power delivery , signal integrity and layer arrangement
sukru , 12-12-2020, 10:51 AM
I am working with RF design and I have 4 layer Pcb design:
L1=Toplayer with ground pour (2.4GHZ signal)
L2=Ground plane
L3=Signal layer with ground pour
L4=Bottom layer with ground pour
Question 1(POWER PLANE OR POWER POUR?)
On the Picture 1 I share, you see L3 layer. I think I have two option first one using ground pour and spliting it for power just like the Picture 1 I share, second one is using power plane for L3 .Which one is the best solution for signal integrity , EMC and power delivery without loss ?
Question2: (POWER DELIVEY ON SIGNAL LAYER OR POWER PLANE?)
I emphasize the 2.4GHZ trace on Picture2. Is it a good power deliver? or Is it better to keep all the power trace on L3 (power plane or pour)?
Question3 : (BEST LAYER ARRANGEMENT FOR 4 LAYER PCBS)
For the best signal integrity on high frequency what is the best layer arrangement on 4 layer pcb design ? and why?
Question4 : (IF TWO SIGNAL ARE SHARING THEIR RETURN PATH)
L1 - Signal
L2 - GND
L3 - Signal
L4 - GND
L5 - Powers
L6 - Powers
L7 - GND
L8 - Signal
L9 - GND
L10 – Signal
If ı use this layer arrangement, Return path of L3 will be on L2 and L4 .L1’s return path will be on the L2 Is this a problem for the L1 and L3 signal ? because they share same return path.
Question 5: (POWER PLANE RETURN PATH AND SIGNAL RETURN PATH ON SIGNAL-GROUND-POWER ARRANGEMENT STACKUPS)
Return path of the signal on L1 is in the L2( ground plane ) and I use power plane or power pour depend on the answer of the Question 1 where is the return path of this power trace at L3? In bottom layer(L4) or in the L2 ? I ask this question because I wonder that is there a possiblity that power plane return path has a bad effect on the signal return path ?
robertferanec , 12-14-2020, 06:32 AM
I am not an RF expert, so I can't really help with this 
sukru , 12-14-2020, 12:33 PM
@robertferanec thank you for reply.Can you give a general answer for this question instead of RF? because I think that will be quite helpfull for people who want to design High speed with good signal integrity and good EMI/EMC result. And the post includes some return path questions which will be also helpfull for every PCB designers.
qdrives , 12-14-2020, 04:23 PM
Signals should have a corresponding return plane below (or above) it.
Do keep the dielectric thickness between the two low (<= 0.2mm).
A signal of 2.4GHz will not have much skin depth (see Saturn PCB tool) so sharing a single return plane is no problem.
Routed power vs power plane I would say comes down to inductance (impedance) of the connection. Also local decoupling is important. Robert has made plenty of videos about decoupling that would make most heads spin ;-)
Do keep the dielectric thickness between the two low (<= 0.2mm).
A signal of 2.4GHz will not have much skin depth (see Saturn PCB tool) so sharing a single return plane is no problem.
Routed power vs power plane I would say comes down to inductance (impedance) of the connection. Also local decoupling is important. Robert has made plenty of videos about decoupling that would make most heads spin ;-)
sukru , 12-14-2020, 05:03 PM
@qdrives thank you for your answer. Signal-Ground plane-power plane-signal is suitable layout according to what you write. If I am triying to make a power delivery for a small area I can deliver it with using small power pour on L3 instead of big power plane is that a good idea? (also ı will search Robert's videos for decopling thanks for sharing your idea)
qdrives , 12-15-2020, 12:43 PM
What signals are you running on layer 4? What use is the power plane/region if there is no Gnd to reference it?
Rick Hartley had some dat on better 4 layer stackup. Try https://www.google.com/search?q=bett...hrome&ie=UTF-8
Rick Hartley had some dat on better 4 layer stackup. Try https://www.google.com/search?q=bett...hrome&ie=UTF-8
sukru , 12-16-2020, 05:57 AM
@qdrives Layer 4 is the bottom layer with ground pour and all the critical signals are on the top layer. thanks for sharing Rick Hartley's videos which are perfect for understanding the layer arrangement.
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