Piotr Samczynski

The evolution of radar technology in the early twentieth century is often narrated through the well-known contributions of Western scientists. Independent pioneering work in Eastern Europe—particularly in Ukraine and Poland—remains underappreciated. This paper considers the early radar experiments and innovations emerging contributed by Ukrainian institutions and experts. In addition, the paper highlights the important contributions of Polish scientists. Together, these untold facts underscore the collaborative and international roots of modern radar.

The fifth-generation (5G) standard has been rapidly gaining popularity as its deployment expands worldwide. With the increasing availability of 5G services, the potential for leveraging its signals for radar applications continues to grow. However, in today's densely occupied spectrum, both radar and communication systems face significant limitations in terms of bandwidth and power. This article introduces the concept and experimental results of a joint communication and sensing (JCAS) system utilizing 5G signals for both active and passive target detection as well as data transmission. A software-defined radio (SDR) was employed as a base station and an active radar node, while a second device emulated a user terminal capable of receiving, demodulating, and decoding the signal, and passively detecting nearby targets. The proposed methodology successfully detected the target and, despite involving only two nodes, precisely estimated its location.

This work focuses on object tracking using multistatic over-the-horizon radar. The proposed tracker consists of two stages. The first stage is a bistatic tracking with linear Kalman filter, and the second stage is a Cartesian tracking using the extended Kalman filter. To deal with the reflections from the ionosphere, the complicated propagation geometry has been reduced to a classical bistatic model using the virtual propagation paths. This approach allows for convenient adaptation of existing multistatic tracking algorithms, keeping the geometric simplification-related positioning error at a relatively low level. The simulation results show satisfactory agreement with the generated data, which confirms the good conditioning of the applied simplification. Combining the use of a virtual path model with a tracking algorithm is a newly developed method that can be possibly used by a multistatic radar. The method was developed within iFURTHER, an EU-funded project studying a Cognitive Network of HF Radars for Europe Defence under the framework of the European Defence Fund.

This article presents results of latest research work on exploiting DVB-S2 signal as source of illumination for passsive bistatic radar. The article starts with brief comparison of different satellite systems that potentially could be used as illuminators of opportunity for passive radars with presenting their advantages and disadvantages. Then the characteristics of DVB-S2 signal is presented as a source of illumination for passive radar. Next, the signal processing for DVB-S2 based passive polarimetric radar is proposed up to the detection stage. The following chapters present design of a laboratory model for DVB-S signal acquisition, description of carried out field measurements and obtained results of target detection. The article ends with presenting detection performance analysis for single polarizations and for the case of non-coherent integration of individual polarization channels.

The main goal of this work was to develop a demonstrative two-channel passive radar system, used for observing objects at Low Earth Orbit. GRAVES (from French Grand Réseau Adapté à la Veille Spatiale) radar was used as a source of signals, which would be deflected from objects above Southern Europe, and then received in central Poland. The receiver setup consists of two omnidirectional antennas, connected to a RSPduo receiver. A training sequence and a generator were used to synchronize the channels, which made it possible to use the digital conventional beamforming technique and beamsweep method. For creating spectrograms, an accelerator-type program was developed, which used a graphics card and CUDA toolkit. Both beamforming and beamsweep methods were implemented as a part of this program, which sped up analysis of received signals considerably.

The Global Navigation Satellite Service (GNSS) has been considered the first choice for providing Positioning, Navigation, and Timing (PNT) services, nevertheless, from the robustness and safety perspectives, alternative PNT solutions must be developed to maintain systems operation in the GNSSdenied environment. Satellites for broadband internet services in Low Earth Orbit, such as Starlink, give rise to a unique opportunity for the development of alternative PNT solutions due to global coverage, higher transmission power, and dense satellite grid deployment. This work presents a self-positioning system based on non-cooperative signals from the Starlink service. The continuously transmitted beacon signals in the user's downlink are exploited for a frequency-based self-location system. A dedicated signal processing scheme is designed to face the current low SNR of the beacon signals and allow the correct operation of the designed self-location system. The proposed system is tested with both simulated and real signals, confirming the feasibility of the proposed solution.

The subject of this paper is a method of representing micro-Doppler radar signatures using a 3 -dimensional function dependent on range, time, and frequency. The analyzed motion signature comes from the measurement of human vital signs. The device used to provide data is the FMCW radar operating at a frequency of 122 GHz with centimeter-scale range resolution. The main idea of signal processing is the time-frequency analysis for each range cell in a selected distance interval. The result was presented as a point cloud reflecting the so-called spatial spectrogram, which contains more information than a standard spectrogram from a single range cell. This allowed for the simultaneous representation of the shape of the signature and its distribution along the range cells. Both respiratory and heart activity were observed in the spatial spectrogram, confirming the effectiveness of the proposed method.

The subject of this paper is passive bistatic synthetic aperture radar (SAR) imaging with a ground stationary receiver using ICEYE-X2 active SAR micro-satellite as an illuminator of opportunity. During the satellite's flyover with signal transmission turned on, a measurement of the signal reflected from the nearby area was carried out using an antenna located on a hill. The recorded data was processed to confirm the correct data collection and SAR hitchhiking. To achieve this goal, a relatively efficient approximation-based method was used, which is much faster than a time-consuming back-projection algorithm and does not cause significant distortion of the image geometry. This is important for low-cost applications where processing power may be a limitation. After overlaying the SAR image on Google Earth view, it was found that the structures such as river banks, hills, or urban areas are well visible in the results. There are also some smaller objects apparent in the image, such as boat ports on the river or a ship. A possible application of the described approach includes low-cost observation of topography changes in the close-to-receiver area. Passive SAR with a stationary receiver can be used as a supplement to the results of active SAR or as a standalone, undetectable imaging system.

This article presents the concept of adjustable inverse synthetic aperture radar (ISAR) image concentration using the Levenberg-Marquardt optimization algorithm and the windowed two-dimensional Fourier transform (W2D-FT). A recently developed method for strong ISAR focusing is revised, allowing the user to obtain a stronger or weaker concentration of energy reflected from scatterers. As a result, the target image obtained using the proposed method can be of an intermediate resolution, leading to a target shape perception that outperforms other methods. The proposed technique fits the current software-oriented ISAR image resolution trend, as the whole method is based on efficient implementation and can work in real-world systems. The presented technique is validated using both simulated and real-life data employing bistatic radar for target imaging. The open-source MATLAB code for the software-oriented ISAR image improvement is also provided.