best 868mhz antenna

Hi all,

I am going to design a short range device at 868MHz, but i am not familiar with the antenna theory. Can anyone suggest which type of microstrip antennas is more suitbale? Loop antenna , open stub antenna or a slot antenna?

The major concern is the size of the antenna.

ThX

Best rgd :D

I would go for a PIFA (Planar Inverted F Antenna)
There are a few main principles to reduce the overall PIFA size:
-Placing a short circuit at the zero electric field line
-The use of a dielectric substrate
-Capacitive loading at the end of the radiator
-Folding of the antenna structure to achieve a resonant path on smaller area

regards

Hi,

This kind of applications are using usually a loop antenna. This kind of antenna can be made small,


regards,


Tony :o

Thanks for your reply. I also think loop antenna is a good choice for 868MHz applications. But i have a problem, what is the main paramemter that dominantes the operating frequency of this kind of antenna? The loop area or the lenght of the loop, also is the length needed to set around 1/4 lamda?

Thx

regard

hi
I think microstrip antenna could be the best for ur application, detailed info about it u can find a tutorial at rfic.co.uk

Hi,

u have several kind of loopantennas; usually the current distribution along the loop is relative constant, this means that the length of the loop should be small compared with the wavelength, the loop is then tuned to resonance with a capacitor, gain of such a antenna in practise is rather low , from -25 dbi to 10 dbi...but they are small
if u have more place u can consider to use a full wavelength loopantenna, this has a very good performance, gains of 2 dbi are feasible

maybe this is of some help to u,

Tony