Real-Time Array Feed Compensation System Demonstration at JPL

A real-time array feed compensation system has been constructed, and is currently undergoing tests at JPL. This sytem was designed to operate at h-band (33.7 GHz) carrier frequencies, where mechanical distortions begin to seriously degrade the performance of large DSN antennas. A compact cluster of seven 22 dBi horns in the focal-plane of a 34-meter beam-waveguide antenna sample the distorted fields, and optimum combining-weights are derived from correlation measurements on the downconverted baseband signals. The instrument used to carry out these measurements is a real-time correlator built primarily for VLBI applications, and hence can be used to observe broadband sources such as quasars and planets. In addition to providing combining information, the correlation coefficients are used to characterize the” atmosphere’s contribution to the total system noise, and to derive pointing corrections which help to keep the antenna pointed on source.