Single-port network analyzer

adventures in building an antenna analyzer

At this time the ham radio market is filled with various options for antenna analyzers. Prices vary with capabilities. I have a pretty good idea of "how" the analyzers work. As with most things, the difference between using somethign and implementing something is pretty big. If I "build" my own antenna analyzer I'll learn quite a bit along with way.

Front panel of my single-port network analyzer

The whole project started with my AD9850 DDS synthesizer project. A single cheap board that makes some RF? Cool. Now how does one go about making an antenna analyzer from this? Turns out there are several ways.

My analyzer uses an AD9850 DDS signal generator, Mini-Circuits PDC-20-3BD directional coupler, and AD8302 RF gain phase detector. The directional coupler has one port for the signal generator and one port for the antenna. The two other ports provide forward and reflected coupled output. These forward and reflected coupled signals are fed to the two input ports on the AD9850 which can provide phase and magnitude between those two ports.

The two AD8302 outputs are connected to two 10-bit ADC ports on the Arduino Mega. The reference pin on the Arduino is used with the AD8302 so that the Arduino ADC uses all 10 bits across the approximate 3.3v output maximum of the AD8302. This also means that any other analog inputs to the Mega should be a maximum of 3.3v to take advantage of the entire 10 bits of precision.

RF components

This is the currently business-end of the device. I suppose the "right" way to do this would be to use striplines of correct impedance and equal length between the directional coupler and AD9850 -- but this is going to operate under 60MHz for the moment and any imbalance should be able to be compensated for in any open-short-load calibrations.

The most difficult part of this project has not so far been simple wiring up a few modules, interfacing in code with the modules or displaying results -- but the user interface!

Tue Jan 2 23:36:02 CST 2018

See for additional project progress. (hint: it's mostly software now...)

This page last modified Tue Jan 2 23:35:57 CST 2018 by timc!

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