What is the Aspect Ratio of a patch antenna?

Can anyone tell me what exactly is Aspect Ratio of a Patch Antenna ?
Is it W/L or L/W and what should be the ideal Aspect Ratio to obtain polarization purity in a Microstrip Patch Antenna. I need to reduce the cross polarization level of a patch antenna array -- any suggestions / ideas are most welcome.

Now depends what type of feeding you use.
For edge fed by a microstrip line the aspect ratio of 1.5 get the minimum cross polarization level.
Other types of feeding needs further simulations.

I am using a EM coupled feed network.