This article describes the circuit of a sampling device capable of sampling signals, under control of a PC-software, with a maximum speed of 3 Megasamples/second. The device uses a fast 8-bit ADC AD775 under control of an ATmega32-microprocessor, both clocked by the same 18.432Mhz clock source.
A possible application of this circuit is the analyzation of the fine structure of molecule lines (masers) or the Hydrogen line on 1420 Mhz.
The board contains the following building blocks:
The transfer speed is max. 76800 baud.
The sampling procedure is controlled by the software of the PC connected to the board. After a start command is sent, sampling is started and the internal RAM-buffer is filled. After sampling is done, the data block is sent to the PC for analysis. Different sampling rates are possible to support oscilloscope functions, though in general FFT-sampling is performed at max. speed.
The ATmega-Software can be downloaded here together with the circuit board layout, all in one zip file.
A suitable PC-Software is available at http://vlbi.wegalink.net.
Circuit Boards are not available. You may download the layout as .bmp-file to do it yourself.
An AD775 can be ordered as a sample from Analog Devices