Jiri Vesely

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°.

The measurement of TDOA short baseline

The main aim of this work was to measure, verify and evaluate accuracy of target-location estimation in time difference of arrival (TDOA) method. Measuring workplace for TDOA measurement was assembled by using three receiving antennas, their distances were around 15 m each. Algorithm for solution of system of hyperbolic equations was created to determine position of signal source which is the intersection point of the hyperbolas. Position of signal source and its accuracy were graphically expressed.

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.

The effectivity comparison of TDOA analytical solution methods

Analytical method has been preferred to optimize computation process and reduce errors in time difference of arrival (TDOA) method, one of the most important and well-known methods used in passive system. In this study we compared the effectivity of two TDOA analytical solution methods for determination of possible target positions - intersection points of hyperboloids. These two analytical methods gave correct solutions, explicit number of solutions as well as be able to define all possible solutions. The advantages and disadvantages of these algorithms were determined and supported by the simulation examples. The first method was based on coordinate transformation from initial system to new system, where we could solve simpler system of equations, whereas the second one was based on matrix.

Analysis of possibilities to target detection by using secondarily emitted signals

One of the fundamental goals of electronic intelligence (ELINT), respectively passive surveillance systems (PSS), is the process of determining the position of the target, the output of which is to estimate the target position. It depends on the analysis of the received radio signals transmitted by the target. Information sources for long-range PSS are especially radio signals from active onboard aircraft systems or more generally flying airborne objects. Due to the physical possibilities for detection are for contemporary PSS real source of information signal shipboard radars, navigation interrogators, identification transponders, jammers and means of data transfer (Data Links). The development of aircraft is mainly focused on the real using of technologies, known collectively as STEALTH, to reduce the effective reflective surface radar aircraft, which is decisive for the detection of range to targets while reducing radio emission targets. In this category we find also Low-dimensional air targets - UVA (Unmanned Aerial Vehicle), UCAV (Unmanned Combat Air Vehicle) and other targets that have minimal reflective surface have given its geometrical dimensions. This article is focused on the analysis of signals of objects of interest in terms of their origin. There are two main groups of sources. Firstly, primary actively generated airborne signals (radar, navigation, identification, jamming, data and communication) and secondarily emitted signals generating due to reflection and scattering of the incident to the performance of the air target asynchronously or synchronously operating terrestrial or airborne transmitters.

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.

History of radar and surveillance technology in Czech Republic

This article s focused on radar technology and radio surveillance systems produced in Czech republic as a part of Czechoslovakia until 1990s. During this era there were produced thousands of radars for military and civil purpose for air traffic control, ship navigation, meteo radars, fire control and air defense radars used worldwide. The special domain in electronic location and surveillance systems where Czech republic leads technology are passive surveillance systems based on Time Different of Arrival principle signal source location. All of these technologies were build upon own complex electronic industry from electronic components and measuring devices to final product.