Zbigniew Gajo

Bio: Zbigniew Gajo is an academic researcher from Warsaw University of Technology. The author has contributed to research in topics: Pulse-Doppler radar & Passive radar. The author has an hindex of 5, co-authored 15 publications receiving 82 citations.

Concept of multistatic Passive radar based on wireless packet communication systems

Abstract: In this paper a concept of passive radar system based on packet wireless network illuminators is presented The network consists of several transmitters/receivers using the same bandwidth, exchanging data packets The passive radar listens to the communication, and decoding packets determines the source transmitter The time windows are used to select transmission form single source and window signal is processed using Passive Coherent Localisation methods to localise targets of interest Paper presents details of the proposed methods, theoretical background, simulations and preliminary measurement results

Quality enhancement of image generated with bistatic ground based noise waveform SAR

Abstract: A new method for quality enhancement in a noise synthetic aperture radar (SAR) image and the first results of its application to the SAR image generated with the use of a bistatic Ka-band ground-based noise waveform SAR (GB NW-SAR) are presented. A SAR image generated with a noise SAR suffers from the masking effect which is tied to residual random fluctuations in noise radar response from bright scatterers in the scene. This is similar to the masking effect present in the deterministic waveform SAR when the signal sidelobes of echoes from bright scatterers may mask the main response from a weaker target. The procedure presented is a variation of the CLEAN algorithm. Knowing precisely the emitted signal and finding positions of the strongest scatterers one may model the echo signal originated from a selected scatterer. Extraction of the modelled signal from the received one reduces the residual fluctuations and makes it possible to clean the image and increase its dynamic range. The final image is constructed from the cleaned signal and the previously removed strongest scatterers. A theoretical background is provided to the proposed procedure and its application to enhance the SAR image using simulated data as well as data generated by the Ka-band bistatic GB NW-SAR is demonstrated. The GB NW-SAR, recently developed and tested in LNDES IRE NASU, may operate in CW and pulse random signal regimes for short range applications.

A simple robust detection of weak target in noise radars

Abstract: This paper presents a concept of the simple robustification of correlation detector in the noise radar. The simulation results show that it is possible to increase the radar sensitivity in the non-Gaussian (impulsive noise) environment by several dB using nonlinear signal processing. Suggested method introduces only moderate losses (0.5-1.5 dB) in the case where input noise is purely Gaussian.

Target Doppler Rate Estimation Based on the Complex Phase of STFT in Passive Forward Scattering Radar

Abstract: 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.

Ground clutter cancellation in MIMO and multistatic noise radars

Abstract: In this paper, ground clutter cancellation in a multi-channel noise radar is presented The radar system under consideration consists of K independent noise transmitters working in the same frequency band and L receivers Independent cancellation of clutter echoes originating from successive transmitters is not fully effective therefore joint cancellation of all clutter echoes is proposed (5 pages)

The CLEAN type algorithms for radar signal processing

Abstract: A new class of signal processing algorithm based on CLEAN methods primary introduced in radio-astronomy is presented in the paper The classical radar signal processing is based on match filtering concept, which is optimal in mean square sense in case, when single target echo is detected against white or colour Gaussian noise Such approach was effective when pulse radar have been widely used The introduction of pulse-compression technique changes significantly the signal model, but still the match filter have been widely The introduction of continuous wave radars, and especially noise and passive radars changed dramatically the situation In such radars all echoes are superimposed and interfere with each other and the simple model no longer fits to that case The straightforward solution - use of inverse problem mathematical solutions such as solving the set of nonlinear equations to find all echoes in received signal - is usually computationally ineffective and often numerically not stable, so suboptimal methods are being developed to improve detections of weak signals in CW radars One of possible solution is to use concept of CLEAN technique an remove all strong echoes from received signal When only weak signals and white noise remains in is possible to use matched filter concept without significant loses of radar sensitivity In the paper several techniques for radar signal processing utilizing CLEAN concept are shown

PaRaDe - PAssive RAdar DEmonstrator family development at Warsaw University of Technology

Abstract: The paper presents a family of passive coherent location (PCL) radar demonstrators, called PaRaDe (passive radar demonstrator), which were developed at Warsaw University of Technology. The systems exploit commercial FM radio transmitters as illuminators of opportunity in order to detect and track airborne targets. In the paper, the details of demonstrator systems are described and the results obtained in tests are presented.

An Experimental Study of HF Passive Bistatic Radar Via Hybrid Sky-Surface Wave Mode

Abstract: This paper presents a description of recent research and development in HF passive bistatic radar (HFPBR) based on DRM digital AM broadcasting at Wuhan University, China First, preliminary evaluation of its detection performance with special focus on the hybrid sky-surface wave propagation mode is introduced Then, DRM broadcasting signal analysis as a radar waveform and associated signal processing techniques are described, consisting of ambiguity function analysis, reference signal extraction, multipath clutter rejection, and target localization Finally, the experimental system and experimental data analysis are provided Initial results from field experiments show that DRM-based HFPBR with hybrid sky-surface wave is a promising system for wide area moving target detection and ocean remote sensing