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<p>Many military communications systems utilize frequency-hopped spread spectrum waveforms to protect  against jamming and enemy detection. These waveforms may be subjected not only to intentional jamming but  may also be unintentionally jammed by other communications signals. While some systems can overcome inband  interference with more signal power, covert systems may be limited to small amounts of transmitted power.  The objective of this thesis was to investigate a method for resolving a frequency-hopped signal embedded in interference  waveforms.  With exponential averaging in the frequency domain, the spectra of the interfering signals can be estimated as  long as they are present over a period longer than that of the frequency-hopped signal. Certain FFT sizes and  weights are more beneficial to achieving this estimate than others. The interference estimate can be used to extract  the desired frequency-hopped signal through spectral division of the received signal with the estimate. This technique  is designated as noise-normalization. Simulations in MATLAB demonstrate the use of the technique and  show how the desired signal can be resolved.
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<br>Subjects: Electronic noise; Communications, Military; Electric interference; Signal detection</div>
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Brown, Christopher K.</div>
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