Triplexer Designs

Hi everyone! I tried to research what kind of triplexer designs are currently used by others. However, I was unable to find much useful information. I am working on my own design and naturally try to avoid possible mistakes that others may already have made before me.

Here's my first prototype PCB. It uses a Mini Circuits 50 to 75 Ohm transformer for proper impedance match. Simple T networks with corner frequencies of around 30 MHz and 120 MHz provide Ref-Clock and IF isolation. After transforming to 75 Ohms system impedance, the DC voltage is injected trhough a RFC.

Here's a better design I implemented in DipTrace that I might send off to a PCB manufacturer for initial tests. The IF traces are kept a lot shorter in comparison to the REF IN traces. Can't wait to check its performance on a VNA.

And this is the schematic of revision 0.1:

it is a Bias-T with an integrated Diplexer and 50 to 75 Ohm transformation. So since it has 3 frequency selective ports, I thought Triplexer was an appropriate name. Plus I thought it was commonly used for this kind of setup.

Why would it be misleading? Triplexer refers to a circuit that splits signals on a single port into 3 different ports depending on the signal's frequency. Or combines 3 signals of different frequencies into one port. That is precisely what this circuit does.

There's a Port for signals with frequencies higher than 120 MHz, a Port for a signal with a frequency below 30 MHz except DC, and a Port passing DC to 7,23 kHz (though only DC is applied). Therefore, this circuit is a Triplexer within the globally accepted meaning of the word. A quick Google search for the apllication of the word to this kind of circuit for QO100 use cases confirms the widespread use of the term. Not trying to refute your argument but I am haveing a very hard time to spot the misleading nature of the term triplexer.

That said, Super Bias-T sounds a lot cooler, which I would have thought of that before I sent the PCB of for manufacturing

Here are some pictures of my prototype

I went ahead and wrote-up my initial prototyping and included some measurements. Unfortunately, I didn't have the correct parts on hand, so measurements are a bit skewed. Nonetheless, this is a great starting point and I'll post updates on the next revision.

Link: Diplexer with integrated Bias-T (Triplexer) for QO-100 and X-band microwave reception using LNBs