planar antennas design

Hi
I have a problem of designing a microstrip planar antenna which can operate in range<1GHz.
I need as large bandwidth as possible.So please tell me how to operate large bandwidths around 500-600MHz at such low frequencies(that means antenna operates in 400-1000MHz).There is no other constraint other than being planar.
But even if you can help me with some other designs I will be thankful to you

You may use printed structures on PCB starting from about 100 MHz. Half-inch long resonator will work well for this frequency even on FR4. For your task probably parallel printed dipole structure with wide elements may be used. Wire version works well for required 2.5 times bandwith.