Small Cassegrain antenna for passive remote sensing at L-band

摘要: Summary form only given. This paper presents the design, construction and results of measurements a dual polarized L- band antenna for NASA Combined Radiometer Radar System. The radiometer covers 1.400 -1.427 GHz. radar 1.250 to 1.350 focus this is on band. designed replace 48 inch diameter truck-mounted paraboloidal dish used in remote sensing applications because its excessive loss. It was found that changes ambient temperature produced fluctuations noise which reduced accuracy calibration. These are caused by dependent Ohmic loss structure, externally mounted cable connecting Newtonian feed patch feed. Therefore principal design goal new eliminate need reduce any additional without degradation electrical performance increasing size weight. A configuration obviates an external feed-to-radiometer connection Cassegrain antenna. Its advantage structure can be have lower than old Since classic antennas generally require reflectors with diameters at least 30 wavelengths designing incorporating reflector 5 6 wavelength represented real challenge. challenge met employs novel low dielectric (Rexolite) conical support subreflector. cone decreases linearly from base apex feature addition supporting subreflector also serves as waveguide illuminates mechanism wave within travels paraboloid toward it partial leakage into surrounding space. resulting efficiency appropriate truckmounted system. input circular supports two orthogonal TE11 modes thus providing necessary polarization. As confirmed simulations gain side lobe levels comparable those