It is possible to achieve amplitude stability of Gunn oscillators in Ka band at level of /spl Delta/P/P=5*10/sup -4/-10/sup -4/ necessary for fast calibration of radio astronomical receiver. Gunn oscillators with improved amplitude stability are manufactured and investigated. Experimental results of measurement of Gunn oscillator samples with improved amplitude stability are presented.

A multi-element MMIC array architecture for the RATAN-600 radio telescope is offered. The proposd solution can be used for other wide-angle reflector radio telescopes with offset illumination as well. The description and characteristics of the MMIC array prototype are given. Antenna characteristics of the RATAN-600 in multi-beam operational mode and some radio astronomical applications are presented.

The amplitude and frequency fluctuations of a synchronized oscillator and the fluctuations of the phase difference between input and output are examined. Synchronization methods are demonstrated for measurement of the frequency fluctuations of ultralow-noise low-power microwave oscillators, for which conventional methods are unsuitable. The methods are verified.

: Contents: Operating Principles and Noisiness of Klystron Oscillators; Parameters Which Characterize Noisiness of Generators, and the Methods of Their Measurement; Requirements, Presented to by Klystron Oscillator in the Radar Devices; Ways of Reduction in the Noises of Klystron Oscillators; Some Information from the Theory of Random Processes; Tables of the Parameters, Utilized for Describing the Spectral Characteristics of Fluctuations.

The results of an experimental investigation of the correlation between fluctuations of the cathode current and amplitude (frequency) fluctuations of the oscillations of a reflex klystron are presented. It is shown that in order to explain the dependences obtained it is necessary to take account of the autodyne effect and the modulation of the cathode current by the currentdistribution flicker noise contained in the beam of electrons returning to the cathode. One of the methods of studying the mechanism of modulating a microwave oscillation by the noise of an electron beam is the investigation of the correlation between amplitude or frequency fluctuations of the oscillation and the cathode-current fluctuations. For a corrrect understanding of the experimental data it is necessary to take account of the entire ensemble of phenomena which affect correlation and, in the first place, the nature of the noise observed in the cathode circuit (this correlation is not simple even in the static operating regime of a klystron [1]). The present paper presents and discusses the results of correlation measurements carried out on experimental reflex klystrons operating in the short-wave portion of the centimeter range. The investigated devices differ in their electron optics and in the structural peculiarities which are related to this. One of them used electron beams which converge in the gun and fountain in the repeller field (viz. Fig. 1 in [1]); the others used an almost cylindrical electron beam and a cathode of smaller diameter. In devices of the first type the number of electrons returning to the cathode was reduced in comparison with devices of the second type, and as a consequence the secondary-electr on current in the gap was evidently greater (a considerable portion of the primary electrons returning from the retarding repeller field was intercepted by the solid portion of the electrode which supported the grid of the rf gap closest to the cathode). Both groups of devices were practically no different in their power-supply regime. 1. Experimental Procedure and Results A convenient measure of the mutual correlation of two random processes x(t) and y(t) is the complex