Pattern measurements of a low-sidelobe horn antenna

The techniques and results of measuring the power pattern of a corrugated horn antenna designed for low sidelobes to levels 90 dB below the main beam maximum on both the E- and H- planes are presented. The study was motivated by a requirement for an antenna with very low side lobes to measure properties of the cosmic microwave background radiation from a satellite. The particular application calls for horn antennas of approximately 7 deg beamwidth, operating at discrete frequencies in the range of 20-90 GHz. It is demonstrated that the side lobes of horn antennas can be measured to significantly lower levels than has been achieved previously. Finally, it is noted that an improvement could be achieved by allowing for longer signal integrations and incorporating a switched reference measurement scheme to enable the accurate determination of very low signal levels.