In the previous articles, we learnt about how drones are classified on the basis of Size & Endurance.The articles gave a good insight on how UAV technological applications have evolved within and outside of the military sphere.
Moving forward, it would be instructive to consider how an UAV performs its missions. Normally, an UAV is controlled from the ground by a Ground Control System (GCS) through a two way Command/ Control V/UHF RF link. This permits the ground station operator to control the flight path of the UAV so that it hovers over the areas of interest. The current position of the UAV is fed to the GCS through a V/UHF Telemetry link using the data from the GPS receiver on board the UAV.
The UAV payload can vary from on-board sensors such as Electro-Optical/Infra-Red cameras, Electronic/ Signal Intelligence suites to missiles and explosives. The UAVs therefore also have a down-link for instantaneous transfer of surveillance information. Continuous video feeds are transmitted by a Video Transmitter on board the UAV on the First Person View (FPV) link. This link normally operates in the C Band. Since operating ranges of the UAV are restricted on account of the RF link distances being limited by Radio Line of Sight (RLOS), some advanced military variants also have satellite receivers on board for extending ranges. Since this would necessarily increase the payload volume and weight, such UAVs normally have wingspans larger than 20 meters implying thereby that they would be susceptible to Radar detection.
Figure-1 given below indicates the various RF links likely to be active during drone operation.
Military UAVs normally use Spread Spectrum Technologies such as Frequency Hopping or Direct Sequence to reduce the probability of interception of command/control links.
Below would be some of the commonly used frequencies by commercial/military UAVs
In the next article from the series of Drone Activity Monitoring Systems, we will bring to you information on Active and Passive methods of detection which involves RADAR Technology & Acoustic sensors.