Petr Hubacek

Analytical solution of the Time Difference Of Arrival method with known target altitude

This article is focused on analytical solution of the target position computing in passive systems using the Time Difference Of Arrival (TDOA) method where the altitude (or Height) above the see is known (TDOAH). Passive surveillance systems using TDOA may be divided into 2-D three positional and 3-D four positional where analytical solution are known. Despite this fact the most task solved in practice is TDOAH in both cases especially for long range electronic intelligence (ELINT) where the target height measuring by 3-D TDOA is inaccurate. This task may be solved with using of iterative method but using of analytic method gives direct solution, the number of solutions and all possible solutions. Direct solution is free of errors given by iterations and possible divergences. Analytic solution gives better conditions for position error estimation and singularity analysis. In this paper is TDOAH method derived and presented on example.

Optimized algorithm for solving phase interferometer ambiguity

Direction finding (DF) system using phase interferometer of long baselines gives high accuracy of angle of arrival (AOA), however, it also involves phase ambiguity and phase error. The paper presents a measurement of phase interferometer system, which was configured with three and four antenna elements, providing information of phase error. Moreover, a method including rotation of measured phase differences, labeling the phase lines and rounding value of phase difference was applied for determination of unambiguous AOA. The algorithm of AOA calculation was fast and optimized. The method was verified by experimental measurement combining with signal processing in MATLAB environment. The RMS error of phase measurement was 5.4° and RMS error of AOA determination was around 0.09°.

X-band FMCW SAR with direct synthesized signal generation via two stage frequency multiplied DDS output

This article is focused on the design of the short range FMCW (Frequency Modulated - Continuous Wave) Synthetic Aperture Radar (SAR) system, in particular, on the design of the transmitting part of this system where the signal generator is based on the direct synthesis via two stage frequency multiplication of DDS (Direct Digital Synthesis) device output. This solution is novel in comparison with commonly used signal generators of present SAR systems. First, the brief overview of several methods of SAR signal generation is presented as a background for following presentation of this new solution. Next, the block diagram of the SAR transmitting part, including proposed direct synthesized signal generator, is described more in detail. Finally, the several results of practical testing of the evaluation SAR system are shown.

Algorithm for obtaining high accurate phase interferometer

Phase ambiguity and phase error in interferometric method are important problems that have to be solved to determine angle of arrival (AOA) of signal. This paper proposes fast algorithm for ambiguity resolution of long baseline interferometric system, which was configured by three- and four-antenna array. In addition, the algorithm also provides information of allowable maximal error in phase measurement. The proposed algorithm also enables to configure a phase interferometric system. The algorithm was tested and verified by experimental results.

UHF/C-band testing of AOA estimation using MUSIC algorithm

This paper presented a study of direction of arrival estimation using multiple signal classification algorithm on two frequency bands (UHF-band and C-band). The used algorithm in the paper is one of the superresolution direction of arrival estimation algorithms and it was simulated to analyze the effects of various parameters on the direction of arrival accuracy and resolution. Then, the measuring workplace was established to verify the results of the simulation. In the practical measurement, two 4-element uniform linear arrays were used to estimate the direction of arrival of the noncoherent signal sources for the different frequency bands. The measured signals were processed in the Matlab using multiple signal classification algorithm for direction of arrival estimation. The measurement system estimated the direction of arrival of the signal in the UHF-band with accuracy around 4° and resolution around 10°. In the C-band, the accuracy and resolution of direction of arrival estimation were around 3° and 10° respectively. In comparison, the measurement results were a bit different from the simulation due to environment condition of measuring workplace.

DOA estimation with different NLA configurations

This paper presents a study of MUSIC algorithm for a nonuniform linear array (NLA) with different configurations. In the case of the same number of sensors, the element spacing of each configuration is selected according to the condition of the Chinese surplus theorem. In the simulation, we provide simulations of three typical NLA configurations for the different aperture of the array in comparison with uniform linear array (ULA) configuration. The first is a comparison between three NLA configurations and ULA in the case of one incoming signal. The second are simulations for the case of two incoming signals. We also show that MUSIC algorithm presents better performance in increasing aperture of the array. In the practical measurement, 4-element NLA was used to verify with one of three NLA configurations in the case of one incoming signal.

Analysis of determining the position of LPI targets by TDOA PSS

This paper follows previous papers and deals with possibilities of radar location determination per TDOA (Time Difference of Arrival) with short base and focused on targets with side antenna beam high suppression (LPI targets).

Analysis of possibilities to passive airborne targets detection with TDOA PSS with short base configuration

In this paper a TDOA (Time Difference of Arrival) method with short base has been proposed. This method is applied on targets with high suppression of antenna side beam (LPI targets). TDOA method generally requires at least three intercepting stations several kilometers from each other. For more precise targeting in 3D the method requires at least four intercepting stations. In consideration of this requirement the TDOA method brings many technological logistical and economical disadvantages. Ineffectual measurement of a target location in space by using TDOA method is one of the key outputs of previous papers. This inaccuracy appears when one of the intercepting stations (three at least) is insufficiently radiated or not radiated at all. In this paper there is analysis based on experiments with size of the intercepting base of the passive surveillance system and ambiguity of time parameter measurements of the signal. This ambiguity has impact on accurate localization of the target in space. In light of mentioned an idea of shorting the baseline occur. It can resolve problem with ambiguity of time measurement and efficient radiation of all intercepting stations.

Probabilistic code extractor for low SNR SIF/IFF mode A, C respond

This article is focused on the design of the new method of the detection (extraction) of pulse groups, especially SIF/IFF responses, in signals with low signal to noise ratio. This solution is novel in comparison with commonly used detection techniques of present Secondary Surveillance Radar or Electronic Intelligence systems. First, the brief overview of present detection methods of groups of pulses is presented as a background for following presentation of this solution. Next, the idea of proposed method is described more in detail. Finally, the several results of simulation of the algorithm performance are shown.

Low-flying target position finding with a seismic system

The development of new sensor systems able to detect, identify and find position of the targets equipped with STEALTH technology began early in 1990s. Some of the sensor systems utilise acoustic, magnetic, seismic and/or other physical effects of target activity. A reason motivating the development of new sensor systems based on other than radar or optical principal of operation in detecting targets is that the systems usually emit no electromagnetic energy during operation. Thanks to their passive principle they provide the users with the advantages of hidden positioning and difficult discovery with reconnaissance tools. Therefore, some of the new UGS systems also allow detecting low-flying targets, such as helicopters, propeller or jet aircraft, etc., in the detection range of up to several kilometres. The information of flight direction is usually estimated and deduced from spatiotemporal sequence detections by multiple interlinked UGS systems. The submitted paper analyses low-flying target position finding principle on Time Direction Of Arrival (TDOA) basis. It presents the qualities of found UGS arrangement topologies and the characteristics of the unambiguous position determination of low-flying targets. It also contains mathematical description of signal digital processing intended to find low-flying targets position. The processed results are presented in table and diagram forms created in Matlab mathematical environment. All the presented detection and identification results were obtained from real recorded signals.