In this paper, we propose a digital implementation of the antenna interface standards group (AISG) modem for the remote control and monitoring of antenna line devices (ALDs) through an antenna feeder cable. The proposed modem is implemented in Altera EP3C16E144C8 device, together with an 8-bit ADC and a BPF. It operates at variable data rates of 9.6, 38.4, and 115.2 kbps based on the OOK modulation scheme. The carrier frequency of the OOK modulated signals is 2.176 MHz. The modem is fully compliant with the 3GPP and AISG standards. To show the validity of the proposed AISG modem, the modem is implemented in FPGA and its functionality is verified using the verification scenario of 3GPP and AISG standards. The proposed AISG modem consumes 0.41 W and 0.6 W with DC power supplies of 10 V and 32 V, respectively. The measured transmit power level is +3.3 dBm, and the measured return loss in pass-band is more than 10 dB. The duty cycle variations for data rates of 9.6, 38.4, and 115.2 kbps are less than ±1 %, ±2 %, and ±4 %, respectively.