Spread Spectrum Flashcards
Define Spread Spectrum
Methods by which electromagnetic energy in a particular bandwidth is deliberately spread resulting in a wider bandwidth.
Why is Spread Spectrum used?
1) Secure Communications
2) Resistance to natural interference
3) Jamming/Preventing Intercept
What is Processing Gain?
The recieved signal fidelity gained at the cost of bandwidth. It’s the ratio of the Radio Frequency bandwidth to the information rate of the transmitted signal.
Expand LPI and AJ
Low Probability of Intercept
Anti Jam
Name the Spread Spectrum technique’s:
- Direct Sequence Spread Spectrum (DSSS)
- Frequency Hop Spread Spectrum (FHSS)
- Time Hop Spread Spectrum (THSS)
- Stacked carrier
- Hybrid
Explain Direct Sequence Spread Spectrum:
DSSS phase modulates with a string of psuedonoise code symbols called CHIPS.
What is the name given to a sequence of chips produced by the transmitter and received at the receiver terminal
A priori.
What is the name given to a sequence of chips produced by the transmitter and received at the receiver terminal
A priori.
What makes multiple DSSS on the same signal possible?
Code Division Multiple Access (CDMA)
What is Spread Spectrum measured in?
Watts per Hertz
Name and explain 3 ways to spread codes:
1) Maximal Length LRS - (2n-1)
2) Gold Codes - Combines two maximal length LRS and the output sequence are modulo 2
3) Composite - Adds two maximal length sequences which equals the least common multiple of periods of two sequences
What are the two types of Frequency Hop Spread Spectrum and their advantages?
FAST = Less prone to jamming SLOW = Less errors
