Cost effective PDN impedance measurements?

[joeqsmith]

I'm looking for a cost effective setup to measure the impedance of power delivery networks (PDN) on PCBs.
..

Frequency range should be somewhere between a couple of kHz up to max. 1GHz ...

Impedance range should go down to maybe 10 m\$\Omega\$ or less. ...

... I could invest something up to 5k$, e. g. for a spectrum analyzer or a low-end VNA. ...

Has someone experience in such PDN measurements and any tips what equipment and accessories to use?

Regards,
feynman

Maybe one of the Signal hound products.  The software interface is well documented.  I have their BB60C and have written custom software for it.   
 
https://signalhound.com/products/usb-tg44a/
https://signalhound.com/products/usb-sa44b/

I have a few vintage VNAs and not one would meet your requirements.  At least in the $5k price range, I am not sure what you could find on the used market.   

I have a NanoVNA V2+4 that has fairly decent performance above 300MHz but the firmware I have limits it to 50KHz. If they were to open this up, I am not sure how well it would perform. 

The NanoVNA I have falls short of your 2kHz lower end.  There is firmware that will allow it to run down to 10kHz but mine will start to get fairly below 20kHz.   You 10mOhm would really be pushing it.   Performance above 300MHz is poor. 

I am in the process of putting together some software and peripherals for it including the DC blocks and transformer.    You can find more details about that in the following two links:

https://www.eevblog.com/forum/rf-microwave/nanovna-custom-software/msg3578610/#msg3578610

https://www.eevblog.com/forum/rf-microwave/impedance-measurement-with-vna-using-series-shuntseries-through-methods/

The software to make these measurements is not yet available.   However, I did attempt to measure the ESR of a popcorn RF capacitor using the current software with both the NanoVNA and the V2Plus4.   There's a little background starting about 5min in, but the actual parts I wanted to show starts about 11mins.    This may give you some idea how poor the performance of these low cost VNAs would be.   Keep in mind that first gen one was $50 and I think the V2+4 was about double that.   From that standpoint, I'm very impressed with their performance.       

[joeqsmith]

Here is the entire setup.