What to use as reference for a coplanar waveguide

[bonf]

Hi all,
I have a PCB with a signal generator and an amplifier on it, which are connected by a ~10cm CPW.
In the amplifier the signal is terminated to VCC_B, so I chose VCC_B as my reference for the CPW.

Do you think that is correct? My fear is that the coplanar waveguide will start acting as an antenna. Apart from the shielding vias that connect the top layer of the CPW with the layer underneath the track there is no other VCC_B plane. The rest of the PCB works with GND as reference, and thus there are lots of GND planes which are stiched together using stiching vias.

Should I use GND as reference like the rest of the PCB? Or should I stick with VCC_B?
Has anybody done simulations on this kind of system?

Regards,
Marc

 

[BigBoss]

As mentioned : Waveguide. Guided waves will flow along the transmission line.
So, well designed a Waveguide will never radiate. It will not act as antenna.

I hope , understood your question.

 

[bonf]

mentioned : Waveguide. Guided waves will flow along the transmission line.
So, well designed a Waveguide will never radiate. It will not act as antenna.

I hope , understood your question.

I think my fear is less for the signal radiating.
I am worried that the shield surrounding the waveguide will start to vibrate due to an external stimulus.
Does that make sense?

 

[FvM]

I'd expect that VCC_A and VCC_B are tightly bypassed to GND. In most cases, CPW would use GND reference.

 

[bonf]

I'd expect that VCC_A and VCC_B are tightly bypassed to GND. In most cases, CPW would use GND reference.

Yes, they are. But I am expecting some ripple as the board has many GHz amplifiers. I was afraid that this would capacitively couple into the waveguide if I used GND as reference (the amplifier works relative to VCC_B).

 

[vfone]

At least for me, never work properly when I used for CPW other ground than the dedicated ground of the PCB.
Probably, if is about a narrow band circuit, may work somehow using proper decoupling of the lines used as a virtual ground, but for wideband circuits would be a big challange.