Low cost open hardware VNA

A 140MHz - 3GHz 2-port T/R VNA and software

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I needed a VNA to design and tune some antennas, filters, and RF amplifiers, but don't have the budget for even a used one, which typically costs several thousand dollars. There is another $200 open source VNA also covered here on hackaday, but after totaling up the costs including the PCB, parts, and shipping it way exceeds $200. I decided that it would be a fun learning experience to design my own anyway, and this is what I came up with.

With this I managed to get a smith chart and graphs cleaner than both the miniVNA and pocketVNA.

I used a single-conversion architecture, meaning RF signals from the directional couplers are downconverted to an IF frequency and then digitized. On the left side of the main PCB you can see the 3 receivers (mixer, filter, baseband amplifier, and ADC).

After the signal is digitized, its phase and amplitude is calculated and averaged on the FPGA. the values are sent to the computer via USB, where the software I wrote displays a smith chart and S11/S21 graphs.

More info and design files on github:


PCB design files, VHDL logic, and software

x-xz - 10.47 MB - 10/25/2017 at 17:53


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