Surface current of a patch antenna

What is the concept behind surface currents of a microstripe patch antenna? what should be its range for good performance of a patch antenna?

Thanx in advance

A patch antenna supports currents on its conductors.

The magnitude of the currents should be larger than zero.

I surmise from these questions that you aren't understanding the operating mechanism of the patch antenna. See texts such as Balanis or even Wikipedia.

@planarMetamaterials: thanx for reply... i know how an antenna operate and i have designed a multiband antenna but i don't know what should be its range (mean maximum upper range limit for working antenna ) my antenna has range of 37 A/m ,60 A/m 45 A/m for different bands

what should be its upper limit i have 39 to 60 A/m

Sorry for the misunderstanding -- I'm still confused, though -- are you asking what's the maximum current density a typical patch antenna can handle before overheating?

yes
planarmetamaterials

Well.... that would depend on a number of factors, such as dielectric material and thickness, trace thickness, ground plane size (for thermal dissipation), etc.