Antenna – Does It Need to Be Impedance Matched to Transmitter Circuit or Transmission Line?

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I am still very new to RF and I am trying to understand Impedance matching, so my question could be stupid.

I have already learned the basics of it, I know how to use Smith charts, which components to use to match it etc. But one question has risen up:

Reading from most sources, matching must be made between the source and the load (antenna). However, reading on antenna-theory.com (which is the source I learned nearly all I know about Impedance matching) it says this: enter image description here

In all examples I have seen on the matching series on the website, the impedance used in the Normalized impedance formula was always 50 ohms (coaxial cable I suppose)

And that's the thing which is confusing me. I am going to try a RF project and I just can't get over this thing.

Best Answer

Does an antenna have to be impedance matched to its transmitter circuit or the transmission line from it?

If the t-line is short i.e. less than one-tenth of a wavelength of the carrier frequency, then match antenna to the transmitter.

Else, match the antenna to the t-line using an L-pad, T-pad or Pi network (or combinations) if the antenna is not particularly close to a resistive impedance.

Normally there's no great need to match the transmitter to the t-line although this is quite often done.

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