Digital receivers for low-frequency radio telescopes UTR-2, URAN, GURT

This paper describes digital radio astronomical receivers used for decameter and meter wavelength observations. This paper describes digital radio astronomical receivers used for decameter and meter wavelength observations. Since 1998, digital receivers performing on-the-fly dynamic spectrum calculations or waveform data recording without data loss have been used at the UTR-2 radio telescope, the URAN VLBI system, and the GURT new generation radio telescope. Here we detail these receivers developed for operation in the strong interference environment that prevails in the decameter wavelength range. Data collected with these receivers allowed us to discover numerous radio astronomical objects and phenomena at low frequencies, a summary of which is also presented.Comment: 24 pages, 15 figure

Interaction of Low- and High-Frequency Oscillations in a Nonlinear RLC Circuit

The interaction of low- and high-frequency oscillations in an RLC circuit with a nonlinear capacitance is studied from the point of the modern theory of dynamical systems. It is found that for a certain range of parameters such an interaction may cause chaotic instability, even under the weakly nonlinear excitation conditions. The scenarios and conditions that give rise to chaotic oscillations are investigated both numerically and analytically. © 1994 IEEEInternational Foundation for ScienceThe authors would like to thank Dr. Ryabov for his fruitful discussions, and Dr. Serbest for his interest in the subject. D. V. is also grateful to the International Science Foundation for their support

INTERACTION OF LOW-FREQUENCY AND HIGH-FREQUENCY OSCILLATIONS IN A NONLINEAR RLC CIRCUIT

WOS: A1994PQ60700007The interaction of low- and high-frequency oscillations in an RLC circuit with a nonlinear capacitance is studied from the point of the modern theory of dynamical systems. It is found that for a certain range of parameters such an interaction may cause chaotic instability, even under the weakly nonlinear excitation conditions. The scenarios and conditions that give rise to chaotic oscillations are investigated both numerically and analytically

Interaction of high-frequency and low-frequency oscillations in the synchronized oscillator

Theoretical analysis of the oscillation synchronization under conditions of simultaneous low-frequency and high-frequency external impact on the oscillator has been conducted using an example of the generalized Van der Pol oscillator. It was shown that the interaction of high-frequency and low-frequency oscillations resulted in the appearance of additional regions of synchronization as a result of three-frequency interaction between the frequencies of such interaction and the natural frequency of oscillator. For the case of three-frequency interaction, characteristics of synchronous oscillations were determined and compared with those for the case of primary tone synchronization of oscillator

Modifications of Range-Doppler Algorithm for Compensation of SAR Platform Motion Instabilities

Two modifications of the range-Doppler algorithm (RDA) have been proposed to solve problems of SAR platform motion instabilities. First, the multi-look processing based on the RDA with an extended Doppler bandwidth has been introduced for correction of radiometric errors. Second, the RDA has been modified to perform SAR image formation on short-time acquisition intervals to use it in a recently-developed local-quadratic map-drift autofocus (LQMDA) method. The performance of the methods is illustrated with experimental data obtained by airborne SAR systems

Modifications of Range-Doppler Algorithm for Compensation of SAR Platform Motion Instabilities

Two modifications of the range-Doppler algorithm (RDA) have been proposed to solve problems of SAR platform motion instabilities. First, the multi-look processing based on the RDA with an extended Doppler bandwidth has been introduced for correction of radiometric errors. Second, the RDA has been modified to perform SAR image formation on short-time acquisition intervals to use it in a recently-developed local-quadratic map-drift autofocus (LQMDA) method. The performance of the methods is illustrated with experimental data obtained by airborne SAR systems