The Effect of Amplifier Gain Compression on Correlation Coefficient
Rick Perley, National Radio Astronomy Observatory
Robert Hayward, National Radio Astronomy Observatory
Modern wideband interferometers will be required to operate in an environment with very strong artificial emissions -- some of which when entering through isotropic sidelobes, will raise the total system power by 20 dB or more above the levels expected from observations of cold sky. In such an environment, high linearity of the total signal processing path is a key requirement for a useful astronomical telescope. In this contribution, we report the results of an experiment where two tones, with powers sufficient to place the VLA's X-band amplifiers into 1 dB and 6 dB compression were added to four of the VLA's antennas. Observations of a strong astronomical source, with and without this injected tone, allowed us to carefully measure the induced error in the correlation coefficient, and hence allow an estimate of the resulting image degradation.