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en:research:sr:manuel:reference-manuel:subsystem [2007/02/23 11:33] brunner created |
en:research:sr:manuel:reference-manuel:subsystem [2007/02/23 11:40] (current) brunner |
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Only the reception-part is treated in this document, as the transmission-part | Only the reception-part is treated in this document, as the transmission-part | ||
is quite simple. | is quite simple. | ||
+ | |||
===== Nyquist ===== | ===== Nyquist ===== | ||
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then f_adc must be chosen so that | then f_adc must be chosen so that | ||
- | |||
<latex>$\frac{f_ adc}{2}N\notin\left[fi_ rx-\frac{wi_ rx}{2}, fi_ rx+\frac{wi_ | <latex>$\frac{f_ adc}{2}N\notin\left[fi_ rx-\frac{wi_ rx}{2}, fi_ rx+\frac{wi_ | ||
rx}{2}\right]$</latex> | rx}{2}\right]$</latex> | ||
- | |||
is fulfilled. Else we get an overlapping of the aliased signal and we loose | is fulfilled. Else we get an overlapping of the aliased signal and we loose | ||
information. | information. | ||
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<latex>f_adc=100MHz</latex>, | <latex>f_adc=100MHz</latex>, | ||
which fullfills the above equation. | which fullfills the above equation. | ||
+ | |||
+ | |||
===== Reception-chain ===== | ===== Reception-chain ===== | ||
- | <wikionly>{{figure.png|The whole chain and the most important part of it} | + | <figure>en:research:sr:manuel:rx-chain|Reception-chain|cap:Reception-chain</figure> |
- | \end{figure}}</wikionly><htmlonly><a id="cap:Reception-chain"></a></htmlonly> | + | <figure>en:research:sr:manuel:ddc|The whole chain and the most important part of it|cap:DDC-chain</figure> |
- | <texit> | + | |
- | \begin{figure}[ht] | + | |
- | \subfigure[Whole Reception chain]{ | + | |
- | \includegraphics[width=0.45\textwidth]{Figures/rx-chain.eps} | + | |
- | \label{cap:Reception-chain} | + | |
- | } | + | |
- | \hfill | + | |
- | \subfigure[DDC-chain]{ | + | |
- | \includegraphics[width=0.45\textwidth]{Figures/ddc.eps} | + | |
- | \label{cap:DDC-chain}} | + | |
- | \caption{The whole chain and the most important part of it} | + | |
- | \end{figure} | + | |
- | </texit> | + | |
The different parameters of fig.<ref>cap:Reception-chain</ref> and | The different parameters of fig.<ref>cap:Reception-chain</ref> and | ||
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<ldt>f_adc</ldt><ldd>[1-100]MHz, the sampling frequency of the ADC.</ldd> | <ldt>f_adc</ldt><ldd>[1-100]MHz, the sampling frequency of the ADC.</ldd> | ||
<ldt>fi_rx</ldt><ldd>[1-500]MHz, the intermediate frequency. Every frequency above <latex>\frac{f_ adc}{2}</latex> will be attenuated due to the sinc of the ADC.</ldd> | <ldt>fi_rx</ldt><ldd>[1-500]MHz, the intermediate frequency. Every frequency above <latex>\frac{f_ adc}{2}</latex> will be attenuated due to the sinc of the ADC.</ldd> | ||
- | <ldt>fs_rx</ldt><ldd>[0-$\frac{f_ adc}{8}$]MHz, the final sampling frequency (the DDC does down-sampling). Contrary to f_adc, fs_rx is measured in complex samples.</ldd> | + | <ldt>fs_rx</ldt><ldd>[0-<latex>\frac{f_ adc}{8}</latex>]MHz, the final sampling frequency (the DDC does down-sampling). Contrary to f_adc, fs_rx is measured in complex samples.</ldd> |
<ldt>w_rx</ldt><ldd>[0.08-0.75], the portion of the final sampling frequency fs_rx which is not cut off by the DDC filters.</ldd> | <ldt>w_rx</ldt><ldd>[0.08-0.75], the portion of the final sampling frequency fs_rx which is not cut off by the DDC filters.</ldd> | ||
</ldl> | </ldl> | ||
- | \begin{comment} | + | <texit> \begin{comment} |
How is the bandwith related to fs_rx? Is it 0.08-0.75 or 0.16 - 1.5? | How is the bandwith related to fs_rx? Is it 0.08-0.75 or 0.16 - 1.5? | ||
- | \end{comment} | + | \end{comment} </texit> |
<ldl> | <ldl> | ||
- | <ldt>sig_type</ldt><ldd>\{ SIG_COMPLEX_ICS, SIG_S16 \} for FPGA_DEFAULT\\ \{ SIG_COMPLEX_S16 \} for FPGA_S16</ldd> | + | <ldt>sig_type</ldt><ldd>{ SIG_COMPLEX_ICS, SIG_S16 } for FPGA_DEFAULT\\ { SIG_COMPLEX_S16 } for FPGA_S16</ldd> |
</ldl> | </ldl> | ||
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For more detail, see the Graychip-documentation on page 11, 3.4.2 and | For more detail, see the Graychip-documentation on page 11, 3.4.2 and | ||
references. | references. | ||
+ | |||
==== w_rx ==== | ==== w_rx ==== | ||
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filters is subject to a subsequent work and thus only pre-calculated filters | filters is subject to a subsequent work and thus only pre-calculated filters | ||
have been used. This is why the bandwith can | have been used. This is why the bandwith can | ||
- | only be one of \{0.085, 0.17, 0.34, 0.40, 0.50, 0.75\}. | + | only be one of {0.085, 0.17, 0.34, 0.40, 0.50, 0.75}. |
Another point here: the filters in //filters.c// are defined for twice this | Another point here: the filters in //filters.c// are defined for twice this |