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diff --git a/chapter06/content_ch06.tex b/chapter06/content_ch06.tex index d8373bb..1a90ab4 100644 --- a/chapter06/content_ch06.tex +++ b/chapter06/content_ch06.tex @@ -1374,14 +1374,63 @@ The Cooley-Tukey \acs{FFT} algorithm can be used to calculate the \ac{IFFT}, too \section{Spread Spectrum} +\begin{figure}[H] + \centering + \begin{tikzpicture} + \begin{axis}[ + height={0.15\textheight}, + width=0.8\linewidth, + scale only axis, + xlabel={$\omega$}, + ylabel={$|\mathrm{S}_{XX}|$}, + %grid style={line width=.6pt, color=lightgray}, + %grid=both, + grid=none, + legend pos=north east, + axis y line=middle, + axis x line=middle, + every axis x label/.style={ + at={(ticklabel* cs:1.05)}, + anchor=north, + }, + every axis y label/.style={ + at={(ticklabel* cs:1.05)}, + anchor=east, + }, + xmin=0, + xmax=10.5, + ymin=0, + ymax=1.2, + xtick={0}, + xticklabels={0}, + ytick={0}, + axis x discontinuity=parallel, + ] + \addplot[blue, smooth] coordinates {(4.6,0) (4.7,0.02) (4.8,0.2) (4.9,0.71) (5,1) (5.1,0.71) (5.2,0.2) (5.3,0.02) (5.4,0)}; + \addlegendentry{Narrow-band signal}; + \addplot[red, smooth] coordinates {(2,0) (2.5,0.01) (3,0.05) (5,0.05) (7,0.05) (7.5,0.01) (8,0)}; + \addlegendentry{Spread spectrum signal}; + \end{axis} + \end{tikzpicture} + \caption[PSD of a narrow-band and spread spectrum signal]{\acs{PSD} of a narrow-band and spread spectrum signal. Both signals carry the same information and have the equal power. The narrow-band signal concentrates the whole signal power in a narrow frequency band. In contrast, the spread spectrum signal distributes the signal power over a wide frequency band.} +\end{figure} + \todo{Purpose: Noise immunity} +\todo{Noise like} + \todo{Purpose: Immunity against narrowband disturbances} -\todo{Purpose: Coexistence with other services} +\todo{Purpose: Coexistence with other services, multiple access} + +\todo{Purpose: Plausible deniability} + +\todo{Purpose: Encryption, confidentiality} \subsection{Direct-Sequence Spread Spectrum} +\todo{pseudorandom number} + \todo{Processing Gain} \subsection{Frequency-Hopping Spread Spectrum} |