Subelement M: M – Communications Technology— Topic 82: Types of Transmissions
Question 3-82M2
Element 3 (GROL)Name two types of spread spectrum systems used in most RF communications applications?
Explanation
Direct Sequence Spread Spectrum (DSSS) and Frequency Hopping Spread Spectrum (FHSS) are the two primary methods used to implement spread spectrum technology. DSSS spreads a signal by combining the original data with a high-rate pseudorandom noise (PN) code, significantly widening the signal's bandwidth. FHSS rapidly changes the signal's carrier frequency pseudo-randomly over a wide range of frequencies. Both techniques make signals more resistant to interference, jamming, and interception by spreading the signal's energy over a wider frequency band.
AM (Amplitude Modulation) and FM (Frequency Modulation) are conventional narrowband modulation types, not spread spectrum. QPSK (Quadrature Phase-Shift Keying), QAM (Quadrature Amplitude Modulation), and APSK (Amplitude and Phase-Shift Keying) are digital modulation schemes that encode data efficiently but do not inherently spread the signal's bandwidth. While they can be used *within* a spread spectrum system, they are not the *types* of spread spectrum systems themselves.
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