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Project Notes

#327 Mixers/RFDiodeRing

A diode ring double-balanced frequency mixer.



My build here is inspired by another great tutorial from w2aew - #167: How a Diode Ring Mixer works | Mixer operation theory and measurement.

Section 5.2 of Experimental Methods in RF Design includes a complete evolution of the diode ring mixer and a very clear explanation of how it works.

See LEAP#326 for my notes on mixer theory and types.

How it works

  • the RF input is connected to the IF via a transformer
  • the transformer-isolated LO switches the conducting diode pairs on each each half of the cycle, thus the polarity of the RF signal to IF
  • classic example of a commutation mixer


Test 1: 7MHz LO + 10MHz RF

This works pretty well, alough my signals are quite noisy.

Scope Channel Signal Detail
CH1 LO 7MHz 0.8V p-p
CH2 RF 10MHz 0.4V p-p
CH3 IF  



Test 2: 5MHz LO + 10MHz RF

With the LO as an even factor of the RF signal, I’m seeing what I’d expect here: very strong sum and difference signals and no other products



Test 2: 18MHz LO + 2MHz RF

With the LO and RF frequencies separated significantly, sum and difference are strong over other products.




I’m using 1N5711 small signal schottky diodes (as did w2aew), which are well suited to this application:

  • high breakdown, low turn-on voltage and ultrafast switching
  • primarly intended for high level UHF/VHF detection and pulse application with broad dynamic range

For the transformers, I’m using 68-26 iron ferrite toroids with 30AWG solid wire (10 turns per winding).




Credits and References

Project Source on GitHub Project Gallery Return to the LEAP Catalog

This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.