Mustafa Secmen

Frequency Diverse Array Antenna with Periodic Time Modulated Pattern in Range and Angle

A general analysis of a frequency diverse transmit array antenna with a periodic modulated pattern in range, angle and time is presented. This antenna array system makes a continuous scanning in range and angle without using any phase shifters. The scanning is achieved using the frequency diversity by inserting a small amount of progressive frequency shift to each antenna element. The theory shows that there is the same modulation pattern in time, range and angle by taking the remaining two parameters fixed. The simulation results for radiation patterns of a binomial distribution array are presented. The expressions for determining the position and the angular bearing of a target for this type of antenna array system are given.

A Dual-Polarized Wide-Band Patch Antenna for Indoor Mobile Communication Applications

This paper proposes the conflguration of a dual- polarized wide-band patch antenna system suitable for indoor mobile communication applications. This conflguration consists of two patch antennas, which have difierent feed structures from classical patch antenna conflguration. These antennas, which are separated by a thin absorber to have a good isolation, are fed independently to obtain dual polarization. The antenna structure is designed, simulated, manufactured and measured. The operation bandwidth spans 1900{ 2700MHz covering Bluetooth, Wireless Local Area Networks (WLAN) and Universal Mobile Telecommunications System (UMTS) bands. The simulations show good agreement with the measurement results that the antennas have return losses higher than 15dB, and the coupling between two antennas is below i20dB within the operation band.

Hierarchical Reconstruction and Structural Waveform Analysis for Target Classification

Classification of objects from scattered electromagnetic waves is a difficult problem, as it heavily depends on aspect angle. To minimize this dependency, distinguishable features can be used. In this paper, we propose a target identification method in the resonance scattering region using a novel structural feature set based on the scattered signal waveform. To obtain robustness at low signal-to-noise ratio (SNR), a multiscale approximation is used for distortion correction prior to the feature extraction. This is achieved by an overlapping grid hierarchical radial basis function (HRBFOG) network topology, which is demonstrated to outperform existing HRBF techniques. The results obtained from the simulations and the measurements performed for various targets show high accuracy for classification with the proposed feature set, robustness through the use of HRBF at low SNR, and efficient computation in real time.

A compact corporate probe fed antenna array

This paper presents a linear antenna array system with a compact corporate feed network. The antenna elements are probe fed circularly polarized microstrip patch antennas. By using probe feed topology, it is possible to combine all the antenna elements on the backside of the array. Besides, the overall size of the feed network is reduced with the proposed special corporate feed topology. An 8 times 1 linear array is designed and produced as the building block of a larger 2D array. The antenna arrays return loss, radiation pattern and polarization characteristics give good agreement with the numerical calculations.

A novel electromagnetic target recognition method by MUSIC algorithm

This paper introduces a novel method for aspect invariant electromagnetic target recognition based on the use of multiple signal classification (MUSIC) algorithm to extract late-time resonant target features from the ultra-wideband scattered data. This approach achieves very high accuracy rates even at very low signal-to-noise ratio (SNR) values although it needs scattered data for classifier design at only a few different aspects and makes use of the MUSIC algorithm in a simple and computationally efficient way. Details of the theoretical background, the classifier design process and the demonstrations for conducting and dielectric spherical targets are presented in the following sections

The comparison of JADE based DOA estimation methods for unknown noncoherent source groups containing coherent signals with frequency matching

In this study, all parameters (including the frequency of each signal group) of direction-of-arrival (DOA) problem are aimed to be extracted in the presence of unknown noncoherent source groups, which are consisting of coherent signals. The antenna elements used in the fading analysis and application are isotropic, linear and uniformly distributed, and all parameters of the complete signal are assumed to be unknown except the number of coherent signal in each noncoherent group. To obtain the desired parameters (number of noncoherent groups, arrival angles, fading coefficients, frequencies), it is proposed a four-step approach. First, the number of noncoherent signal groups is determined by the minimum description length (MDL). Then, effective steering vectors are estimated using the joint approximate diagonalization of eigenmatrices (JADE) algorithm. In the third step, by using these steering vectors some popular high-resolution DOA methods such as the modified forward backward linear prediction (MFBLP), estimation of signal parameters via rotational invariance techniques (ESPRIT) and root multiple signal classification (MUSIC) algorithms are realized to calculate the angle and fading coefficient of each coherent signal. Finally, a frequency matching is realized to assign the possible frequency to each group. The proposed approach is summarized, and simulation results comparing the performance of high-resolution methods are demonstrated. According to the results, MFBLP is found to have better accuracy performances.

Null control in linear antenna arrays with ensemble differential evolution

This paper describes a synthesis method for null insertion in linear antenna array geometries by using newly proposed ensemble differential evolution (DE) algorithm. The given ensemble DE algorithm uses the advantages of several types of DE algorithms, and fuses them within a single algorithm. In the application, the algorithm searches for the minimization of the difference between the produced radiation pattern of the antenna array and desired radiation pattern, which contains null(s) at some specific aspect angle(s). Simulation results are illustrated for a Chebyshev radiation pattern and the effectiveness of the algorithm is validated. Besides, the results of ensemble DE algorithm are compared with bees algorithm, and the superiority of the proposed algorithm to bees algorithm is demonstrated.

Comparison of the Detection Performance of an FMCW Coastal Surveillance Radar for V and H Polarizations

The present work supports the use of V-polarization instead of H-polarization under CFAR detection in FMCW coastal surveillance radars due to its statistical advantage. The sea clutter reflectivity, sigma0 , is about 3-5 dB less for H-polarization than for V-polarization. However, the sea clutter echoes are spikier for H-polarization than V-polarization for a high resolution radar. It has been suggested that for a high resolution radar V-polarization is to be preferred over H-polarization for a fixed threshold detection below a critical radar height (Watts, 1996). The new numerical results for the detection performance of an FMCW radar with CFAR detection supporting the above argument will be given in the following sections.

Effective permittivity and permeability of dielectric resonator arrays in rectangular waveguide for metamaterial applications

The study describes the effective permittivity and permeability calculation of dielectric resonator arrays embedded in a WR90 rectangular waveguide structure. The scattering parameters are extracted and verified with full-wave simulations and measurements within 8-14 GHz. Then, the effective permittivity and permeability values are acquired with the retrieval method. The results reveal that the structure shows double negative (DNG) characteristics at some frequencies when the distance between resonators is close enough. Therefore, the structure can be considered in the design of metamaterial applications.

The comparison of LMS Based Algorithms For Active Cancellation Of Motor Noise

In this paper, an active noise cancellation system to decrease the motor noise arriving to car driver is proposed. This system can be considered as a feedforward control system since it enables taking motor noise as the reference signal. The coefficients of adaptive filters in this structure are obtained with LMS (Least Mean Square) algorithm. In this study, both standard (LMS and normalized LMS) and more advanced (variable tap length LMS and variable step size LMS) LMS algorithms are used and their performances are compared. For the different models belonging to different configurations of the system, the acoustic noise simulations, which contains real noise signal belonging to motor of an accelerated car, are realized. According to the results of these simulations, the advanced LMS algorithms are observed to converge more rapidly and have better error performances within whole signal and steady-state as compared to classical algorithms.