Yahhhh. High Speed Digital. Some sort of parallel processor thing that 
     runs at a Ghz. He wants to do the isolated Coaxial thing without 
     coplanar waveguide. He wants to produce a ground via barrier that 
     separates digital from control. (Probably on advanced <cleaner than 
     normal> materials)
     Groovster
     
     
______________________________ Reply Separator _________________________________
Subject: Re: FAB: RFI/EMI Vias
Author:  [log in to unmask] at SMTPLINK-HADCO 
Date:    5/23/96 7:44 PM
     
     
     
          Groove man,
     
          I would first ask: Does the customer want controlled 
          impedences on the board?  (I'm assuming they do...)
     
          Doug
     
     
______________________________ Reply Separator _________________________________
Subject: FAB: RFI/EMI Vias
Author:  [log in to unmask] at internet-mail 
Date:    5/23/96 5:46 PM
     
     
     
        I have a customer who has asked me if I know about shielding vias.
     I don't know much about these. All I know is that the size of the PTH 
     and the distance apart are based, somehow, on what frequency the 
     logic (PCB) is operating at. (Yessss?)
     
        Now I don't have IEEE text books anywhere near this facility. 
     I'm a simple fabricator. Can someone who's savvy with RF <or even 
     Microwave> design give me some pointers to what kind of formulas are 
     used to determine this shield via barrier technique.
     
     
     Thanks in advance for any and all replies.
     
     Groovy