In order for a jamming system to respond to the plethora of commercially made radio control devices, the jamming system must cover a considerable bandwidth from 20 to 2500 MHz and beyond in a very short period of time. Almost any commercially made radio device, whether it be a hobby radio, garage door opener, cellular telephone or a handie-talkie for example, can be with little technical knowledge fashioned into a threat device. These devices operate in various parts of the spectrum, using different modulation formats, protocols and intelligence. To assign a receiver for each frequency where every commercial device operates would not only be impractical but very costly. Furthermore, there still needs to be a mechanism to decide quickly whether to attack the signal or leave it alone.
For a jamming system to be effective in the urban environment for policing protection and intervention, several primary requirements need to be met. (1) The system should jam both hostile voice/data communication equipment and also accommodate the larger growing threat of radio control devices being used to detonate explosives by a hostile force during, for example, a motorcade escort. On this point alone, prior art systems fail primarily because the jam algorithms are not properly tailored to the target device and as a result either premature actuation of the explosive will result or ineffective jamming will prevail. (2) The system should jam radio signals surreptitiously. Very few people in the urban neighborhood should be alerted to the presence of the jamming equipment when transmitting, particularly the terrorist, and therefore it should be selective about which frequencies it must jam as well as how long the jammer can transmit. (3) The system should be real-time adaptable to the multiplicity of radio signals received in the urban environment to accommodate a variety of radio control and communication signal threats. (4) Coverage of the radio spectrum should be continuous and as widebanded as possible since the threat may occur at any time and at any frequency unbeknown to the operator of the system. If the system is reactive in nature, the reaction time must be faster than the time it takes for a commercially marketed radio control device to decode a command from the moment of initiation. (5) The system should be easy to transport. (6) The system should be easy to operate. (7) The system should not be costly.
In many ways the requirements put forth for jamming radio control devices are even more demanding than a conventional communication jammer since if the hostile transmission is not properly addressed it is not simply a voice instruction that is missed, but moreover, perhaps a loss of life and property. If the system can handle radio control devices, voice/data communication jamming can also be handled.
In the prior art, the known architectures do not show the necessary versatility and operational efficiency to function in the urban environment for policing protection against the aforementioned threats in real-time. The “barrage” jamming method, where jamming noise is radiated indiscriminately across a very wide radio spectrum, fails on requirements 1, 2, 3, 6 and 8. “Selective” jamming, which concentrates the jamming noise into multiple narrow spectral bandwidths, fails on requirements 1, 3 and 4. Known reactive jamming architectures, which introduce a receiver to guide the jammer, fail on requirements 1, 3, 5 and 7. Many of these techniques are described in more detail in electronic warfare literature such as “Electronic Countermeasures”, Peninsula Publishing, Chp. 6, 7 and 12, 1979, ISBN-0-932146-00-7.
Therefore, there is a need for improved jamming methods that can meet a majority of the above-listed criteria.