Using measured fields as field sources in computational electromagnetic (CEM) solvers

Transcription

1 Using measured fields as field sources in computational electromagnetic (CEM) solvers Presenter: Lucia Scialacqua

2 Content Domain decomposition techniques have been know for some time in Computational Electro- Magnetics (CEM). In this presentation we will discuss the derivation of an accurate description of the measured antenna/device suitable as field source in much larger CEM problems. 2

3 Content Application examples: Antenna placement (putting antennas on larger platforms) 3

4 Content Application examples: EMC (Electro-Magnetic Compatibility) 4

5 Table of contents Introduction Antenna Measurements Multi-probe system Introduction to measurement post-processing using INSIGHT Source modeling, suitable for numerical computation and import in CEM tools. Link between INSIGHT and CEM tools. Application examples: Antenna placement problems EMC applications Conclusion 5

6 Testing Workflow NF Measurement Equivalent Current processing Processing EMC investigations CST simulations 3m (FF) Emission NF calculation 6

7 Testing Workflow NF Measurement Equivalent Current processing Processing EMC investigations CST simulations 3m (FF) Emission NF calculation 7

8 SNF Measurement: Multi-probe system Near field probe array measurements SNF example Elevation Scanned Electronically via Probe Array Azimuth Scanned Mechanically via Turntable From 0deg to 180deg In a few minutes an antenna or other device of diameter 10λ can be measured (+20 frequency points). IEEE Recommended Practice for Near Field Antenna Measurements. IEEE Std

9 Testing Workflow NF Measurement Equivalent Current processing Processing EMC investigations CST simulations 3m (FF) Emission NF calculation 9

10 Use of Measured Sources Equivalent Currents From an antenna designer point of view it is highly desirable to obtain more information than just the radiation pattern to really understand the inner workings of the measured antenna. Post processing of the measured antenna data can give access to information similar to what is available from numerical simulation. Measurement of source antenna EQC representation of measured source F. Mioc, J. Araque Quijano, G. Vecchi, E. Martini, F. Milani, R. Guidi, L. J. Foged, M. Sabbadini, Source Modelling and Pattern Enhancement for Antenna Farm Analysis, 30th ESA Antenna Workshop May

11 Antenna Measurements & INSIGHT Processing Equivalence principle: all sources/scatterers within a closed volume conformal to the antenna can be substituted by a distribution of equivalent electric and magnetic currents (J, M) lying on an enclosing surface Σ R, radiating the same fields at Σ M. M J M J J M J M Dual integral equation enforcing the boundary condition of zero internal field to determine the two unknown currents J/M on the surface conformal to the antenna. The system of equations can be solved very efficiently with Method Of Moment (MOM) techniques. J. L. Araque Quijano, G. Vecchi. Improved accuracy source reconstruction on arbitrary 3- D surfaces. Antennas and Wireless Propagation Letters, IEEE, 8: ,

12 Link to Commercial Software => Huygens Box Commercial simulation SW are not able to import the equivalent currents on a geometry conformal to the source shape. A simple box fully enclosing the AUT must be used instead. Huygens Box 12

13 INSIGHT Multiple Applications Provide In-depth Understanding of Antenna Radiation Characteristics Antenna Diagnostics Measurement Diagnostics and Filtering Source for CEM numerical tools NF/NF Transformation Data Interpolation / Extrapolation EMC/ Detect spurious radiation Echo Suppression 13

14 INSIGHT Link: Application Examples Complex Environment EMC Application Reflector antenna fed by a SH4000 horn Antenna Placement Printed Circuit Board (PCB) SMC2000 monocone antenna on a rectangular plate SM6000 monopole on a mock-up of a space plane (only simulation) 14

15 Application Example SR40-A Reflector fed by SH4000 Dual Ridge Horn 15

16 SH4000 Measured Source : Equivalent Currents Good agreement is found! Directivity elevation plane pattern of the offset reflector antenna fed by the dual ridge horn at 8 GHz Reference: CST MWS Simulation Equivalent Currents (measured source) in CST MWS L. J. Foged, L. Scialacqua, F. Saccardi, F. Mioc, D. Tallini, E. Leroux, U. Becker, J. L. Araque Quijano, G. Vecchi, Bringing Numerical Simulation and Antenna Measurements Together, 8th European Conference on Antennas and Propagation, EuCAP, April 2014, Den Haag, Netherlands 16

17 Application Example Flush mounted antenna: SMC2200 monocone on a flat plate 17

18 Validation using Flush Mounted Antenna Antennas flush mounted on the structure represent cases of practical interest. 5λ The antenna measured in free-space cannot be considered unless a proper (local) boundary condition is reproduced. The preparation of the measured source for such problems is a bit more elaborate with respect to a free-space antenna. Measurement has to be carried out with particular attention to the proximity of the scattering object that modifies the current distribution on the antenna structure itself. 10λ Monocone antenna (MVG SMC2200) mounted directly on the plate in an off center 5.28GHz. 18

19 Validation using Flush Mounted Antenna Preparation and use of the measured source Measurement of the SMC2200 with 7λ diameter gnd plane If the antenna is flush mounted on the structure - we have to measure the antenna with a minimum of representative ground plane to impose the correct local boundary condition. We then need to eliminate the edge scattering from the ground plane in an additional post processing step. 19

20 Antenna placement problem : source modeling Source antenna modeling + EQC Representation Monocone antenna with limited ground plane measured in MVG StarLab (*) L.J. Foged, F. Mioc, B. Bencivenga M. Sabbadini, E. Di Giampaolo, Accurate infinite groundplane antenna measurements, AMTA, Salt Lake City, Utah, November (*) Infinite Ground Plane Boundary Condition Source Edge Diffraction Extraction (SDE) Equivalent Currents as measured source in CST EQC 20

21 SMC2200 monocone on a rectangular plate (1/2) Measurement vs. Link, φ = 0 21

22 SMC2200 monocone on a rectangular plate (2/2) Measurement vs. Link, φ = 90 22

23 Application Example Flush mounted antenna: SM6000 monopole on a Space Plane mock-up 23

24 SM6000 monopole on a space plane mock-up SM6000 Monopole antenna [6-18]GHz SMC2200 Monocone antenna Rectangular plate [0.6 x 0.3] m Mock-up of a space plane 24

25 SM6000 monopole on a space plane mock-up CAD Model of SM6000 monopole on the space plane mock-up SM6000 monopole replaced by measured source 25

26 SM6000 monopole on a space plane mock-up Full-Wave Simulation Difference on predicted peak directivity is 0.36dB Simulation with measured source 26

27 Using NF EQC sources in CST (1/2) NF Measurement MVG system Equivalent Current processing Direct import/export NF &FF (copy and paste) Export currents to CST via a set of data file (NFS format) 27

28 Using NF EQC sources in CST (2/2) Browse for the NFS folder. Select all the 24.xml files using CTRL. E -field H -field 28

29 Application Example EMC Pre-Compliance, Diagnostics and Problem Solving using Near-Field measurements and post processing techniques 29

30 Introduction old-style EMC testing new-style EMC testing 3-D Near Field measurement techniques Pre-Compliance : NFFF transformation Diagnostics : Equivalent surface currents Problem solving : Import measurement in computational EM tools 30

31 EMC Testing Workflow Printed Printed Circuit Board Board (PCB) (PCB) NF Measurement Equivalent Current processing Processing EMC investigations EMC investigations 3m (FF) NF, FF study Emission scattering object is a wire NF calculation in a shielding box NF Source NF Source Diagnostics Diagnostics 31

32 Printed Circuit Board (PCB) model Measurement Simulation Frequency band [ ] MHz Our investigation at 640MHz PCB, Single layer, FR mm x 225 mm with substrate thickness 2mm. Three 50Ω traces and ground plane. One trace is excited and terminated, 50Ω source and load impedance. Low emission through coupling between the traces. >99% of the power is absorbed by the load. 32

33 Field Emission at 3m Distance phi=0 Measurement Source: INSIGHT measured source in CST Full Wave Simulation: Reference 33

34 Field Emission at 3m Distance phi=90 Measurement Source: INSIGHT measured source in CST Full Wave Simulation: Reference 34

35 Computational Analysis: Wire Close to the PCB Wire dimensions [2x2x200]mm The wire is in front of the fed strip D =75 mm, 0.16 Equivalent model with the NF source wire d 224mm 150mm PCB Fed strip 75mm 35

36 Presence of the wire: impact on the FF pattern at 640MHz PCB PCB with the wire Directivity radiation Presence of the wire causes an 2 db increase in peak directivity 36

37 Computational Analysis: Wire Close to the PCB Full wave simulation - PCB + wire Equivalent source (PCB) + wire 37

38 Computational Analysis: Wire Close to the PCB Reference Full wave NF source (PCB) + wire NF sou (PCB) + GP + wire NF sou (PCB) + GP + FR4 + wire PCB + wire 38

39 Computational Analysis: Wire Close to the PCB Reference Full wave PCB + wire NF sou (PCB) + GP + FR4 + wire 39

40 Max Radiation Comparison : 640MHz Full Sim (REFERENCE) Sim S Sim S +GP Sim S + GP +FR4 Max radiation [dbi] The predicted emission difference is 0.37dB 40

41 Next steps Radiated emission analysis using numerical computation and measured source. Comparison with StarLab measurement of PCB with wire. 41

42 PCB Inside Enclosure Example Full wave simulation (FDTD) Measured PCB in the simulation (FDTD) scatterer Shielding box Measured NF source 42

43 PCB Outside Enclosure Example Full wave simulation (FDTD) Measured PCB in the simulation (FDTD) Measured PCB 43

44 Electric Field Reference: Full wave simulation (FDTD) Measured PCB in the simulation (FDTD) 50dB dynamic range E peak inside the NFS 44

45 Electric Field Reference: full wave NF source NF source FR-4 substrate + ground plane 50dB dynamic range 45

46 Electric Field Reference: full wave NF source FR-4 substrate + ground plane Good agreement 46

47 Far Field Radiation Reference: full wave NF source FR-4 substrate + ground plane The predicted emission difference is 0.3dB 47

48 Comments & Conclusion INSIGHT processing, has been proposed as the missing link between numerical simulation and antenna measurements. The method has been applied in various scenarios including the case of flush mounted low directivity antennas in antenna placement scenarios. The achieved agreements (Measurements/Fullwave and Link Simulations) are considered sufficient for most antenna placement applications. We are continuing to improve the source representation using INSIGHT processing and The Link. 48

49 Comments & Conclusion Different applications in EMC pre-compliance scenarios have been investigated A representative PCB has been measured and measurements/simulation compared at 3m distance. Radiated emission analysis using measured sources and numerical computation of different scenarios show (very) promising results. 49

50 Thank You! 50

51 References: Equivalent Currents/Source Method J. L. Araque Quijano, G. Vecchi. Improved accuracy source reconstruction on arbitrary 3-D surfaces. Antennas and Wireless Propagation Letters, IEEE, 8: , J. L. A. Quijano, G. Vecchi, L. Li, M. Sabbadini, L. Scialacqua, B. Bencivenga, F. Mioc, L. J. Foged "3D spatial filtering applications in spherical near field antenna measurements", AMTA 2010 Symposium, October, Atlanta, Georgia, USA. L. Scialacqua, F. Saccardi, L. J. Foged, J. L. Araque Quijano, G. Vecchi, M. Sabbadini, Practical Application of the Equivalent Source Method as an Antenna Diagnostics Tool, AMTA Symposium, October 2011, Englewood, Colorado, USA J. L. Araque Quijano, L. Scialacqua, J. Zackrisson, L. J. Foged, M. Sabbadini, G. Vecchi Suppression of undesired radiated fields based on equivalent currents reconstruction from measured data, IEEE Antenna and wireless propagation letters, vol. 10, 2011 p L. J. Foged, L. Scialacqua, F. Saccardi, F. Mioc, D. Tallini, E. Leroux, U. Becker, J. L. Araque Quijano, G. Vecchi, Bringing Numerical Simulation and Antenna Measurements Together,, IEEE Antennas and Propagation Society International Symposium, July 6-11,

52 References: EMC Investigation Technology M. Sorensen, O. Franek, G. Pedersen, " Recent Developments in Using Measured Sources in Computational EMC", to be presented at Antennas and Propagation (EuCAP), th European Conference on, April 2015 M. Sorensen, I. Bonev, O. Franek, G. Petersen, and H. Ebert, "How to handle a Huygens' Box Inside an Enclosure," in Electromagnetic Compatibility (EMC), 2013 IEEE International Symposium on, Aug 2013, pp O. Franek, M. Sorensen, H. Ebert, and G. Pedersen, "Influence of nearby obstacles on the feasibility of a huygens box as a field source," in Electromagnetic Compatibility (EMC), 2012 IEEE International Symposium on, Aug 2012, pp M. Sorensen, O. Franek, G. Pedersen, A. Radchenko, K. Kam, and D. Pommerenke, "Estimate on the Uncertainty of Predicting Radiated Emission from Near-field Scan Caused by Insufficient or Inaccurate Nearfield Data: Evaluation of the Needed Step Size, Phase Accuracy and the Need for all Surfaces in the Huygens' Box," in Electromagnetic Compatibility (EMC EUROPE), 2012 International Symposium on, Sept 2012, pp

53 References: Measurement and INSIGHT Tools (HW & SW) L.J. Foged, A. Scannavini, Efficient testing of wireless devices from 800MHz to 18GHz, Radio Engineering Magazine, Vol 18, No 4, December Foged, L.J.; Estrada, J.; Iversen, P.O.; Spherical near field testing of small antennas from 800MHz to 18GHz, IEEE International Symposium on Antennas and Propagation 2007, June 10-15, Honolulu, HI, USA. Foged, L.J.; Duchesne, L.; Durand, L.; Herbiniere, F.; Gross, N.; Small Antenna Measurements in Spherical Nearfield Systems, The second European conference on Antennas and propagation, EuCap2007, Nov