This LinkSprite ATWIN Quad-band GPRS/GSM shield has PCB etched antenna, so no need for external antenna.

ATWIN Quad-band GPRS/GSM shield is an ultra compact and high quality wireless module base on infineon UCL2 platform with industy-standard interface.

This is a SMT package with small dimension, low power consumption, quad-band (AT139) and dual-band (AT139D) GSM/GPRS module.

It can provide Voice, SMS and Fax.

for more info see WIKI