possible to have 2 - 4 GHz VCO/PLL design on FR-4?

Hi all,

Could anyone tell me that is it possible to have a VCO/PLL design which is working in 2 - 4 GHz frequency range on FR-4 substrate?
The maximum output power of the VCO is 3 dBm.
I'm planning to generate a stepped frequency sweep output by configuring the PLL using a microcontroller
The design would be used as a transmitter in a small FMCW radar sensor.

Without going for expensive substrates, can I design the PCB on FR-4 substrate to work in 2 GHz - 4 GHz range?

cheers,

Sure, no problem. Just avoid components that are very sensitive to eps_r tolerances, and expect increased transmission line loss. You might want to use a thin FR4 substrate, to reduce via inductance.

Thanks volker_muehlhaus
I guess increased transmission line losses would not be a big issue for this design.

Don't worry about Tx line loses - just make sure that you follow good design rules. Proper termination schemes for high speed lines is very important!

Thanks shaiko,
Could you please explain what did you mean by proper termination schemes?

Did you mean terminating the transmission lines with a matching impedance?

cheers,

Yes, but not just that.
Here are a few rules that you should follow:

1. Always keep the adjacent planes of tx lines continuous.
2. Avoid vias as much as possible.
3. Route the fastest signals first and keep them as short as possible.
4. Preffer Striplines over of microstips for ultra sensitive signals (such as clocks).
5. Avoid star topology for multiple rx signals.
6. Choose components with the loowest possible rise/fall times.
7. Place decoupling capacitors as close as possible to active pins.
8. Preffer series terminations over parallel when you can.
9. Keep series termination resistors close to the Tx buffer and parallel termination resistors close to the Rx buffer.
10. Filter noise from DC/DC converters or use LDOs when you can.

And most important - simulate your design to DEATH. Pre and post layout.

Thanks a lot shaiko...
This is great!

a really useful set of advices for a beginner for RF PCB design like me...

cheers