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A cross‐correlation receiver for radio astronomy employing quadrature channel generation by computed Hilbert transform
Author(s) -
Lo W. F.,
Dewdney P. E.,
Landecker T. L.,
Routledge D.,
Vaneldik J. F.
Publication year - 1984
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1029/rs019i005p01413
Subject(s) - baseband , interferometry , computer science , quadrature (astronomy) , hilbert transform , software defined radio , physics , radio astronomy , radio telescope , group delay and phase delay , cross correlation , algorithm , optics , bandwidth (computing) , mathematics , telecommunications , spectral density , mathematical analysis , astronomy , astrophysics
A real‐time digital signal processor for an earth rotation synthesis radio telescope is described. The processor accepts 4 MHz baseband signals, quantizes them to three levels, and performs delay equalization, cross correlation, and phase rotation. The inphase cross correlation of the input signals is calculated for 16 values of delay spaced by 62.5 ns. The quadrature correlator output is produced from the inphase output by numerical computation by using a band‐limited form of the Hilbert transform. The values of inphase and quadrature visibility at the exact value of delay are derived by interpolation. Errors arising in this signal processing method are investigated and shown to be small in the adopted design. A high‐speed, 16‐bit microcomputer is employed to allow many of the required operations to be performed in software. The processor produces four complex interferometer outputs simultaneously and is capable of producing ten such outputs. Interferometer visibility records of the radio source 3C66 are presented.