What is difference between Single Band Jammer, Frequency Swept Jammer and Pulse Jammer?
How they work ? any tutorial ?
important parameters of each jammer?
There are various books available on these topics, for the time being read this document.
Hi Zafar
See book "Modern Communications Jamming Principles and Techniques" By Richard A. Poisel. In chapter 6 of this book, jamming strategies are studied and categorized into these:
- Partial Dwell Jamming
- Noise Jamming
- Tone Jamming
- Swept Jamming
- Pulse Jamming
- Follower Jamming
- Smart Jamming
Sweep jamming is when a jammer's full power is shifted from one frequency to another. While this has the advantage of being able to jam multiple frequencies in quick succession, it does not affect them all at the same time, and thus limits the effectiveness of this type of jamming. Although, depending on the error checking in the device(s) this can render a wide range of devices effectively useless.
Pulse jamming produces noise pulses with period depending on radar mast rotation speed thus creating blocked sectors from directions other than the jammer making it harder to discover the jammer location.
I confirm the book recommended by Mr Farhang will provide you with more insight about the different jamming strategies. Having worked 10 years in the field of military telecommunications (mainly modems) I can add the following; In additon to encryption of the source and/or modulated modulation symbols, secure communications are mainly provided by;
- frequency hopping modems, a pseudo-random sequence controls the hops between a discete set of modulated carrier frequencies. This implies use of digital frequency synthesizers in the modem, the number of hops per second can be 16k+. The same sequence is repeated on receiver side, allowing demodulation. The only efficient jamming strategy ion this case is to use a multi-tone jammer and try and reconstruct the hop pattern to be ablew to efficiently jam the communication. While this is not impossible it requires huge processing power.
- Spread spectrum, the carrier bandwidth is spread via a pseudo-random sequence of several dozen up to several hundred times the useful data comm. rate. The spectrum of the carrier is thus spread (check comm. theory, there are excellent tutorials on SS on the net) and may even be hidden in noise. On receiver side the same sequence allows "unspreading" the modulated carrier. The communication might even be impossible to detect as the signal might be hidden in noise. A single tone jammer would be spread by on the receiver side in this case and be inefficient (in jamming the comm.). In this case pulse jamming might be efficient as it could saturate input stages of the receiver.
- single tone or pulse jammer might be efficient for jamming an "unprotected" comm. link, e.g. when no frequency hopping or SS is used.
Channel coding strategires are also used to counteract jammers, e.g. bit and/or symbol interleaving, block coding... making it very difficult to efficiently jam well designed comm. systems.
Hope it gave a bit more insight.
Kind regards
Patrick
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