This is the follow up to:
This is a S21 and S31 analysis of an oversized 385 Mhz 50 Ohm to 90 Ohm balun between 100 Mhz and 600 Mhz I tested phase separation and transmission loss for both ports.
If I interpret the results correctly, phase separation is pretty good over the 300 - 400 Mhz range. Transmission loss however is not good (more than 6dB loss, ideal should be 3dB loss) with one port more lossy than the other. I did not compute the common-mode rejection yet, I know there is a simple formula to calculate it from the VNA data. I did not test port isolation.
Now I will rethink the balun from scratch and scale it down. My questions are :
- Do smaller 43 ferrite cores (10 mm OD, 7mm ID, height 3mm) will have acceptable performance at 400 Mhz ? (currently using 61 material 23 mm OD, 14 mm ID)
Also, port 1 ground and port 2 and 3 center tap are grounded to their respective PCB bottom layers. The PCB is split in two to prevent the grounds from contacting.
- Is it acceptable practice to use a ground layer in baluns ? or should I discard grounds and connect grounded leads to their respective connector leads ?
For a detailed schematic, please refer to the previous post linked atop.