# Impedance Matching of an Antenna

I am reading about antenna design and have a few questions which I could not get clarified.

I read about "Stubs". I got to know that Stubs are used for impedance matching of an Antenna either by leaving it as an open circuit in one end or as an short circuit.

Question - How to find the input impedance of an Antenna of a particular length? Is there any method and how to calculate the stub length? Is there any formula?

Would really help me if someone could provide an example for calculating the input impedance of the antenna and the stub length for impedance matching

Question - How to find the input impedance of an Antenna of a particular length?

This is for a monopole but there are equivalent diagrams to be found for other antennas such as dipoles etc..

You've seen this before in a question I answered here.

Is there any method and how to calculate the stub length? Is there any formula?

This is the formula that folk use: -

• $$\V_P\$$ is velocity of propagation and is around 0.7c for your average coax cable.

Picture taken from my answer here.

• Thank you for your answer and the formula. If you could provide an example with numbers & calculation relating to the signal frequency, wavelength and finally to match the impedance,your stub length calculation, it would be really helpful for my understanding May 16 '20 at 15:45
• I fully recommend that you use something like excel and try it out for yourself. This can be compared with many instances of calculations like this to be found on-line. May 16 '20 at 15:48