han Gok

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.

Sub-band equalization of modulated wideband converter for improved dynamic range performance

In this work, we propose a new method to improve the dynamic range performance of the Modulated Wideband Converter (MWC), which is multi-channel sampling system for digitizing wideband sparse signals below the Nyquist limit without loss of information by using compressive sensing techniques. MWC achieves high dynamic range assuming that subband frequency responses of the system are identical. However, in hardware implementations of MWC, the resulting sub-band frequency responses are not identical and dynamic range performance of the system drops significantly which makes it unusable in practical applications. Proposed method iteratively designs FIR filters for equalizing frequency responses of the all sub-bands. Obtained results from the extensive computer simulations of the MWC system show that proposed method improves the dynamic range performance of the MWC system significantly.

Radar fingerprint extraction via variational mode decomposition

In iMs paper, a novel method for extracting radar fingerprint using the unintentional modulation on radar signals is proposed. Proposed technique decomposes the unintentional modulations into its components using Variational Mode Decomposition (VMD) technique. Then, features that characterize each component are calculated. Simulations using real radar data show that proposed technique can classify radars in the dataset with high performance.

SNR improvement in electronic support measures systems via pulse integration

In ESM (Electronic Support Measures) systems, detection of intentional or unintentional modulation on pulses requires high SNR. By integrating the collected pulses emitted from the radar, SNR can be increased. For utilizing pulse integration, all the pulses should be aligned in time very accurately. In this work, we propose a new method, which estimates the time shifts between the pulses with very high accuracy and resolution. Experiments on both synthetic and real data sets show that proposed method aligns the radar pulses very successfully.

Faster OMP computations by sensing matrix column reduction

Compressed sensing is an emerging technique that allows to reconstruct sparse signals sampled at sub-Nyquist rates. However, it requires high computational effort to reconstruct the compressively sampled signal, which makes real-time application of it very hard. We therefore, present a novel, generic method that decreases the computational complexity of Orthogonal Matehing Pursuit (OMP) like reconstruction algorithms that exploit the correlation of columns of a dictionary (sensing matrix). The proposed method reduces the column number of the dictionary in a systematic manner to speed up the correlation calculations. Simulation results show that in sparse scenarios, reconstruction speed increases significantiy with a negligible decrease in the reconstruction accuracy.

Sub-band equalization filter design for improving dynamic range performance of modulated wideband converter

In this work, we propose an iterative method to improve the dynamic range performance of the Modulated Wideband Converter (MWC), which is multi-channel sampling system for digitizing wideband sparse signals below the Nyquist limit without loss of information by using compressive sensing techniques. Our method jointly designs FIR filters for each sub-band to equalize the frequency response characteristics of the all sub-bands of the MWC. Obtained results from the extensive computer simulations of the MWC system show that the proposed method improves the dynamic range performance of the MWC system significantly.

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.