Accurate Gain Measurements for Large Antennas Using Modified Gain-Transfer Method

The classic gain-transfer method assumes a uniform plane wave incident over the apertures of the gain-transfer standard (typically a standard-gain horn) as well as the antenna under test. Variations in the incident field over the quiet zone of an antenna test range can produce large errors in the estimated gain of the antenna under test. These errors can be significant, especially when there is a large difference in aperture dimensions between the antenna under test and the standard-gain horn. In this letter, a modified gain-transfer method is described to reduce errors in gain measurements when antennas significantly larger than the standard-gain horn are measured in a test range using the gain-transfer method. The aperture of the antenna under test is usually much larger than that of the standard-gain horn, and therefore these antennas will typically be exposed to different variations in the incident field. Measured results are presented to illustrate accurate gain measurements for antennas significantly larger than the standard-gain horn.