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How to define port at EM

Question asked by A.C on Dec 30, 2017
Latest reply on Jan 2, 2018 by volker_muehlhaus

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hi everyone,

i have a Layout with EM and i want to generate it to EM symbol and connect Lump resistors (pi attenuator) so i don't .

.know how to define my port because i have GND planes(2 layers) in the layout and the pi attenuator at the TOP layer

???how i need to define my port differential or with global GND

it's ok if I define the P7 positive and P8 negative and P9 positive and P10 negative and P11 positive and P12 negative.

Port1: P1 positive terminal, P2 and P3 negative terminals

Port2: P4 positive terminal, P5, P6 negative terminals.

in this illustrate i didn't use with global GND symbol and all the ports are diffirentials

Note: the blue points they Vias ,connect the top GND and the layer 2 and layer 3 GND and they are defined in the substrate like this

(in addition, the question is if the layers 2 and 3 need to be defined as a slot plane or like this(strip plane

regard,

aviad.

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volker_muehlhaus Jan 1, 2018 4:23 AM

Hello,

if you draw the metal, then "strip" layer is correct.

Your understanding of port and is correct.

However, to keep symmetry, I would split each shunt resistor into two resistors (one to each GND).

Regards

Volker

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A.C @ volker_muehlhaus on Jan 2, 2018 12:58 AM

thank you Volker for your response,

if I understand you right regarding to the resistors you mean to connect 1 of them to the ground on the other side but still with differential ports like the picture from my first post

and i have last question for multilayers stuckup, ,if i have line 50 ohm and in my layout i connect it to wider pad and i need to open layers only below the Pad thus He will feel a different layer of GND, for example if the line 50 ohm on the Top layer and the wider pad connect to the line, so i open below the pad 6 layers but only below the Pad

and now i want to connect pins to the pad(like P1 P2 P3) and i'm asking you about the location of pins namely, if i need to connect the pins of the port on Top layer(where the Pad exists) or because i opened 6 layers below the pad i need to connect them (minus pins) to layer 7 because it is the GND for the Pad

regards ,

aviad

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volker_muehlhaus @ A.C on Jan 2, 2018 5:43 AM

Hi Aviad!

if I understand you right regarding to the resistors you mean to connect 1 of them to the ground on the other side but still with differential ports like the picture from my first post

Yes, I mean to have a total of 4 shunt resistors for symmetry, with the same total resistance. Connetion as additional differential ports and as you showed.

and i need to open layers only below the Pad thus He will feel a different layer of GND, for example if the line 50 ohm on the Top layer and the wider pad connect to the line, so i open below the pad 6 layers but only below the Pad

I didn't get this, can you explan again? I would make the phyiscal size (distance) as small as possible, so that you minimize transmission line effects within the attentuator pad.

and now i want to connect pins to the pad(like P1 P2 P3) and i'm asking you about the location of pins namely, if i need to connect the pins of the port on Top layer(where the Pad exists) or because i opened 6 layers below the pad i need to connect them (minus pins) to layer 7 because it is the GND for the Pad

You should model the actual current flow in the hardware. Ground is where you connect ground return path. This looks like wafer probes connecting at top metal, so I would place my pins there at the top model, for measured/simulation agreement. In the final circuit, if your ground is on a lower layer, use that.

Best regards

Volker

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3 Replies

volker_muehlhaus Jan 1, 2018 4:23 AM
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Hello,

if you draw the metal, then "strip" layer is correct.
Your understanding of port and is correct.
However, to keep symmetry, I would split each shunt resistor into two resistors (one to each GND).

Regards
Volker
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- A.C @ volker_muehlhaus on Jan 2, 2018 12:58 AM
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  thank you Volker for your response,
  if I understand you right regarding to the resistors you mean to connect 1 of them to the ground on the other side but still with differential ports like the picture from my first post
  and i have last question for multilayers stuckup, ,if i have line 50 ohm and in my layout i connect it to wider pad and i need to open layers only below the Pad thus He will feel a different layer of GND, for example if the line 50 ohm on the Top layer and the wider pad connect to the line, so i open below the pad 6 layers but only below the Pad
  and now i want to connect pins to the pad(like P1 P2 P3) and i'm asking you about the location of pins namely, if i need to connect the pins of the port on Top layer(where the Pad exists) or because i opened 6 layers below the pad i need to connect them (minus pins) to layer 7 because it is the GND for the Pad
  regards ,
  aviad
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  - volker_muehlhaus @ A.C on Jan 2, 2018 5:43 AM
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    Hi Aviad!
    
    if I understand you right regarding to the resistors you mean to connect 1 of them to the ground on the other side but still with differential ports like the picture from my first post
    Yes, I mean to have a total of 4 shunt resistors for symmetry, with the same total resistance. Connetion as additional differential ports and as you showed.
    
    and i need to open layers only below the Pad thus He will feel a different layer of GND, for example if the line 50 ohm on the Top layer and the wider pad connect to the line, so i open below the pad 6 layers but only below the Pad
    I didn't get this, can you explan again? I would make the phyiscal size (distance) as small as possible, so that you minimize transmission line effects within the attentuator pad.
    
    and now i want to connect pins to the pad(like P1 P2 P3) and i'm asking you about the location of pins namely, if i need to connect the pins of the port on Top layer(where the Pad exists) or because i opened 6 layers below the pad i need to connect them (minus pins) to layer 7 because it is the GND for the Pad
    You should model the actual current flow in the hardware. Ground is where you connect ground return path. This looks like wafer probes connecting at top metal, so I would place my pins there at the top model, for measured/simulation agreement. In the final circuit, if your ground is on a lower layer, use that.
    
    Best regards
    Volker
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