KEYWORDS: Spectroscopy, Terahertz radiation, Control systems, Field programmable gate arrays, Signal to noise ratio, Data acquisition, Sensors, Modulation, Data communications, Laser beam diagnostics
This paper discusses the development of data acquisition and control system (DACS) for a portable terahertz time-domain spectrometer (THz-TDS). In this system, field programmable gate array (FPGA) severed as main control unit (MCU), which controls and harmonizes other functional modules of the spectrometer, including the linear delay stage, high voltage modulation and the AD converter. A digital lock-in amplifier implemented within the FPGA is employed to restore the weak THz signal. USB is used as the communication interface between the FPGA and the computer, which transfers commands and THz waveform data. The spectrometer can scan a waveform within a 30-ps time window in about 10 seconds, which has a spectral resolution better than 50GHz and a dynamic range up to 49dB.
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