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Slides ma sc defense final

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masters thesis defense - broadband negative group delay phase shifters

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Slides ma sc defense final

  1. 1. Broadband Microwave Negative Group Delay Transmission Line Phase Shifters Sinan Keser M.A.Sc. Thesis Defense October 1, 2012
  2. 2. Outline• Introduction• Background• Loaded Transmission Lines• Negative Group Delay (NGD) Phase Shifter Design• Simulation & Experimental Results• Conclusions 2
  3. 3. Phase shifters BasicsTransmission-type phase shifter phase 𝜙 = arg 𝑆21 𝜙 phase delay 𝜏 𝑝 = − 𝜔 𝜕𝜙 group delay 𝜏 𝑔 = − 𝜕𝜔 𝜙 𝑡𝑜𝑙 phase BW Δ𝜔 ≈ 𝜏 𝑔 𝜔0 3
  4. 4. Motivation• Design a NGD network to cascade with an equivalently matched phase shifter with an equal but positive group delay to achieve a flat phase response (zero group delay). 4
  5. 5. Background – NGD CircuitsNGD & NRI Loaded TL Unit Cell NGD feedback Amplifier Microwave NGD FET Amplifier Mojahedi, et al. (2004) Kandic, et al. (2011) Ravelo, et al. (2007) X Non reciprocal X Narrowband X High Return & Insertion Loss / Poor Efficiency X Combining Gain and NGD into one stage is not beneficial 5
  6. 6. Background – Metamaterial TLs Negative Refractive Index Composite Right/Left-HandedTransmission Line (NRI-TL) Transmission Line (CRLH-TL) Eleftheriades, et al. Caloz, et al.  Passive  Broadband  Low Return loss  Low Insertion loss  Positive or Negative Phase Delay … But Always Positive Group Delay 6
  7. 7. Proposal• Design a broadband impedance matched loaded TL with a specified negative group delay, and: – Determine relationship between NGD, Insertion Loss and NGD Bandwidth. (trade-offs) – Minimize the frequency variation of both group delay and gain.• Given the specifications of a phase shifter: – Select either positive or negative phase delay on the basis of group delay minimization, and – Combine with NGD unit cell to produce a zero group delay phase over a wideband. 7
  8. 8. Loaded TL Unit Cell Small host TL 𝜃 𝑇𝐿 ≪ 1 𝐿 𝑇𝐿 = 𝑗𝑍0 𝜃 𝑇𝐿 𝐶 𝑇𝐿 = 𝑗𝑌0 𝜃 𝑇𝐿Balanced Condition Metamaterial-TL (MTM-TL) 𝑍 𝑌 = ≪1 𝑍0 𝑌0 Loading Elements Host TL 0 𝑒 −𝑍 𝑍0𝑆 𝑀𝑇𝑀 ≈ 𝑒 −𝑗 𝜃 𝑇𝐿 𝑒 −𝑍 𝑍0 0 Impedance matched and Reciprocal 8
  9. 9. MTM-TL Characteristics Equivalent TL 1 𝛾= 𝑍𝑛 𝑍0 𝑛 1ln 𝑆21 = − 𝑅 + 𝑅2 + ⋯ + 𝑅 𝑛 • Insertion Losses add 𝑍0 1 1 𝜙21 = − 𝑋 + 𝑋2 + ⋯ + 𝑋 𝑛 • Phases add 𝑍0 1 1 𝜕𝑋1 𝜕𝑋2 𝜕𝑋 𝑛 𝜏𝑔 = + +⋯+ • Group delays add 𝑍0 𝜕𝜔 𝜕𝜔 𝜕𝜔 9
  10. 10. Lossless MTM-TL & Group Delay• Lossless unit cells always have a positive group delay proportional to the stored energy Wav (in reactive elements) 𝑊𝑎𝑣 1 𝜕𝑋 𝜏𝑔 = = >0 𝑎2 𝑍0 𝜕𝜔Use 1st order MTM-TLs to minimize group delay 1 𝜔𝑐 = , 𝑍0 = 𝐿/𝐶 𝐿𝐶 10
  11. 11. Low-Pass & High-Pass S21 Responses low loss S21 Polar Plot 𝜔≫1𝜙 𝐿𝑃 ≈ −𝜔/𝜔 𝑐 𝜔↑ 𝜙 𝐻𝑃 ≈ 𝜔 𝑐 /𝜔 𝜔≪1• The balanced NRI-TL is the combination of both low-pass and high-pass unit cells (band-pass).• To minimize its group delay, the host TL length should be minimized. 11
  12. 12. Proposed NGD Unit Cell S21 Polar Plot NGD 𝑍 𝑌 𝐴 𝛾= = = 𝑍0 𝑌0 1 + 𝑗𝑄 𝜔 − 𝜔0 𝜔0 𝜔 𝑅𝑧 𝑍0 1 𝐿𝑧 𝐶𝑦 1 1𝐴= = , 𝑄= = 𝑅𝑦 , 𝜔0 = = 𝑍0 𝑅𝑦 𝑅𝑧 𝐶𝑧 𝐿𝑦 𝐿 𝑧 𝐶𝑧 𝐿 𝑦 𝐶𝑦 12
  13. 13. NGD Unit Cell Phase and Magnitude Response Δ𝜙 𝑝𝑝 = ILmax = 𝐴 𝜔0 𝐼𝐿 𝑚𝑎𝑥 Δ𝜔 𝑁𝐺𝐷 = 𝑄 𝜏 𝑔,𝑚𝑎𝑥 =2 Δ𝜔 𝑁𝐺𝐷 2𝐴𝑄 𝜏 𝑛𝑔𝑑 ,𝑚𝑎𝑥 = 𝜔0 13
  14. 14. Constant NGD with varying Insertion Loss BW5 A=5dB BW3 A=1dB BW1 A=3dB A=1dB A=3dB A=5dBFor a constant NGD, Bandwidth increases with increasing Insertion Loss 𝐼𝐿 𝑚𝑎𝑥 = 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡 Δ𝜔 𝑁𝐺𝐷 14
  15. 15. Maximum Return Loss per NGD unit cell Return Loss vs. Frequency Max. Return Loss vs. Max. Insertion Loss • Return loss increases as Insertion loss increases • For a low return loss, the insertion loss (and thus bandwidth- NGD product) per unit cell must be kept sufficiently low. 15
  16. 16. ADS Ideal Microstrip Simulation Setup• NGD unit cell component values are determined by specifying the phase shifters 1. centre frequency, 2. characteristic impedance, 3. NGD (to produce zero group delay) and 4. maximum Insertion Loss. TL lengths determine phase delay 16
  17. 17. Simulated -300 NGD TL Phase Shifter ±20 phase bandwidth Unloaded TL:105 MHz NGD: 550 MHz NGD NGD Unloaded TL Unloaded TL NGD Return Loss • Return loss < 40dB • Insertion Loss < 3dB NGD Unloaded TL 17
  18. 18. Simulated -900 (two-cells) NGD TL Phase Shifter NGD NGD unit cell unit cell NGD NGD Unloaded TL Unloaded TL ±50 phase bandwidth Unloaded TL: 87 MHz NGD: 650 MHz NGD Unloaded TL NGD Return Loss • Return loss < 37dB • Insertion Loss < 8dB 18
  19. 19. -450 Two-Cell Stagger Tuned NGD Phase Shifter NGD NGD unit cell 1 unit cell 2two-cell NGD unit cell 1 unit cell 2 Unloaded TL ±20 phase bandwidth Unloaded TL: 105 MHz NGD: 905 MHz input port output port • Return loss < 33dB • Insertion Loss < 4dB • Low IL ripple 19
  20. 20. Hybrid NRI-NGD 00 Phase Shifter ±2o Phase bandwidth NRI only: 79MHz NGD-NRI: 553MHz• Combination of NRI (high-pass) and NGD (lossy resonator) into one non-symmetric unit cell.• Low return loss (< 20 dB) & Insertion Loss (< 2.5 dB)• Reduced size & number of components 20
  21. 21. Beam Squint for a Linear Series-Fed Antenna Array 𝐴𝑟𝑟𝑎𝑦 𝐹𝑎𝑐𝑡𝑜𝑟 𝐵𝑒𝑎𝑚 𝑆𝑞𝑢𝑖𝑛𝑡 2𝑚𝜋 𝜕𝜃 𝜏𝑔 − 𝜏𝑝 + = 𝜔 𝜕𝜔 𝜔𝑑 𝐸 𝑐 cos 𝜃 𝜕𝜃 to remove beam squint =0 : 𝜕𝜔 1) m=0 main lobe  NRI-TL 2) equal phase and group delay  NGD ±50 beam angle Phase Shifter Bandwidth -3600 Unloaded TL 27 MHz 00 NRI –TL 122 MHz Hybrid 00 NGD NRI-TL 607 MHz 21
  22. 22. Experimental SetupRogers RT Duroid 5880 substrate (εr=2.2) – 50Ω Microstrip TLsRF surface mount components (0402, 0603) – Coilcraft ceramic inductors – Murata ceramic capacitors – Vishay thick film resistorsModelithics component models – Empirical data models – Substrate scalable, pad dimension scalable 22
  23. 23. -300 NGD TL Phase Shifter (3dB loss) component values ½Z Y R 8Ω 156 Ω L 1.5 nH 20 nH C 16 pF 1.2 pF 23
  24. 24. -300 NGD TL Phase Shifter (3dB loss)Summary• ±20 phase bandwidth: 610MHz – 1240MHz (63%) 450% increase over unloaded TL (14%)• Measured Insertion Loss < 3.1dB• Measured Return loss < 20dB 24
  25. 25. -300 NGD TL Phase Shifter (2dB loss) component values ½Z Y R 5.9 Ω 210 Ω L 1 nH 33 nH C 14 pF 0.8 pF 25
  26. 26. -300 NGD TL Phase Shifter (2dB loss) Insertion Loss [dB]Phase [deg] Return Loss [dB]Summary• ±20 phase bandwidth: 680MHz – 1160MHz (51%) 364% increase over unloaded TL (14%)• Measured Insertion Loss < 2.12 dB• Measured Return Loss < 20dB• Less Ins. Loss but also less NGD bandwidth 26
  27. 27. 00 NGD NRI-TL Phase Shifter component values ½Z Y NRIR 10 Ω 100 Ω -L 3.6 nH 30 nH 56 nHC 11 pF 2.7 pF 27 pF 27
  28. 28. 00 NGD NRI-TL Phase Shifter Measured NGD NRI-TL phase error (700MHz) = +3.60 ±20 phase bandwidth NRI-TL: 71 MHz NGD NRI-TL: 188 MHz Measured • Return loss < 14 dB • Insertion Loss < 3.37 dB 28
  29. 29. Conclusions• Passive Broadband NGD Unit Cell Proposed – Frequency, Impedance and NGD scalable – Quasi-linear phase at centre frequency – NGD, Insertion Loss and Bandwidth trade-off identified• NGD combined with lossless phase shifters to significantly increase phase bandwidth• Beam Squint may only be removed entirely with NGD phase shifters.• Experimentally verified microstrip NGD phase shifters with both positive and negative phase delays at 0.5GHz – 1.2GHz. 29

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