# Coupled line hybrid coupler parameters

I am designing a coupled line hybrid coupler as a part of of term evaluation at my university. So from my conceptual understanding here coupled line hybrid coupler implies a coupled line coupler with coupling coefficient -3 dB . Parameters given were substrate thickness 0.8 mm , amd frequency 3 GHz . I used the website emtalk for microstrip line calculations ( required to use this only ) and used the w and s from that in my design. But the graph coming out is incorrect, but when I was trying out L of different orders ( randomly) it gave me correct graph at 25cm but that is not suitable for fabricating. I need help in calculating S and L . Please help me out here.

• I'm almost certain that if it is an evaluation thing at your university, using a website to calculate the width and then not being able to explain how you arrived at the numbers is not going to give you full credit. So, trying to figure out how to calculate them correctly is a good step forward! Commented Oct 20, 2022 at 18:47
• Now, I'm 100% sure that you have had courses on transmission line design, and that the course material would explained a simplified formula, which you could also use as a start (instead of some shady website). However, reality is that your simulation might be more detailed than the simplified formulas allow – so you'll have to tune things yourself. Do you understand which properties make "the graph coming out" incorrect? That would be a first step in solving this and earning your credit! Commented Oct 20, 2022 at 18:50
• Hey thanks for the reply, I did try the tuning feature on AWR office. And guess what it's actually giving the desired graph but now the issue is that S is coming out to be 0.002 which my lab instructor said is too small for fabricating and told me to find values atleast higher than 0.25. Commented Oct 21, 2022 at 15:32