| 14,7 → 14,7 |
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| \maketitle |
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| \begin{abstract} |
| The goal of this project is design of Software Defined Receiver suitable for radioastronomy purposes. The receiver which has been developed replacing the old analog construction such as RadioJOVE and others. |
| This paper describe a design of Software Defined Receiver suitable for radioastronomy purposes. The receiver which has been developed in this project replacing the old analog construction such as RadioJOVE and others. |
| \end{abstract} |
| |
| \begin{figure} [htbp] |
| 46,18 → 46,22 |
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| \section{Description of construction} |
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| \subsection{Circuit} |
| Construction of the receiver is delivered from the DR2G receiver \cite{DR2G} which uses CMOS componnents completely. The main change is on the local oscillator input which allow to receiver works at higher frequencies, because do not divide input frequency by 4, such as original construction but only by 2. In addition there was be replaced switches in sampling mixer by faster type and board layout was more optimized to higher frequencies and noise rejection. |
| Construction of the receiver is delivered from the DR2G receiver \cite{DR2G} which uses CMOS components completely. The main change in this construction is a local oscillator input circuit which allow to receiver work at higher frequencies, because this construction do not divide the input frequency by 4, such as original construction but only by 2. In addition there was be replaced switches in the sampling mixer by faster type and board layout was optimized for higher frequencies and better noise rejection. |
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| \includepdf[pages={1,2,3,4},landscape=true]{../../SCH/sdrx.pdf} |
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| The necessary part of the receiver is a local oscillator which must be connected to receiver via SATA cable. The LO may be a CLKGEN01B module populated 570ABB000107DG. SATA cable should be as short as possible to minimize ground loop. |
| The necessary part of the receiver is a Local Oscillator (LO), which must be connected to receiver via SATA cable. The LO may be a CLKGEN01B module populated by the 570ABB000107DG chip. SATA cable should be as short as possible to minimize ground loops. |
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| \includepdf[pages={1},landscape=true]{../../CAM_DOC/O1.pdf} |
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| \includepdf[pages={1},landscape=true]{../../CAM_DOC/O2.pdf} |
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| \subsection{EMI suppression} |
| For proper function of receiver is necessary to use proper low noise symmetric power supply (classical PC power supply is unacceptable). There is need for proper routing of grounding wires, which must be routed in star topology. In addition there is few jumpers on the board of receiver to allow proper selection of ground connection. |
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| \subsection{Mechanical construction} |
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| Mechanická konstrukce je řešena na dvouvrstvé desce s geometrií se základovou deskou MLAB (Pro lepší odstínění přijímače je vhodné použít duralovou desku ALBASE). Dvouvrstvý plošný spoj je zvolen hlavně kvůli kvalitnímu odstínění okolního rušení horní měděnou vrstvou. To umožňuje přijímače instalovat i velmi blízko sebe případně i nad sebe avšak všechny konektory kromě NF audio výstupu předpokládají přivedení kabelu kolmo na rovinu desky. SMA konektor je možné osadit i úhlový s přivedením kabelu do boku, ale za cenu nepatrně vyššího útlumu úhlového konektoru. Při těsné montáži je potřeba počítat i s určitou teplotní stabilizací, neboť digitální část okolo spínaného směšovače má poměrně velký příkon a způsobuje zahřívání zhruba o 15$^\circ C$ nad okolní teplotu. A pokud je od přijímače vyžadována dlouhodobá stabilita je ho vhodné umístit do termostatovaného boxu společně s LO. |
| The mechanical construction of the receiver resulted (For better EMI suppression is suggested use of metal MLAB base such as ALBASE). Two layer PCB is chosen mainly because of better shielding by top cooper layer and even because better grounding. In case where long term stability is required receiver must be inserted to thermostatic box together with LO. |
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| \subsubsection{Setting} |
| There is one easy step for proper setting of the receiver. The trimmer P1 must be tunned to value where the strength of mirror frequencies is minimized or zero. This can be achieved by tunning the receiver to some strength AM transmitter and slowly turning by P1 until the mirror of signal in frequency spectrum is minimized. |