COMPARISON OF THE CHARACTERISTICS OF THE CORRELATION-INTERFEROMETRIC BELLOWS WHEN USING DIRECTIONAL AND NON-DIRECTIONAL ANTENNA ELEMENTS

При создании корреляционно-фазовых пеленгаторов, как правило, в качестве антенных элементов используют ненаправленные антенные элементы (АЭ). Для использования измерений направленных АЭ требуется модифицировать алгоритмы пеленгации. Представлены соответствующие модификации алгоритмов и проведено сравнительное исследование точности пеленгования применительно к двухканальным корреляционно-интерферометрическим стандартным пеленгаторам, использующим плоские антенные решетки из направленных и ненаправленных АЭ. Рассмотрена также возможность определения пеленгов лишь по энергетическим измерениям, отсутствующая применительно к пеленгаторам с ненаправленными АЭ. Показано, что применение направленных АЭ позволяет снизить вероятность возникновения аномальных ошибок, повысить точность пеленгования при существенно больших значениях угла места, определяющего направление на источник радиоизлучения, снизить негативное влияние отказа от учета сферичности приходящей волны и, следовательно, уменьшить размеры ближней зоны пеленгатора, для которой характерно появление аномальных ошибок пеленгования. В многосигнальной радиообстановке использование направленных свойств АЭ позволяет также формировать пеленгационную диаграмму, обеспечивающую частичное подавление помеховых сигналов. Вместе с тем эффективное использование направленных свойств антенных АЭ требует максимально точного учета их диаграмм направленности (ДН). Погрешности описания ДН могут приводить к заметным ошибкам при определении пеленга, поэтому повышение качества работы пеленгационной системы за счет использования направленных АЭ сопровождается повышением требований к определению и точности практической реализации ДН АЭ When creating correlation-phase direction finders, as a rule, non-directional antenna elements (AE) are used. To use directional AE measurements, it is necessary to modify the direction finding algorithms. We present the corresponding modifications of the algorithms and we carried out a comparative study of the direction finding accuracy in relation to two-channel correlation-interferometric standard direction finders using flat antenna arrays of directional and non-directional AEs. We also considered the possibility of determining bearings only from energy measurements, which is absent in relation to direction finders with nondirectional AE. We show that the use of directional AEs makes it possible to reduce the probability of occurrence of anomalous errors, to increase the accuracy of direction finding at significantly large values of the elevation angle, which determines the direction to the radio emission source, to reduce the negative effect of refusing to take into account the sphericity of the incoming wave and, consequently, to reduce the size of the near-field zone of a bearer, which is characterized by the appearance of abnormal direction finding errors. In a multi-signal radio environment, the use of the directional properties of the AE also makes it possible to form a direction finding diagram that provides partial suppression of interference signals. At the same time, the effective use of the directional properties of antenna AEs requires the most accurate consideration of their directional patterns (DP). Errors in the description of the pattern can lead to noticeable errors in determining the bearing, therefore, improving the quality of operation of the direction finding system due to the use of directional AEs is accompanied by increased requirements for the determination and accuracy of practical implementation of the pattern of AE

Robust Data Fusion of UAV Navigation Measurements with Application to the Landing System

To perform precise approach and landing concerning an aircraft in automatic mode, local airfield-based landing systems are used. For joint processing of measurements of the onboard inertial navigation systems (INS), altimeters and local landing systems, the Kalman filter is usually used. The application of the quadratic criterion in the Kalman filter entails the well-known problem of high sensitivity of the estimate to anomalous measurement errors. During the automatic approach phase, abnormal navigation errors can lead to disaster, so the data fusion algorithm must automatically identify and isolate abnormal measurements. This paper presents a recurrent filtering algorithm that is resistant to anomalous errors in measurements and considers its application in the data fusion problem for landing system measurements with onboard sensor measurements—INS and altimeters. The robustness of the estimate is achieved through the combined use of the least modulus method and the Kalman filter. To detect and isolate failures the chi-square criterion is used. It makes possible the customization of the algorithm in accordance with the requirements for false alarm probability and the alarm missing probability. Testing results of the robust filtering algorithm are given both for synthesized data and for real measurements.

ANOMALOUS ERRORS IN DETERMINING FOCUS COORDINATES EARTHQUAKES AND SUGGESTIONS FOR THEIR ELIMINATION

Objectives The aim of the study is to develop a method for estimating the speed of seismic waves in different directions of propagation and by taking into account the dimensions of the focus, reducing the error in determining the coordinates of the hypocenter. Method To find the hypocenter of the earthquake, the data of the seismic wave velocities, the differences in the times of arrival of seismic waves on seismic sensors and the error in determining the time difference are used. The data with an error determine the coordinates of the hypocenter using information from various combinations of seismic sensors. Processing the resulting array of coordinates, estimates the seismic wave velocities / or determines the spatial shape of the earthquake source and the coordinates of the hypocenter. According to the coordinates of the cinema center, the differences in the travel time of seismic waves are corrected and the distances to the seismic sensors are refined. Results After preliminary determination of the coordinates and shape of the earthquake source, if there are a large number of seismic sensors, it is possible to clarify the coordinates of the earthquake hypocenter taking into account the recommendations given in the works. Conclusion Using the proposed method implies the presence of a large number of sensors to determine the complex shape, the earthquake source.