Development of a 4 Gbps multifunctional very long baseline interferometry data acquisition system

摘要

A 2048 Msps (megasamples per second) very long baseline interferometry (VLBI) data acquisition system (DAS) that has the ability to directly acquire intermediate frequency signals up to 1024 MHz bandwidth has been developed. By using these systems, 4 Gbps ( 4 gigabits per second = 2048 Msps, 2 bits) VLBI experimental observations were performed on 2005 November 25, and fringes were successfully detected with a newly developed software correlator. Both the data sampling rate ( 2 Gsps) and the total data rate ( 4 Gbps) were the highest rate ever used for VLBI observations. One of the applications realized with the DAS is differential VLBI measurements of deep space spacecraft, for which a wide-band recording is used for phase-reference quasars and a narrow bandwidth digital filtering is used for spacecraft. This paper describes the features of the developed DAS and cross-correlation system, results of the experimental observations, expected applications realized with the newly developed systems, and effectiveness of wide-band data acquisition for differential VLBI experiments for spacecraft navigation.