Virtual Center Arraying

One way to increase the amount of data that can be received from weak signal sources (such as spacecraft in the vicinity of the outer planets) is to array several ground antennas in such a way as to increase the total effective aperture of the receiving system. One such method is virtual center arraying (VCA). In VCA, a combined carrier reference is derived at a point that is, conceptually, the geometric center of the array. This point need not coincide with any of the actual antennas of the array. This paper includes a noise analysis of the VCA system and exhibits formulas for the phase jitter as a function of loop bandwidths and the amount of loop damping. If the ratio of the loop bandwidths of the center loop to the vertex loops is greater than 100, then the jitter is very nearly equal to that expected for ideal combined carrier referencing.