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Portable digitally controlled function generator
Graf, Daniel ; Kufa, Jan (oponent) ; Kolář, Ondřej (vedoucí práce)
This bachelor thesis is devoted to designing a printed circuit board and constructing of portable digitally controlled function generator using AD9833 direct digital synthesis integrated circuit. The generator is capable of generating three waveforms (harmonic, triangle and square), switching between output impedance modes (50\,$\Omega$ and HighZ), generating waveforms with frequency up to 12.5\,MHz. The device is also capable of amplitude and DC offset adjustments. Theoretical part includes the procedure of designing the device and explains the intended functionality. Choosing suitable battery cells, microcontrollers, basic direct digital synthesis theory or design of an analog backend for amplitude and DC offset adjustments are described. Hardware design part includes explanation how individual parts were chosen, which problems occurred and how they were solved, how the user interface is implemented and how the software was programmed for this application which allows user to control the generator through a computer with a serial terminal thanks to the SCPI protocol which was programmed as a part of the software. The Measurements chapter deals with not only results of individual measurements, but also with solving complications which occurred due to a design mistake of the PCB. The chapter contains circuit diagrams, measurement charts and tables, evaluation of the measurement and comparison of the results of the device with commercial variants available on the market.
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