GSM AND MICROWAVE ANTENNA?

[RFKING]

please help me..my teacher asked me why gsm antenna are rectangular in shape and microwave antennas in circular...please help...thanks

[shariq.nav]

Antenna efficiency is measured by electromagnetic waves. Rectangular antenna eliminates the radiation resistance from impedance without changing the loss.it avoid any disturbance both at near end and far. Within the antenna the main aim is to reduce the cross sectional junctions.
Radio antenna we need maximize the bandwidth to cater maximum coverage footprint, and in case of a 4-sector and 6-sector site it is not feasible for a tower to bear the load.
Now in case of microwave which has higher frequency and doesn't have to cater any bandwidth it is kind of flash line from Point to point so its kind of circular.

Rgds / Sharique