measure bandwidth using hfss

Hi,

How do I measure the -3dB bandwidth of an antenna in HFSS?
Is it by plotting the S11 and obtain the bandwidth from there? If yes, do I measure the bandwidth with reference to the -3dB point on the S11 curve? Or is it some other reference point?

Also, in real-life measurements, how can I measure my antenna bandwidth using a network analyzer?

I would really appreciate it if anyone could give me advice on this.

Thanks in advance.

In usual case, we refer the antenna impedance bandwidth with respect to -10dB return loss bandwidth.

Regards,

Asdfaaa !

If you have a VNA (vector network analyzer) you can measure the first and the lat point of frequency where they below -10dB (or greater then |10dB|) this will be your BW of the antenna !!!

About the HFSS - look for the plots of the farfield - from there you can see the BW or you can do exaclty what I've just told you with the VNA - with the S11 graph of the HFSS.

Bye.

Does this mean that it is the same in HFSS and when I'm using a network analyser, that is, I can measure my antenna bandwidth from the S11 curve (return loss) with respect to the -10dB point?

Can anyone explain why it is at -10dB? Does -10dB at the S11 plot correspond to the half-power point (i.e. -3dB)? If yes, how is it related?

Thanks very much for all your replies!!

Hello Kin !

About your 1st quest. : The -10dB of R.L. is an acceptable level of value to describe the loss of the power which reflects back from the antenna (and not radiated). For example, a -16dB (or -15dB) is acceptable value to describe matched device like filter or amplifer to the system - in Antenna 10dB is sufficent (or higher)
About the relation with the -3dB : the -3dB points are the half power points (in linear vlaue) the -10 dB is calculated as follow:

Inv Log [-10/20]=0.31 which means that 1-0.31=0.69 of power ratio goes throw the antenna (insted of half - 0.5 which disspited or reflected back).

Good Day !
Hoped Its helpful,

Itzik

Hi "itzikhaim" and "asdfaaa",

Thanks very much for all your help. I have a better understanding now.

:D :D :D :D :D