right now i am designing printed loop antenna with U shaped tuning element which is situated on my feeding port, and i have designed it in HFSS. and I am getting S11 of around -15dB but i want to make it more than -10dB, so what are the possible options i have?i can't increase my feeding power so what are the possible ways to achieve S11 of -10dB?instead of U shaped any other possible shape or any guess?
USUALLY I DON'T GET ANY REPLY BUT I HOPE THIS TIME I WILL GET SOME REPLY.
hi dear i think u never response because of u questions
what u mean when u said u want to increase from -15 to -10 Db when usually other opposite of u?
I give you some hints if you want to get answers to your questions.
- Print (picture or pdf) the antenna, the measurement/simulation plots, and post them on the forum.
- Hand draw and scanned pictures are usually more explicit, than CAD pictures with many grids on the background.
- Place very clear questions and also some next steps you intend to do.
You are looking for Reflection Coefficient S11 to be WELL ABOVE -10dB !? How much above? In case of antennas S11 cannot be greater than 0dB.
I think you intend to make S11 to be WELL BELOW -10dB.
Things staying like this, you forgot to mention at what frequencies you want to improve S11 (I mean, to be BELOW -10dB).
From the attached plot S11 is already BELOW -10dB between 1.8GHz and 3GHz.
-10 dB results in that 10% of transmitted power is not accepted by the antenna and will reflect back into transmitter stage.
-15 dB result in that 3% of total power reflects back into transmitter.
Therefore: -15 dB makes the antenna to seem 7% more powerful then if the reflection is -10dB for same amount of TX power.
(Assume that antenna resistive losses is the same in both cases.)
One method to achieve higher reflection: reduce height above ground and re tune the antenna by shorten its length.
from db how can you find how much power is reflected back?
10 dB results in that 10% of transmitted power is not accepted by the antenna and will reflect back into transmitter stage.
-15 dB result in that 3% of total power reflects back into transmitter.
how you can come to know that for -15db it will reflect only 3% not 15%?
what is the formula to convert db to reflected power?
if according to you -15dB is better than why every place its written that its a ideal case to have S11 of below -10dB for antennas???
hi randy
at first i suggested u read more about antenna and propagation u can download a thesis by Johanna Paule in MIT in Google which talk clearly about antenna definition and u can see there how relation between s parameter and other like power and efficiency
and using antenna with lower S is better but it essential only in some radar and communication system in other hand we use and accept upper S or VSWR for mobile system all related to your application but u say other thing and it is unacceptable