| /dokumenty/skolni/diplomka/diplomka.tex |
|---|
| 24,7 → 24,7 |
| \studyinfo {Aircraft and Space Systems} % Study programme etc. |
| \workname {Dokumentace} % Used only if \worktype [O/*] (Other) |
| % optional more information about the document: |
| \workinfo {\url{http://wiki.mlab.cz/doku.php?id=cs:sdrx}} |
| \workinfo {\url{http://wiki.mlab.cz/doku.php?id=en:sdrx}} |
| % Title / Subtitle in minor language: |
| \title {Fast multi-channel data acquisition system for radio-astronomy receiver} |
| %\subtitleEN {the plain\TeX{} template for theses at CTU} |
| 50,7 → 50,6 |
| V diplomové práci jsem navrhl a realizoval zkušební verzi zařízení. Experimentoval jsem s ním. Ze zkušeností vyplývají doporučení pro opakovanou realizaci přijímačů, kterou chceme v amatérské síti pro sledování meteorů mnohonásobně zopakovat. |
| %Aktuální radioastronomická pozorovnání jsou dnes z důvodu existence rušení a potřeby získat velké úhlové rozlišení realizována jako multi anténní přijímací systémy. Takto konstruovaná zařízení mají ale značné nároky kvalitu zpracování signálu z více kanálů. V této práci je navržena možná realizace digitalizační části takového přijímače. Popsaná realizace je optimalizována na vysoký dynamický rozsah vstupních signálů a dobrou fázovou stabilitu, což jsou nejvýznamnější parametry pro použítí ve více anténních systémech. Konstrukce je koncipována jako open-source hardware řešení, které má zatím jedinnečné parametry v oblasti přístrojů určených pro amatérskou i profesionální radioastronomii. |
| } % If your language is Slovak use \abstractSK instead \abstractCZ |
| 61,7 → 60,7 |
| \keywordsCZ { Radioastronomie, digitalizace signálu, A/D konverze |
| } |
| \thanks { Chtěl bych poděkovat Ing. Martinu Matouškovi, Ph.D. a Ing. Ondřeji Sychrovskému za věcné připomínky. Dále pak Fluktuacii a prof. Ing. Václavu Hlaváčovi, CSc. za jazykové korekce. |
| \thanks { Chtěl bych poděkovat Ing. Martinu Matouškovi, Ph.D. za věcné připomínky a Ing. Ondřeji Sychrovskému za VHDL implementaci funkcí FPGA. Dále pak Fluktuacii a prof. Ing. Václavu Hlaváčovi, CSc. za jazykové korekce. |
| } |
| \declaration { % Use main language here |
| /dokumenty/skolni/diplomka/introduction.tex |
|---|
| 24,9 → 24,9 |
| Today, we have an access to components with much higher quality, repeatability and a lower price as compared to the components accessible to previous generation of radioastronomers. That is why we can develop a better radioastronomical equipment, powerful enough to make new astronomical discoveries possible.\fnote{Most of astronomy-related discoveries in the last fifty years came from the field of radioastronomy.} |
| We have the capacities necessary to develop a receiver which will have a wide bandwidth, a high third-order intercept point and preferably an option for phase and frequency locking to other receivers located at another radioastronomical site on the Earth. Currently there exist several receivers with the above-mentioned parameters, for example USRP2, USRP B210 \glos{USRP}{Universal Software Radio Peripheral} or HackRF which are commercially available. However all of them lack scalability and have higher prices unaffordable to our amateur radioastronomical network. Scalability and redundancy are the main requirements of noise reduction algorithms which acted as a motivation for this diploma thesis. |
| We have the capacities necessary to develop a receiver which will have a wide bandwidth, a high third-order intercept point and preferably an option for phase and frequency locking to other receivers located at another radioastronomical site on the Earth. Currently there exist several receivers with the above-mentioned parameters, for example USRP2, USRP B210 \cite[USRP-sdr] \glos{USRP}{Universal Software Radio Peripheral} or HackRF \cite[hackrf-sdr] which are commercially available. However all of them lack scalability and have higher prices unaffordable to our amateur radioastronomical network. Scalability and redundancy are the main requirements of noise reduction algorithms which acted as a motivation for this diploma thesis. |
| New radio astronomy systems such LOFAR\glos{LOFAR}{Low-Frequency Array} are explicit examples of the scalability and redundancy approach. LOFAR has a completely different and novel structure developed to solve the problems of radioastronomy signal reception. It uses exclusively multi-antenna arrays and mathematical algorithms for signal handling. Radio signals recorded by LOFAR can be used in multiple ways: radio images can be computed (if sufficient cover of $u/v$ plane is achieved), the radiation intensity can be measured, the spectrum can be analysed for velocity measurement, etc. |
| New radio astronomy systems such as LOFAR\glos{LOFAR}{Low-Frequency Array} are explicit examples of the scalability and redundancy approach. LOFAR has a completely different and novel structure developed to solve the problems of radioastronomy signal reception. It uses exclusively multi-antenna arrays and mathematical algorithms for signal handling. Radio signals recorded by LOFAR can be used in multiple ways: radio images can be computed (if sufficient cover of $u/v$ plane is achieved), the radiation intensity can be measured, the spectrum can be analysed for velocity measurement, etc. |
| \sec Required receiver parameters |
| 39,16 → 39,16 |
| \label[dynamic-range-theory] \secc Dynamic range |
| The dynamic range represents a huge problem of current radioastronomical receivers. This parameter is enforced by humans which are present everywhere and create electromagnetic inference (EMI\glos{EMI}{Electromagnetic interference}) radiation in the radio frequency (RF\glos{RF}{Radio frequency}) band. The modern radioastronomy receiver must not be saturated by these high levels of signals but still needs to have enough sensitivity to see faint signals from natural sources. The dynamic range is limited either by the construction of analog circuitry in the receiver or by the digitization unit. |
| The dynamic range represents a huge problem of current radioastronomical receivers. This parameter is enforced by humans which are present everywhere and create electromagnetic inference (EMI\glos{EMI}{Electromagnetic interference}) radiation in the radio frequency (RF\glos{RF}{Radio frequency}) band. The modern radioastronomy receiver must not be saturated by these high levels of signals but still needs to have enough sensitivity to see faint signals from sources being observed. The dynamic range is limited either by the construction of analog circuitry in the receiver or by the digitization unit. |
| The maximal theoretical dynamic range of analog-to-digital converter (ADC \glos{ADC}{analog-to-digital converter}) could be estimated from ADC bit depth using a following formula~\ref[dynamic-range] |
| The maximal theoretical dynamic range of analog-to-digital converter (ADC)\glos{ADC}{analog-to-digital converter} could be estimated from ADC bit depth as |
| \label[dynamic-range] |
| $$ |
| D.R. \; [dB] = 20 \cdot \log(2^n) \eqmark |
| $$ |
| dynamic range \; [dB] = 20 \cdot \log(2^n) \eqmark |
| $$. |
| The formula \ref[dynamic-range] provides values shown in Table~\ref[ADC-dynamic-range] below. |
| The maximal theoretical dynamic range for standard bit depths of ADC is shown in Table \ref[ADC-dynamic-range]. |
| \midinsert \clabel[ADC-dynamic-range]{Dynamic range versus bit depth} |
| \ctable{cc}{ |
| 68,8 → 68,12 |
| \secc Bandwidth |
| Historically, the bandwidth parameter in radioastronomical receivers used to be within the kilohertz range. Such a narrow bandwidth was acceptable because observations were processed directly by listening or by a paper chart intensity recorder. The chart recorder integrated the energy of a signal over a defined narrow bandwidth which was suitable for detecting the intensity variance of a microwave background. No wide-band transmitters existed in that era (except for TV\glos{TV}{Television} transmitters) and tuning to other neighbouring frequency was easy as they were mostly vacant. Parallel observations from several places were unnecessary as well because the electromagnetic conditions were nearly the same at all locations. |
| Historically, the bandwidth parameter in radioastronomical receivers used to be within the kilohertz range. Such a narrow bandwidth was acceptable because observations were processed directly by listening or by a paper chart intensity recorder. The chart recorder integrated the energy of a signal over a defined narrow bandwidth which was suitable for detecting the intensity variance of a microwave background. No wide-band transmitters existed in that era (except for TV\glos{TV}{Television} transmitters) and tuning to other neighbouring frequency was easy as they were mostly vacant. Parallel observations from several places were unnecessary as well because the electromagnetic conditions were nearly the same at all locations. |
| Currently we are not able to use an clear part of radio-frequency spectrum for radioastronomical observations. |
| %% |
| \sec State of the art in receivers' digitization units |
| Only a few digitization systems dedicated to radioastronomy exist currently. Today's systems use either a custom design of the whole receiver or they are constructed from commercially available components. Open-source principle attempts are very rare in the radioastronomy field. |
| 76,7 → 80,7 |
| \secc Custom digitization system |
| Custom designs usually use non-recurring engineering for the development of a specific solution for an observational 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}. |
| Custom designs usually use non-recurring engineering for the development of a specific solution for an observational 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} \cite[alfa]. |
| 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 an innovative radioastronomy system which uses a phased antenna array approach at 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. |
| 87,7 → 91,7 |
| \caption/f One LOFAR LBA\glos{LBA}{Low Band Antenna} antenna element. |
| \endinsert |
| 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 on a massive 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]. |
| 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 on a massive scale for other than scientific use. LBA antennas' masts are made from a standard Polyvinyl chloride (PVC\glos{PVC}{Polyvinyl chloride}) plastic waste pipes \ref[lofar-antenna]. 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]. |
| \secc Modular digitization systems |
| /dokumenty/skolni/diplomka/mybase.bib |
|---|
| 27,8 → 27,7 |
| @MANUAL{lofar, |
| AUTHOR = {M. P. van Haarlem, M. W. Wise, A. W. Gunst, G. Heald, J. P. McKean, J. W. T. Hessels, A. G. de Bruyn, R. Nijboer, J. Swinbank, R. Fallows, M. Brentjens, A. Nelles, R. Beck, H. Falcke, R. Fender, J. Hörandel, L. V. E. Koopmans, G. Mann, G. Miley, H. Röttgering, B. W. Stappers, R. A. M. J. Wijers, S. Zaroubi, M. van den Akker, A. Alexov, J. Anderson, K. Anderson, A. van Ardenne, M. Arts, A. Asgekar, I. M. Avruch, F. Batejat, L. Bähren, M. E. Bell, M. R. Bell, I. van Bemmel, P. Bennema, M. J. Bentum, G. Bernardi, P. Best, L. Bîrzan, A. Bonafede, A.-J. Boonstra, R. Braun, J. Bregman, F. Breitling, R. H. van de Brink, J. Broderick, P. C. Broekema, W. N. Brouw, M. Brüggen, H. R. Butcher, W. van Cappellen, B. Ciardi, T. Coenen, J. Conway, A. Coolen, A. Corstanje, S. Damstra, |
| O. Davies, A. T. Deller, R.-J. Dettmar, G. van Diepen, K. Dijkstra, P. Donker, A. Doorduin, J. Dromer, M. Drost, A. van Duin, J. Eislöffel, J. van Enst, C. Ferrari, W. Frieswijk, H. Gankema, M. A. Garrett, F. de Gasperin, M. Gerbers, E. de Geus, J.-M. Grießmeier, T. Grit, P. Gruppen, J. P. Hamaker, T. Hassall, M. Hoeft, H. Holties, A. Horneffer, A. van der Horst, A. van Houwelingen, A. Huijgen, M. Iacobelli, H. Intema, N. Jackson, V. Jelic, A. de Jong, E. Juette, D. Kant, A. Karastergiou, A. Koers, H. Kollen, V. I. Kondratiev, E. Kooistra, Y. Koopman, A. Koster, M. Kuniyoshi, M. Kramer, G. Kuper, P. Lambropoulos, C. Law, J. van Leeuwen, J. Lemaitre, M. Loose, P. Maat, G. Macario, S. Markoff, J. Masters, D. McKay-Bukowski, H. Meijering, H. Meulman, M. Mevius, E. Middelberg, R. Millenaar, J. C. A. Miller-Jones, R. N. Mohan, J. D. Mol, J. Morawietz, R. Morganti, D. D. Mulcahy, E. Mulder, H. Munk, L. Nieuwenhuis, R. van Nieuwpoort, J. E. Noordam, M. Norden, A. Noutsos, A. R. Offringa, H. Olofsson, A. Omar, E. Orrú, R. Overeem, H. Paas, M. Pandey-Pommier, V. N. Pandey, R. Pizzo, A. Polatidis, D. Rafferty, S. Rawlings, W. Reich, J.-P. de Reijer, J. Reitsma, A. Renting, P. Riemers, E. Rol, J. W. Romein, J. Roosjen, M. Ruiter, A. Scaife, K. van der Schaaf, B. Scheers, P. Schellart, A. Schoenmakers, G. Schoonderbeek, M. Serylak, A. Shulevski, J. Sluman, O. Smirnov, C. Sobey, H. Spreeuw, M. Steinmetz, C. G. M. Sterks, H.-J. Stiepel, K. Stuurwold, M. Tagger, Y. Tang, C. Tasse, I. Thomas, S. Thoudam, M. C. Toribio, B. van der Tol, O. Usov, M. van Veelen, A.-J. van der Veen, S. ter Veen, J. P. W. Verbiest, R. Vermeulen, N. Vermaas, C. Vocks, C. Vogt, M. de Vos, E. van der Wal, R. van Weeren, H. Weggemans, P. Weltevrede, S. White, S. J. Wijnholds, T. Wilhelmsson, O. Wucknitz, S. Yatawatta, P. Zarka, A. Zensus, J. van Zwieten}, |
| AUTHOR = {M. P. van Haarlem, et. al.}, |
| TITLE = { LOFAR: The LOw-Frequency ARray}, |
| YEAR = {2013}, |
| MONTH = May, |
| 35,6 → 34,15 |
| NOTE = {\url{http://arxiv.org/abs/1305.3550}}, |
| } |
| @MANUAL{alfa, |
| AUTHOR = {Fernando Camilo, Robert Minchin, Chris Salter}, |
| TITLE = {ALFA: Arecibo L-Band Feed Array}, |
| YEAR = {2012}, |
| MONTH = May, |
| NOTE = {\url{http://www.naic.edu/alfa/}}, |
| } |
| @MISC{astron-devices, |
| AUTHOR = {Astron}, |
| TITLE = {Design and development}, |
| 91,6 → 99,27 |
| URLDATE= {2014-5-3}, |
| } |
| @MISC{USRP-sdr, |
| AUTHOR = {Ettus Research, A National Instruments Company}, |
| TITLE = {URSP Series products}, |
| YEAR = {2013}, |
| MONTH = , |
| NOTE = {\url{https://www.ettus.com/product/category/USRP-X-Series}}, |
| URLDATE= {2014-5-3}, |
| } |
| @MISC{hackrf-sdr, |
| AUTHOR = {Michael Ossmann}, |
| TITLE = {HackRF One an open source SDR platform}, |
| YEAR = {2013}, |
| MONTH = , |
| NOTE = {\url{http://greatscottgadgets.com/hackrf/}}, |
| URLDATE= {2014-5-11}, |
| } |
| @MISC{MLAB-GPSDO, |
| AUTHOR = {J. Kakona, M. Kakona}, |
| TITLE = {Software Defined GPS disciplined oscillator - GPSDO01A}, |
| /dokumenty/skolni/diplomka/testing.tex |
|---|
| 4,30 → 4,31 |
| \sec Measured parameters |
| Two prototypes of ADC modules were assembled and tested. The first prototype, labeled ADC1, has LTC2190 ADC chip populated with LT6600-5 front-end operational amplifier. It also has a 1kOhm resistors populated on inputs which give it an ability of an internal attenuation of the input signal. The value of this attenuation $A$ is calculated by the following formula \ref[ADC1-gain] |
| Two prototypes of ADC modules were assembled and tested. The first prototype, labeled ADC1, has LTC2190 ADC chip populated with LT6600-5 front-end operational amplifier. It also has a 1kOhm resistors populated on inputs which give it an ability of an internal attenuation of the input signal. The value of this attenuation $A$ is calculated by |
| \label[ADC1-gain] |
| $$ |
| A = {806 \cdot R_1 \over R_1 + R_2} \eqmark |
| A = {806 R_1 \over R_1 + R_2} \eqmark\,, |
| $$ |
| Where the letters stand for the following: |
| % |
| where |
| \begitems |
| * $A$ - Gain of an input amplifier. |
| * $R_1$ - Output impedance of signal source (usually 50 Ohm). |
| * $A$ - Gain of an input amplifier, |
| * $R_1$ - Output impedance of signal source (usually 50 $\Omega$), |
| * $R_2$ - Value of serial resistors at operational amplifier inputs. |
| \enditems |
| We have $R_2 = 1000 \Omega$ and $R_1 = 50 \Omega$ which imply that $A = 0.815$. That value of A was further confirmed by the measurement. |
| In our measurement setup we have H1012 Ethernet transformer connected to inputs of ADC. We have used this transformer for signal symetrization from BNC connector at Agilent 33220A signal generator. Circuit diagram of the used transformer circuit is shown in picture \ref[balun-circuit] and circuit realization in photograph \ref[SMA2SATA-nest]. |
| We have $R_2 = 1000\, \Omega$ and $R_1 = 50\, \Omega$ which imply that $A = 0.815$. This value of A was further confirmed by the measurement. |
| In our measurement setup we have H1012 Ethernet transformer connected to inputs of ADC. We have used this transformer for signal symetrization from BNC connector at Agilent 33220A signal generator. Circuit diagram of the used transformer circuit is shown in Figure~\ref[balun-circuit] and circuit realization in Figure~\ref[SMA2SATA-nest]. |
| \midinsert |
| \clabel[balun-circuit]{Balun transformer circuit} |
| \picw=10cm \cinspic ./img/SMA2SATA.pdf |
| \picw=7cm \cinspic ./img/SMA2SATA.pdf |
| \picw=8cm \cinspic ./img/SMA2SATA_nest1.JPG |
| \caption/f Simplified balun transformer circuit diagram. |
| \endinsert |
| The signal generator Agilent 33220A which we used, does not have optimal parameters for this type of dynamic range measurement. Signal distortion and spurious levels are only -70 dBc according to Agilent datasheet \cite[33220A-generator]. We have managed to measure an ADC saturation voltage of 705.7 mV (generator output) with this setup, mostly due to an impedance mismatch and uncalibrated measurement setup, with 1V ADC range selected by sense pin. This is a relatively large error, but the main result of our measurement, seen as a FFT plot shown in image \ref[ADC1-FFT], confirms $>$80 dB dynamic range at ADC module input. |
| The signal generator Agilent 33220A which we used, does not have optimal parameters for this type of dynamic range measurement. Signal distortion and spurious levels are only -70 dBc according to Agilent datasheet \cite[33220A-generator]. We have managed to measure an ADC saturation voltage of 706 mV (generator output) with this setup. The main result of our measurement, seen as a FFT plot shown in Figure~\ref[ADC1-FFT], confirms $>$80 dB dynamic range at ADC module input. |
| \midinsert |
| \clabel[ADC1-FFT]{ADC1 sine test FFT} |
| 36,19 → 37,15 |
| \endinsert |
| Similar test was performed at ADC2 module. For ADC2 we have to use formula with a different constant \ref[ADC1-gain]. The ADC2 module has LT6600-2.5 amplifiers populated on it with a gain equal to $A = 2.457$ and uses the same $R_2$ resistors. We measured saturation voltage of 380 mV (generator output) at channel 1 on this ADC. It is well within the parameter tolerances of the used setup. |
| Similar test was performed at ADC2 module. For ADC2 we have to use formula with a different constant |
| \label[ADC2-gain] |
| $$ |
| A = {1580 \cdot R_1 \over R_1 + R_2} \eqmark |
| $$ |
| A = {1580 R_1 \over R_1 + R_2} \eqmark\,. |
| $$ |
| % |
| The ADC2 module has LT6600-2.5 amplifiers populated on it with a gain equal to $A = 2.457$ and uses the same $R_2$ resistors. We measured saturation voltage of 380 mV (generator output) at channel 1 on this ADC. It is well within the parameter tolerances of the used setup. Again, FFT plot shown in Figure~\ref[ADC2-FFT] confirms $>$ 80 dB dynamic range. |
| Where the letters stand for the following: |
| \begitems |
| * $A$ - Gain of an input amplifier. |
| * $R_1$ - Output impedance of signal source (usually 50 Ohm). |
| * $R_2$ - Value of serial resistors at operational amplifier inputs. |
| \enditems |
| \midinsert |
| \clabel[ADC2-FFT]{ADC2 sine test FFT} |
| 56,8 → 53,6 |
| \caption/f Sine signal sampled by ADC2 module with LTC2271 and LT6600-2.5 devices. |
| \endinsert |
| Computed FFT spectra for measured signal are shown in the images \ref[ADC2-FFT] and \ref[ADC1-FFT]. Both images confirm that ADCdual01A modules have input dynamical range of at least 80 dB. |
| \midinsert |
| \clabel[SMA2SATA-nest]{Used balun transformer} |
| \picw=15cm \cinspic ./img/SMA2SATA_nest1.JPG |