RCS Computation, Reduction and Stealth Design

Transcription

1 RCS Computation, Reduction and Stealth Design Micah Li PhD EM Application Engineer Flomerics U.K.

2 Agenda Introduction Background of TLM (MICROSTRIPES) Numerically predicting the radar signature Luneberg Lens reflector example Reduction and stealth design Conclusions

3 Introduction EM Simulation can solve larger and larger computational EM problems Installed antenna Lightening simulation Cable coupling How about RCS? RCS measurement Indoor range Limitation on size of the targets that can be measured Outdoor range Suffers as much as 35 % downtime due to unfavourable weather conditions High Costs AS-1735 UHF antenna radiating at 300 MHz RCS Outdoor Range China Lake Naval Weapons Center, US

4 Modelling Radar Cross Section (RCS) How simulation can help on modelling RCS Provides flexibility in design procedure Shorten the time from idea to design Visibility of performance matrix Requirements for EM simulation tool Accuracy & speed Capable of handling electrical big structures CAD import capability

5 Background of MICROSTRIPES Background knowledge TLM (Transmission Line Matrix) based solver Time domain Some of the key features Auto Lumping (enable to solve electrically large structure) Compact models Wires Slots Lump Circuits Perforated panel CAD Import

6 . TLM Based EM Simulation Background Impulse Excitation Radiation Pattern Geometric Model Surface Current and E Field Impulse Response Scatter Parameters

7 Auto Lumping

8 Advanced Meshing Cells in Basic Grid (k) Cells in Solver Model (k) Computing Time (mins) Required Memory (MB) No Lumping Automatic Lumping Octree meshing results in saving of ~93% over reference Majority of the variation within ± 0.2 db

9 Wire Feature Can be used where the dimensions of the physical size are small compared with the rest of the geometry; HF wire AV-457 UHF Dipole UHF Satcom XDipole AV201 Antenna Prologic, USA

10 Standard file formats; *.sat *.igs *.stp *.stl *.dxf Imported from MCAD Solid Works PRO/E CATIA Geometry Import

11 Numerically Predicting Radar Signature 3 Easy Steps 1; Generate Geometry Direct within MicroStripes Or import from MCAD 2; Assign EM Properties Materials Boundary Conditions Excitations Outputs 3; Discretised the model, solve and visualise results

12 Application Example---Luneberg Lens Reflector 8 concentric spheres (the outmost layer is hidden in the figure) εr = 2 (r/r)2 Luneberg lens reflectors are commonly carried by yachts, and other small craft, in order to increase the size of their radar signature. The RCS was calculated at 9.41 GHz, the typical operating frequency for X-band radar.

13 Visualize RCS in MICROSTRIPES MICROSTRIPES 7 Project Window RCS Results Mono-static & bi-static RCS Pick on the results on the far field pattern RCS cut plots are available Boresight axis default to the minus illumination direction Mono-static appears at 0 degree

14 Design to Increase RCS A series of closely spaced thin wires orientated at 45 around the outer sphere; Thin wire compact model is used; No need for detail meshing on the wires; Exhibit a single back scattered lobe.

15 Improvement on RCS Metal Band Wire Band RCS cut on E-Plane ( m^2) RCS cut on H-Plane ( m^2) RCS increased by 10 ducks by using wire band (1 duck = 0.1 m^2)

16 RCS Reduction & Stealth Design Basic Techniques to reduce RCS Shaping Radar absorbing materials Passive cancellation Active cancellation Radar Frequency Band 3 MHz to 300 GHz VHF radar deployed as long-range surveillance system Use 300MHz in the application example

17 F117 vs. Airliner F117 Stealth Bomber Length 20 m Wingspan 13 m Airliner Length 27 m Wingspan 26 m Illuminated by a -45 from the horizontal axis polarised field at 300MHz, incident of 45 both from the horizontal and vertical axis

18 Shaping Techniques to Reduce RCS

19 Shaping Techniques to Reduce RCS RCS cut on E-Plane ( m^2) Comparison of RCS for F117 and Airliner Surface current on F117 at 300 MHz

20 Radar Absorbing Material Materials library Metal Dielectric Thin film Frequency dependant material New materials can be defined in the library Debye calculator to determine EM parameters for frequency dependant material

21 Conclusions 3D EM modelling is an efficient method for RCS computation and stealth design; It reduces the cost and time for prototyping RCS products; Steps to compute the mono-static and bi-static RCS have been discussed in the presentation; EM modelling has constraints on the electrical size of the model

22 . I think Flomerics has hit a homerun with MicroStripes. It is easy to use, gives accurate results and the support is incredible. I would highly recommend MicroStripes to anyone that needs to solve complex 3D real world problems in a hurry Larry Fry, Prologic, USA