Computer Simulations with a 25 µm Silicon (Er=11.9) Subtrate


Electric field of probe in a fullheight waveguide

HFSS Simulations Results
    Si based E-probe inside waveguide  
  • 3-D rendering of probe  
  • Top view of probe  
  • Probe Impedance on Smith Chart  
  • Probe Impedance in Cartesean units
         Effect of breaking WG wall (Substrate not suspended, i.e. no air underneath substrate yet)  
  • 3-D rendering of probe and substrate extending outwards from waveguide,  
  • E-field in substrate, view from waveguide
        Note the importance of extending substrate across the waveguide.  
  • E-field in substrate, view from IF channel  
  • Impedance (Smith Chart) showing effect of taking probe out of the waveguide:
        Note also that the "gap source" simulation has no air directly above substrate, has 25 µm airgap underneath the subtrate,
        and behaves very similar to the case of a very small (40 x 25 µm) waveguide port.
         Effect of exctending substrate for structural support across the waveguide  
  • 3-D rendering of stubstrate extending all the way across the full height waveguide  
  • Impedance (Smith Chart)
         Probe impedance as a function of Probe Radius and throat width  
  • 3-D rendering of 80 µm probe on 25 µm substrate. Airgap below substrate: 25 µm. Waveguide port: 140 x 25 µm  
  • E-field in ground plane, maximum extend.  
  • E-field in ground plane, maximum extend.  
  • Impedance (Smith Chart) for R=70 µm and R=80 µm. Thoat width varied from 1.3µm to 3.0 µm
         Introduction of a RF Choke, the effect on the probe impedance when perfect ground is replaced.  
  • 3-D rendering of a 2-section RF Choke Substrate: 140 x 25 µm. Airgap at the side of the substrate: 10 µm
        Air_bottom: 25 µm, Air_top: 25 µm, Gap-source  
  • 3-D wire frame of 2-Section RF Choke  
  • Impedance (Smith Chart) for both perfect ground and 2-Section RF Choke.Note that the significant reduction of Probe impedance (real and imaginary) when the ground is no longer touching the waveguide wall. This effect has been confirmed with scale model measurements. In addition, increasing the probe radius, changes it's shape and slightly raises the impedance. It has also been observed that increasing the substrate material changed the Probe's reactive component, and increasing the airgap at the wg Wall effects the probe's real impedance.  
  • 3D rendering of a 4-section RF ChokeThe white blocks represent wire bonds  
  • 3D rendering of a 4-section RF ChokeThe white blocks represent wire bonds  
  • Impedance (Smith Chart) for a 2-Section and 4-section RF Choke. We notice a large effect when going from a perfect ground to a RF choke. However going from a 2-Section RF Choke to a 4-Section RF choke has very little effect on the probe impedance. This can be understood in light of the dramatic field distribution change near the troat of the probe with the introduction of the RF choke.  
  • Maximum extend of the E-Field distribution in a 4-section RF Choke. The white whire frame blocks represent wire bonds  
  • Minimum extend of the E-Field distribution in a 4-section RF Choke. Note the evanescent fields extending slightly (15-25 µm)
        in to the IF channel.
         Effect of non-perfect grouding near WG Wall  
  • 3-D rendering of inperfect ground contact Substrate: 140 x 25 µm. Airgap at the side of the substrate: 10 µm  
  • Impedance (Smith Chart) for both inperfect ground (0, 25 µm, 50 µm) airgaps. Result shows that the
        ground situation at the waveguide is cirtical.
         Effect of non-ideal RF choke, needed to fit RF Matching network  
  • 3D rendering of a 4-section modified RF choke  
  • Impedance (Smith Chart) for both ideal and imperfect RF Choke.
         Effect of misalligning RF/Choke at WG Wall  
  • Top view of misalligned RF choke (-4% of b-dim Wg).  
  • Top view of misalligned RF choke (+4% of b-dim Wg).  
  • Top view of a perfectly alligned RF choke (+0% of b-dim Wg).  
  • Impedance (Smith Chart) for both ideal and imperfect RF Choke. A slight misalignment can be used to slightly alter the probe impedance.
         Effect of changing length first section of the RF Choke  
  • 3D rendering of a 4-section final RF choke/e-plane probe. Simulated wirebonds are 25µm, and airgap is 25 µm  
  • Impedance (Smith Chart) showing the effect of increasing/reducing the first section of the RF Choke.
        Final centroid impedance is 28 Ω real for the Silicon probe (yellow curve).
     
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            Web Page created and last updated on April 16, 2001, by: Jacob W. Kooi