Том 61, № 7 (2018)

Spatial-harmonic magnetrons with cold secondary-emission cathode are efficient high-power sources throughout the millimeter wavelength band. In this paper, resent advances in design, modeling, and fabrication of such magnetrons are described. Low-voltage magnetrons, sub-THz tubes, and magnetrons with metamaterial anode structure are described to illustrate these advances. The issue of the lifetime of the magnetrons with a cold secondary-emission cathode is also addressed. The main problems related with the usage of an auxiliary cathode in such tubes are considered and alternative solutions are discussed. Potentials for further improving the performance of spatial-harmonic magnetrons are analyzed as well.

Indian Regional Navigation Satellite System (IRNSS) is a satellite based navigation system developed by Indian Space Research Organization (ISRO). The positional accuracy of IRNSS is limited by several errors including ionospheric delay. Ionospheric delay can be estimated with precise calculation of total electron content (TEC). However, TEC is biased by multipath and thermal noise. Therefore, multipath and thermal noise free relative TEC measurements are made and compared with two other methods, namely, code TEC and IRNSS Receiver Software (IRS) techniques. In this investigation L5 (1176.45 MHz) and S1 (2492.028 MHz) signals from IRNSS 1A to 1G satellites are considered. The results indicate that relative TEC estimation technique removes the multipath and thermal noise from the TEC measurements. Further, the TEC for signals coming from various IRNSS satellites are evaluated by calculating the standard deviation (SD). In the analysis the data is divided into segments with duration of 1 h each. The results indicate that SDs for the relative TEC estimation (2.5 TECU in case of IRNSS 1B) are lesser than the other two techniques indicating the relative TEC can be used in the receiver for the estimation of ionospheric delay. Further, the high ratio of the operating frequencies indicates a better TEC estimation.

Under the conditions of the combined interference, the operation efficiency of the radar equipment is substantially deteriorated. This is due to the decorrelation of the signals of the point source of active interference acting on the radar by passive interference. In this article methods of formation of the classified training sample, generated only by active interference, are considered for adaptation of the weight coefficients of spatial filters under conditions of combined interference presence. An effective method of forming the classified training sample generated by active masking interference was developed for spatial processing of radar signals under conditions of simultaneous exposure to passive interference. The developed method of forming the training sample is based on estimating the width of the normalized autocorrelation function in each element of the distance resolution. The current analysis of the combined interference components in each resolution element improves the quality of the interference component classification and, as a result, minimizes the effect of passive interference on the adaptation process of the spatial filter. The theoretical and practical aspects of the formation of the classified training sample are considered. The functional scheme of the classifier for the combined interference components is developed. The efficiency of the proposed method is compared with known correlation methods. The current analysis of the combined interference components in each element of the range resolution improves the quality of interference classification, which is important in the context of complex hydrometeorological conditions.