Abstract
THERMAL methods for the measurement of power at centimetre wave-lengths normally involve a substitution process in which the high-frequency power is assumed to be identical in magnitude with the d.c. power causing the same rise in temperature or change in resistance. While in some techniques this assumption results in no appreciable error, it is a general limitation of thermal methods that the high-frequency and d.c. powers are not dissipated in precisely the same manner. This feature of existing methods is particularly evident at low power-levels, of the order of 1 milliwatt, at wave-lengths of 3 cm. and less. Although a calibration of centimetre-wave milliwattmeters can be made against standard equipment operating at higher power-levels, this operation requires much auxiliary apparatus and attenuation measurements of high precision. There is a need, therefore, for further convenient power-measuring techniques at the milliwatt-level in which the limitations inherent in existing methods are avoided. It seems probable that a form of film radiometer or bolometer, in which the ideal of accurate substitution of d.c. power for high-frequency power is approached very closely, will fulfil these requirements; the results of some preliminary experiments in the development of such an instrument are summarized in this communication.
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References
Collard, J., Proc. Inst. Elect. Eng., IIIA, 93, No. 9, 1399 (1946).
Gordon-Smith, A. C., Proc. Inst. Elect. Eng., B, 102, 685 (1955).
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LANE, J. A Film Radiometer for Centimetre Wave-lengths. Nature 177, 392 (1956). https://doi.org/10.1038/177392a0
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DOI: https://doi.org/10.1038/177392a0
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