| 77,31 → 77,27 |
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| \secc Custom digitization system |
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| Custom designs usually use non-recurring engineering for the development of a specific solution for an observation project. Consequently, such instruments are very costly if the developed instrument is not reproduced many times. A typical example of the instrument developed and manufactured in a single piece with enormous funding requirements was the Arecibo ALFA\glos{ALFA}{Arecibo L-Band Feed Array} survey multi beam feed Array. |
| Another opposite example for custom receiver and digitization unit design is LOFAR system developed by Astron in Netherlands \cite[lofar]. |
| Custom designs usually use non-recurring engineering for the development of a specific solution for an observation project. Consequently, such instruments are very costly if the developed instrument is not reproduced many times. A typical example of the instrument developed and manufactured in a single piece with enormous funding requirements was the Arecibo ALFA\glos{ALFA}{Arecibo L-Band Feed Array}. |
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| LOFAR is innovative radioastronomy system which uses the phased antenna array approach in enormous scale and thousands (around $2 \cdot 10^4$) of antennas are manufactured an deployed on field. The centrer of LOFAR system is situated in Netherlands and peripheral antennas and connection network are extended to other European countries. |
| Another example, this time a custom-designed receiver and digitization unit design but duplicated many times is LOFAR system developed by Astron in the Netherlands~\cite[lofar] |
| LOFAR is the innovative radioastronomy system which uses a phased antenna array approach in an enormous scale. Thousands (around $2 \cdot 10^4$) of antennas are manufactured an deployed in the field. The centrer of LOFAR system is situated in the Netherlands and peripheral antennas and a connection network are extended to other European countries. |
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| \midinsert |
| \clabel[lofar-antenna]{Lofar antenna configuration} |
| \picw=10cm \cinspic ./img/lofar_antenna.jpg |
| \caption/f One LOFAR LBA \glos{LBA}{Low Band Antenna} antenna element. |
| \caption/f One LOFAR LBA\glos{LBA}{Low Band Antenna} antenna element. |
| \endinsert |
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| LOFAR project must use low cost hardware due to systems scale. Special construction techniques are used to keep overall project budget at acceptable levels (specially designed polystyrene supporting blocks for HBA \glos{HBA}{High Band Antenna} antennas for example). Many of used components are manufactured in mass scale for other than scientific use LBA antennas masts are made from standard PVC \glos{PVC}{Polyvinyl chloride} plastic waste pipes and LOFAR uses low cost direct sampling receiver. Whole project has been designed by Netherlands Institute for Radio Astronomy, which produces many similarly sophisticated devices\cite[astron-devices]. |
| LOFAR project must use a low cost hardware due to the system scale. A special construction techniques were employed to keep the overall project budget at acceptable levels (specially designed polystyrene supporting blocks for High Band Antenna (HBA\glos{HBA}{High Band Antenna}) for example). Many of used components are manufactured in a mass scale for other than scientific use. LBA antennas masts are made from a standard Polyvinyl chloride (PVC\glos{PVC}{Polyvinyl chloride}) plastic waste pipes. LOFAR uses low cost direct sampling receiver. The entire project was designed by the Netherlands Institute for Radio Astronomy, which produces many similarly sophisticated devices~\cite[astron-devices]. |
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| \secc Modular digitization systems |
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| Due to cost restrictions in science and astronomy instruments development, an reuse of engineering work should be useful. One modular digitization and data processing system currently exit. It is being developed at Berkley\cite[casper-project]. CASPER \glos{CASPER}{Collaboration for Astronomy Signal Processing and Electronics Research} is in development from around 2005. CASPER's designers an engineers remarkably noticed a lack of such hardware in radioastronomy science, theirs ideas are summarised in paper \cite[casper-paper]. Unfortunately they use proprietary connector standard and technology and develops modular system based purely on Tyco Z-DOK+ connectors family. CASPER data processing board with Z-DOK connectors is shown in picture \ref[casper-roach]. Z-DOK connectors have relatively high pricing (around 40 USD) \cite[Z-DOK-connectors]. Z-DOK connectors are high quality differential pairs connectors, but price of these connectors is comparable with value of one ADC channel in our design described in following part of document. |
| Due to cost restrictions in science and astronomy instruments development, a reuse of engineering work is preferable. There is one example of a modular digitization and data processing system. The system Collaboration for Astronomy Signal Processing and Electronics Research (CASPER\glos{CASPER}{Collaboration for Astronomy Signal Processing and Electronics Research}) has been in development at the University of Berkeley~\cite[casper-project] since around 2005. CASPER designers an engineers noticed a remarkable lack of such a hardware in radioastronomy science. Their ideas are summarised in the paper~\cite[casper-paper]. Unfortunately they use a proprietary connector standard and technology. They developed a modular system based purely on Tyco Z-DOK+ connectors family. CASPER data processing board with Z-DOK connectors is shown in Figure~\ref[casper-roach]. Z-DOK connectors have a relatively high pricing (around 40 USD)~\cite[Z-DOK-connectors]. Z-DOK connectors are a high quality differential pairs connectors. However, the price of these connectors is comparable with the price of one ADC channel in our design described in this diploma thesis. |
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| \midinsert |
| \clabel[casper-roach]{CASPER's ROACH data processing board} |
| \picw=10cm \cinspic ./img/Roach2_rev0_2xcx4mezz.jpg |
| \caption/f CASPER project ROACH-2 \glos{ROACH}{ Reconfigurable Open Architecture Computing Hardware (ROACH) board} data processing board. White Z-DOK connectors for daughter ADC Boards can be easily seen in front. |
| \caption/f CASPER project ROACH-2 \glos{ROACH}{ Reconfigurable Open Architecture Computing Hardware (ROACH) board} data processing board. White Z-DOK connectors for daughter ADC Boards can be easily seen in the front of the board. |
| \endinsert |
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| In opposite to professional astronomers which uses proprietary digitization units, amateur radioastronomers currently uses multichannel sound cards \cite[amateur-fringes] or self designed digitalisation units. Devices constructed by amateurs are usually non reproducible \cite[amateur-sdr] . It is evident that current radioastronomy lacks of proper hardware which could be used on both communities - professionals and amateurs. Optimal solution for this situation should be open-source hardware. |
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| In the contrary to professional astronomers, who use proprietary digitization units, amateur radioastronomers have been using multichannel sound cards~\cite[amateur-fringes] or self designed digitalisation units. Devices constructed by amateurs are usually non reproducible \cite[amateur-sdr]. It is evident that the current radioastronomy lacks a proper hardware which could be used by both communities, professionals and amateurs. The optimal solution in such a situation should be the open-source hardware. We follow this path in this diploma project. |