Hi!
I have seen quite a lot that subharmonic diode mixers (also often called "russian mixesr" or the "Polyakov RA3AAE mixers") are quite popular in many amateur radio construction, from HF up to microwave bands. I am more interested in the microwave band use of this mixer, as at HF it is quite easier to make it work as it should.
Here is what is going on:
I would like to ask, if you have any tips for literature or have a first hand experience building these. Especially, I am interested in how these things are supposed to be designed to work properly at microwave frequencies.
Supposed I want to try designing a mixer for a 9cm band (3400MHz) - which is actually what I want to try. I have already had a go with this about two years ago, copied a design from some "schematic collection book", but the performance was really crap, totally unusable. Now that I have access to some proper test gear, I would like to give it a second chance.
Those lambda/4 or lambda/2 stubs are the only things straightforward I understand there. What I am after is how to guesstimate:
1) The impedance of the transmission lines to be used around the diodes
2) How to match these so the mixer will become as close to 50ohm as possible on all three ports.
The proper mixer diode pair I have available is
HSMS-2822 (datasheet), which I think should be sufficient.
Please understand this is more like an experiment, mainly out of my curiosity and to improve some knowledge. I know that there are plenty of ready made 50ohm matched passive and even active mixers these days, that are very easy to implement into a design.