The transmission-line diode as noise source at centimetre wavelengths

After a short survey of existing methods of absolute calibration of receivers in the centimetre waveband, the transmission-line noise diode is described and its operation explained. The available noise power is calculated on the assumption of arbitrary terminations of the "active" line, i.e. of the part of the line across which emission current is flowing. Two special cases are considered in detail, the case when the active line is "matched" at both ends, particularly suitable for absolute calibrations of receivers, and the case when the line is "resonant," giving increased noise output, and particularly suitable as a relative source of noise or as a transfer standard. Results of experiments on the absolute noise output, on the electronic attenuation, on the influence of transit-time and on space-charge smoothing are given, the last showing that some mechanism of noise-reduction exists even at frequencies as high as 3 000 Mc/s. Details are given of applications of the resonant diode in practice.