1,212
edits
Changes
→Monopole
[[File:Monopole2.png|thumb|600px|Monopole Antenna]]
* It is the simplest kind of antenna. It's just a wire and a ground plane with the wire perpendicular to ground plane. From electromagnetic theory, the ground plane acts as a mirror and the monopole antenna acts as a dipole antenna of twice its length. Hence most of its properties are same as a dipole antenna of twice length
* The main points of difference between a monopole and dipole are its resonant length, input impedance and directivity. A dipole resonates at 0.48 fraction of wavelength while the monopole resonates at half this length as monopole acts as a dipole twice its length. The input impedance of monopole is half of a dipole of twice length i.e. 36.5 + j21.25 ohm (for length 0.25*wavelength). The directivity of monopole is twice (+3 in dB) of dipole antenna i.e. 5.15 dB.<ref>http://www.antenna-theory.com/antennas/monopole.php</ref>
* In this discussion we have assumed the ground plane to be infinite. It is not so in any practical application, so the characteristics of this antenna can change slightly due to finite ground plane. The characteristics can be simulated using various simulation softwares.
* They are a very popular choice due to their small size simplicity and are used in almost all common antenna applications.