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

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

(OP)
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

### RE: How to measure antenna bandwidth???Pls Help??

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

Buding

### RE: How to measure antenna bandwidth???Pls Help??

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.

### RE: How to measure antenna bandwidth???Pls Help??

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

### RE: How to measure antenna bandwidth???Pls Help??

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

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