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\chap Trial version of the digitizer
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\chap Trial version of the digitizer
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The whole design of the radioastronomic receiver digitization unit is meant to be used in a wide range of applications and tasks related to digitization of a signal. A good illustrating problem for its use is the signal digitization from multiple antenna arrays. Design and implementation of the system is presented in this chapter.
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The whole design of the radioastronomic receiver digitization unit is meant to be used in a wide range of applications and tasks related to digitization of a signal. A good illustrating problem for its use is the signal digitization from multiple antenna arrays. Design and implementation of the system is presented in this chapter.
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\midinsert
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\clabel[expected-block-schematic]{Expected system block schematic}
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\picw=\pdfpagewidth \setbox0=\hbox{\inspic ./img/Coherent_UHF_SDR_receiver.png }
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\par\nobreak \vskip\wd0 \vskip-\ht0
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\centerline {\kern\ht0 \pdfsave\pdfrotate{90}\rlap{\box0}\pdfrestore}
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\caption/f Expected realization of signal digitalisation unit.
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\endinsert
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\sec Required parameters
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\sec Required parameters
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We require the following technical parameters in order to overcome the existing digitization units solutions. Primarily, we need a wide a dynamical range and a high third-order intercept point (IP3\glos{IP3}{Third-order intercept point}). The receiver must accept signals with the wide dynamics because a typical radioastronomical signal is a weak signal covered by a strong man-made noise or other undesired noises as lighting, Sun emissions, etc.
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We require the following technical parameters in order to overcome the existing digitization units solutions. Primarily, we need a wide a dynamical range and a high third-order intercept point (IP3\glos{IP3}{Third-order intercept point}). The receiver must accept signals with the wide dynamics because a typical radioastronomical signal is a weak signal covered by a strong man-made noise or other undesired noises as lighting, Sun emissions, etc.
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This design ensures that all system devices have access to the defined phase and the known frequency.
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This design ensures that all system devices have access to the defined phase and the known frequency.
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\sec System description
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\sec System description
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This section deals with the description of the trial version based on Xilinx ML605 development board, see Figure~\ref[ML605-development-board], available at the workplace. This FPGA parameters are more than sufficient of what we need for the fast data acquisition system being developed.
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This section deals with the description of the trial version based on Xilinx ML605 development board, see Figure~\ref[ML605-development-board], available at the workplace. This FPGA parameters are more than sufficient of what we need for the fast data acquisition system being developed. Expected system configuration is shown in Figure~\ref[expected-block-schematic]. The system consist antennas equipped by
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%% dopsat celkovy popis systemu.
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\midinsert
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\clabel[expected-block-schematic]{Expected system block schematic}
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\picw=\pdfpagewidth \setbox0=\hbox{\inspic ./img/Coherent_UHF_SDR_receiver.png }
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\par\nobreak \vskip\wd0 \vskip-\ht0
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\centerline {\kern\ht0 \pdfsave\pdfrotate{90}\rlap{\box0}\pdfrestore}
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\caption/f Expected realization of signal digitalisation unit.
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\endinsert
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\secc Frequency synthesis
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\secc Frequency synthesis
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We have used a centralized topology as a basis for frequency synthesis. One precise high-frequency and low-jitter digital oscillator (GPSDO\glos{GPSDO}{GPS disciplined oscillator}) has been used \cite[MLAB-GPSDO]. The other working frequencies have been derived from it by the division of its signal. This central oscillator has a software defined GPS\glos{GPS}{Global Positioning System}  disciplined control loop for frequency stabilization.\fnote{SDGPSDO design has been developed in parallel to this diploma project as a related project, but it is not explicitly required by the thesis itself and thus it is described in a separate document.}
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We have used a centralized topology as a basis for frequency synthesis. One precise high-frequency and low-jitter digital oscillator (GPSDO\glos{GPSDO}{GPS disciplined oscillator}) has been used \cite[MLAB-GPSDO]. The other working frequencies have been derived from it by the division of its signal. This central oscillator has a software defined GPS\glos{GPS}{Global Positioning System}  disciplined control loop for frequency stabilization.\fnote{SDGPSDO design has been developed in parallel to this diploma project as a related project, but it is not explicitly required by the thesis itself and thus it is described in a separate document.}
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We have used new methods of software frequency monitoring and compensation in order to meet modern requirements on the radioastronomy equipment, which needs the precise frequency and phase stability over a wide baseline scales for effective radioastronomy imaging.
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We have used new methods of software frequency monitoring and compensation in order to meet modern requirements on the radioastronomy equipment, which needs the precise frequency and phase stability over a wide baseline scales for effective radioastronomy imaging.