This paper describes about multipurpose, band specific antenna design for a wireless authentication device. Various design challenges are discussed for the antenna development as related to the product design. Specific tuning methods for different types of antenna are illustrated with a brief overview of the antenna selection possibilities. This authentication device has three band-specific antennas for 900MHz GSM/GPRS, 2.4GHz Wi-Fi and 1.5GHz GPS frequency bands. In this paper, design possibilities for GSM/GPRS antenna is proposed and one of the antenna design was carried out with the available space constraints and better than 50% efficiency has been achieved.