A modified radiometric method for measuring antenna radiation efficiency

Radiation efficiency of antennas is shown to be measurable by a modified radiometric technique where the antennaʹs physical temperature is varied, rather than the noise temperature of its surroundings. The method is accurate, flexible and much more convenient for routine use. A means of avoiding errors caused by temperature-dependent antenna impedance is described. The accuracy of the method is verified by measuring the radiation efficiency of a horn antenna with a 3 dB attenuator to simulate a 50% efficient antenna, and by using microstrip patch antennas, whose measured efficiencies compared well with values computed from a transmission-line model.