General description

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While working on RF stuff I got to the point where I had to tune filters and measure frequency response of amplifiers and other tuned circuits.
This implies having access to a VNA.
As something like that is out of reach, and buying an existing one is out of my budget I started out designing one from scratch.
For that I’ve used the N2PK VNA as a starting point with some small changes that I though will be useful.

The entire system will have:

  1. Two AD9851 based generators, each with 2 buffered outputs
  2. One AD8302 based detector that measures phase and amplitude differences
  3. One system control board, that offers to the driving computer a SPI and an I2C interface

Each board has a 12V input and local LDO’s for all needed voltages.
12V was chosen because the value of the MMIC’s bias network was high enough to require just a generic inductor.
I’ve used 5V for all internal supplies as all chips used that voltage.
Also, I’ve used a common PCB template – so the boards can be stacked with M3 spacers.
That will also simplify making some shielded cases, if needed – just one case template.

The overall system architecture looks like this:

Category: VNA
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