D. Kabakchieva

Detection and estimation of pulsar signals for navigation

The paper focuses on scientific issues related to new application of pulsar signals for airplane-based navigation. A possible algorithm for processing of pulsar signals that consists of epoch-folding, matched filtering and detection is proposed and evaluated in this paper. The algorithm proposed is verified using the real experimental data obtained from the radio observatory Dwingeloo, the Netherland. The serious trouble in this study is that the total number of the input data within a repetition period is much more of the number of samples in a pulsar template taken from the EPN database. Therefore have been developed and evaluated two new algorithms for epoch-folding, which not only improve Signal-to-Noise Ratio of pulsar signals but as well reduce the number of samples of the output signals to the required number.

Detection and classification of objects from their radio shadows of GPS signals

The paper focuses on scientific issues related to new application of GPS in radar networks using the effect of Forward Scattering (FS) of electromagnetic waves to detect, locate and classify objects by their GPS radio shadows. The aim of the paper is to make experimental studies of GPS radio shadows of different objects irradiated by GPS signals and to develop methods and algorithms for automatic detection, estimation and classification of the shadows of these objects. The practical utility of the results obtained is to use a specific processing of the received signal in the GPS receiver, then to use the extracted information for positioning and classification of moving objects; for accurate assessment of the geographic location of fixed objects by method triangulation in systems for transport management, security of zones, subsequent identification of the detected objects from digital geographical maps.

Signal processing of GPS radio shadows formed by moving targets

This paper focuses on scientific issues related to new application of GPS in the construction and development of radar networks using the effect of Forward Scatter (FS) of electromagnetic waves for detection of objects by using of their GPS radio shadows. The paper theme is new, it combines two thematic areas: processing of GPS signals and processing of radar signals in FS radar systems.

Analysis of multi-sensor radar detection based on the TBD-HT approach in ECM environment

This paper describes in details the performance of an advanced detecting algorithm for multi-sensor target Track Before Detection (TBD) through the Hough Transform (HT). The detection algorithm employs the idea of using the Hough Transform for joint detection of linear trajectory targets. The polar modification of the TBD-HT approach is applied to a multi-sensor Polar Hough detector for multi-sensor target/trajectory detection in ECM environment with a Stand-off-Jammer (SOJ). A CFAR detector is proposed for signal detection in the (r-t) space instead of fixed thresholding in order to enhance the target detectability in ECM environment. In this paper a centralized structure of a multi-sensor Polar Hough detector is considered. The expressions calculating the probability characteristics, i.e. the probability of target/trajectory detection and the false alarm probability, are analytically derived. The multi-channel TBD-HT detector probability characteristics are compared with those for the conventional signal processing.

The study of target shadows using passive FSR systems

The paper describes one possible algorithm for object detection by using of Forward Scatter (FS) radio shadows created by objects. The algorithm is verified on the experimental data collected by a GPS receiver with a small commercial antenna. The results obtained show the possibility for object detection when its FS shadow is present.

Time of arrival estimation in pulsar-based navigation systems

This paper focuses on the Time of Arrival (TOA) estimation problem related to new application of pulsar signals for airplane-based navigation. The aim of the paper is to propose and evaluate a possible algorithm for TOA estimation that consists of epoch folding, filtering, CFAR detection, cross-correlation and TOA calculation. The TOA estimation algorithm proposed is verified using real experimental data obtained from the Westerbork radio observatory in The Netherlands. The performance of the proposed TOA algorithm is evaluated in terms of SNR at the cross-correlator input and the TOA accuracy.

Experimental verification of target shadow parameter estimation in GPS FSR

In this paper we analyze the power budget and calculate signal to noise ratio (SNR) and radar cross section (RCS) for different ground targets using a forward scattering radar (FSR) system, which consists of a transmitter mounted on a satellite of GPS and a receiver located on the Earths surface. The FSR is a specific bistatic radar system where the bistatic angle is near 180o, and the target is located near the transmitter-receiver baseline. Theoretical and numerical calculations of SNR and RCS are presented for different ground targets when the GPS L1 signal is transmitted by satellites. The SNR and RCS are also estimated by using real records of the GPS signal shadows from different targets. The obtained numerical and experimental results are analyzed and discussed.