Issues when transferring from 4 layers microstrip PCB to 2 layers RF PCB
I have 2.4GHz transceiver reference design witch is 4 layer microstrip PCB design.
But due to the cost and customer requirements i need to transfer these on to 2 layer PCB
Reference design has 0.4mm PCB thickness and 35um copper thickness.
I am planning to use CPW ground PCB design with 0.8mm board thickness with 35um copper and according to these RF track thickness will be changed(using TXline calculator).
Please suggest if there any other changes required other than the above and what are all the parameter should I required to take care while transferring from 4 layers to 2 layers in RF PCB circuit
Thanks and regards
can you explain why 4 layers are used for?
1.when u go from Microstrip to Co Planar T.L. to calculate the equivalent Impedance of the old Microsrip Zo by the given W width & depth of pcb stack up and eps of the used material & the operating frequency
2.make sure the copper thickness is really 35um as it could be 1oz or 1/2 oz
The main problem I see is not the I/O RF transmission line, but the power and ground planes and connections of your active and passive devices. 4 layers are probably used because there are at least 2 power planes (like Vcc, Gnd) with very short connections (vias to planes) to the parasitic-inductance-sensitive devices and components.
Another important consideration.
The impedance of micro-strip lines, is not the same if the dielectric thickness change.
IF strip-lines are used in the four layer, this may result in a big problem into 2 layer board.
Skywalker.
be careful with CPW most board houses will not put lines that close together for a good match you usually need either really wide lines or a really close ground plane.
One takes up a lot of space and if you keep the line small it will cost a great deal more and you might as well be using a 4 layer board.
good luck,