Electronic – How to i create a SWR meter that works for 0dBm sources @ 2.4Ghz

RFswr-meter

I've stumbled upon this, but it only works for outputs between 15db and 20dBm. How can I modify it to work for 0dBm sources?

I'm planning to use this to roughly tune my matching circuit for the interface between a RF transmitter and a chip antenna.

Best Answer

The host has another project, Field Strength Sensor for Wifi ISM band (2.4 GHz), that incorporates a preamplifier. WiFi signals are <5mW (<7dBm) broadcast, so this must be picking up <<5mW.

I don't see a reason why you couldn't adapt this preamp stage into the bridge of the SWR meter. The host uses a diode detector in the bridge; you would want to swap out the diode and everything to the right of it in his/her diagram. Resistor values all seem sensible; I'm not sure about the caps.

Disclaimer: I am not an RF engineer! I have made a few GHz amps and played with some microwave structures, but I certainly can't guarantee this will work. (It certainly sounds like fun, though!)

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