The Very Long Baseline Interferometry (VLBI) technique uses small radio telescopes to construct a huge synthetic telescope through earth rotation, resolving details as fine as 0.1 milliarcsecond. This paper introduces the principle of the VLBI synthesis and presents the mathematic model of the powerful high-speed FX type Chinese VLBI Network correlator. The principle of the delay and phase compensation, the signal transformation in the correlator, and the final complex visibility function are also presented, as well as the correlator's block diagram. The model is great helpful in designing and adjusting the FX VLBI correlator. Examples demonstrate how to use the model to judge the output visibility function and analyze the observing station performance and the astronomical line spectrum.
[1]
Weimin Zheng,et al.
The high-speed FX correlator of Chinese VLBI network-a super spectrum analyzer based on programmable ASIC
,
2000,
IEEE APCCAS 2000. 2000 IEEE Asia-Pacific Conference on Circuits and Systems. Electronic Communication Systems. (Cat. No.00EX394).
[2]
Jonathan D. Romney,et al.
Theory of Correlation in VLBI
,
1995
.
[3]
A. R. Thompson,et al.
The interferometer in practice.
,
1986
.
[4]
P. J. Napier.
The Very Long Baseline Array
,
1991
.
[5]
James Ulvestad,et al.
Radio astronomy's resolution machine: the very long baseline array
,
1999
.