Oscillator devices employed in microwave radiometers are discussed. In order to stabilize the frequency and reduce the noise of the Gunn-effect oscillator, it is proposed to employ trapped-mode waveguide dielectric resonators, which are diffraction-excited in a rectangular waveguide either on a step-shaped H-inhomogeneity or on an E-inhomogeneity in the form of a parallelepiped with a gap along the wide wall of the waveguide. For calibration of the radiometers: wide-range noise sources have been developed, based on impact avalanche-and-transit time diodes (IMPATTD) and Shottky barrier diodes (SBD), which are highly stable with respect to the level of generation power. These sources employ the detected effects of the output signal self-modulation and self-thermostabilization.
Faculty of Physics, Moscow State University, Leninskie Gory, Moscow, 119992, Russia
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