PRI 4 FT

False Target Delay R1

R2

R4

R3

But Only for Constant PRI!


Benefits of PRI Prediction• Works in many cases where trackers won’t • Generate up-range false targets even with

staggered PRI patterns• Compensate for jammer throughput delay• Fade + Fast re-acquisition on scanning

radars• Operate in dense environment

– Pulse train sorting– DRFM write control


RGPI >> PRI, 4 el Stagger

Video_In


(5sec) Fade + Re-Acq

Video_In


PRED Series Features

• Fast “learning”– No a priori data used– Not susceptible to war modes

• 0.5 µs < PRI < 20 ms

• > 128 stagger positions

• Adaptive acquisition

• Prediction < 250 ns


Features (2)

• 4 parallel predictor channels • Real-time de-interleaving • Automatic channel selection,

timesharing, ECM selection• Integrated coherent ECM

– RGPI

– CRBM (v.s. head-to-tail)

– FT Range >> PRI

• Embedded user memory


Jamming 1 of 6

Video_In


Head to Tail

Video_In


CRBM

Video_In


Performance


PRED Block DiagramCRBM 4xCRV

Timeshare

User Interface

ConfigurationRegisters

BIT

39-bit Bi-DirectionalParallel Bus

(10xaddr+27xdata+2xctl)

RF and Time Gate Controller

Ch 0 Ch 2

Ch 3Ch 1

Data Collect

PredictionAlgorithms

Data Collect


Data Collect


Data Collect


High Speed Interface to RF andDRFM sub-systemsDRFM_R, DRFM_W, DDS offset,4 x DDS Gates, video, RF_Tag


Operating Modes

• Acquisition– Adaptive process– One complete pattern frame max.– Multiple threads for more efficient pattern handling

• Verification– Ensures proper PRED lock– User defined # PRIs: usually >10


Prediction Algorithm

Process 2

Process N

Process Configuration

PRI DataAcquisition

...

PredictionArbitrator

Process 1

Predicted PRIPRI


Operating Modes (2)

• Track– Monitors PRI, breaks if error > tolerance– DRFM Write command “gated” to prevent

overwriting memory

• Fade mode– False target strobes generated for defined

period– Fast reacquisition


TG Pre-triggerDetected Video

and RF TagFrom RF Sub-

System

DRFM

JTAGPort PRED

ReadCommands TG

WriteCommands

TG Trigger(previously Video)


Integral FT Generator

Detected Video and RF TagFrom RF Sub-System20-Bit False

TargetRange W ord(s)

Dow n RangeFalse Target

Strobes

DRFM

JTAG PortPRI Predictor

FT Gen

Techniques Generator

DIO

Up RangeFalse

TargetStrobes

PW Meas.RBM

Generator


Adaptive Prediction• Does not require a priori radar information• Responds very quickly – great for long staggers or

small illumination times• Improved performance against scanning radars

– Predictions can be accurate during acquisition of pattern

– fast reacquisition – typically only a few PRI

– increased ECM effectiveness.

• Multiple Adaptive Processes during acquisition– Refine prediction within PRI as needed


Adaptive Prediction


Dwell Shift

Dwell Shift Performance

0

20

40

60

80

100

0 20 40 60 80 100 120 140

PRIs per frame

% C

orr

ect

Pre

dic

tio

ns


Dwell ShiftDwell Shift Performance

0

2

4

6

8

10

12

14

0 10 20 30 40 50 60

PRI #

PR

I Val

ue

(us)

PRI

Correct FT @ -1 us


Challenges• Missing pulses: fades, effective jamming,

scanning radar modes, receiver blanking

• Extra pulses: interleaved pulse trains, jammer OOB response (spurs, harmonics)– Time gating and frequency sorting very

effective

• Sine or wobbulated PRI patterns


(25%) Missing Pulses

Video_In

DRFM_Read


Missing Pulses


Dense Environment

0

20

40

60

80

100

0 10 20 30 40 50 60 70

Interference Duty Cycle (%)

% C

orr

ect

Pre

dic

tio

ns


Sinusoidal PRI patterns


Wobulation/Sine Pattern Tests

• >10,000 waveforms tested (variations about nominal parameters) On average, PRED locked on in ~100 PRI

• Overall accuracy during acq: ~40%

• Overall accuracy during track: ~99%


RF & Time Gating• Composite video sorted and RF windows

assigned dynamically to each channel• Active channel selected based on:

– Signal activity– Scanning/non-scanning priority– ECM: channel not selected if NO_ECM

specified

• Up to 8 RF reject bands defined by user, updated real-time


Timesharing

• (IR&D) application of PRI Prediction

• Use a single DRFM to jam multiple radars simultaneously

• Encompasses both:– Real-time pulse de-interleaving– Real-time control of DRFM Read and Write

• Algorithm calculates optimal allocation


Timeshare Architecture

ECM Select

MUX

PRED Channel #1

PRED Channel #4

Composite Video& RF Words

RF_SELDRFM_W

&DRFM_R

Channel Assignment Manager

TG

RFSortedVideo

ChannelSelect

Signal Type,PRED Status

.

.

.

RF PRED

AgileRF Word


Timeshare, ECM Selection

• 1 of 8 ECM techniques assigned based on:– PRI range (low, medium, high)– PW range (narrow or wide)– Scanning or non-scanning

• Permits selective jamming of specific emitters or radar modes simply with time gating DFD/IFM.


Signal Environment


Signal Environment

Video_In


Timeshare & ECM Select


Auto ECM Selection

Video_In


Jam 1 – 6 of the Emitters

Timeshare Results

0

10

20

30

40

50

60

70

80

90

100

1 2 3 4 5 6

Video Generator

% C

orr

ect

Pre

dic

tio

ns

Tracking EachIndividually

Tracking 1&2

Tracking 1,2,3& 4

Tracking all 6


Benefit of RF Sorting

Deinterleaving Comparison

0

10

20

30

40

50

60

70

80

90

100

1 2 3 4 5 6

Video Generator

% C

orr

ect

Pre

dic

tio

ns

With DFD

Without DFD


Applications - Isolation

• Many antennas compete for little space in most EW installations– Leads to insufficient isolation to transmit and

receive simultaneously– Precludes cover pulse ECM OR– Prevents DRFM contents

from being updated

• Situation corrected with PRI prediction


A Second Problem Situation

• Weapon Systems that use separate Acquisition and Track radars– (Generally) not good enough to jam just the tracker


Timeshare Track & Acq

Timeshare Results: Video #1 Non-scanning

0

10

20

30

40

50

60

70

80

90

100

1 2 3 4 5 6

Video Generator

% C

orr

ect

Pre

dic

ito

ns

Tracking 1&2


RF Agility

• Many non-Coherent threats

• RF Agility can be implemented as:– Switching between preset channels– Spin tuned magnetron

• The process involved in attempting RF prediction is quite similar to PRI prediction


RF Agile Sources


RF Prediction


Adding RF PRED

ECM Select

MUX

PRED Channel #1

PRED Channel #4

Composite Video& RF Words

RF_SELDRFM_W

&DRFM_R

Channel Assignment Manager

TG

RFSortedVideo

ChannelSelect

Signal Type,PRED Status

.

.

.

RF PRED

AgileRF Word


Typical RF Agility• 200 Hz or 5 ms cycle• If PRI < 1ms, can get

shape of curve• RF made "random" by

staggering the PRI• Need to predict PRI

first, then get next RF from curve

8800

8850

8900

8950

9000

9050

9100

9150

9200

0 2000 4000 6000 8000 10000

Time (µs)

RF

(M

Hz)


Summary (1)

• PRI prediction greatly improves the effectiveness of a DRFM in modern EA applications– Prediction circuitry is not standard in most systems

• MC Countermeasures has developed a line of predictors that can be easily interfaced to existing systems– Can be integrated with existing TG

– Provide additional TG capability

– Work around insufficient antenna isolation


Summary (2)

• PRI prediction channels can be used to selectively track or ignore specific emitters.

• PRI prediction reduces the effects of overlapping or missing pulses.

• Timesharing – jam multiple radars with a single ECM asset– Automatic ECM selection (mini-receiver)


Summary (3)

• RF Prediction can be added to a PRI predictor in order to extend the capability of the jammer.

• Chipset to be available in 2005 for OEM requirements.

Questions

For further information, please feel free to contact us at:

MC Countermeasures Inc. http://www.mc-cm.com

39 Robertson Road, Suite 256

Nepean, Ontario, K2H 8R2 Canada

Tel: +1 (613) 721-1552 [email protected]

Fax: +1 (613) 721-1553 [email protected]

Using PRI Prediction to Improve ECM Effectiveness By Scott McDonald & Ken McRitchie Ottawa, Ontario,...

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