Mtt 08 Poster Holzman 3 14 08

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Mtt 08 Poster Holzman 3 14 08

  1. 1. Analyzing Broad-Band Electromagnetics Problems with Commercial Software— Time Domain vs. Frequency Domain Eric Holzman 1 , William Nelson 1 , Brian Swift 1 , James Willhite 2 and Shrikrishna Hegde 2 1 Northrop Grumman, Baltimore, MD 21240, USA 2 Sonnet Software, Syracuse, NY 13212, USA
  2. 2. Outline of Our Comparison <ul><li>Overview of finite element EM software </li></ul><ul><li>Solving in time vs. frequency domain </li></ul><ul><li>Analyze 4 problems in both domains </li></ul><ul><li>Use commercial software from CST* </li></ul><ul><li>Compare the CPU time and RAM </li></ul><ul><li>Which domain is superior? </li></ul>*Computer Simulation Technology, www.cst.com
  3. 3. Finite Element 3-D EM Software <ul><li>Time and Frequency domain </li></ul><ul><li>Mature, cell-based algorithms </li></ul><ul><li>Available commercially (CST, ANSOFT) </li></ul><ul><li>Inputs: arbitrary 3-D structure geometry </li></ul><ul><li>Outputs: S-parameters, radiation patterns, radar cross section, fields </li></ul>
  4. 4. Theory: Time vs. Freq Domain Which requires less CPU time and RAM? (Direct solver only) 1 solution  NxN N solutions  NxN S-parameters Any  ,  incidence Normal incidence Periodic structures No Yes Transient problems 1 solution  1 pt 1 solution  All Frequency response (2  L/  ) 3 (2  L/  ) 3 Number of cells Frequency Time Feature
  5. 5. Analyze real problems in time & freq <ul><ul><li>ring hybrid </li></ul></ul><ul><ul><li>1:4 divider </li></ul></ul><ul><ul><li>conical antenna </li></ul></ul><ul><ul><li>pillbox antenna </li></ul></ul>time freq Analyze 4 devices in both solver domains Comparison criteria Use CST Microwave Studio ™ for all analysis CPU Time RAM
  6. 6. IBM PC platform for all problems Ring Hybrid 1:4 divider Conical antenna Pillbox antenna Freq-domain analysis of pillbox requires a 64-bit CPU 16 3 3 3 3 3 3 3 RAM (GB) 3.0 3.6 3.6 3.6 3.6 3.6 3.6 3.6 Speed (GHz) 64 32 32 32 32 32 32 32 No. of bits Freq Time Freq Time Freq Time Freq Time CPU features
  7. 7. Ground Rules <ul><li>Generate a single model of each device </li></ul><ul><li>Refine mesh to convergence </li></ul><ul><li>Time domain mesh: uniform </li></ul><ul><li>Frequency domain solver: iterative </li></ul><ul><li>Frequency domain sweep: interpolating </li></ul>
  8. 8. March’s Ring Hybrid in Stripline ports ports S. March, “A Wideband Stripline Hybrid Ring,” IEEE Trans. Microwave Theory & Tech , p. 361, June 1968. Bandwidth: 7-11 GHz return loss isolation insertion loss FD TD
  9. 9. Stripline 1:4 Wilkinson Divider output ports common port Bandwidth: 6-16 GHz Port separation is large isolation Common port return loss insertion loss FD TD
  10. 10. Conical Antenna over Ground Bandwidth: 0.15-1.00 GHz Coax feed Antenna Ground Frequency (GHz) -40 -30 -20 -10 0 0 0.2 0.4 0.6 0.8 1 |S11| (dB) FD TD
  11. 11. Pillbox—a very large antenna E. L. Holzman, “Pillbox Antenna Design for Millimeter-Wave Base Station Applications,” IEEE Ant. & Prop. Mag. , Vol. 45, #1, pp.27-37, Feb. 2003 . Reflector surface Waveguide Port Radiating aperture FD TD TD: 23-32 GHz FD: 28-32 GHz ~40 
  12. 12. Time Domain—fastest & least RAM Ring Hybrid 1:4 divider Conical antenna Pillbox antenna 86 1001 20 1001 14 1001 11 1001 # of freqs 1 1 1 1 25 25 16 16 # of S-pars 13 h 3.6 h 17 m 0.5 m 86 m 26 m 10 m 0.9 m CPU Time 6.4 0.68 0.59 0.020 1.38 0.192 0.26 0.011 RAM (GB) Freq Time Freq Time Freq Time Freq Time Parameter
  13. 13. Summary--TD advantage over FD <ul><li>3 to 30 times in CPU time </li></ul><ul><li>6 to 30 times in RAM </li></ul><ul><li>$ savings --less powerful PCs solve the same problems faster in time domain </li></ul><ul><li>Time domain’s biggest advantages for </li></ul><ul><ul><li>Broadband devices </li></ul></ul><ul><ul><li>Electrically large devices </li></ul></ul>Holzman (eholzman@ieee.org)

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