Caner Ozdemir | Mersin University (original) (raw)

Papers by Caner Ozdemir

In this paper; the capability of compressed sensing (CS) for near-fleld inverse synthetic apertur... more In this paper; the capability of compressed sensing (CS) for near-fleld inverse synthetic aperture radar (ISAR) imaging is addressed. Considering two-dimensional, millimeter- wave ISAR imaging geometry, a CS-based reconstruction technique is developed and its potential is assessed through numerical simulations and measurements applied to hypothetical as well as various complex targets. It is shown for most cases that the target shapes can be accurately and su-ciently reconstructed from a very low number of samples of the whole collected data (e.g., 1.7%) thereby demonstrating the validity of the CS technique. Nevertheless, it is also shown that, the increasing complexity (i.e., low sparsity) of the target scene may somewhat degrade the success of the approach.

In this study, a filtering method based on the threshold value of normalized synthetic aperture r... more In this study, a filtering method based on the threshold value of normalized synthetic aperture radar (SAR) data is proposed to eliminate clutter in millimeter wave ground based synthetic aperture radar (GB-SAR) images. In the proposed method, first, stepped frequency continuous wave SAR data are reconstructed by using the back-projection algorithm and focused complex SAR data are obtained. Then, the amplitude values of the complex SAR data are normalized and the best threshold values to distinguish the target from clutter is determined by the OTSU's thresholding method. Next, a filter mask is created that cancels all data below the computed threshold values. The mask matrix is finally multiplied with the resulted GB-SAR data to eliminate all clutter from the image. With the proposed technique, the best threshold value is determined automatically by directly processing the raw data without converting the SAR data into any RGB images. The proposed technique is validated through real GB-SAR experiments that were carried out in the frequency band of 78-81 GHz. In the experiments, challenging GB-SAR data are obtained using high cluttered background materials, and very successful filtering operations are performed with the proposed technique.

International Journal of Engineering and Geosciences, 2020

Journal of Electrical and Computer Engineering, 2017

An algorithm for detecting cavities inside a tree-body is presented with simulation and measured ... more An algorithm for detecting cavities inside a tree-body is presented with simulation and measured examples. The details of the imaging algorithm that is based on sinusoidal template focusing routine are given. First, the algorithm is tested with the simulation scenario for which perfect reconstruction of the simulated cavity structure together with tree-body is successfully formed in MATLAB programming environment. Then, the algorithm is applied to the measurement data that have been collected from a laboratory set-up. Collected backscattered measurements from the tree-body (with cavity) structure are used to generate the image of the scene by the help of our proposed algorithm. The resultant radar images of the measured data collected from the laboratory arrangement have shown the applicability of the developed algorithm for the detection of cavity structures inside tree-bodies.

Turkish Journal of Engineering, 2017

In this paper, we propose an ultrawide band design for the double ridged horn (DRH) antenna to be... more In this paper, we propose an ultrawide band design for the double ridged horn (DRH) antenna to be used behind the obstacle radar (BOR) applications such as ground penetrating radar (GPR) and through the wall radar (TWR) imaging. The design is developed and optimized by the help of full electromagnetic simulator code; CST. The design parameters such as frequencies of operation and the half power beam width (HPBW) are taken into account by considering the BOR application requirements. The design double ridged horn antenna provides a frequency bandwidth between 1.5 GHz and 7 GHz and HPBW around 30° around the center frequency that are very suitable for GPR and TWR applications. The final optimized design that is formed by CST is physically manufactured and measured. The prototyped DRH antenna's measurement antenna parameter results are in good agreement with the simulated ones.

2015 IEEE Radar Conference, 2015

In this work, we present radiometric images for several concealed object experiments that were me... more In this work, we present radiometric images for several concealed object experiments that were measured at TUBITAK - Marmara Research Center (MRC) facilities. The radiometric imaging system that collects the cosmic background radiation from the target is utilized on a 2D data collection grid to have the millimeter-wave image of the target. A detection algorithm is developed to point out the region of the hidden object beneath the cloth. The raw and processed passive millimeter wave images of various targets with concealed objects are shown after applying our detection algorithm. The resultant images have demonstrated that the passive imaging system together with our detection routine produces successful images of the targets.

In this work, several cancellation techniques for undesired clutter in various SAR images are pre... more In this work, several cancellation techniques for undesired clutter in various SAR images are presented. As a good example of SAR imagery, publicly released MSTAR images are taken as the practical application. The modelling of clutter is done by probabilistic approach. Target detection techniques including CFAR (Constant False Alarm Rate) is applied. To find the best fit for the background clutter, higher-order statistics are implemented and various distributions from Rayleigh to Weibull are tested. By using adaptive threshold CFAR detectors MSTAR targets are effectively segmented from clutter backgrounds.

2008 14th European Wireless Conference, 2008

... 2261-2268. [7] Kucuk K., Kavak A., and Yigit H.: Smart Antenna Module using OMNeT++ for Wirel... more ... 2261-2268. [7] Kucuk K., Kavak A., and Yigit H.: Smart Antenna Module using OMNeT++ for Wireless Sensor Network&amp;quot;, 4th IEEE International Symposium on Wireless Communication Systems, Norway, (2007). [8] Nasipuri A ...

2008 IEEE Radio and Wireless Symposium, 2008

In this work, we introduce a novel location estimation technique which uses adaptive antenna arra... more In this work, we introduce a novel location estimation technique which uses adaptive antenna arrays (AAA) at the central node in wireless sensor networks (WSN). This localization technique can be used at the setup phase in the routing protocol. This technique is based on scanning the desired region in azimuth and radial directions by changing parameters of downlink beam. This sweeping process can activate the nodes in the desired region which is specified by beamwidth and beamdirection of the transmit beam and also by minimum and maximum thresholds (R min and R max) for the received signal strength indicator (RSSI). Active nodes in the desired region transmit their IDs and RSSI levels via multi hop communication to the central node. Unlike GPS-based or beacon based localization techniques, the proposed technique does not require any modification in the sensor nodes. The accuracy of location estimation depends on beamdirection, beamwidth and transmit power for downlink beams. The results show that by carefully adjusting these parameters, desired performance can be achieved.

Wireless Personal Communications, 2008

Development of practical algorithms for beamforming in 3G CDMA systems and their software radio i... more Development of practical algorithms for beamforming in 3G CDMA systems and their software radio implementations are still a challenging task, which will facilitate upgrading of traditional base stations into smart antenna capable 3G base stations. In this paper, we propose a practical space-code correlator (SCC) receiver structure for its software radio implementation a DSP. SCC's advantage comes from the fact that it doesn't require any training sequence or learning parameter as in other algorithms (LMS or CM). DSP implementations of the SCC are performed using Texas Instruments C67xx family platforms. In the simulations, reverse link base band signal format of CDMA2000 is used and the effects of different array topologies (uniform linear array-ULA or uniform circular array-UCA) are considered. The implementation results regarding beamforming accuracy, weight vector computation time (execution time), search resolution effect on DOA estimation accuracy, DSP resource utilization, and received SINR are presented. The results show that DSP based SCC beamformer can estimate weight vectors within less than 10 ms with DOA search resolution of 2 • especially when C6713 DSP is used. With faster DSPs and

Mathematical Problems in Engineering, 2013

International Journal of Infrared and Millimeter Waves, 2007

IEEE Access, 2020

An assessment of polarimetric inverse synthetic aperture radar (Pol-ISAR) imaging is accomplished... more An assessment of polarimetric inverse synthetic aperture radar (Pol-ISAR) imaging is accomplished for realistic target models with the use of our recently developed high-frequency radar cross-section simulator tool called PREDICS. X-band, narrow-angle and full-polarimetric ISAR data for the CAD models of the well-known test object SLICY and a ground vehicle, namely a backhoe loader are analyzed to infer their structural characteristics. Experimental data obtained from a tower-turntable ISAR measurements of a T-72 tank target have also been utilized to assess the validity of the simulator. First, the intensity images in linear and circular polarization bases are directly utilized to evaluate the data quality and to characterize target features for classification. Then, the Pauli image decomposition scheme is applied to separate the basic scattering mechanisms occurring at target pixels. The identifiable canonical target forms are successfully extracted as single, double and multi-bounce scattering mechanisms that are pinpointed at their true locations. The results indicate that PREDICS is able to generate high-fidelity synthetic Pol-ISAR signatures of complex targets whereby successful interpretation of innumerous target scattering mechanisms and features can be achieved through Pauli decomposition scheme for classification purposes. INDEX TERMS PREDICS radar cross-section (RCS) simulator, inverse synthetic aperture radar (ISAR), Pauli decomposition, polarimetric ISAR.

2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama), 2018

The microwave backscattering from a complex environment is subject to numerous factors such as wa... more The microwave backscattering from a complex environment is subject to numerous factors such as wavelength, viewing geometry, polarization of the transmitted wave and target attributes including roughness, shape, size, orientation and dielectric properties. Therefore, the characteristics and amount of backscatter data varies from case to case. In an effort to better understand this complex mechanism of backscattering from distributed surfaces, the SAR image characteristics of a typical land area are assessed through a readily feasible polarimetric ground-based synthetic aperture radar (GB-SAR) system working at L-band frequencies. Because of their standard use in data calibration, trihedral corner reflectors (TCR) as well as dipole-like objects are also deployed in the measurements to extract their polarimetric GB-SAR image features.

Microwave and Optical Technology Letters

2018 22nd International Microwave and Radar Conference (MIKON)

Horizontally polarized patch antenna array design is proposed for frequency modulated continuous ... more Horizontally polarized patch antenna array design is proposed for frequency modulated continuous wave (FMCW) marine radar applications. The array consists of series-parallel fed 96 elements printed on microwave substrate. The array configuration is optimized for minimum line loss and maximum aperture efficiency. The target frequency band is 9.3–9.4 GHz. Antenna parameters such as return loss, peak gain, half-power beam width and side-lobe levels are presented for marine radar applications.

This paper presents a simple method for determining the dielectric constant of microwave PCB subs... more This paper presents a simple method for determining the dielectric constant of microwave PCB substrates. In the presented method, a bandpass microstrip filter on the PCB substrate with a user-predicted dielectric constant value is designed for a given center frequency, and it is implemented. The simulation results of the designed bandpass filter are obtained by the help of electromagnetic analysis software; XFDTD. Experimental results regarding the filter frequency characteristic are accomplished by means of a vector network analyzer. The simulation results of the designed filter are modified to overlap with the experimental ones by varying the dielectric constant value. When the simulation and experimental results are overlapped, the value of dielectric constant is accurately selected. In order to illustrate the validity of proposed method, the dielectric constant values of flame resistant-4 (FR4) substrates are acquired at IEEE 802.11b/g and IEEE 802.11a wireless local area networ...

2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama)

In this study, we present Passive Millimeter Wave (PMMW) radiometric images for several concealed... more In this study, we present Passive Millimeter Wave (PMMW) radiometric images for several concealed object experiments. PMMW is an imaging technique that is realized by collecting the existing cosmic background radiation (CBR) from the target and surrounding environment based on their temperatures and electromagnetic wave reflectivity. PMMW imaging, one of the detection and classifying methods for determining and localizing concealed objects in the cases where security is prioritized is presented without employing any active radiation and so preventing the human health. We present a detection algorithm based on the histogram of the raw data and applying an auto-segmentation routine to the data.

In this study, an experimental study on Through-the-Wall radar imagery was ac- complished for the... more In this study, an experimental study on Through-the-Wall radar imagery was ac- complished for the purpose of imaging life-sign symptoms. The proposed system is based on a stepped frequency continuous wave radar with the help of a Vector Network Analyzer (VNA- Agilent E5071B ENA), antenna (C-band), and the control computer. Breathing and heartbeat information is extracted from the backscattering electromagnetic fleld exploiting a change detec- tion routine. The experimental results show that both breathing and the heartbeat signatures from real human beings are gathered. 1. INTRODUCTION Through-the-Wall Radar (TWR) is an emerging technology which is very useful for detecting and identifying unknown objects behind walls. It can be used in difierent applications ranging from survivor detection in rescue, hostage operations, to people localization in anti-terrorist operations or life detecting under earthquake rubble (1). Recently, microwave Doppler radars were developed for remote sens...

In this study, an efficient and practical approach is proposed to increase the bandwidth of narro... more In this study, an efficient and practical approach is proposed to increase the bandwidth of narrow-band antennas by designing lossless impedance matching network with the simplified real frequency technique. Our algorithm does not require prior knowledge of network analytical topology of the load impedance that is to be matched. Any frequency-dependent data such as antenna radiation data (either measurement or simulated) can be easily matched via the proposed algorithm. The matching network realized by this technique is relatively simple and gives superior gain properties compared to that obtained by other methods. The proposed method is tested with various data sets for different antenna configurations. The results validate the effectiveness and the success of the algorithm.