A Modelling and Simulation Tool for the Prediction of Electronic Attack Effectiveness John Baldwinson#1, Irina Antipov #2 #
Electronic Warfare and Radar Division, Defence Science and Technology Organisation, Bld. 205L, West Avenue, Edinburgh, SA, 5111, Australia 1
[email protected] 2
[email protected]
Abstract — The presentation describes a Modelling and Simulation tool developed by Electronic Warfare and Radar Division of Defence Science and Technology Organisation, Australia. This tool can be used for the prediction of jamming effects on the airborne radar performance by Electronic Attack systems currently available on the market or under development. It also highlights the impact of a Maritime Patrol Aircraft radar antenna pattern and signal processing system parameters on the specifications and performance parameters of Electronic Attack systems used for ship self-protection in a maritime environment.
I. INTRODUCTION Anti Ship Missiles (ASM) continue to step-up lethality through increases in terminal speed and launch range and improvements in radar guidance systems. There are various options available to counter the ASM to Naval ships [1] – [9]. Not ignoring the importance of these measures, there is an opportunity to improve ship survivability against ASM attack by using layered defence. In a layered defence, an onboard Electronic Attack (EA) system can be used to delay or prevent detection of a ship by Maritime Patrol Aircraft (MPA) radar and therefore delay or prevent the ASM launch (see Fig.1). MPA or Maritime Helo
Navy ship with onboard EA > 80 nmi
Counter-surveillance/ Counter-targeting
< 15 nmi
Counter-acquisition ASM
Counter-acquisition
Counter-surveillance/ Counter-targeting z
Attack the targeting platform – Deny/Degrade detection – Prevent or degrade acquisition – Prevent or degrade class/ident – Degrade targeting
z
Attack ASM target acquisition – Degrade detection – Prevent or degrade acquisition
Fig.1 ASM engagement events required to be addressed by an onboard EA system in a layered defence.
Aircraft and helicopters armed with ASMs have demonstrated distinct operational advantages over ship-, submarine-, and land-based systems since they allow greater employment flexibility and superior sensor range. The largest
percentage of the successful ship strikes using missiles over past five decades has come from aircraft. Today more than twenty nations possess air-launched versions of the ASM [2]. MPA, such as the P-3 Orion, Nimrod, Atlantic/Atlantique 2, S-3B Viking, F-27/F-50 Enforcer, and other similar aircraft have the range, payload, and sensor systems to effectively employ Exocet, Harpoon, and ASM-1 class ASM [2], [4], [7]. Therefore, the ability to protect high value maritime platforms from being successfully detected and identified by the enemy surveillance radars would provide Navy with a significant capability enhancement. This presentation describes a Modelling and Simulation (M&S) tool developed by Electronic Warfare and Radar Division of Defence Science and Technology Organisation (DSTO), Australia, for the prediction of the jamming effects on MPA radar performance by EA systems currently available on the market or under development. It also highlights the impact of an MPA radar antenna pattern and signal processing system parameters on the specifications and performance parameters of EA systems used for ship self-protection in a maritime environment. The M&S tool is based on well-established models of a generic MPA radar, the environment and EA systems. The tool allows the variation of radar parameters, EA parameters and the jamming scenario, and it is very useful for the evaluation of the effectiveness of different EA techniques implemented in the maritime environment. II. GENERIC SPECIFICATION FOR A LONG-RANGE SURFACE SURVEILLANCE MODE OF A MARITIME RADAR SYSTEM An essential role of a MPA radar is the detection and identification of ship targets at long ranges. This function may be met by a Long-Range Surface Surveillance (LSS) mode that meets a generic requirement, which may be formulated as follows: “The radar system shall be capable of automatically detecting a ship target with a Radar Cross Section (RCS) of 10,000 squared meters, moving at a velocity of up to 38 knots and exposed for 37 seconds or less, with a probability of detection of 0.5 or more and a false alarm rate of 1 in 25 minutes or less up to and including range of 140 nautical miles in Sea States up to and including 3 when scanning the 360° azimuth coverage of the radar system at altitudes up to and including 13,000 ft” [10] – [13]. The main operating parameters for one of the possible LSS mode designs that are capable of achieving the specified
detection performance are shown in Table 1. It is assumed that the LSS mode transmits a stepped frequency waveform, and that the generic maritime radar system uses an antenna pattern with low sidelobe levels (see Fig. 2). TABLE 1 GENERIC SPECIFICATION FOR A LSS MODE OF A MARITIME SURVEILLANCE RADAR SYSTEM
Operating Centre Frequency Peak Transmitter Power Transmit Pulse Width Number of Frequency Steps Synthesized Bandwidth Scan Rate Field of Regard PRF Polarization Antenna Gain Azimuth Beamwidth Elevation Beamwidth Antenna Sidelobes Digital Filter Gain Pulse Compression Gain Coherent Addition Gain (IFFT) Beamshape Loss Radome Loss Transmission Line Loss Noise Bandwidth System Noise Temperature CFAR & Signal Processing Losses Average Probability of Detection False Alarm Rate Reduction scan to scan Average False Alarm Rate Instrumented Range, Nautical Miles Track-While-Scan (TWS), Number of Targets
9.1 GHz 3500 w 50 µs 24 12 MHz 6 rpm 360° 500 Hz VV 36.4 dBi 2° 3° -30.0 dB 13.0 dB 14.0 dB 13.8 dB 1.57 dB 1.0 dB 3.5 dB 10 MHz 675°K 5.5 dB ≥ 0.5 2 out of 3 1 in 25 min 5 to 150 500
Figure 2 Received signals power gain for the generic radar system LSS mode
For the chosen LSS model, received signals, which are reflected either from the sea surface only or from the sea surface and the target of interest, are digitised by an analog-todigital (A/D) converter. The digitised signals are preprocessed in the receiver and in the radar signal processor that implements the multi-stage pulse compression of each received pulse. Then the radar signal processor performs the motion compensation, the Inverse FFT (IFFT) of stepped
frequency waveform samples and calculates the absolute value of the IFFT output. These pre-processed signals are passed to the input of the radar data processor that performs the chosen target detection algorithms providing a Constant False Alarm Rate (CFAR) [10] - [12]. The LSS mode specification presented in Table 1 will be used for providing some examples of assessment of the vulnerability of the generic maritime radar system LSS mode to non-coherent and coherent counter-surveillance/countertargeting EA techniques generated by an EA system installed onboard ship, and the ability to use these techniques for providing effective ship self-protection. Depending on parameters of the EA equipment, particular jamming scenario and relative position of the radar threat and the ship, a number of different non-coherent and coherent EA techniques can be implemented. To evaluate the effectiveness of different non-coherent and coherent EA techniques and equipment, the Electronic Warfare and Radar Division of DSTO, Australia, has developed a M&S tool that is based on well-established models of a generic MPA radar, the environment and EA systems [10] – [15]. This tool, called PEAEF (Prediction of EA Effectiveness), allows the variation of radar parameters, EA parameters and the jamming scenario. The PEAEF M&S tool produces results useful for the evaluation of non-coherent denial and coherent deception EA techniques effectiveness in the prevention or delay in the detection of a ship by a radar in such an LSS mode with specifications outlined in Table I. III. NON-COHERENT DENIAL EA TECHNIQUES Non-coherent denial jamming [13] – [15] is the most common type of EA, and it is effective against most types of radars. One of the advantages of this type of jamming is that in comparison with coherent deception jamming, very little needs to be known about the characteristics of the victim MPA radar to be effective. It was shown [10] – [12] that for a given probability of false alarm, the probability of detection of a specified target that can be achieved in the maritime environment is determined only by the ratio of the signal power to the clutter plus noise power and the clutter statistical properties. Modern maritime surveillance radars use automatic target detection algorithms that employ CFAR processors to adapt the detection threshold automatically to the local background clutter and noise power in an attempt to maintain an approximately constant false alarm rate. This is achieved at an expense of a detection loss associated with the CFAR threshold setting. Hence, given a fixed signal power, it is possible to make the probability of detection as small as desired by increasing the receiver noise power using noncoherent EA techniques while the radar is attempting to maintain an approximately constant false alarm rate, and the optimum non-coherent jamming signal has the characteristics of receiver noise. Consider, as an example, the results that the PEAEF M&S tool produced for non-coherent denial EA techniques: the first modelled EA technique is 50 MHz barrage noise, and the second is 12.5 MHz spot noise. It was assumed that the MPA is flying at the altitude of 13,000 ft and that the ship with the onboard EA equipment is at a range of 70 nautical miles from the aircraft, and that this ship has a mean RCS value that does not exceed 40 dBm2. It
was also assumed that the EA system has the same specification as the Chameleon III3B Electronic Counter Measures (ECM) simulator (see Table 2 from [16]); the jamming transmitter power is 200 Watt and the transmitting antenna gain is 33dBi (i.e. the jamming Effective Radiated Power (ERP) is 56 dBW). Such an EA system can be effectively used to generate counter-surveillance and countertargeting non-coherent and coherent self-protection EA techniques (see Fig. 3). TABLE 2 SPECIFICATION OF THE SHIP-BORNE EA SYSTEM
Frequency range: Bandwidth: Sensitivity: Dynamic range: ERP EA techniques:
DRFM memory depth: DRFM delay resolution: DRFM Doppler:
0.8-18 GHz (continuous operation, 26.5-40 GHz option) 500/800 MHz (instantaneous) -60 dBm >100 dB 56 dBW amplitude modulation, barrage noise, blinking noise, burst noise, coherent clutter, co-ordinated Range-Gate Pull-Off (RGPO)/I and VelocityGate Pull-Off (VGPO)/I, inverse gain, range and velocity bin masking, range/frequency false targets, RGPO/I, spot noise, swept noise, synthetic continuous wave and stretch pulse, velocity noise and VGPI 8 ms
Fig. 4 Jamming-to-signal ratio at the input of the radar receiver of the modelled LSS mode for a mean target RCS of 40 dBm2 and a Barrage jamming bandwidth of 50 MHz.
