Suppression in Active Devices-Circuits. Volume III. Noise in Gunn Effect Devices.
Final technical rept. 1 Oct 67-31 Oct 70,
CORNELL UNIV ITHACA NY SCHOOL OF ELECTRICAL ENGINEERING
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Measurements of the FM noise of CW X-band Gunn oscillators indicate that two noise sources must be considered in developing an oscillator noise model. One source is the thermal noise in the vicinity of the carrier frequency, which may be generated by hot electrons in the high field domain. The second source is low frequency flicker 1f noise current, which is thought to be generated by traps associated with impurity states. An expression for the FM noise deviation caused by a thermal noise source has been derived by Edson. This component of a Gunn diodes FM noise is white i.e., constant with frequency from the carrier. The author has calculated the flicker noise sources contribution by considering it as a small signal frequency modulation. The FM noise produced by this source falls roughly as 1f with frequency from the carrier. Since the two sources are physically unrelated, their noise spectra are uncorrelated and will add as mean squares. This model agrees well with measured noise spectra. Once three parameters of the model are established for a particular device, its noise performance in any circuit may be calculated from data obtained by simple microwave measurements. Typically, FM noise is below 10 Hz in a 1 KHz bandwidth to within 2 KHz of the carrier, for circuit loaded Qs between 50 and 100. A high loaded Q approximately 1000 circuit produced FM noise below .7 Hz in a 1 KHz bandwidth at 1 MHz from the carrier. Author
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