Resonant EBG-Based Common Mode Filter for LTCC Substrates

Transcription

1 UAq EMC Laboratory Resonant EBG-Based Common Mode Filter for LTCC Substrates C. Olivieri, F. De Paulis, A. Orlandi S. Connor, B.Archambeault UAq EMC Laboratory, University of L'Aquila, L'Aquila, Italy D.J. Pommerenke IBM System and Technology Group, Research Triangle Park, 3039 Cornwallis Rd, NC 27709, USA Dec 25, 2015 Missouri University of Science & Technology, EMC Laboratory, Rolla, MO 65401, USA

2 OUTLINE The resonant EBG-based CM filter Resonant EBG-based CM filter design 8 GHz Design 1.5 GHz Design Results for the Two Designs Decreasing the direct EM radiation Conclusions NEXT STEPS 2

3 OUTLINE The resonant EBG-based CM filter Resonant EBG-based CM filter design 8 GHz Design 1.5 GHz Design Results for the Two Designs Decreasing the direct EM radiation Conclusions NEXT STEPS 3

4 The resonant EBG-based CM filter Initial Geometry A quarter-wavelength resonator based filter constructed on a ceramic LTCC substrate is taken into account for the present study. According to [1] one end of the resonator is terminated through a via V to the ground plane, while the other endisleftopeninthesubstrate. V GND via L Length Traces Resonator GND Metal layers thickness = 8 μm 137μm 137μm F Resonator fingers [1] Q. Liu, S. Xui, D. Pommerenke, "Narrowband and broadband common mode filter based on a quarter-wavelength resonator for differential signals", IEEE Trans. on Electromagnetic Compatibility, early article access, August

5 OUTLINE The resonant EBG-based CM filter Resonant EBG-based CM filter design 8 GHz Design 1.5 GHz Design Results for the Two Designs Decreasing the direct EM radiation Conclusions NEXT STEPS 5

6 Resonant EBG-based CM filter design Using the reported formula the resonator can be tuned on a specific target frequency L = c 0 4 f ε r In this case 8 GHz [db] [db] Scc21 - Starting Configuration Frequency [GHz] Sdd21 - Starting Configuration Frequency [GHz] 6

7 Resonant EBG-based CM filter design However the originally designed geometry suffers of some problems: 1. Excessively big occupied surface 2. Unwanted resonances [db] Both the problems can be addressed through some design reworks -15 Scc21 - Starting Configuration Frequency [GHz] The elimination of some proper structures can allow a reduction of size and in the meanwhile cancel the undesired resonances 7

8 Desired resonance: Field monitor analysis Fiel 8.18GHz. Cutplane position: Z= Resonance of the main notch designed around 8 GHz

9 Undesired resonance: Field monitor analysis Fiel GHz. Secondary notch resonance due to the GND fingers. Cutplane position: Z= This resonance can be eliminated removing the GND fingers enabling also an horizontal shrinking

10 OUTLINE The resonant EBG-based CM filter Resonant EBG-based CM filter design 8 GHz Design 1.5 GHz Design Results for the Two Designs Decreasing the direct EM radiation Conclusions NEXT STEPS 10

11 8 GHz Design: 1st Trial In the first trial the following steps have been addressed: 1. Elimination of the GND fingers 2. Comparison with the original geometry 0 Scc21 behaviour V F L 4230μm [db] μm -15 "Initial" Configuration "Trial 1" Frequency [GHz] 11

12 8 GHz Design: 2nd Trial In this trial the following changes have been operated: 1. Folding of the fingers in order to reduce the space 2. Shrinking of the resonator structure 0 Scc21 behaviour V F L 3232μm [db] μm -15 "Initial" Configuration "Trial 1" "Trial 2" Frequency [GHz] 12

13 8 GHz Design: 3rd Trial The final configuration is obtained moving the stitching via V toward the traces, at the center of the EBG, while the electrical length of the resonant EBG is kept around the same. 0 Scc21 behaviour V F L 2403μm 1740μm [db] "Initial" Configuration "Trial 1" "Trial 2" "Final" configuration Frequency [GHz] The final resonator size is much smaller than the original one. The CM IL behaviour is quite satisfactory for filtering purposes. 13

14 OUTLINE The resonant EBG-based CM filter Resonant EBG-based CM filter design 8 GHz Design 1.5 GHz Design Results for the Two Designs Decreasing the direct EM radiation Conclusions NEXT STEPS 14

15 1.5 GHz Design: 1st Trial The design steps followed for the 8 GHz design were replicated for a 1.5 GHz filter V F L The initial geometry has been obtained tuning the resonator length L according to the general formula 6740μm 9403μm Following the basic approach the overall size has been limited bending the fingers in a spiral way 15

16 1.5 GHz Design: 1st Trial Preliminary Results 0 Scc21 behaviour [db] "initial" design Frequency [GHz]

17 1.5 GHz Design: 2nd Trial Loaded CM filter configuration V L F 7703μm 5640μm IDEA: Addition of a loading capacitance helping to reduce the structure size. Further shrinking obtained narrowing the trace structures so increasing the distributed inductance and also adding a capacitive loading patch at the end of the fingers. 17

18 1.5 GHz Design: 2nd Trial Loaded CM filter configuration: RESULTS 0 Scc21 behaviour -5 [db] % Room Frequency [GHz] "Initial" design "loaded" config. Lower filtering feature but reduced occupied surface 18

19 1.5 GHz Design: 3rd Trial Cascaded filter configuration IDEA: Cascading of more unit cell filters to increase the notch depth. 9403μm 13880μm The expected result is that the notch depth will increase almost doubling its initial value. Consequent doubling also of the area 19

20 1.5 GHz Design: 3rd Trial Cascaded filter configuration: RESULTS 0 Scc21 behaviour -10 [db B] % Filtering -30 "Final" 1.5 GHz configuration "Cascaded" 1.5 GHZ configuration Frequency [GHz] Clear increase of the filtering performance, as expected. Filtering action improvement despite of doubled surface 20

21 OUTLINE The resonant EBG-based CM filter Resonant EBG-based CM filter design 8 GHz Design 1.5 GHz Design Results for the Two Designs Decreasing the direct EM radiation Conclusions NEXT STEPS 21

22 Results for the Two Designs Differential mode IL behaviour [db] "Initial" Configuration "Trial 1" "Trial 2" "Final" configuration Sdd Frequency [GHz] [db] [ Sdd21 "Final" 1.5 GHz configuration "Final" Cascaded 1.5 GHz configuration Frequency [GHz] Basically unchanged Sdd21 among all the 8GHz trials, slight degradation for the 1.5GHz cascaded configuration case. 22

23 Results for the Two Designs The performances of the various solutions have been compared with regard to different FoMs. Comparisons: Classical EGB Vs Resonator Figure of Merit CLASSIC EBG RESONANT RESONANT EBG EBG (Initial) (Final) Occupied Surface [mm 2 ] S cc21 Notch Depth [db] Notch Amplitude/Surface [db/ mm 2 ] BW [MHz] Best FoM 23

24 Results for the Two Designs The same thing has been done also comparing the solutions 8GHz and the ones Comparison: Resonator Stand-alone Vs Cascaded Figure of Merit RESONANT EBG RESONANT EBG CASCADED S cc21 Notch Depth [db] Occupied Surface [mm 2 ] Notch Amplitude/Surface [db/ mm 2 ] 9.4 x x dB [MHz] - 54 Best FoM 24

25 Results: TRP Comparisons In order to have an idea about the performances of the resonator with regard to the radiated power, a TRP comparison can be done Comparisons: Classical EGB Vs Quarter Wavelength Resonator -20 TRP Comparison of R-EBG with 5RectPatches and Quarter Wavelength Resonator R-EBG (RECT patches) TRP (dbw) Scc21 [db] Resonator 8 GHz "Final" R-EBG with 5 RectPatches Best FoM R-EBG with 5 Rectangular patches Frequency [GHz] Frequency (GHz) 25

26 OUTLINE The resonant EBG-based CM filter Resonant EBG-based CM filter design 8 GHz Design 1.5 GHz Design Results for the Two Designs Decreasing the direct EM radiation Conclusions NEXT STEPS 26

27 Decreasing the direct EM radiation The resonant EBG was overlaid by a thin sheet of lossy material in order to increase the bandwidth of the filter Copper patch Absorbing material D Cross section of the resonator including also the lossy material d d= 137μm D=1mm The differential traces exciting the resonator structure are overlaid in turnbyametalpatch The lossy material was originally thought also in order to obtain a twofold benefit: the increase of the bandwidth and the reduction of the radiated power. 27

28 Decreasing the direct EM radiation 0 Scc21 behaviour -5 [db] No Lossy Material and Patch Lossy material - BSR1 Lossy material - MCS Lossy material - FGM40 Resonator with added patch only Frequency [GHz] The presence of the lossymaterials gives rise to an increase of the bandwidth, without heavily altering the design center frequency 28

29 OUTLINE The resonant EBG-based CM filter Resonant EBG-based CM filter design 8 GHz Design 1.5 GHz Design Results for the Two Designs Decreasing the direct EM radiation Conclusions NEXT STEPS 29

30 CONCLUSIONS The presented stepped design procedure enables to reach a final design with equal notch depth (and same differential mode performances) of the initial one but with a much more reduced occupied surface. Combining planar EBG-based common mode filters with a quarter-wavelength resonator has been demonstrated to have beneficial effects in terms of reduction of the dimension of the planar filter. 30

31 OUTLINE The resonant EBG-based CM filter Resonant EBG-based CM filter design 8 GHz Design 1.5 GHz Design Results for the Two Designs Decreasing the direct EM radiation Conclusions NEXT STEPS 31