  Radio astronomical imaging arrays comprising large numbers of antennas,
O(10^2-10^3) have posed a signal processing challenge because of the required
O(N^2) cross correlation of signals from each antenna and requisite signal
routing. This motivated the implementation of a Packetized Correlator
architecture that applies Field Programmable Gate Arrays (FPGAs) to the O(N)
"F-stage" transforming time domain to frequency domain data, and Graphics
Processing Units (GPUs) to the O(N^2) "X-stage" performing an outer product
among spectra for each antenna. The design is readily scalable to at least
O(10^3) antennas. Fringes, visibility amplitudes and sky image results obtained
during field testing are presented.
