I'm trying to characterize the performance of a power supply module, one of the criteria being power supply noise rejection, in particular at different frequencies.
For testing 10Hz to 100kHz, I was planning on using a power opamp to inject a function generator onto the input power supply (12V, <2.5A). The bandwidth of the opamp stops you injecting frequencies any faster.
However, the power board is being used to power an ASIC which operates in the GHz range, and is sensitive to noise 1GHz to 40GHz. Realistically, I think most significant sources of noise and going to be 5GHz and below (Wifi, GSM/LTE-4G etc), so 5-10GHz test and measure is a reasonable target. The entire system will be running in a lab environment, which is supposed to be no mobile phones/wifi etc, but its rarely enforced and it's unlikely our customers will enforce it either.
The power supply board is a fairly typical cascade of LDOs hanging off switching regs, and we've never had issues with it, so I am not anticipating any problems with it. However, it has never been fully benchmarked before.
Can anybody think of a way to inject sine waves at high frequency onto a 12V, power supply? I have access to function generators, oscilloscopes and spectrum analyzers at 20/40GHz.
Perhaps some kind RF amplifier with a bias set to 12V?