5.8 Communications Jamming

The primary difference between radar and communication jamming is in the geometry. Figure 5.28 shows the communication jamming geometry. Whereas a typical radar has both the transmitter and the associated receiver at the same location, a communication link, because its job is to take information from one location to another, always has its receiver in a different location from that of the transmitter.

Figure 5.28: The communications-jamming geometry has one-way links from the desired transmitter and the jammerto the receiver.

Note that you can only jam the receiver. Of course, communication is often done using transceivers (each including both transmitter and receiver), but only the receiver at location B in the figure is jammed. If transceivers are in use and you want to jam the link in the other direction, the jamming power must reach location A.

There are some important communications cases in which transceivers are not used, for example, in UAV links as shown in Figure 5.29. This figure shows the data link (or "downlink") being jammed. Again, you jam the receiver.

Figure 5.29: A jammer operating against a UAV data-link must jam the receiver at the ground station.

Another difference from radar jamming is that the radar signal makes a round trip to the target, so the received signal power is below the transmitted power by the fourth power of the distance (often stated as 40 log range). Since the jammer power is transmitted one way, it is only reduced by the square of...