Marcin Kamil Baczyk

Passive ISAR imaging of air targets using DVB-T signals

This paper presents a concept of passive ISAR imaging of air targets using DVB-T transmitters as illuminators of opportunity. The presented concept has been successfully proved using both simulated and real data collected during a measurement campaign carried out by the Warsaw University of Technology in Poland. All stages of the signal processing algorithm for bistatic passive ISAR imaging have also been described. Passive ISAR images created of different air targets as a result of the proposed signal processing method have been included.

Passive bistatic SAR imaging — Challenges and limitations

In this article, a concept of passive bistatic SAR (PB-SAR) imaging using a spaceborne SAR radar transmitter of opportunity is presented. This was proposed for the first time in the beginning of this century by Krieger et al and Griffiths et al. Because passive imaging is completely covert and relatively cheap, as it does not require its own transmitter, and the rapid growth of the computational power of processors has made it possible, the topic has attracted the attention of many research institutes. Recently, several bistatic radar experiments have been carried out using ground stationary receivers and spaceborne illuminators, and the results have shown new capabilities of SAR imaging. In most of these trials, cooperative illuminators were used and placed on satellite platforms developed by the country conducting the experiment, means that the receiver has exact a priori information about the transmitters parameters (e.g., carrier frequency, signal parameters, chirp duration, pulse repetition frequency [PRF], etc.). To obtain a passive SAR image when the parameters are roughly known, additional techniques for signal analysis and parameter estimation have to be applied, which make the processing more sophisticated. In this article, the challenges and limitations of the PB-SAR imaging are discussed, and the differences in the signal processing chain in mono- and bistatic configurations are indicated. Finally, the recent results of real passive SAR images are presented. The results were obtained by the Warsaw University of Technology (WUT) in 2013, using their passive radar demonstrator mounted on the ground. As the transmitter of opportunity, the TerraSAR-X satellite was used.

SAR/ISAR imaging in passive radars

This paper presents a study on the possibility of using Synthetic Aperture Radar (SAR) and Inverse SAR (ISAR) imaging techniques in passive radars, utilizing commercial continuous wave transmitters as illuminators of opportunity. In presenting potential applications of this novel technology, obtainable maximum ranges and resolutions in passive SAR/ISAR technology are discussed. In the paper the main stages of a signal processing chain for SAR/ISAR imaging in passive radar are presented and discussed, showing the challenges and limitations which have to be addressed in designing the passive SAR/ISAR system. Additionally, real SAR and ISAR images obtained by passive radar demonstrators utilizing Digital Video Broadcasting-Terrestrial (DVB-T) illuminators are presented as the proof of concept of the presented technology.

Identification of helicopter rotor parameters using multistatic passive radar

This paper presents results of the analysis of a helicopter echo in a passive radar based on a DVB-T signal. It contains a theoretical study of the main rotor blade echo in a multistatic configuration. The simultaneous use of more than one transmitter-receiver pairs enables estimation of additional parameters of the rotor. By processing real data, the authors have shown the possibility of estimating the radial velocity and the number of main rotor blades of a helicopter. Parameters extracted by the analysis of a helicopter echo can be further used for target classification.

X-band receiver for passive imaging based on TerraSAR-X illuminator

The paper describes an X-band receiver constructed from Commercial Off-The-Shelf (COTS) elements that was used to capture a radar signal transmitted by the TerraSAR-X satellite. The motivation was to use recorded waveforms to perform ground-based imaging of the surrounding area. The paper describes the motivation, receiver setup and the results of the measurement campaign.

Preliminary results of noise radar experiments

The paper describes the first results of noise radar experiments carried out at Warsaw University of Technology. The radar system was built with Commercial Off-The-Shelf (COTS) components: log-periodic antennas, an arbitrary waveform generator and a two-channel spectrum analyzer. The radar operated in the continuous-wave mode, and the aim was to detect moving targets in the received signal. The paper shows the system setup as well as the numerical results obtained from the recorded signals.

The impact of reference channel SNR on targets detection by passive radars using DVB-T signals

Passive radar uses signals from two channels to calculate the cross-ambiguity function: reference and surveillance. In most analyses only the surveillance channel is fully modeled with multipath components and noise, whereas the reference channel is assumed to be ideal - noiseless and without multipath. This paper highlights the case where a reference channel is distorted and has low SNR. Such a situation is common when a transmitter located far away is used for illumination. Additionally, an interesting alternative is analyzed, where a signal from a single channel only is used for target detection. The theoretical considerations have been verified using real data.

Passive radar detection range enhancement using forward scatter geometry

The classical passive radar has very low sensitivity in the direction of the transmitter. The sensitivity losses in this direction are caused by the direct signal removal procedure. The application of digital reconstruction algorithms can significantly reduce this problem and enable a passive radar to detect targets in forward scattering geometry. This geometry leads to a significant increase of the target radar cross-section and thus an increase of the detection range of a passive radar. This paper presents a detailed discussion of the detection range and limitations exploiting forward scattering geometry.

Supersonic target detection in passive radar

The detection of supersonic targets in passive radar is a challenge due to the high speed and acceleration of the targets. In the classical approach, where the crossambiguity function is used, the integration time is limited by the range and Doppler migration. In this paper the application of the extension of the crossambiguity function to the 3-dimensional range-Doppler-acceleration is presented. The target of interest was a supersonic target - a sounding rocket launched by the Student Astronautical Group of the Warsaw University of Technology. As an illumination signal the DVBT-signal was selected.

Wind farm interferences in Passive Coherent Location

Rapid growth in the number of wind farms may influence the performance of many radar systems. The radar echoes originating from wind turbines blades and tower may mask existing objects or generate false plots. In the presented paper the authors analyze the influence of a wind turbine on Passive Coherent Location radars and discuss the effectiveness of simple methods used to overcome problems associated with it. The results of a simulation along with the recorded echoes of the wind turbine gathered by DVB-T based passive radar demonstrator are also shown in the paper.