The measurement I've mentioned/described can be done with tracking gen. and SA. It is equivalent to what VNA does as s21, minus the phase. If you are measuring just passives, phase can be calculated out of the measurements. But amplitude is usually all that is needed.
Ad 10uf capacitors:
some LISNs have the capacitors as add on module - both due to safety reasons, and it is more versatile. There are other regulations that are using 5uH LISN, but do not use the cap. If you are only after the required impedance profile, big foil cap across terminal is all what is needed. If you need to filter out hf crap from outside, as mentioned previously feed through cap is way to go. If you want to implement it on the pcb, and want really the best performance, layout is important.
Ad Layout:
The signal has to be forced through the capacitor pins, ie. fuse - pins of first cap - pins of second cap - pins of nth cap. Just trace, which is narrowed down just to solder pad of the capacitor at the cap pins. If you go with polygons, I'd slot it around the pins, so signal has to go through the pins. Same on the return. I'm usually a big proponent of solid unslotted (ground) planes, but in this case slotting is in order. It will definitely work as it is now, but the effect of the routing will be measurable at the higher end of LISN bandwidth.
No ground plane under the inductors/traces. I'd put the inductors further away from each other, and provide connections for possible damping resistors/RCs.
Minicircuits has nice power limiter VLM-33W-2W-S+
You might be also interested in noise splitters and parasitic coupling of components - google for "Characterization and Cancellation of High-Frequency Parasitics for EMI Filters and Noise Separators in Power Electronics Applications" - by Shou Wang
Oi! I guess I misinterpreted your post then. Well, I guess I have two options then, though I still have to learn about the measurement principles.
Regarding the 10uF capacitors: It's a good point you make. There's a possibility we'd want to test CISPR25 (auto/vehicle), but I really can't be certain. CISPR25 is 1uF.
CISPR25 also uses a more "standard" voltage measurement via BNC/N-type connector on LISN to measurement resistor. DO-160, on the other hand (what I'm currently after), only uses current probe measurement. I suppose it's possible to convert the limits between voltage and current measurements?? But per the standards, that's how they want you to test.
Regarding the layout: I've seen this kind of slotted polygon layout many times before in EMI filter designs, but to be honest, I don't understand why they help. I assumed the lowest inductance/impedance connection would be appropriate, so what's the mechanism here? High frequency currents maybe tend to scatter and bypass the capacitors? (Just seems counter-intuitive from what I know, but I'm sure my current mental models are flawed.)
Is this what you were thinking?
Indeed, no ground plane under the inductors as that will likely affect the SFR among other things.
Regarding the Minicircuits power limiter: This is a new type of component for me. As I understand it, it will pass 100% of the power between 0 and 12dBm. Above 12dBm and below 33dBm, it will limit the power to approx 12dBm. Sound correct? VSWR looks a little high at 200KHz. (Does it matter?) Also, seems like SA damage/problems often occur due to low frequency overdrive, i.e. at the fundamental switching frequency of a power supply...which could be <100KHz. Would this do much to attenuate those signals?
Regardless, this could be an interesting quick solution for me. I just do not have much time at the moment to work on transient limiters, etc, especially since the standard I'm trying to test to doesn't even use that method. If I go for a "DO-160 only" LISN, then I might just remove the BNC outputs altogether, and just put a 49.9R dummy resistor on the PCB and call it a day.
The other option is to maybe include 1uF on the PCB, then allow for connection of ~9uF outside the enclosure. Or no capacitors inside and swap out 1uF or 10uF externally, so that it can be used for CISPR25 or DO-160. But, then I'd need to add provision for voltage measurement internal to the LISN.
Thanks!