Project Yamhill Double-Balanced Diode Ring Mixer Module
A classic
OK, I’ve got the first real RF module of Project Yamhill designed in KiCad and ready to send to fabrication! It seemed fitting to start with a real classic, go-to part of many homebrewed radios: the double-balanced diode ring mixer. This mixer has a lot of good things going for it: it is passive, has 50-ohm terminations, is relatively simple, and has good performance.
The circuit design is the same that you see just about everywhere this mixer is used. Two trifilar transformers are used to interface with four diodes placed in a ring topology, each cathode of one diode connected to the anode of the adjacent one. I chose Schottky diodes (although a home builder could use standard silicon diodes just as well) and binocular ferrite cores for the transfomers, which are a bit easier to wind compared to toroid cores, in my experience.
There’s really not much more to say about this cheap and cheerful board, so we’ll keep this post short and move onto the next design.
What’s Next
Every receiver needs to have front-end filtering, and a typical filter found in many radios is the double-tuned circuit bandpass filter. The board I’m envisioning will have space for two double-tuned circuits with 50-ohm terminations. Each filter will be selectable via a simple jumper block. This one shouldn’t take very long to design, so stay tuned for it!