ShortWave Infrared Dual Band Laser Countermeasure System ReporterHueiKai

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

Outline Ø Abstract Ø Motivation Ø Literature Reviews § Electro-Optical Countermeasures § In-Band 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 Ø Estimation Effective Range § Effects of Atmospheric Attenuation § Estimation of Counter Distance § Estimation of Detecting Distance 2

Outline Ø 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 Ø Experimental Results and analysis Ø Conclusion and Future Work Ø Reference 3

Abstract A. 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. B. 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 4

Motivation A. 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. B. 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. 5

Literature Reviews：Electro-Optical Countermeasures Ø 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? 6

Literature Reviews：In-Band Out-of-Band technique Ø It is necessary for in-band technique to be successful , it has to be satisfied at least these conditions : A. The target sensor to be looking at the countermeasure system. B. 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 Out-of-Band defeat mechanism. 7

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

Active Positive Deviation Jamming System Laser detector Convergent lens 1 Convergent lens 2 Electric delay circuit Laser generator Fig. 2 Active jamming system. Ø 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 9

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 coupling element Fiber coupler Delay fiber Reflector Fig. 3 The delaying fiber jamming system. 10

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

Pulsed TOF Transmitter MCU & Processor Timer Receiver d Fig. 5 Pulsed Time-of-Flight laser range finder. Ø 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. …………Eq. 1 12

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

Estimating Effective Range P 0 Kt Kr φ θ Pr D Photo Detector Laser R Fig. 8 Relationship between laser countermeasure system and laser range finder. Ø Receiving Power of Photo Detector： Ø The maximum ranging distance： …………Eq. 6 Ø …………Eq. 9 The distance can be calculated by Eq. 7： …………Eq. 7 14

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

Estimation of Counter Distance Table. 1 The parameters of estimation of counter distance For APD Photodiode: -0. 1024 R ) Visibility =20 km ( Tσ = e Visibility =20 km ( Laser countermeasure Laser range finder system transmitter receiver λ 905 nm Prmin 3. 16*10 -11 W Kt Kr 80 % P 0 0. 5 m. W D 26 mm θ 30° φ 0° By Eq. 9 maximum counter range: …………Eq. 11 For Table 1. Parameters: 16

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

Estimation of Detecting Distance Ø Transmitting power of laser range finder must know before estimate detecting range by Eq. 4. Table 2 Parameters of laser range finder Laser range finder (Rmax=1000 m) Transmitter Receiver λ 905 nm Prmin 3. 162*10 -11 W Kt 80% Kr 80% Tσ (V=10 km) 81. 485% D 26 mm φ 0° Ar 5. 309*10 -4 m 2 ρ 60% 18

Estimation of Detecting Distance …………Eq. 12 Table 3 The parameters of estimation of detecting distance -0. 20475 R ) Visibility =10 km ( Tσ = e Visibility =10 km ( Laser range finder Laser countermeasure transmitter system receiver λ 905 nm Prmin Kt 80% Kr P 0 1 W D θ 1° AΦ φ 0° LAPD-2000 PIN Photodiode： 4. 23*10 -10 W Eq. 9 rewrites as： 4*10 -6 m 2 …………Eq. 13 19

System Structure Ø 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. Ø TOF pulsed laser range finders measure the distance more finders than 1000 m. Therefore, this mode of laser range finder become the counter object. Ø In-Band mechanism to be a starting point, designing an active. In-Band mechanism positive deviation counter system. 20

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

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

Infrared Receiver Responsivity (A/W) Table 4. Specifications of LAPD-2000 Active Diameter (mm) 2 Wavelength Range (um) 0. 9 -1. 7 Dark Current@-5 V (n. A) Capacitance (p. F) @-5 V 10 (A/W) 20 Responsivity Max. Reverse Voltage (V) Fig. 13 Spectral response of LAPD-2000. 200 0. 65 μm 0. 05 0. 85 μm 0. 20 1. 31 μm 0. 90 1. 55 μm 0. 95 NEP@ 1550 nm Wavelength (nm) 0. 04 Fig. 14 Dark capacitance of LAPD-2000. 23

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. 24

Infrared Receiver-Auto Gain Control Fig. 18 Auto gain control Circuit. Ø AD 603 voltage Input range： 250 m. V~1. 4 V Ø According to TIA, output voltage is： Ø By Eq. 9： 25

Recognition circuit -Inverting Schmitt Trigger Ø Recognition circuit consists of inverting schmitt trigger、 inverting schmitt trigger pulse stretching、 pulse stretching frequency to voltage 、 to voltage analog to digital Converter and MCU Ø 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. VP >3 V VO VI VI VN VH VH VN VO VP Fig. 19 Transfer characteristic. 26

Recognition circuit-Pulse Stretching Vcc (8)Vcc (4)Reset R (3)Output Vo (7)Discharge (6)Threshold + VC _ Vtrigger Duty 5% 100 Hz C (2)Trigger (1)GND Pulse 100 Hz (5)Control Voltage 0. 01μF 2. 5 ms Duty 95% 1. 9 k. Hz Fig. 20 Monostable mutlivibrator circuit. …………Eq. 12 27

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

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

Laser Diode Laser Driver Table 5 Electrical and Optical Characteristics of 980 nm laser diode Parameter Symbol Condition Min. Typ. Max. Unit Threshold Current Ith - - 12 20 m. A Operating Current Iop Po=25 m. W - 44 70 m. A Operating Voltage Vop - 1 1. 5 2. 1 Volt Slope Efficiency η 0. 5 0. 8 - m. W/m. A Monitor Current Im Po=25 m. W - 0. 1 0. 2 m. A Parallel θ// Po=25 m. W 8 13 18 deg. Perpendicular θ⊥ Po=25 m. W 25 30 35 deg. λ Po=25 m. W 970 980 990 nm Beam 20 m. W-10 m. W I 20 m. W-I 10 m. W Divergence (FWHM) Lasing Wavelength 30

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

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

Experimental Results and analysis Laser Countermeasure System Fig. 30 Wavefronts of Photodiode and output of SN 75451 Fig. 31 Δt between Photodiode and Voltage output of SN 75451 Laser Rangefinder R Fig. 29 Experimental architecture of laser counter measurement. Fig. 32 Countermeasure system laser out signal and Voltage output of SN 75451 33

Conclusion & Future Work A. Presently it has established laser countermeasure system for 905 nm pulsed laser range finder. B. 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. Ø 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. 34