| /dokumenty/skolni/diplomka/description.tex |
|---|
| 31,9 → 31,9 |
| \sec Sampling frequency |
| The sampling frequency is not limited by the technical constrains in the trial version. This parameter is especially limited by the sampling frequencies of the analog-to-digital conversion chips available on the market and interface bandwidth. Combination of the required parameters -- dynamic range requiring at least 16bit and a minimum sampling frequency of 1$\ $MSPS \glos{MSPS}{Mega-Samples Per Second} leads to the need of high end ADC chips which does not support such low sampling frequencies at all. Their minimum sampling frequency is 5$\ $MSPS. |
| The sampling frequency has not been a limiting factor in the trial version. Generally, the sampling frequency is mostly limited by the sampling frequencies of the analog-to-digital conversion chips available on the market and by the interface bandwidth. The combination of required parameters -- dynamic range needing 16 bits at least and a minimum sampling frequency of 1 Mega-Samples Per Second (MSPS\glos{MSPS}{Mega-Samples Per Second}) -- leads to the need of the high-end ADC chips. However, they do not support such low sampling frequencies at all. Their minimum sampling frequency is 5$\ $MSPS. |
| We calculated a minimum data bandwidth data rate for eight receivers, 2 bytes per sample and 5$\ $MSPS as $8 \cdot 2 \cdot 5\cdot 10^6 = 80\ $MB/s. Such data rate is at the limit of the actual writing speed of classical HDD \glos{HDD}{Hard disk drive} and it is almost double the real bandwidth of USB 2.0 \glos{USB 2.0}{Universal Serial Bus version 2.0} interface. As a result of these facts we must use faster interface. Faster interface is especially needed in cases where we require faster sampling rates than ADC's minimal 5$\ $MSPS sample rate. |
| We calculated the minimal data bandwidth data rate for eight receivers, 2~bytes per sample and 5$\ $MSPS as $8 \cdot 2 \cdot 5\cdot 10^6 = 80\ $MB/s. Such data rate is at the limit of the actual writing speed of a classical hard disk drive (HDD\glos{HDD}{Hard disk drive}) and it is almost a double the real bandwidth of USB~2.0\glos{USB 2.0}{Universal Serial Bus version 2.0} interface. As a result of these facts, we must use a faster interface. Such a faster interface is especially needed in cases in which we require faster sampling rates than ADC's minimal 5$\ $MSPS sample rate. |
| The most perspective interface for use in our type of application is USB 3.0 or PCI Express interface. However, USB 3.0 is a relatively new technology without good development tools currently available. We have used PCI Express \glos{PCI Express}{Peripheral Component Interconnect Express} interface as the simplest and the most reliable solution. |
| \sec System scalability |
| /dokumenty/skolni/diplomka/diplomka.tex |
|---|
| 37,8 → 37,8 |
| \abstractEN { |
| Due to the ubiquitous presence of interference and a need for a large angular resolution, the current radioastronomical observations are carried out using multi-antenae receiver systems. Construction of such devices places great demands upon the quality of signal processing. A source of inspiration for my diploma thesis has been my own amateur radioastronomical activity in the field of meteor observations. |
| The thesis deals with a possible realization of a digitalization unit for a radioastronomical signal receiver. The implementation described in the thesis is optimized for a high dynamic range and good phase stability, both being the most important parameters for its application in the multi-antenae systems. Design and the instrument implementation have been created as open-source hardware solutions, so far having unique characteristics among the devices used in amateur or professional radioastronomy. |
| Due to the ubiquitous presence of interference and a need for a large angular resolution, the current radioastronomical observations are carried out using multi-antennas receiver systems. Construction of such devices places great demands upon the quality of signal processing. A source of inspiration for my diploma thesis has been my own amateur radioastronomical activity in the field of meteor observations. |
| The thesis deals with a possible realization of a digitization unit for a radioastronomical signal receiver. The implementation described in the thesis is optimized for a high dynamic range and good phase stability, both being the most important parameters for its application in the multi-antennas systems. Design and the instrument implementation have been created as open-source hardware solutions, so far having unique characteristics among the devices used in amateur or professional radioastronomy. |
| I have devised and implemented a trial version and made further experiments with it. A resulting recommendations for repeated implementations of the receivers, that we are planing to use in the amateur meteor observing networks, are based on these experiences. |