wat is "monopole ground plane"

[ngstty]

monopole ground plane

hi
can any one help
whether there is any particular formulae for the length of microstrip feed
or we can take any length for the feed
why we define a negative port for ground plane in micro strip feeding

 

[biff44]

+quarterwave +monopole +gain +dbi

Back in the day, people only used dipole antennas. They were half a wavelength long in total length. They did not need a ground plane because they behaved "differentially", that is one quarterwave rod was excited positively, and the other quarterwave rod was excited negatively.

Then a smart fellow said, why not only use one quarter wave rod, and use a metal surface acting like a mirror, to reflect a ghost image of itself. That way it will act like a half wavelength antenna, but only be a quarterwavelength long. This worked fine when the ground plane was "big" with respect to a quarterwavelength.

Then some not so smart fellows started saying things like "why do we need all that ground plane size?". And the ultimate evolution is that you have very small radius (or sometimes even no) ground plane, and some sort of whip antenna that people HOPE acts like a quarterwave monopole.

The reality is that if you use an electricaly short whip (less than a quarter wavelength), or an electrically small ground plane (less than ~ a quarter wavelength in radius), your antenna will have poor gain.

I have used short antennas on small ground planes that, while they looked like they might be monopoles, actually had -30 dBi of gain.
Some interesting papers on the subject:
**broken link removed**
**broken link removed**


Rich
www.MaguffinMicrowave.com