There maybe a way to use acoustic transducers to pin-point incoming enemy ordinance such as mortar rounds in order to shoot them down.
Directional sound waves from acoustic transducers set at specific locations around friendly locations can create artificial barriers, which the incoming ordinance will have to pass to reach its target and thus be detected and triangulated or quadrangulated for interception.
A set of five units would be set up around the base camp is a specific arrangement and exact dimensions point upward into the sky.
As the incoming mortar round crossed the sound wave it would be detected and set off an Event Code.
As the mortar round again traveled forward it would hit yet another and another air-wall and a trajectory would be formed and mathematically computed.
At this point the computer would decipher this information and send up a kill projectile to hit the round in mid-air.
The incoming mortar or enemy round would thus be eliminated in a similar fashion by directing the kill projectile to its continued and future trajectory.
With a series of mirrors and five acoustic transducers creating the sound wave barriers this should be possible to protect our troops.
Although I have not done all the math required to prove this will work; I believe it will.
If you have knowledge in this realm; think about and let me know what you come up with.