I'm working on a L-BAND project (850 MHz to 2.4 GHz) and RF components are on the top and bottom layers, so I need to use via.
PCB is 10 layer, with two dielectrics: Astra- MT77 5-mil, DK=3 (top & bottom), and FR4 5-mil, DK=4.6
I'm using "Saturn PCB toolkit: for calculating via impedance and parameters (hole,pad, spacing).
What value should I use for DK?
Do I need to have via pad on the internal layers, both GND planes and non GND layers?
Thanks in advance.
Karo

 

What value should I use for DK?

Average the DK from the different materials - you haven't provided enough info for us to do it.

Do I need to have via pad on the internal layers, both GND planes and non GND layers?

This will depend on your PCB package. If it allows you, then don't have a pad on non-connected layers.

Under your RF components, keep ALL layers empty and treat it as a two layer board.

 

Hello SLK001 and thank you very much.
PCB stack-up is:
Top RF-signal 2 OZ --- MTA-77 5 mil --- GND 1 OZ --- FR4 5 mil --- Logic 1 OZ --- FR4 5 mil --- PWR 1 OZ --- FR4 5 mil ---
Logic 1 OZ --- FR4 5 mil --- PWR 1 OZ --- FR4 5 mil --- Logic 1 OZ --- FR4 5 mil --- PWR 1 OZ --- FR4 5 mil --- GND 1 OZ ---
MTA-77 5 mil --- Bottom RF-signal 2 OZ.
I hope this has enough info.
For the vias, do you mean I should treat them as two layers board too? Don't via pads need to be referenced against GND plane like RF traces?

 

For Dk, use the result of:

3⋅(5/45) + 4.7⋅(5/45) + 4.7⋅(5/45) + 4.7⋅(5/45) + 4.7⋅(5/45) + 4.7⋅(5/45) + 4.7⋅(5/45) + 4.7⋅(5/45) + 3⋅(5/45)

For the vias, do you mean I should treat them as two layers board too? Don't via pads need to be referenced against GND plane like RF traces?

I don't understand the questions.

I question the wisdom of putting a μwave circuit on a 10 layer PCB. Put complete circuits on a single side only - i.e., put all of the amplifier components on a single side. Use the TH vias as a transmission line only between components - i.e., the amp on one side, the mixer circuit on the flip side fed from the amp by a via.

 

It is a 24x12 L-Band switch array, we have only resistive-splitters and Hittite MMIC switches (2x1 & 4x1) and we are using vias between switches. we have to go with 10 layers, because of logic-control lines.
Thank you.