As is known in the art, a jamming signal can be used to reduce the effectiveness of a radar or communication system. In many cases, however, this same jamming signal can also interfere with unintended (so-called “friendly”) communication channels. To address this problem, techniques for combining the communication signal with the jamming signal are known.
Conventional systems and techniques for communicating while jamming involve separating the communication and jamming signals in either the time or frequency domain. For example, the communications are sent either during times the jamming signal is turned off, or a small frequency band is left unjammed for the communications system to use. If encryption is to be used to prevent a third party (e.g. an adversary or “enemy” in a military application) from listening in, then there may be a shared key established beforehand. If an encryption key is not already shared between allies, to ensure security this key must itself be securely transmitted sometimes making use of encryption impractical.
As is also known, a far-field radiation pattern of most antennas includes a pattern of “lobes” at various angles. In a directional antenna in which the objective is to emit electromagnetic energy (e.g. radio frequency (RF) signals) ideally in one direction, the lobe in that direction has a larger field strength than the others and is typically referred to as a “main lobe” or “main beam.” The other lobes which are not the main lobe are referred to as “side lobes.”
Even in highly directional array antennas, antenna side lobes always exist. Electromagnetic energy emitted through such side lobes can be received by highly sensitive antenna systems. Excessive side lobe radiation wastes energy and may interfere with operation of other equipment. Accordingly, in conventional systems, attempts are made to reduce (and ideally minimize) antenna side lobe levels as much as possible, with no attempt to utilize them for additional functionality.