VNA advice

[Marco]

Doesn't TDR/TDT and some software give you a rough VNA?

[KJDS]

Hi everyone, first thing this morning I was looking up VNA techniques and found a very interesting MSc thesis by Marcos Martinez and then the very same day RadioDude posts a reply on the forum about VNA advice. Wierd, what are chances of that.
But here is a link to the paper https://riunet.upv.es/bitstream/handle/10251/34999MartinezArgudo,%20Marcos_Movilidad_Abierto.pdf?sequence=1.

It's a really interesting thesis as it replaces directional couplers with bridged-T networks. Link to Choi and Zhao's paper,https://www.researchgate.net/publication/3429059_Compact_mixer-based_1-12_GHz_reflectometer.

Which is great, but state of the art has been to use a bridge instead of a coupler for at least fifteen years and probably longer than that.

[chris_leyson]

Which is great, but state of the art has been to use a bridge instead of a coupler for at least fifteen years and probably longer than that.

Wow, I really am out of touch with state of the art VNAs.

[KJDS]

Which is great, but state of the art has been to use a bridge instead of a coupler for at least fifteen years and probably longer than that.

Wow, I really am out of touch with state of the art VNAs.

I only know this as I friend introduced me to the bloke in charge of Agilent (or possibly HP) VNA design at a European Microwaves do many years ago. From memory, they were working more using a wheatstone bridge arrangement to 40GHz. Couplers are a nightmare as you go lower and lower in frequency, unless you just want to stay at low frequency.