microwave theory question

[ginebra]

Good day to all. I am currently designing an H-plane T junction. After reading several references regarding this device, i feel that I understand its functionality. However, I am a bit confused regarding the interpretation of its s-parameters.

Based on what i've read, i should take note of the values of s11, s12,s13 and s22. Is it better to have a -12db value for s11 or should it be as close to zero as possible?

 

[akedar]

s11 rep resents return loss of the port so it should be always better than -10 db for all ports

 

[ginebra]

Thanks for the quick reply sir. Thats the confusing part for me. From my understanding, When it is said to be better than -10 db, since the measurements I get are negative, the s parameters should be -9.99db to 0 db. Did I interpret that correctly sir?

 

[venu.gongal]

When u mean it as return loss....... u interpret as "15dB return loss" is better than "10dB return loss"....


I hope u understand this terminology.

 

[ginebra]

I see sir. Its desired for a return loss of 20 db or higher since it means that less power is reflected back on that port. Thanks for your explanations.

Added after 4 hours 23 minutes:

by the way here's what im getting right now with regards to the s parameters

s11 = -12.26db
s21 = -1.39 db = s12
s31 = -6.91db = s32 = s13 = s23
s22 = - 12.27db
s33 = -2.35 db

ive seen that increasing the length of the collinear arm affects s33 greatly. any tip to improve this measurements or should I just accept this and fix the problem with tuning screws instead?