Rain attenuation and depolarization over an earth-space path at 12 GHz - Experimental results using the CTS beacon

Measurements of attenuation and depolarization, primarily due to rain, of the 12-GHz communication technology satellite (CTS) beacon have been made at Crawford Hill, Holmdel, NJ. The measurement system used a 6-m aperture, fully steerable, horn reflector antenna fitted with a dual-sense circular polarized feed. The amplitudes of the copolarized and cross-polarized signal components were measured with a two-branch, stable, narrowband, frequency tracking receiver. Measured data for a 3-1/2 year period beginning April 1976 show significant year-to-year variation in copolarized rain attenuation. For example, at a 27 deg path elevation angle, the time over which a 10 dB attenuation was exceeded varied between 47 and 120 min/year. The depolarization showed a decrease with increasing copolarized rain attenuation and lower path elevation angle. At an attenuation of 10 dB and an elevation angle of 27 deg, a median depolarization level of -15 dB were measured. This decreased to -13 dB at a 9 deg elevation angle for the same attenuation.