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Impedance bandwidth of UWB antennas

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jossion

jossion

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hi,

Can anyone give information about the impedance bandwidth criterion
needed for UWB antennas -- such as the value of S11 to be satisfied
(eg. S11<-10dB) and the like.
 

as you know ideal antenna is the antenna with zero input reactance and matched resistance in all frequencies. because the reactance of antenna leads to stored energy in near field of antenna not radiation which is similar to dissipation of input antenna power and mismatch of the resistance leads to reflafction of power from antenna enterance and dissipation too. so in real world it is very crucial for antennas that the reactance be around zero in all bandwidth and the VSWR be less than 2 in all frequencies.
 

For antenna desing all the characterizing parameters are related to each other, like if you know the return loss i.e S11 you can get VSWR
VSWR=1+S11/1-S11

Impedance bandwidth indicates the bandwidth for which the antenna is sufficiently matched to its input transmisison line. Its include the characterization for VSWR and Return Loss.
 

for uwb,a vswr<=2(or Return Loss<=-10dB) from 3.1GHz to 10.6GHz is often used.
 

yes it is as ryfnjust said, the return loss <= -10dB in the whole operating band of the antenna. However, the operating band should not be 3.1-10.6 except for UWB radio, othe applications such as GPR may need this in the range 2-6GHz.

Also, you shouldn't consider only the input impedance. since the radiation pattern, gain, dipersion and polarization are all important factors to consider.

Best regards,
Adel
 

I will add to adel_48
All mentioned characteristics for UWB system depends upon the system requirment except radiation pattern which is indeed have to be inherent for all the system. Now a day UWB reseach is quite mature and lot of emphasziz is now concentrated on balance among radiaiton pattern and impedance BW.
Regards:D
 

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