OCTAD-S: Digital Fast Fourier Transform Spectrometers by FPGA

Abstract

We have developed a digital fast Fourier transform (FFT) spectrometer made of an analog-to-digital converter (ADC) and a field-programmable gate array (FPGA). The base instrument has independent ADC and FPGA modules, which allow us to implement different spectrometers in a relatively easy manner. Two types of spectrometers have been instrumented, one with 4.096 GS/s sampling speed and 2048 frequency channels and the other with 2.048 GS/s sampling speed and 32768 frequency channels. The signal processing in these spectrometers has no dead time and the accumulated spectra are recorded in external media every 8 ms. A direct sampling spectroscopy up to 8 GHz is achieved by a microwave track-and-hold circuit, which can reduce the analog receiver in front of the spectrometer. Highly stable spectroscopy with a wide dynamic range was demonstrated in a series of laboratory experiments and test observations of solar radio bursts.

arXiv comment20 pages, 7 figures, accepted for publication in Earth, Planets and Space

References in corpus (4)

• GREAT: the SOFIA high-frequency heterodyne instrument
• High-resolution wide-band Fast Fourier Transform spectrometers
• Digital Spectro-Correlator System for the Atacama Compact Array of the Atacama Large Millimeter/submillimeter Array
• A broadband FFT spectrometer for radio and millimeter astronomy

Cited by in corpus (5)

• Multiple injections of energetic electrons associated with the flare/CME event on 9 October 2021
• Why "solar tsunamis" rarely leave their imprints in the chromosphere
• Solar energetic particles injected inside and outside a magnetic cloud: The widespread solar energetic particle event on 2022 January 20
• A data-scientific noise-removal method for efficient submillimeter spectroscopy with single-dish telescopes
• Observational demonstration of a low-cost fast Fourier transform spectrometer with a delay-line-based ramp-compare ADC implemented on FPGA