Karol Abratkiewicz

This article presents a new approach to the estimation of shift and rotation between two images from different kinds of imaging sensors. The first of the image is an orthophotomap that is created using optical sensors with georeference information. The second one is created utilizing a Synthetic Aperture Radar (SAR) sensor.The proposed solution can be mounted on a flying platform, and, during the flight, the obtained SAR images are compared with the reference optical images, and thus it is… Pokaż więcej

This article presents a new approach to the estimation of shift and rotation between two images from different kinds of imaging sensors. The first of the image is an orthophotomap that is created using optical sensors with georeference information. The second one is created utilizing a Synthetic Aperture Radar (SAR) sensor.The proposed solution can be mounted on a flying platform, and, during the flight, the obtained SAR images are compared with the reference optical images, and thus it is possible to calculate the shift and rotation between these two images and then the direct georeferencing error. Since both images have georeference information, it is possible to calculate the navigation correction in cases when the drift of the calculated trajectory is expected. The method can be used in platforms where there is no satellite navigation signal and the trajectory is calculated on the basis of an inertial navigation system, which is characterized by a significant error. The proposed method of estimating the navigation error utilizing Affine Scale-Invariant Feature Transform (ASIFT) and Structure from Motion (SfM) is described, and techniques for improving the quality of SAR imaging using despeckling filters are presented. The methodology was tested and verified using real-life SAR images. Differences between the results obtained for a few selected despeckling methods were compared and commented on. Deep investigation of the nature of the SAR imaging technique and noise creation character allows new algorithms to be developed, which can be implemented on flying platforms to support existing navigation systems in which trajectory error occurs. Pokaż mniej

This paper presents a novel approach to fast and accurate non-linear pulse signal reconstruction dedicated for electromagnetic sensors and their applications such as ELectronic INTelligence (ELINT), electronic warfare (EW), electronic reconnaissance (ER) systems, as well as for passive bistatic radar purposes in which other pulse radars are used as a source of illumination. The method is based on the instantaneous chirp rate (CR) estimation in the time-frequency (TF) domain providing a… Pokaż więcej

This paper presents a novel approach to fast and accurate non-linear pulse signal reconstruction dedicated for electromagnetic sensors and their applications such as ELectronic INTelligence (ELINT), electronic warfare (EW), electronic reconnaissance (ER) systems, as well as for passive bistatic radar purposes in which other pulse radars are used as a source of illumination. The method is based on the instantaneous chirp rate (CR) estimation in the time-frequency (TF) domain providing a calculation of the frequency rate between every two consecutive samples. Such a new method allows for the precise reconstruction of the non-linear frequency modulated (NLFM) signal to be carried out in significantly shorter time in comparison to methods known in the literature. The presented approach was tested and validated using both simulated and real-life radar signals proving the usability of the proposed solution in practical applications. The results were compared with the precise extended generalized chirp transform (EGCT) method as a reference technique, using optimal matched filtration as the main concept. Pokaż mniej

A new approach to micro-Doppler signal analysis is presented in this article. Novel chirp rate estimators in the time-frequency domain were used for this purpose, which provided the chirp rate of micro-Doppler signatures, allowing the classification of objects in the urban environment. As an example verifying the method, a signal from a high-resolution radar with a linear frequency modulated continuous wave (FMCW) recording an echo reflected from a pedestrian was used to validate the proposed… Pokaż więcej

A new approach to micro-Doppler signal analysis is presented in this article. Novel chirp rate estimators in the time-frequency domain were used for this purpose, which provided the chirp rate of micro-Doppler signatures, allowing the classification of objects in the urban environment. As an example verifying the method, a signal from a high-resolution radar with a linear frequency modulated continuous wave (FMCW) recording an echo reflected from a pedestrian was used to validate the proposed algorithms for chirp rate estimation. The obtained results are plotted on saturated accelerograms, giving an additional parameter dedicated for target classification in security systems utilizing radar sensors for target detection. Pokaż mniej

The article presents the concept of a system architecture which uses Synthetic Aperture Radar (SAR) images to aid navigation systems when Inertial Navigation System (INS) measurements are not accurate enough to eliminate drifts from a planned trajectory. The basic idea is to infer the position and altitude of an aerial platform by making a comparison between a SAR image and an optical image or digital terrain model (DTM). To obtain estimates of the coordinate drifts, a few algorithmic… Pokaż więcej

The article presents the concept of a system architecture which uses Synthetic Aperture Radar (SAR) images to aid navigation systems when Inertial Navigation System (INS) measurements are not accurate enough to eliminate drifts from a planned trajectory. The basic idea is to infer the position and altitude of an aerial platform by making a comparison between a SAR image and an optical image or digital terrain model (DTM). To obtain estimates of the coordinate drifts, a few algorithmic approaches have been proposed. Such a system can also be used in GPS denied environments, or for high-speed maneuvering platforms where GPS navigation is unable to work properly. It can also be used as an additional landing assistant platform for civilian aircraft, especially in bad weather conditions or when an airport is not equipped with modern electronic devices such as an Instrument Landing System (ILS). Pokaż mniej

This article presents the concept of using a new K-band radar demo kit operating on the carrier frequency of 24GHz for the measurement of micro-Doppler signatures. The system used, which is a low-budget radar for research and academic applications, is described and its operation presented through an example of human movement measurement and analysis. Thanks to its small size and low price, the system can be used for research related to the detection and classification of drones, people… Pokaż więcej

This article presents the concept of using a new K-band radar demo kit operating on the carrier frequency of 24GHz for the measurement of micro-Doppler signatures. The system used, which is a low-budget radar for research and academic applications, is described and its operation presented through an example of human movement measurement and analysis. Thanks to its small size and low price, the system can be used for research related to the detection and classification of drones, people, animals, vehicles, etc. Additionally, the use of the time-frequency reassignment technique is proposed to boost the quality of micro-Doppler signatures. Such an approach allows processing to be improved in the object classification routine. The method consists in concentrating energy on the time-frequency plane allowing significant components to be separated. Pokaż mniej

This article presents a novel approach to the estimation of motion parameters of objects in passive forward scattering radars (PFSR). In such systems, most frequency modulated signals which are used have parameters that depend on the geometry of a radar scene and an object’s motion. Worth noting is that in bistatic (or multistatic) radars forward scattering geometry is present thus in this case only Doppler measurements are available while the range measurement is unambiguous. In this article… Pokaż więcej

This article presents a novel approach to the estimation of motion parameters of objects in passive forward scattering radars (PFSR). In such systems, most frequency modulated signals which are used have parameters that depend on the geometry of a radar scene and an object’s motion. Worth noting is that in bistatic (or multistatic) radars forward scattering geometry is present thus in this case only Doppler measurements are available while the range measurement is unambiguous. In this article the modulation factor, also called the Doppler rate, was determined based on the chirp rate (equivalent Doppler rate) estimation concept in the time-frequency (TF) domain. This approach utilizes the idea of the complex phase of the short-time Fourier transform (STFT) and its modification known from the literature. Mathematical dependencies were implemented and verified and the simulation results were described. The accuracy of the considered estimators were also verified using the Cramer-Rao lower bound (CRLB) to which simulated data for the considered estimators was compared. The proposed method was validated using a real-life signal collected from a radar operating in PFSR geometry. The Doppler rate provided by a car crossing the baseline between the receiver and the GSM transmitter was estimated. Finally, the concept of using CR estimation, which in the case of PFSR can be understood as Doppler rate, was confirmed on the basis of both simulated and real-life data. Pokaż mniej

This paper presents the concept of utilizing a Scale-Invariant Feature Transform (SIFT) in the applications of SAR-based augmented integrity systems. SAR-based navigation systems are used for platform navigation corrections in the case of a lack of global navigation satellite system (GNSS) signals. In such a case, SAR images collected in real-time are matched with on-board image databases. In the past, some algorithms have been proposed based on the correlation of characteristic objects in… Pokaż więcej

This paper presents the concept of utilizing a Scale-Invariant Feature Transform (SIFT) in the applications of SAR-based augmented integrity systems. SAR-based navigation systems are used for platform navigation corrections in the case of a lack of global navigation satellite system (GNSS) signals. In such a case, SAR images collected in real-time are matched with on-board image databases. In the past, some algorithms have been proposed based on the correlation of characteristic objects in images, such as roads, buildings, etc. [1, 2]. In this paper, existing algorithms for SAR images matched with optical databases, including neural networks, are revised and analyzed. The application of the SIFT method in SAR-based navigation system applications was also proposed, which seems to be an efficient approach to solve the problem of matching characteristic points in SAR and optical images. The application of the SIFT algorithm was intensively tested and verified using real SAR images. Selected results of these tests are presented in this paper. Pokaż mniej

This paper presents a new approach to sonar pulse detection. The method uses chirp rate estimators and algorithms for the adaptive threshold, commonly used in radiolocation. The proposed approach allows detection of pulses of unknown parameters, which may be used in passive hydrolocation or jamming detection in underwater communication. Such an analysis is possible thanks to a new kind of imaging, which presents signal energy in the function of chirp rate. The proposed method relies on chirp… Pokaż więcej

This paper presents a new approach to sonar pulse detection. The method uses chirp rate estimators and algorithms for the adaptive threshold, commonly used in radiolocation. The proposed approach allows detection of pulses of unknown parameters, which may be used in passive hydrolocation or jamming detection in underwater communication. Such an analysis is possible thanks to a new kind of imaging, which presents signal energy in the function of chirp rate. The proposed method relies on chirp rate estimation of the received signal, and the calculation of the local threshold level depends on noise and reverberations which make detection of a particular type of signal possible. Pokaż mniej

In this paper, we present nonlinear estimators of nonstationary and multicomponent signal attributes (parameters, properties) which are instantaneous frequency, spectral (or group) delay, and chirp-rate (also known as instantaneous frequency slope). We estimate all of these distributions in the time-frequency domain using both finite and infinite impulse response (FIR and IIR) narrow band filers for speech analysis. Then, we present few examples including a novel type of imaging joining energy… Pokaż więcej

In this paper, we present nonlinear estimators of nonstationary and multicomponent signal attributes (parameters, properties) which are instantaneous frequency, spectral (or group) delay, and chirp-rate (also known as instantaneous frequency slope). We estimate all of these distributions in the time-frequency domain using both finite and infinite impulse response (FIR and IIR) narrow band filers for speech analysis. Then, we present few examples including a novel type of imaging joining energy and phase acceleration in a single picture. Finally, we provide an open-source project - ccROJ - Time-Frequency C++ Framework of which we are authors and that is used for computing the presented figures. Pokaż mniej

Radar signal parameter estimation, in the context of the reconstruction of the received signal in a passive radar utilizing other radars as a source of illumination, is one of the fundamental steps in the signal processing chain in such a device. The task is also a crucial one in electronic reconnaissance systems, e.g., electronic intelligence systems. In order to obtain accurate results it is important to measure, estimate and precisely reconstruct the considered signal. Then it is necessary… Pokaż więcej

Radar signal parameter estimation, in the context of the reconstruction of the received signal in a passive radar utilizing other radars as a source of illumination, is one of the fundamental steps in the signal processing chain in such a device. The task is also a crucial one in electronic reconnaissance systems, e.g., electronic intelligence systems. In order to obtain accurate results it is important to measure, estimate and precisely reconstruct the considered signal. Then it is necessary to identify it. The following paper presents a new approach to the estimation of the phase parameters of radar pulses. The novel method of chirp-rate estimation is described and used to analyze such signals. First, the method was examined by simulated pulses, and then true measured signals collected from the air traffic control radar were utilized. Using the phase accelerogram, an instantaneous chirp-rate was computed thanks to three novel estimators and the results were compared to results acquired using a different, already known, and estimation method of the phase coefficients based on matching filtration– extended generalized chirp transform. Pokaż mniej