Aydin Bayri

Emitter localization based on antenna scan properties

In this paper, finding the location of a passive emitter by using its scan period (T), with a single moving platform is analyzed. With the developed method it is shown that location of an emitter can be found with single channel, single sensor and simple receiver structure. Also the method needs less time resolution and time synchronization. Performance is compared for different noise types. Emitter localization ability can be gained to existing electronic support systems (ESM) without any additional hardware change with the proposed method

Phase only wide beam synthesis

In this paper, an algorithm which calculates element weights of an antenna array by using phase-only element weights to construct wide beams is introduced. Since controlling the amplitude of each element is not always practical to implement and more power as such is possible, beam synthesis by phase shift only is of growing importance. The proposed method aims to widen the beam of the antenna array by steering each element of the array into different directions. Directions of each element are optimized using a cost function. Simulations are presented to validate the proposed method.

Hybrid iterative TDOA emitter localization using two different techniques

Two well developed techniques in emitter location estimation using time difference of arrival (TDOA) are analyzed and compared for different situations and noise values. These techniques are a passive localization algorithm and a closed-form solution based on association by clustering. The advantages and disadvantages of these techniques are determined and supported by the simulation examples. Also, a hybrid model, using these two methods and including an iterative process based on maximum likelihood (ML) is presented and analyzed in performance.

Performance of the interacting multiple model filter under high measurement rates

Interacting Multiple Model (IMM) is one of the most successful techniques proposed for maneuvering target tracking. The method works as a filter bank where each model represents a possible target motion and knows how the other models perform. One of the performance parameters, perhaps the least attended, is the predetermined Markov chain transition matrix. In this paper we present a study on how to determine the elements of the matrix and support it with simulation results.

HMM based track-before-detect strategy for FMCW/CW emitter detection

Detection of FMCW/CW (Frequency Modulated Continuous Wave / Continuous Wave) radars is a critical problem for applying electronic counter measures. Since these radars use continuous waves with very low amplitude levels, their detection is very difficult. In this work, a new HMM (Hidden Markov Model) based track-before-detect type iterative method for detection of FMCW/CWradars is proposed. In each iteration, instantaneous frequency of one single emitter is tracked and detection is performed based on the success of the track. Conducted experiments show that, proposed method can successfully identify FMCW/CWemitters in very low (-15dB) signal-to-noise ratios.

Emitter localization based on angle of arrival measurements using digital terrain elevation data

In this paper, passive localization of an emitter by using its estimated azimuth and elevation angles, with a single moving platform is analyzed. Beyond angle of arrival measurements, the distance between target and platform is estimated by using stored digital terrain elevation data (DTED) and a better performance is achieved compared to the direction-finding (DF) only method. Location estimates found by different DF lines are combined by minimizing a defined cost function. Since this problem has not a closed-form solution, two different search algorithms are used: grid search and particle swarm optimization (PSO). Speed and performance of these two algorithms are compared. After initial position of the target is estimated, with a new measurement (azimuth and elevation angle), and the estimated distance information by using these measurements, target position is updated with Kalman filter.

Direction finding with a rotating antenna

Finding the direction of the emitters is a problem to be solved in many areas. One of the methods used for that purpose is that using a rotating directional antenna and obtaining the direction estimate by processing the measured signal amplitudes. Direction estimation, in principle, is based on the own antenna pattern modulation on the measured signal. In the paper, direction estimates of one or more emitters are found with two different methods (matched filtering and Wiener deconvolution), and performances (signal-to-noise ratio, changing emitter power, etc.) of these methods are studied.

Wide beam synthesis via convex modelling

As the solid state technology develops and cheapens down, using the same antenna aperture for different applications requiring different beam patterns has become possible. Since different applications use different beam-widths, synthesis of beam patterns with different beam-widths and high effective radiated powers (ERP) by using the same antenna aperture is an important problem. In this work, a new method for synthesizing beam patterns which are uniformly localized in the given azimuth interval and suppressed in the remaining parts with high ERPs for linear antenna arrays by using the antenna weights is proposed. The problem is formulated as a convex optimization problem first for finding the optimal values of antenna weights yielding a uniform distribution of the beam pattern in the given azimuth interval. By using the iterative beam synthesis method, high ERP condition is satisfied. Experiments for different beam-widths show that the proposed method is capable of forming beam patterns with required beam widths and high ERPs.