Short-Wave Infrared Dual Band Laser Countermeasure System

1. Short-Wave Infrared Dual Band Laser Countermeasure System Reporter：Huei-Kai Lai Adviser ：Dr. Der-Chin Chen 2013 / 12/19

2. Outline • Abstract • Motivation • Literature Reviews • Electro-Optical Countermeasures • In-Band and Out-of-Band technique • Jamming Methods on Laser Rangefinder • Classification of Deception Jamming Methods • Active Positive Deviation Jamming • Passive Positive Deviation Jamming • Pulsed Time of Flight Laser Range Finder • Laser Ranging Equation • Estimation Effective Range • Effects of Atmospheric Attenuation • Estimation of Counter Distance • Estimation of Detecting Distance

3. Outline • System Structure • Analyze Time-of-Flight Signal • The Countermeasure System Structure of Laser Range Finder • Infrared Receiver-Photodiode • Infrared Receiver-Transimpedance Amplifier (TIA) • Infrared Receiver-Auto Gain Control • Recognition circuit -Inverting Schmitt Trigger • Recognition circuit-Pulse Stretching • Recognition circuit -Frequency to Voltage • Analog to Digital Converter + MCU + LCM • Laser Diode Laser Driver • Experimental Results and analysis • Conclusion and Future Work • Reference

4. Abstract • The purpose of this research is to construct the countermeasure system of laser range finder. By realizing the mode of laser range finder and analyzing the system architecture to find out the mechanism of counter measurement. The direct way is receiving and duplicating the signal from laser rangefinder, and return interfering signals with the same frequency back through the original optical axis. It will make laser range finder get misjudgment. • Laser range finder countermeasure system architecture and circuit design have been established. For 905 nm pulsed laser range finder, laser countermeasure system can copy the ranging signal successfully, and makes laser rangefinder ranging error has occurred. Keywords：Laser range finder, Countermeasure, Laser diode

5. Motivation • With the Optics, Semiconductor and Electronic technology have greatly advanced, the foundation of laser range finder has an extremely advancement as well. It is widely used in civil engineering and architecture, traffic, aviation and Industrial production…etc. • It also provides people accurate and quick information about distance of data. In addition to those fields, laser range finder also widely used in military. Therefore, in order to ensure the safety of the chariot, laser range finder countermeasure system emerges as a result.

6. Literature Reviews：Electro-Optical Countermeasures • The countermeasure of laser range finder is only a part of Electro-Optical Countermeasures. With the rapid development of laser and infrared technology, Electro-Optical countermeasures technology in the military confrontation is widely used. What is the definition and classification of Electro-Optical countermeasures?

7. Literature Reviews：In-Band and Out-of-Band technique • It is necessary for in-band technique to be successful , it has to be satisfied at least these conditions : • The target sensor to be looking at the countermeasure system. • The target’s optical train must be transparent to the incident laser wavelength, i.e. the laser energy must pass to the detector. In-Band Laser Input Out-of-Band Fig.1 In-band and Out-of-Band defeat mechanism.

8. Literature Reviews：Jamming methods on Laser Rangefinder Table.1 Jamming methods on laser rangefinder. Jamming Methods on Laser Range Finder Passive Active Material Without Light Source With Light Source High-Power Negative Deviation Positive Deviation

9. Active Positive Deviation Jamming System • This laser jammer system transmits the pulse signal which is always slower than the reflected pulse signal of actual target , it can only get positive deviation jamming. Laser detector Electric delay circuit Convergent lens 1 Convergent lens 2 Laser generator Fig.2 Active jamming system.

10. Delaying Fiber Jamming System • Germany has developed a countermeasure system of laser range finder that uses delaying fiber technology, as shown in Fig.3. Convergent lens Fiber coupler Fiber coupling element Delay fiber Reflector Fig.3 The delaying fiber jamming system.

11. The Mode of Laser Range Finder • The Mode of Laser Range Finder • Interference • Triangulation • Time-of-Flight • Pulsed • Phase-shift • MCW

12. Transmitter Receiver Pulsed TOF • When the speed of light is known, by calculating the number of the clock which travel between the system and target, the distance can be obtained. MCU & Processor Timer d Fig.5 Pulsed Time-of-Flight laser range finder. …………Eq.1

13. Laser Pt Al Ar O θ N Detector Pr R Laser Ranging Equation τα ρ ƞt ƞr Fig.7 Relationship between ranging system and the target diagram. …………Eq.4 …………Eq.5

14. Pr P0 Kt Kr D φ θ Photo Detector Laser R Estimating Effective Range • Receiving Power of Photo Detector： Fig.8 Relationship between laser countermeasure system and laser range finder. • The maximum ranging distance： …………Eq.6 …………Eq.9 • The distance can be calculated by Eq.7： …………Eq.7

15. Effects of Atmospheric Attenuation Fig.9 Relationship between 905 nm laser atmosphere transmittance and visibility and transmission range. …………Eq.10

16. Estimation of Counter Distance For APD Photodiode: Table.1 The parameters of estimation of counter distance By Eq.9 maximum counter range: …………Eq.11 For Table 1. Parameters:

17. Estimation of Counter Distance Fig.10 Relationship between operating range and laser power and visibility.

18. Estimation of Detecting Distance • Transmitting power of laser range finder must know before estimate detecting range by Eq.4. Table 2 Parameters of laser range finder

19. Estimation of Detecting Distance …………Eq.12 Table 3 The parameters of estimation of detecting distance LAPD-2000 PIN Photodiode： Eq.9 rewrites as： …………Eq.13

20. System Structure • This study constructed laser countermeasures system, the first step must be set out basic requirements. They are as follows: (a) Dual-band receiver and transmitter: 905 nm, 1550 nm (b) Detect and counter the distance over 1000 m. • TOF pulsed laser range finders measure the distance more than 1000 m. Therefore, this mode of laser range finder become the counter object. • In-Band mechanism to be a starting point, designing an active-positive deviation counter system.

21. Measuring beam t Analyze Time-of-Flight signal LD PD Reflected beam Jamming beam t Fig.11 Analysis of pulsed signal.

22. 905 nm 1550 nm The Countermeasures System Structure of Laser Range Finder (1) Infrared Receiver (3) Processer PIN Photo Detector TIA ＋ AGC Schmitt Trigger F to V Converter (2) Repeater MCU ＋ ADC Duplicate Circuit Memory (4) Infrared Transmitter Laser Diodes Laser Drivers Alarm & Display 905 nm 1550 nm Fig.12 Laser counter measurement structure diagram.

23. Infrared Receiver Table 4. Specifications of LAPD-2000 Fig.13 Spectral response of LAPD-2000. Responsivity (A/W) Wavelength (nm) Fig.14 Dark capacitance of LAPD-2000.

24. Infrared Receiver-Transimpedance Amplifier (TIA) Fig.16 Compensation Capacitance v.s. Feedback Resistance. Fig.15 Transimpedance Analysis Circuit. …………Eq.11 …………Eq.12 Fig.17 Bandwidth v.s. Feedback Resistance.

25. Infrared Receiver-Auto Gain Control Fig.18 Auto gain control Circuit. • AD603 voltage Input range：250 mV~1.4V • According to TIA, output voltage is： • By Eq. 9：

26. VP >3V VO VH VI VN VI VO VH VN VP Recognition circuit -Inverting Schmitt Trigger • Recognition circuit consists of inverting schmitt trigger、pulse stretching、frequencyto voltage 、analog to digital Converterand MCU. • There are two reasons for using inverting schmitt trigger： (1)Pulse stretching circuit input should be negative- edge-triggered. (2)To be the input signals of laser driver circuit. Fig.19 Transfer characteristic.

27. (8)Vcc (4)Reset R Vo (3)Output (7)Discharge (6)Threshold + VC C _ (2)Trigger (5)Control Voltage Vtrigger (1)GND 0.01μF Recognition circuit-Pulse Stretching Vcc Pulse 100 Hz Duty 5% 100 Hz 2.5 ms Duty 95% 1.9 kHz Fig.20 Monostable mutlivibrator circuit. …………Eq.12

28. Recognition circuit -Frequency to Voltage Fig.21 Frequency to voltage converter circuit. Fig.22 Frequency to voltage transfer diagram

29. Analog to Digital Converter + MCU + LCM Fig.23 ADC+MCU+LCMcircuit

30. Laser Diode Laser Driver Table 5 Electrical and Optical Characteristics of 980nm laser diode

31. Laser Diode Laser Driver Fig.24 Optical Output Power v.s. Forward Current Fig.25 Laser driver circuit

32. Experimental Results and analysis (a) Fig.26 Bushnell 905 nm laser range finder. (b) Fig.28 Transmitting wavefront of 905 nm laser range finder. Fig.27 Spectrogram of 905nm laser range finder.

33. R Experimental Results and analysis Laser Rangefinder Laser Countermeasure System Fig.30 Wavefronts of Photodiode and output of SN75451 Fig.29 Experimental architecture of laser counter measurement. Fig.31 Δt between Photodiode and Voltage output of SN75451 Fig.32 Countermeasure system laser out signal and Voltage output of SN75451

34. Conclusion & Future Work • Presently it has established laser countermeasure system for 905 nm pulsed laser range finder. • Laser countermeasure system using laser diode with wavelength of 980 nm by point-to-point testing, and the experimental results shows that this system can interference laser range finder. • Future Work (1) Add 1550 nm laser diode into countermeasure system. (2) Use high power pulsed laser diode and APD photodiode. (3) Receiver and Transmitter lens. (4) Calculate time delay. (5) Test More laser range finder.