Jamming: Downlink Jamming

Downlink jammers target the users of a satellite by creating noise in the same frequency as the downlink signal from the satellite. A downlink jammer only needs to be as powerful as the signal being received on the ground and must be within the field of view of the receiving terminal’s antenna. This limits the number of users that can be affected by a single jammer. Since many ground terminals use directional antennas pointed at the sky, a downlink jammer typically needs to be located above the terminal it is attempting to jam. This limitation can be overcome by employing a downlink jammer on an air or space-based platform, which positions the jammer between the terminal and the satellite. This also allows the jammer to cover a wider area and potentially affect more users. Ground terminals with omnidirectional antennas, such as many GPS receivers, have a wider field of view and thus are more susceptible to downlink jamming from different angles on the ground.