PRI and RF Prediction Enabling Technology By Ken McRitchie, Rémi Gauvin & Scott McDonald Ottawa,...

PRI and RF Prediction

Enabling Technology

ByKen McRitchie, Rémi Gauvin & Scott McDonald

Ottawa, Ontario, Canada

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

MC Countermeasures Inc.

AOC Virginia Beach 2005 2Visit us at http://www.mc-cm.com

Overview

• Introduction• Electronic Attack Problem: Pulse to Pulse

Agility• What is PRI & RF Prediction?• Prediction in a Corrupt or Multi- Emitter

Environment• Prediction Applications• Summary


Good Radar Design

• PRI changes help eliminate blind speeds and ambiguous ranges in MPRF and MTI radar modes

• RF changes help de-correlate and hence reduce sea clutter

• Both are effective ECCM/EPM


The EA Task

• Provide effective jamming in a typical radar environment:

– Many emitters: interleaved pulse trains

– Radar TX misfire: missing pulses

– Scanning modes: short illumination time

– PRI and/or RF agility: stagger, sliding, sine, jitter

– RF jitter may be sinusoidal, but generally random, non-coherent radars


Noise - SOJ

• Bandwidth tailored to radar’s RF agility bandwidth: 10’s to 100’s MHz

• Complete range masking so PRI agility not a factor

• Need lots of power, dedicated aircraft


Deception - SPJ

• Frequency Memory Loop– Limited delay due to noise build-up after few

times around loop, generally 10 us max– Restricted to down-range false targets only– Negated by leading edge track, guard gates


Deception - DRFM

• DRFM– Indefinite delay, enables full PRI delay so up-

range false targets are possible– Initially developed for pulsed Doppler radar– Ok for high PRF constant PRI modes– Rendered ineffective by pulse-pulse agility

common in low or medium PRF modes


Problem - Agility

• PRI Agility:– Limits deception based system to down range

capability

• RF Agility:– Limits deception based system to down range

capability– Noise jamming requires high power / wide

bandwidth


Staggered PRI

Two Frames of a 5 - Element, 25 - Position Staggered Pattern

0

1

2

3

4

5

0 5 10 15 20 25 30 35 40 45 50

PRI Stagger Level

PR

I Ele

me

nts


Without Prediction Only Down-Range FT Are Possible

Staggered PRI

PRI A FT

PRI B FT

PRI C FT

False Target Delay Range 1

False Target Delay

False Target Delay

Range 2

Range 3


PRI Prediction

• To take full advantage of DRFM, TOA of next pulse is required

• Even with prediction, need to adjust DRFM delay for each pulse

• Hence, need to closely integrate techniques generator with Predictor


Up-Range Targets

Variable Delay Creates Up-Range FT

PRI A FT

PRI B FT

PRI C FT

False Target Delay 2

False Target Delay 3

Range 1

Range 1

False Target Delay 1 Range 1


Benefits of PRI Prediction

• Compensate for jammer throughput delay

• Fade + Fast re-acquisition on scanning radars

• Improve low isolation performance

• Improved ECM– RGPI– CRBM – RGPI/O >>PRI


Achieving PRI Prediction

Multiple Parallel Processes

Process 2

Process N

Process Configuration

PRI DataAcquisition

...

PredictionArbitrator

Process 1

Predicted PRIPRI


RF Agile Sources

From: Radar Technology Encyclopedia, D.K. Barton & S.A. Leonov editors, 1997


Sine RF, Staggered PRI

8800

8850

8900

8950

9000

9050

9100

9150

9200

0 2000 4000 6000 8000 10000

Time (µs)

RF

(M

Hz)


Sine RF, Staggered PRI


RF Agility

• With RF prediction in addition to PRI prediction:– Fast tuning VCO can be used to generate

consistent false targets– Switch frequency at halfway point in PRI


Why RF Prediction?

• Because DRFM generates false targets by delaying a copy of the previous radar pulse, any RF agility is fatal

• Even with prediction, up-range false targets are at the wrong frequency

• Wide Bandwidth / High Power needed for noise jamming


Benefits of RF Prediction

• Smarter noise jamming

• Generate up-range false targets that integrate non-coherently

• Greatly reduce power required for effective ECM, possibly by 10-20 dB

• Provide training for RF agile radar modes


Achieving RF Prediction

• Isolate agile emitter first

• Stagger RF:– Track PRI & RF

independently in parallel

• Sine RF:– RF requires PRI

prediction input


System Integration

Predictor TG

DRFM

VIDEO&

RF TAG

Write

Trigger

Predicted RF

Modulated Output

Output Control

RF IN

Output Control

Blanking / Look ThruControl

ReadRead

RF OUT

VCO


Test Setup• Can Generate Complex

Video Environment– 6 independent emitters

• Predictor Control• Predictor Performance

Assessment• Pre-trial Parameter

Adjustment & Optimization


Video Generation Features

• 6 Emitters, each with :– Illumination and scan control– Multiple bursts of complex staggered or sine

PRI– RF and PW Control


RF Prediction Accuracy

• Preliminary results for sine RF prediction

• Main sources of error are:– DFD measurement error– Prediction error– VCO tuning error

• Prediction error almost totally dependent on DFD error: 90% of predictions within DFD error limits


Sine RF Prediction• PRI: 2.333 ms• RF mean: 9100 MHz• RF dev: 200 MHz• RF period: 100 ms• DFD res: 1 MHz• DFD error: 0

0

10

20

30

40

50

60

70

80

90

100

-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10+

Error (MHz)

% o

f P

red

icti

on

99% < 1MHz


Sine RF Prediction• PRI: 2.333 ms• RF mean: 9100 MHz• RF dev: 200 MHz• RF period: 100 ms• DFD res: 1 MHz• DFD error: 1.5 MHz

0

5

10

15

20

25

30

35

-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10+

Error (MHz)

% o

f P

red

icti

on

97% < 3MHz


Sine RF Prediction• PRI: 2.333 ms• RF mean: 9100 MHz• RF dev: 200 MHz• RF period: 100 ms• DFD res: 1 MHz• DFD error: 3 MHz

0

5

10

15

20

-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10+

Error (MHz)

% o

f P

red

icti

on

91% < 5MHz


RF Agility Demonstration

Sinusoidal RF Agile Emitter with:

Mean RF of 9.1 GHz

Deviation of 150 MHz

Cycle Time of 1.667 ms

Mean PRI of 400 us

Lock time = 46 PRI


Lock Time = 18.4 ms




Mean RF of 9.1 GHz


Cycle Time of 50 ms

Mean PRI of 2.333 ms

Input Error Versus Output Error


± 10 MHz

DFD (Input) Error VCO Tuning (Output) Error Visit us at http://www.mc-cm.com


± 10 MHz





Mean RF of 9.1 GHz


Cycle Time of 50 ms

Mean PRI of 2.333 ms

Lock Versus Output Error


Lock

Acq / Lock VCO Tuning (Output) Error Visit us at http://www.mc-cm.com


Lock



Implementation Challenges

• Multi-Signal Environment

• Dropped Pulses – By the Radar or Receiver

• System Limitations– Non-Simultaneous Transmit / Receive


Example Signal Environment


Example Signal Environment (2)


Prediction Challenge

• Accounting for Dropped and Interfering Pulses– Interference can be removed using:

• RF, AOA, PW or Expected Time of Arrival

– Missing Pulses can be Added using:• Expected Time of Arrival

• Filtering by Expected TOA Makes SenseVideo Signal X Y

Expected TOA

False Target

X denotes dropped pulse and Y denotes interfering pulse


Pulse Train De-interleaving

• Multiple parallel PRI prediction channels permit real time de-interleaving

• Signals present on their own at least part of the time for pattern acquisition

• Multiple scanning emitters, even with 1 or 2 non-scanning emitters

• Can select single emitter to jam based on PRI, PW and pattern length

• Or timeshare, first come first served


Acquisiton(MAP) CPU’s

TrackCh5

TrackCh4

TrackCh3

TrackCh2

TrackCh1

TrackCh0

Video PulsePre-Processor

Track Channel Selection Logic

AndPre-trigger Generator

Lookthru Generator

User SelectCriteria

Timeshare

User Configuration

Video_In

DRFM_WDRFM_RLockFadeLook_ThruExpctd_VideoStagger_PositionEM_ID

Constant - Dwell Shift Channel

Adaptive Acquisition

TDDTime Domain De-interleaving


TDD ResultsSelecting 1 Emitter at a Time

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5Emitter #

%

Predictor Effectiveness

Present Alone


TDD ResultsSelecting 1 Emitter at a Time

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5Emitter #

%


Present Alone


Effects of Dropped PulsesSelecting Emitter 2 - Varying Drop Outs

0

10

20

30

40

50

60

70

80

90

100

0 2 5 7 10Drop Out %

% O

vera

ll



Effects of Dropped PulsesSelecting Emitter 2 - Varying Drop Outs

0

10

20

30

40

50

60

70

80

90

100

0 2 5 7 10Drop Out %

% O

vera

ll


Acquired on First Scan


Application: System Control

• Controlling a Receiver / Transmitter using the Look-Through Method– Non coverpulse technique

– Cover Pulse Technique

Video Signal

Receiver Enable

Transmitter Enable

Video Signal

Receiver Enable

Transmitter Enable


Application: Timesharing

• Use a single DRFM to jam multiple (scanning) radars simultaneously

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

• Algorithm calculates optimal allocation based on signal present, predictor accuracy, first come first served, scan priority


Timeshare Application

• Weapon Systems that use separate Acquisition and Track radars– Acq can provide good set-on to 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


Application: Timeshare


Application: Fade + Re-Acq


Application: Head to Tail


Application: CRBM


Application: RGPI >> PRI


Application: ESM / RWR

• A Multi-Channel Predictor used to de-interleave the Received Video could greatly speed up the identification of threats in order to begin jamming sooner

• Predictor could act as a real-time filter for known emitters and enable the ESM / RWR system to process the unknown faster


PRED-5 Features

• Small 3” x 6” PMC format• Pod or lab use• 4 or more parallel channels – multi-threat

capability• Adaptive Acquisition• Constant, dwell shift, sliding, stagger (> 192

pos), embedded sine• Add or improve ECMs• RF prediction can be used to control VCO


PRED-5 Features• Time domain or RF de-interleaving, timeshare &

controller• Embedded user memory• Available soon as chip set: Stratix II FPGA plus flash

memory

33 mm x 33 mm Chip PMC Card


Prediction:Summary (1)

• No a-priori radar information is required– Real-time “learning”

• Easily added to a system– Variety of form factors

• Solves systems issues

Agile threatsScanning radarsMissing Pulses

Antenna isolationDRFM contaminationExtra pulses


Summary (2)

• Applications Include:– Real-time de-interleaving– Rx/Tx switching (look-through)– Advanced ECM functions

• Up-range false targets

• CRBM

• CRV

– ECM Timesharing among multiple emitters– ESM/RWR pre-filter


Acknowledgement

The authors would like to acknowledge the contributions of the other members of the MC Countermeasures team including:

• Dan Grise

• Colin Jackson

Questions

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

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

260 Hearst Way, Suite 207

Kanata, Ontario, K2L 3H1 Canada [email protected]

Tel: +1 (613) 592-0818 [email protected]

Fax: +1 (613) 592-2818 [email protected]

PRI and RF Prediction Enabling Technology By Ken McRitchie, Rémi Gauvin & Scott McDonald Ottawa,...

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