one PCB or multiple PCB [hlp]

[No one]

Hello Everyone;
For implementing a circuit containing digital and RF wideband circuits, wether is better? Implementing whole circuit on 1 PCB or dividing it to multiple PCB?

 

[hkBattousai]

Of course you should compile it in a single PCB.
Doing this way, you reduce noise in your circuit.

Multiple PCB circuits are often open to undesired noise effects. Especially when working RF frequency circuits.

 

[livemath]

Hi,

You must consider Loading due to discontinuities, it also include the time of propagation across the distance with respect to edge times. you must also take note that each discontinuity will allow the signal to flow down the line with a little amount of signal to reflect back to the source and it can cause reflection or crosstalk.

it's very common to separate RF and Digital circuitry, but use of multiple PCB is not a good choice. PCB layout engineer has developed a good techniques to isolate the circuitry by their function, they call it Moating or isolation/ partitioning. There's a lot of good literature about it, one is the book published by IEEE ECS and it's all about PCB design techniques.


one more advice, if separation is really your last resort, you must implement known termination methodologies techniques and that mean additional materials to your design.


Goodluck...

 

[Azulykit]

There no a clear answer. There are many competing parameters and requirements to consider. Some situations are better with a single board and some are better with multiple boards.

Think of it this way: What is the best car? There is no clear answer. I note that a Ferrari dies not look like a Volkswagon and both are considered to be excellent automobiles.

 

[No one]

Hello;
livemath wrote:

it's very common to separate RF and Digital circuitry, but use of multiple PCB is not a good choice. PCB layout engineer has developed a good techniques to isolate the circuitry by their function, they call it Moating or isolation/ partitioning. There's a lot of good literature about it, one is the book published by IEEE ECS and it's all about PCB design techniques.

Which IEEE book?

 

[livemath]

HI,

It's good to have this two,

1.EMC and the Printed Circuit Board: Design, Theory and layout made simple
2.Printed Circuit Board Design Techniques for EMC Compliance.

both By Mark Montrose


Goodluck...

 

[rogerynt]

One single board with careful layout is ok.

1.) Separate e.g RF_VDD and Digital_Vdd right at the supply.

2.) Both RF and digital gnd MUST separate. Only connect near power supply region.

3.) Make sure component connect to appropriate gnd and Vdd.

4.) Correct decoupling caps are needed.

5.) Try to insert a good gnd directly underneath ic. ( I mean good gnd not just putting a piece of copper. A floating copper or very, very poor gnd copper plate is meaningless )

6.) Small resistors or decoupling caps. can insert to traces connecting between rf and digital circuit with careful design and measurement. ( These component MUST not affect the signal except for limiting noise or high order harmonics. )

Rogerynt