What is VSWR in antenna theory?

What is VSWR in antenna theory?

I think that it has the same meaning as in field theory.

As any antenna has an input impedance, so there will be a certain VSWR if the antenna isn't matched to the transmission line, which feed the antenna.

I'm totally agree with what eng_semi said

Hi

I have here some example read the last pages.

PL

VSWR voltage standing wave ration, that means the ratio between transmitted signal from source to the reflected signal from the load (antenna), ideal case is VSWR=1, but of course it's not exists in the real life so the good ratio swinging between 1.0 to 1.2, over 1.5 is bad. as signal amplitude (voltage) is a proportion of impedenace (we talk about AC not DC so it's impedeance not resistance)
so VSWR equals to ration between load impedance and transmit media impedance, any differnce will cause high VSWR,
ex: transmission line with impedance 50 ohm (regular coax) should connected to antenna of 50 ohm impedance
i hope that i give you usefull information
thanks
Shafee

VSWR is general term it's not related specially to antenna theory. It is used to specify the amount of missmatch.
Look allso: https://www.edaboard.com/viewtopic.p...highlight=vswr

VSWR also gives idea how good the load receives the energy from the generator. When VSWR is close to 1 - almost all the energy from the generator is delivered to the load (radiated from the antenna). If VSWR is higher - 3, 4 and more, the most of RF energy will be reflected from the load input, back to the generator (like from mirror). Intereference in the transmission line between incident and reflected waves is VSWR.

Since the power delivered to the load in a transmission line , excited by a source with impedance Z0 is given by

,
so it follows that the magnitude of the load reflection coefficient ,

(which is related to the VSWR), provides a measure of what portion of

is delivered to the load .
Now in an antenna

is the power propagated by the antenna , and

is the available source power connected to the input port of the antenna.
if you couldn"t understand the formulas please notify me.

a parameter to indicate matching.
VSWR=(1+ge)/(1-ge), where ge = abs[(Za - 50)/(Za+50)]