978-1-4673-1184-7/12/$31.00 ©2012 IEEE 1476

2012 5th International Conference on BioMedical Engineering and Informatics (BMEI 2012)

Modeling and Simulations of ECCM of Ocean Surveillance Satellite Electronic Intelligence

Xianjun PAN, Yanhong WU The Academy of Equipment

Beijing, China

Abstract—Utilizing passive location technology, the target, such as, Radar, communication transmitter etc, on the sea can be located by the ocean surveillance satellite (OSS).The capability of passive location system of the OSS can be impaired by jammers, and the operational capacity would be damaged. In this paper, the principle and characteristics of passive location technique are analyzed. According to principle of information processing of OSS electronic intelligence (ELINT), the simulation model of electronic reconnaissance satellite is established. Finally, numerical experiments of ECCM of OSS ELINT are conducted. The results prove that the model is effective.

Keywords- Ocean Surveillance Satellite; ECCM; Electronic Intelligence; TDOA location; passive location

I. INTRODUCTION In modern warfare, electronic warfare decides outcome of

war, winning or losing, in a way. And the radiation sources (such as radar) location technology is one of some key technologies in electronic warfare. With the remarkable development of space technology, various satellites have become the primary means of information acquisition because they can be applied in all-weather and in all-time. The Ocean surveillance satellite (OSS), which can acquire information of ocean-going naval fleet timely, is the extremely important space reconnaissance equipment. The OSS system includes one or several signal intelligence (SIGINT) satellites which collect electronic intelligence (ELINT) for military. The OSS is running in the low Earth orbit to detect radio transmissions from ships at sea. Then the position of the ship can be calculated with the "Time Difference of Arrival" technique. The operational capability of the OSS system is mainly demonstrated by the ability of obtaining the geographical position of the navy fleet timely. The interference to OSS passive location system can reduce the operational capability of it. The specific location technique and method are research emphases [1~6] at present. Modeling and Simulations of ECCM of the OSS are scare. The paper attempts to build the model and simulation system of the OSS.

II. ELECTRONIC INTELLIGENCE (ELINT) OSS AND INTERFERENCE

A. passive location technologies The ELINT of the OSS system can intercepted radio signals

from ground radar system. The parameters of pulse frequency, pulse width, pulse amplitude, time of arrival (TOA) ,intra-pulse and inter-pulse of radio signals can be obtained through

onboard signal processing and ground data processing system. The OSS constellation has two or three satellites. The distance between them is from dozens of kilometers to of hundreds of kilometers. The OSS system locates and tracks ships at sea by detecting their radio transmissions. The time-difference-of-arrival (TDOA) technique is utilized to calculate the location of radio source. If the constellation consisting of four satellites obtains the TOA of a pulse signal of the same radiation source, three measurement equations are generated. The position of radio source can be work out by solving the three equations. In the practice, the Triple Satellite Formations Location technology makes use of three satellites to accomplish two-dimensional positioning of radar emitters. Two equations of TDOA are generated. The Earth geometry model is the third constraint equations because it is assumed that the radio source is on the surface of the Earth. The specific positioning solution methods have been seen in [1], [2] and other relevant information is not repeated here.

B. The OSS system vulnerability analysis The spaceborne ELINT system detects radio transmissions

from opponent ships at sea and captures the enemy intelligence. In terms of ELINT system, the OSS has many advantages in obtaining intelligence because of the superiority of the platform. However, from the point of view of electronic countermeasure (ECM), there are still many weaknesses in the OSS ELINT as listed below.

(1) The interference power will not be too high due to the high sensitivity and the wide dynamic range of the ELINT of the OSS.

(2) The interference power can enter the OSS ELINT system easily because ELINT system is wide open receiver.

(3) The OSS ELINT system can be saturated by high-density electronic pulse stream due to the limitations of signal storage and processing capacity onboard.

C. ECM technology of the OSS The analysis of the weakness of the OSS gives some hints

of interference methods. Currently, the general ECMs of the OSS ELINT are listed as follows: radio silence, advanced target technology, active jamming, etc. Meanwhile more attentions are being paid to the active deception jamming technology, which has a unique advantage.

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III. THE ANALYSIS OF TDOA LOCATION TECHNOLOGY ELINT analysis often involves interleaved pulse trains. It

means that many pulse signals appear simultaneously in the system. The successive pulses may come from the different emitters. Using the "Time Difference of Arrival" technique, the key parameters are the TDOAs of the signal emitted from the radiate sources in Triple Satellite Formations systems. How to obtain the true TDOA of the radio source is a primary problem to be solved. High density of pulse trains de-interleaving is a research focus. The statistical technique is applied in deinterleaving processing. Delta-T histogram technique is the most commonly method. The pulse sorting technique is described in detail in reference [3] [4] [5]. The proposed method of active deception jamming aims at the inherent characteristics of pulse sorting algorithm. The jammer receives the signal from radio source, then duplicates it and transmits it. The similar jamming pulse signal will enter into ELINT receiver. So the correlative TOA sequences are captured by ELINT processor. There are false correlation peak values in correlation processing. They will disturb the ELINT receiver. The ELINT system will obtain false TDAO values, resulting in a false location of a false target. The TDOA location technique is described as follow.

The coordination of emitter is ( , , )br x y z .The coordination of the satellites of the constellation

is ( , , )si i i ir x y z , where i=1, 2, 3. So the distance between emitter and the satellite-i is given by the formula (1). If the pulse is transmitted for emitter at Tr, it arrives at the satellite-i at tsi, it can be described by the formula (2). At the same time, the converting relationships between longitude, latitude and altitude coordinate (L, B, H) and Cartesian coordinate (x, y, z) is given by formula (3) in geodetic coordinates system.

2 2 2( ) ( ) ( )i i i ir x x y y z z= − + − + − (1)

( )si r ic t T r⋅ − = (2)

2

( )cos cos( )sin cos

(1 ) sin

x N H L By N H L B

z N e H B

⎧ = +⎪⎪ = +⎨⎪ ⎡ ⎤= − +⎪ ⎣ ⎦⎩ (3)

Where, i=1, 2, 3, c is the velocity of light, the constant, and

2 2

2 22

2

1 sinaN

e Ba be

a

=−−=

It is supposed that the attitude of the emitter is zero. So the

principle of TDOA location is described by the formula below.

1 2 1 2

1 3 1 3

( )( )

s s

s s

c t t r rc t t r r

⋅ − = −⎧⎨ ⋅ − = −⎩

(4)

2 2 2 2( sin )H x y z N e B N= + + + ⋅ − The Equation (4) can be solved by Newton’s method.

The key problem is how to obtain the time difference of arrival. The solutions are described in the next paragraph.

It is assumed that there are N emitters, ( ), 0,1,2jkP t k =

is the pulse signal of the j-th emitter received by k-th satellite of the OSS. ( ), 0,1,2kP t k = are the functions of TOA of pulse trains received by the main satellite(k=0) and the auxiliary satellite No.1(k=1) and No.2(k=2). 1

jΔ is the TDOA of the j-th emitter signal between the main satellite and the auxiliary satellite No.1. 2

jΔ is the TDOA of the j-th emitter signal between the main satellite and the auxiliary satellite No.2. So

( ), 0,1,2kP t k = are given by

( )

( )

0

0 0

0 0

0 0 0,1 1 1

1 1 1, 1, 11 1 1 1 1

2 2 2, 2, 21 1 1 1 1

( ) ( ) ( )

( ) ( ) ( ) ( )

( ) ( ) ( ) ( )

j

j j

j j

MN Nj j

ij j i

M MN N Nj j j j

i ij j i j i

M MN N Nj j j j

i ij j i j i

P t P t t TOA

P t P t t TOA t TOA

P t P t t TOA t TOA

δ

δ δ

δ δ

= = =

= = = = =

= = = = =

⎧= = −⎪

⎪⎪⎪ = = − = − + Δ⎨⎪⎪⎪ = = − = − + Δ⎪⎩

∑ ∑∑

∑ ∑∑ ∑∑

∑ ∑∑ ∑∑

(5)

Where, ,j

k iTOA are TOA of the i-th pulse of the j-th emitter

received by the k-th receiver within the measure period, jkM

are the number of pulses of the k-th receiver. When 0k = , receiver is the main satellite. When 1,2k = , the receiver is the auxiliary one.

Within measure periodT , pulse pairing histogram can be described by cross-correlation function of TOA function of main satellite and auxiliary one’s in mathematics. It is given by formula (6)

1

1 0 10

22 0 20

2( ) ( ) ( ) ,0

2( ) ( ) ( ) ,0

T

T

LH t P t t P t dt tcLH t P t t P t dt tc

⎧ Δ = − Δ < Δ <⎪⎪⎨⎪ Δ = − Δ < Δ <⎪⎩

∫

∫ (6)

1( )H tΔ is histogram statistic function of TDOA between

the auxiliary satellite No.1 and the main one. 2 ( )H tΔ is histogram statistic function of TDOA between the auxiliary satellite No.2 and the main one. 1L is baseline length of

between the auxiliary satellite No.1 and the main satelite. 2L is

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baseline length of between the auxiliary satellite No.2 and the main satellite. Histogram statistic function peak occurs when

tΔ equal to the true value of TDOA of between the main satellite and the auxiliary one.

It is assumed that the Pulse Repetition Interval (PRI) of 2 emitters are , 1,2iPTI i = , the baseline length of between the main satellite and the auxiliary one is L , the pulses received by the main and the auxiliary within T are described by formula (7).

0 01 2

0 01 2

1 11 2

1 11 2

0 00 1 1 1 2 2 2

0 0

1 11 1 1 1 1 2 2 2 2

0 0

( ) ( ) ( )

( ) ( ) ( )

N N

n n

N N

n n

P t t n PRI t t n PRI t

P t t n PRI t t n PRI t

δ δ

δ δ

= =

= =

⎧= − − + − −⎪

⎪⎨⎪ = − − − Δ + − − − Δ⎪⎩

∑ ∑

∑ ∑ (7)

Where, , 1,2it i = is the TOA of the first pulse to the main

satellite, satisfying uniform distribution within[0, ]iPTI . The number of pulses from two emitters received by the main satellite is 0 1, ( 1,2)iN i+ = . The number of pulses from two

emitters received by the auxiliary satellite is 1 1,( 1,2)iN i+ = .

, 1,2i iΔ = is TDOA of between the main satellite and the auxiliary one.

By substitution of Equation (7) into Equation (6), the integral is calculated. According the property of δ function,

1 21 2

1 2

1,( ) ( )

0,t t

t t t tt t

δ δ=⎧

− ⋅ − = ⎨ ≠⎩ (8)

It can be proved that each integral term in Equation (6) is not equal to zero with the following conditions:

1 01 1 1 11 02 2 2 2

1 01 1 2 2 1 2 11 02 2 1 1 2 1 2

( )

( )

20

t n n PTI

t n n PTI

t n PTI n PTI t t

t n PTI n PTI t tLtc

⎧⎪Δ = − + Δ⎪

Δ = − + Δ⎪⎪Δ = − + − + Δ⎨⎪Δ = − + − + Δ⎪⎪

< Δ <⎪⎩

(9)

Obviously, PTI T< . The false peaks will occur in delta-T statistical histogram for pulse pairing of the high repetition frequency pulse trains. There are ambiguous TDOAs. The interval of false peaks is a multiple of the true PRIs. The ambiguity will occur when the pulse repetition frequencies are high. In these cases, the solution is given in [6].

IV. THE MODELING OF TDOA LOCATION TECHNOLOGY According to the principle of ECCM of OSS ELINT, the

schematic diagram of model is established as diagram followed.

Figure 1. Model of ECCM of OSS ELINT

The model system consists of seven sub-systems, namely, emitter model, spatial geometric model, jammer model, receiver model, PWD (Pulse Description Words) generation, data processing and location showing.

The emitter model can setup parameters of emitter, such as position, carrier frequency, pulse repeat frequency, pulse width, modulation types, etc. Jammer model sets up jammer parameters, such as position, jamming mode, etc. The delay time, the most important information in TDOA location algorithm, is generated by the spatial geometric model according to position of the emitter and jammer. The receiver model can measure the frequency, TOA (Time of Arrival), PW (Pulse Width) of radio source. The spatial geometric model normalizes the measured parameters to form PDW. The PDW generation sub-system formats the output of Receiver Model to form the normative PDW. The data processing sub-system is playing the most important pole in simulation system. Pulse trains’ de-interleaving is accomplished by the data processing sub-system. At the same time, the TDOA location algorithm is implemented. And the locating result is shown by location showing sub-system.

In the simulation, the spatial relationship between the emitter and satellites is generated by STK (Satellite Tool Kits) software. The TOA of pulses of one emitter generation flow chart is given by Figure 2.

V. SIMULATION AND CONCLUSION

A. Simulation experiment Simulation conditions: The parameters of the of satellites

position are listed in Table 1. The parameters of jammers and Radar are listed in Table 2. The Duration time is 20ms.

The results of data processing are shown in Figure 3 and Figure 4. The histogram of TDOAs between the main satellite and satellite 1 is shown in Figure 3. The histogram of TDOAs between the main satellite and satellite 2 is shown in Figure 4.

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START

Generate Trrandomly

Generat Delaytime Td(k)

Spatialrelationship

Add measurementnoise tn

Add Pulserepetition Interval

PRI

Generate TOA:Tsi(k) = Tr+Td(k)+tn+PRI

Tsi(k)>T?

END

Yes

k=k+1

NO

Figure 2. Generation TOA flow chart

TABLE I. SATELLITE POSITION

Lat (deg) Lon (deg) Alt (km)

Main Satellite 33.678 150.347 1108.897083

Auxiliary No.1 33.101 150.041 1108.722082

Auxiliary No.2 33.773 149.581 1108.926301

TABLE II. PARAMETERS OF JAMMER AND RADAR

When there are some active jammers, the output of the OSS ELINT system includes some false target. The processing result is shown in Figure 5. The mark “●” denotes the position of Radar. The mark “△” denotes the position of Jammer. The mark “□” denotes the output of TDOA Location system.

Although the positions of the true radio sources occur in the outputs, it takes a little time to discard what is false and keep what is genuine. That can delay the opponent’s decision.

Figure 3. Histogram of TDOA between the main satellite and the satellite 1

Figure 4. Histogram of TDOA between the main satellite and the satellite 2

Figure 5. Location Output with active jamming

B. Conclusion The numeric experiment indicates that the simulation

system can be used directly for research on ECCM of OSS ELINT economically and flexibly. The PDWs generated by simulation system can be used as the input of the new ELINT system when it is in the engineering development phase. In this way, both time period and cost used to develop the equipment can be reduced

La t(deg)

Lon (deg)

Alt (km)

Fc (GHz)

PRF (kHz)

PW (us)

Jammer 1 33.7323 149.9767 0.0000

- - - Jammer 2 34.0021 150.3365 0.0000

Jammer 3 34.3618 150.8761 0.0000

Radar 33.7323 150.2465 0.0000 6.00 1.50 0.25

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ACKNOWLEDGMENT

The authors would like to thank the anonymous reviewers for their very constructive and encouraging criticism, helping to improve the final paper.

REFERENCES [1] Xie Kai, Zhong Danxing, Deng Xinpu, Zhou Yiyu, “A New Algorithm

for the Time Difference Location in Aerospace”, Signal Processing,, Vol.2, Aprril, 2006, pp129-135.[in Chinese]

[2] CHEN Yong-guang, LI Chang-jin, LI Xiu-he, “A Precision Analyzing & Reckoning Model in Tri-Station TDOA Location”, Acta Electronica Sinica, Vol.32,No.9,2004,pp1451-1455.[in Chinese]

[3] Richard G. Wiley, “ELINT The Interception and Analysis of Radar Signals”,ARTECH HOUSE INC.,2006, pp322-330.

[4] W. H. Foy. “Position-location solutions by Taylor-series estimation”.IEEE, Trans. Mar.1976,AES-12, NO.2,pp187~194

[5] D. J. Torrieri. “Statistical theory of passive location systems”.IEEE, Trans. Mar.1984,AES-20 NO.2 pp183~198

[6] LI Tao, JIANG Wen-li;,ZHOU Yi-yu, “TDOA Location With High PRF Signals Based on Three Satellites”, Electronic Warfare Technology, July,2004,Vol.19, pp7-11;[in Chinse]