MMA Memo #190

A System Design for the MMA

A. R. Thompson [1]

November 6, 1997

Keywords: system design, receivers, local oscillator, digital samplers, optical fiber, IF transmission, photonic LO

This report is concerned with the MMA receiving system and is based upon discussions of the MMA systems group. The part of the system considered here includes the signal paths from the outputs of the front ends to the digital samplers, and the local oscillator (LO) system, but does not include details of the front ends, the digital delays or the correlator. The system described is designed to work with optical fiber transmission of IF signals in analog form from the antennas to the electronics building at the site. Digital transmission is not ruled out, but remains under study. Two 8 GHz- wide or four 4 GHz-wide IF bands can be brought from each antenna to the electronics building. The full bandwidth is available for continuum observations, and for spectral line observations up to eight bands can be selected, the widths of which are selectable from 2 GHz in steps of two down to 31.25 MHz. These are then digitized and go to the delay system and correlator. A photonic system is under investigation for generating the the first LO signals, and as an alternative a more conventional multiplier system will also be developed. Sideband separation, fringe rotation, phase switching and round-trip phase requirements are also discussed.

[1] NRAO

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Last modified: 09 December, 1999