Antenna S11 parameter

Status
Not open for further replies.
V

vfurlan

Full Member level 2
Joined
Mar 27, 2006
Messages
133
Helped
10
Reputation
20
Reaction score
2
Trophy points
1,298
Location
Slovenia
Visit site
Activity points
2,185
s11 parameter

Hi,

I have a question regarding S11 parameter.
Usually it is sad that antenna should not have S11 above -6dB (or even -10dB).
I have an antenna with acceptable gain (about 3dBi) but with S11 = -4dB. Is this a problem? Why? I know that S11 represents how much power is reflected from the antenna, but if gain is OK, why this should be a problem? Maybe with the power reflected back to the transmitter?

Thanks for the answer.
 

antenna s11

IMHO, the bigger magnitude of S11 you have the more it is bad coz it means that all you transmitted most will be lost because the reflected is almost equal to the incident. you still need to tune your antenna, it is maybe mismatch with your transmission line, i guess.
 

    V

    vfurlan

    Points: 2
    Helpful Answer Positive Rating
acceptable s11 for antennas


vfurlan - in general your statement about reflected power is the answer. in receive antennas the impedance can be quite bad even worse then you've described and still function acceptably. while in the tx side its possible to imagine large reflected power being an issue.

however if you have the opportunity to improve impedance than typically this is done, because now you have a more efficient system.

also if you think of mobile phone antennas, the impedance can exist around - 4 to -6 dB at the band edges easily and still function.

it really depends on the system design, your customers expectations and your expectations.
 

    V

    vfurlan

    Points: 2
    Helpful Answer Positive Rating
antenna s11 and input impedance

high s11 is generally due to the mismatch in the transmission line as
jongjong said. By studying impedance matching networks, u can decrease
ur s11.
Study stub matching and quarterwave transformer
 
Reactions: Bara'a

    B

    Bara'a

    Points: 2
    Helpful Answer Positive Rating
Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…