Transmitters, Modulation and Processing
spread spectrum - frequency hopping, direct sequence
What term describes a wide-band communications system in which the RF carrier varies according to some predetermined sequence?
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Correct AnswerSpread spectrum communication
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Amplitude-compandored single sideband
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AMTOR
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Time domain frequency modulation
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What is the term used to describe a spread spectrum communications system where the centre frequency of a conventional carrier is altered many times per second in accordance with a pseudo-random list of channels?
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Direct sequence
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Time-domain frequency modulation
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Frequency compandored spread spectrum
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Correct AnswerFrequency hopping
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What term is used to describe a spread spectrum communications system in which a very fast binary bit stream is used to shift the phase of an RF carrier?
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Frequency hopping
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Phase compandored spread spectrum
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Correct AnswerDirect sequence
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Binary phase-shift keying
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Frequency hopping is used with which type of transmission?
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Correct AnswerSpread spectrum
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AMTOR
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Packet
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RTTY
Tags: none
Direct sequence is used with which type of transmission?
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Correct AnswerSpread spectrum
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AMTOR
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Packet
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RTTY
Tags: none
Which type of signal is used to produce a predetermined alteration in the carrier for spread spectrum communication?
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Frequency-compandored sequence
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Quantizing noise
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Correct AnswerPseudo-random sequence
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Random noise sequence
Tags: none
Why is it difficult to monitor a spread spectrum transmission?
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It requires narrower bandwidth than most receivers have
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It varies too quickly in amplitude
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The signal is too distorted for comfortable listening
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Correct AnswerYour receiver must be frequencysynchronized to the transmitter
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What is frequency hopping spread spectrum?
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The carrier is amplitude-modulated over a wide range called the spread
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The carrier is frequency-compandored
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Correct AnswerThe carrier is altered in accordance with a pseudo-random list of channels
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The carrier is phase-shifted by a fast binary bit stream
Tags: none
What is direct-sequence spread spectrum?
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The carrier is amplitude modulated over a range called the spread
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The carrier is frequency-compandored
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Correct AnswerThe carrier is phase-shifted by a fast binary bit stream
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The carrier is altered in accordance with a pseudo-random list of channels
Tags: none
Why are received spread-spectrum signals so resistant to interference?
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The receiver is always equipped with a special digital signal processor (DSP) interference filter
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Correct AnswerSignals not using the spectrum-spreading algorithm are suppressed in the receiver
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If interference is detected by the receiver, it will signal the transmitter to change frequencies
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The high power used by a spreadspectrum transmitter keeps its signal from being easily overpowered
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How does the spread-spectrum technique of frequency hopping (FH) work?
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Correct AnswerThe frequency of an RF carrier is changed very rapidly according to a particular pseudo-random sequence
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If interference is detected by the receiver, it will signal the transmitter to change frequency
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If interference is detected by the receiver, it will signal the transmitter to wait until the frequency is clear
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A pseudo-random bit stream is used to shift the phase of an RF carrier very rapidly in a particular sequence
Tags: none
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