Material for power biasing boards

[rkarnaty]

I am looking to create a PCB to provide bias for my 30 GHz PA . My PA chip has instability issues around 3-4 GHz due to the bias path. So I am building a PCB board to mount the chip. The PCB provides the gate and drain bias with additional bypass circuitry to stabilize the PA(by providing specific drain impedances). So my dilemma is if can get away with using Fr4 material for my PCB since it is cheap. But is it an issue because FR4 may not be a good option above 1 GHz? Even though the biasing is at DC, I am using circuitry for defining specific drain impedances up to 5 GHz. I am using a combination of SMD components for this.

Any suggestions would be appreciated. Thanks