08-08-2012, 01:13 PM
Direct Sequence Spread-Spectrum with Frequency Hopping
[attachment=30561]
What is spread spectrum?
Methods by which energy generated in a particular bandwidth is deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth.
used for a variety of reasons, including the establishment of secure communications, increasing resistance to natural interference and jamming, and to prevent detection.
Why do we need this?
In some situations it is required that a communication signal be difficult to detect, and difficult to demodulate even when detected. Here the word ‘detect’ is used in the sense of ‘to discover the presence of’.
In other situations a signal is required that is difficult to interfere with, or ‘jam’.
Commercial use
Initial commercial use of spread spectrum began in the 1980s in the US with three systems: Equatorial Communications System's very small aperture (VSAT) satellite terminal system for newspaper newswire services, Del Norte Technology's radio navigation system for navigation of aircraft for crop dusting and similar applications, and Qualcomm's OmniTRACS system for communications to trucks
Benefits
Resistance to intended or unintended jamming.
Sharing of a single channel among multiple users.
Determination of relative timing between transmitter and receiver.
[attachment=30561]
What is spread spectrum?
Methods by which energy generated in a particular bandwidth is deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth.
used for a variety of reasons, including the establishment of secure communications, increasing resistance to natural interference and jamming, and to prevent detection.
Why do we need this?
In some situations it is required that a communication signal be difficult to detect, and difficult to demodulate even when detected. Here the word ‘detect’ is used in the sense of ‘to discover the presence of’.
In other situations a signal is required that is difficult to interfere with, or ‘jam’.
Commercial use
Initial commercial use of spread spectrum began in the 1980s in the US with three systems: Equatorial Communications System's very small aperture (VSAT) satellite terminal system for newspaper newswire services, Del Norte Technology's radio navigation system for navigation of aircraft for crop dusting and similar applications, and Qualcomm's OmniTRACS system for communications to trucks
Benefits
Resistance to intended or unintended jamming.
Sharing of a single channel among multiple users.
Determination of relative timing between transmitter and receiver.