antenna-theory.com

[peshalnayak]

Can any one tell me what a parasitic resonator is and what it does?
I read an IEEE paper titled - "Dual Wideband Printed Monopole Antenna for
WLAN/WiMAX Applications" in which a trapezium shaped patch is placed under the main rectangular patch on the other side of the dielectric. The author calls this as the parasitic resonator electrically coupled with the main patch.

I contacted the authors for help but received no reply.

Also it is written that the parasitic resonator creates an additional band due to an over-coupling condition. What is this condition?

Please help me as I need this information urgently.

[Schubert]

A parasitic resonator is an antenna element that is located near your antenna, but does not physically touch it. Fields are capacitively coupled onto the resonator, which then gives rise to its own radiation.

As an example, you may have a patch antenna that radiates at a low frequency, and want to have radiation at some higher frequency. You could then put a parasitic resonator (tuned for the higher frequency) very close to your antenna, and in that fashion induce the new radiation mode.

[abid.ali]

Really you care about efficiency, and for WLAN applications it matters what type of range for a given data rate you are trying to achieve.

If you want something that works about as well as a typical phone, you can get away with a crappier antenna.

-6dB is equivalent to a VSWR of 3, which is generally about as high as you want to go for mismatch loss. Some people will expect better, but it really depends on the application.

Anyway, its tough to answer your question because in some applications -6dB is ok and in some you need -10 dB return loss.