How to measure antenna bandwidth???Pls Help??

[raymondli]

Hi all friends,

I recently study the microstrip antenna, however, I have some problem, that is I really dont know the criteria for measuring its bandwidth.

Its formula for measurement:

voltage standing wave ratio(vswr) < 2

Bandwidth = {(S-1) / Qx (S power1/2)} x100%

Q= center freq / delta freq at certain level related to vswr

But I dont know why sometimes calculated at vswr =1.7 sometimes =1.8, whatever?????
For the formula, is S = vswr ??? as the book does not indicated clearly.........
Is that a standard to measure??


Thank you for your attentions!

Regards,

raymond

 

[jbartos]

Suggestion: Visit

http://www.cebik.com/bw.html

etc. for more info

 

[buding]

As I know it is enough if You know VSWR. Bandwidth of the antenna will be the bandwith were VSWR is < 2.

Buding

 

[5636]

Sweep the antenna with a spectrum analyzer and tracking generator. The bandwidth is the area (freq) between points
where the signal is 3db below maximum.

 

[jbartos]

Suggestion to the previous posting. Theoretically, there could also be only one point at which the curve is 3db below plateau.

 

[blakor65]

a network analyzer (HP8713C) or better will give you the best indicator of the anttena's bandwidth
Ideally a Return Loss (reflection ) measurement with a min of 15 dB is your indicator of your highest frequency

 

[jbartos]

Suggestion: Visit

http://www.educatorscorner.com/experiments/pdfs/exp94/exp94b.pdf

http://www.swissatv.ch/documents/patch_slot_antenna.pdf

etc. for more info on the antenna bandwidth