Zvonko Radosavljević

We present a software-defined radar digital back-end (DBE) applicable in fully coherent radars with a power amplifier (PA) transmitter. DBE includes a digital exciter (DEX), receiver digital front-end (DFE), and radar signal processor (RSP). DEX performs direct digital synthesis of the transmit waveform and the local oscillator signal, along with synchronization signals. DFE accepts the intermediate-frequency signal and performs digital down-conversion, filtering, and decimation. Pulse compression, Doppler filtering, and constant false alarm rate detection are performed in the RSP. We use a commercial off-the-shelf, high-performance embedded computing platform to implement the DBE, with DEX and DFE implemented on a field-programmable gate array, and RSP implemented on a general-purpose processor. To test the DBE, we connect it with an existing PA-based analog front-end (AFE), antenna sub-system, and radar data processor. Field tests show that DBE enables the function of a fully coherent pulsed air-surveillance radar, capable of continuously tracking a multitude of aircraft, on both short and long distances, while successfully mitigating both clutter and noise interference. Although the field tests are performed only with very high frequency (VHF) band radar hardware, if connected with an appropriate AFE, DBE could be used in radars operating at higher frequencies.

Methods for calculating the interception point of the trajectory of a projectile and a moving target are the subject of many projects and are being solved in several directions. Initially, these were trigonometric methods, while nowadays probabilistic methods or methods of integrating differential equations are used. The paper proposes a classical method of integrating differential equations of projectile motion using the Runge-Kutta method, based on the initial azimuth and elevation angles of the projectile launch parameters, using the known initial projectile velocity. Future target positions are predicted based on the radar target tracking and calculated meeting time of the projectile and the target, using the interpolation method of the target's position coordinates and acceleration. The simulation results showed satisfactory accuracy for targets in the air at a distance of 2000 m with standard deviation of error position on 15 m.

The Integrated Track Splitting (ITS) is a multi-scan algorithm for target tracking in a cluttered environment. The ITS filter models each track as a set of mutually exclusive components, usually in the form of a Gaussian Mixture. The purpose of this research is to determine the limits of the ‘endurance’ of target tracking of the known ITS algorithm by analyzing the impact of target detection probability. The state estimate and the a-posteriori probability of component existence are computed recursively from the target existence probability, which may be used as a track quality measure for false track discrimination (FTD). The target existence probability is also calculated and used for track maintenance and track output. This article investigates the limits of the effectiveness of ITS multi-target tracking using the method of theoretical determination of the dependence of the measurements likelihood ratio on reliable detection and then practical experimental testing. Numerical simulations of the practical application of the proposed model were performed in various probabilities of target detection and dense clutter environments. Additionally, the effectiveness of the proposed algorithm in combination with filters for various types of maneuvers using Interacting Multiple Model ITS (IMMITS) algorithms was comparatively analyzed. The extensive numerical simulation (which assumes both straight and maneuvering targets) has shown which target tracking limits can be performed within different target detection probabilities and clutter densities. The simulations confirmed the derived theoretical limits of the tracking efficiency of the ITS algorithm up to a detection probability of 0.6, and compared to the IMMITS algorithm up to 0.4 in the case of target maneuvers and dense clutter environments.

Track While Scan (TWS) radars are generally used in defense systems, which supervise the positions of the target and generate the measurements, scan by scan. They measure a target's coordinates, determine its trajectory, and predict its next location. The selection and adaptation of the technical requirements of the optimal hardware for processing and displaying the radar image is related to several serious challenges, such as the availability and price of components on the market, the type of modulation, frequency agility, shielding from interference, computational complexity of processing, type and technology of the antenna system. In the paper, a complete example of coherent hardware processing (reception and transmission) of signals for VHF band radar is proposed. The proposed hardware generates trigger signals, modulates the transmit signal, transmits via a semiconductor HPA transmitter and then at the reception receives signals in the analog domain, converts them, processes them and displays the radar image on the monitor. The numerical experiments have shown the possibility of signal processing in real time on the selected platform showed the justification of the application.

: The radar multi target tracking (MTT) technique requires prior knowledge of a number of parameters about the sensor, the target and backgrounds. The Integrated Track Splitting (ITS) is a fully automatic track-while-scan (TWS) target tracking algorithm capable of extracting and tracking a target in a dense clutter environment using quality false track discrimination (FTD) methodology. The computational complexity in ITS algorithm is limited, compared to other algorithms they use statistical methods to discriminate between false and true tracks, such as multiple hypothesis tracking (MHT), mainly due to the FTD performed. The paper provides an analysis of tracking parameters that allows determining the limit of the possibility of successful target tracking. Extensive experiments have confirmed that the recursive determination of the probability of the existence of a track during tracking can confirm a true track and reject a false track. The clutter density, number of random occurred targets, targets load during the maneuver and the target detection probability were varied. The results of experiments, carried out via Monte Carlo simulations, shown over representative confirmed true tracks (CTT) diagrams, root mean square error position and normalized tracking efficiency parametric diagrams allow the user to select optimal multi-target tracking parameters for different scenarios and clutter densities.

The track quality measuring by the track probability existence in order to determine the limits of the possibility of effective target tracking is present in this paper. The most known algorithms for radar target tracking do not have tools to measure track quality. There is no valid procedure that guarantees the verification of the optimal algorithm for a specific application in targets tracking. Standard Integrated Track Splitting (ITS) is the efficient, fully automatic multi target tracking algorithm with initialization, maintenance and deletion tracks and is well-known single and multi target tracking algorithm, also proposed for the purpose of testing the limits of successful tracking. The paper allows the user to choose optimal parameter by the proposed parameters - thresholds of confirmed and false tracks in order to achieve better false track discrimination (FTD). In particular, a diagram of RMSE position errors is also given in the comparison of the proposed algorithm.

Each radar has the function of surveillance of certain areas of interest. In particular, the radar also has the function of tracking moving targets in that territory with some probability of detection, which depends on the type of detector. Constant false alarm ratio (CFAR) is a very commonly used detector. Changing the probability of target detection can directly affect the quality of tracking the moving targets. The paper presents the theoretical basis of the influence of CFAR detectors on the quality of tracking, as well as an approach to the selection of CFAR detectors, CATM CFAR, which enables better monitoring by the Interacting Multiple Model (IMM) algorithm with two motion models. Comparative analysis of CA and CATM algorithm realized by numerical simulations has shown that CATM CFAR gives less tracking error with proportionally the same computer resources.

Uvod/cilj: Na osnovu binomne funkcije gustine raspodele verovatnoće, u ovom radu je predstavljen novi verovatni model predviđanja položaja zrakoplova. Metode: Predloženi algoritam sastoji se od tri različita bloka: pridruživanje podataka, praćenje/procena hibridnog stanja i izračunavanje verovatnoće sudara. Informacije o njihovim trenutnim položajima i planovima leta koriste se za dobijanje algoritma za otkrivanje mogućih sukoba između vazduhoplova. Predviđanje situacija u kojima se vazduhoplov može približiti drugom na većoj udaljenosti izračunava se s velikom verovatnoćom. Procena položaja i neodređenost odnose se na pridruživanje podataka ciljeva, kada u „prozor’’ validacije padnu dva traga korišćenjem filtra sa pridruživanjem podataka po verovatnoći. Rezultati: Dizajniran je efikasan algoritam za otkrivanje sudara, koji se testira na mnogim višestrukim praćenjima ciljeva. Zaključak: Rezultati simulacije prevencije sudara aviona u dva scenarija putanje potvrđuju efikasnost predloženog algoritma.

Each multi target tracking system must have a track management procedure. It is an integral part of tracking systems and often used together with data association, state estimation and other parts of systems. On the other hand, the family of C-band frequency agile, low to medium altitude pulse Doppler air search radars, are designed to detect low-altitude, low cross-section aircraft targets in conditions of clutter and electronic countermeasures. Within the framework of its modernization, the receiver is conceived on the basis of software defined radar. The implementation of target tracking system within software defined radar, is also suggested. The paper describes the procedure of track management system procedure in the framework of multi target tracking system. It includes complete procedure of initialization, maintenance and deletion of tracks. Part of the numerical experiments is given at the end of the paper, in order to describe a good property functional of the TMS system.

The Integrated Probabilistic Data Association (IPDA) type filters provide estimates of the underlying target probability of existence as well as they track state maintenance. For each scan, IPDA recursive calculates the probability of target existence in order to resolve the uncertainty. Likewise, Random Finite Set (RFS) is a method for single target and multi-target tracking. It provides a Bayesian recursion of multi-target distribution through the Finite Set calculus. Practical implementation of multi-target posterior recursion is too difficult. It was analytically proved that IPDA algorithm can be derived from the RFS based filter recursion under the linear Gaussian assumptions. Probability hypothesis density (PHD) filter is an alternative to this problem where only the first order moment of the complete multi-target posterior is propagated in time. In this article, IPDA and Gausian Mixtures PHD (GM PHD) filters in a single target tracking scenario are derived and compared. Simulations have demonstrated the superiority of IPDA filters in heavy clutters.