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    Detection of Moving Targets by Passive Radar Using FM Signals on Moving Platforms
    (Univ Osijek, Tech Fac, 2022) Ileri, Kadir; Tezel, Necmi Serkan
    In this study, using FM radio signals for transmitters of opportunity, detection of moving targets by passive radar on moving platforms is investigated. Ground reflectivity is modelled as discrete patch approximation with uniform distribution in phase and Rayleigh distribution in amplitude. The target echo is modelled as Doppler shifted and delayed form of the transmit signal based on the target's angular position, range, and velocity. The clutter echoes, received by surveillance antennas, are also modelled by the superposition of Doppler shifted and delayed form of the transmit signal. Displaced Phase Center Array (DPCA) method is used for clutter rejection and moving target detection. Both matched filter and reciprocal filter are used in the pulse compression stage. The performance of the proposed method is evaluated by using an improvement factor (IF). DPCA with reciprocal filter outperforms DPCA with matched filter with the improvement value of 5,1 dB due to the reciprocal filter producing time -invariant impulse responses.
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    Effects of pH on the optical, structural and supercapacitive properties of BiTe thin films produced via CBD
    (Indian Acad Sciences, 2021) Tezel, Necmi Serkan; Tezel, Fatma Meydaneri; Kariper, Ishak Afsin
    In this study, BiTe thin films are grown on glass substrates by chemical bath deposition method, at different pH levels. Crystallographic structures, crystal dimensions, dislocation densities and crystallization numbers of thin films are characterized by X-ray diffraction, whereas surface morphologies, roughness and film thicknesses are characterized by scanning electronic microscopy and atomic force microscopy. Surface tensions are calculated by Zisman method using different liquids. Capacitance, energy and power densities are calculated for each pH level by using time-dependent current-voltage measurements. Monocrystalline thin films of Bi2Te3 are observed at pH 3 and Bi4Te5 at pH 11, whereas polycrystalline Bi2Te3 and Bi4Te5 structures are formed at pH 7 and 9, respectively. Surface roughness and film thicknesses of polycrystalline thin films are found to be significantly higher than monocrystalline thin films. Capacitance, energy and power density of BiTe thin films produced at pH 3, 7, 9 and 11 are calculated as 503, 562, 569 and 512 F g(-1); 55.19, 61.66, 62.43 and 56.17 Wh kg(-1); and 3311.4, 3699.6, 3745.8 and 3370.2 W kg(-1), respectively. These results show that capacitance, energy and power density of polycrystalline thin films produced at pH 7 and 9, which have high surface load activity, are higher. Electrical resistivity of Bi2Te3 and Bi4Te5 monocrystalline films are lower than those of the polycrystalline BiTe films.
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    Electromagnetic scattering from a isotropic inhomogeneous impedance cylinder of arbitrary shape
    (Natl Inst Optoelectronics, 2016) Tezel, Necmi Serkan; Tezel, Fatma Meydaneri
    In this study, the electromagnetic scattering from anisotropic inhomogeneous impedance cylinder of arbitrary shape is presented for both TM and TE plane wave illuminations. In the solution of scattering problem, scattered TE and TM fields are expressed as single layer potentials. Using the boundary condition and jump relations of single layer potential on the boundary, boundary integral equation is obtained and solved via Nystrom method. Obtained results are compared with those obtained by analytical method for inhomogeneous anisotropic impedance cylinder and good agreements are observed.
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    The Impact of Channel Errors in Passive Coherent Location Radar using FM Base Stations
    (Gazi Univ, 2022) Ileri, Kadir; Tezel, Necmi Serkan
    This paper presents the impact of channel errors for an FM based passive bistatic radar system mounted on mobile platforms for ground moving target indication (GMTI). Reciprocal filter, which is effective compared to conventional matched filter (MF), is performed for the pulse compression stage to remove the time-variant structure of the signal. The displaced phase centre antenna (DPCA) method is applied for the clutter cancellation and target detection. This technique is effective if the hardware is well calibrated. Thereby, the influences of calibration errors between the receiving channels are studied for different FM waveforms. The simulation results of the amplitude and phase errors are analysed separately.
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    The impact of channel errors in passive coherent location radar using fm base stations
    (2022) Ilerı, Kadir; Tezel, Necmi Serkan
    This paper presents the impact of channel errors for an FM based passive bistatic radar system mounted on mobile platforms for ground moving target indication (GMTI). Reciprocal filter, which is effective compared to conventional matched filter (MF), is performed for the pulse compression stage to remove the time-variant structure of the signal. The displaced phase centre antenna (DPCA) method is applied for the clutter cancellation and target detection. This technique is effective if the hardware is well calibrated. Thereby, the influences of calibration errors between the receiving channels are studied for different FM waveforms. The simulation results of the amplitude and phase errors are analysed separately.
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    The impact of pH on the structural, surface, electrical and optical properties of nanostructured PbSe thin films
    (Iop Publishing Ltd, 2019) Tezel, Necmi Serkan; Tezel, Fatma Meydaneri; Kariper, I. Afsin
    This study involves PbSe deposits fabricated on glass substrates at different pH. Some optical properties of these deposits, including reflectance, extinction coefficient, refractive index, and dielectric constant were calculated by using absorbance values at room temperature with UV spectrophotometer according to wavelength. The surface properties and compositions were examined by SEM and EDX, respectively. Surface tensions were measured by Zisman Method, and obtained to be 39.0, 42.1, 43.1 and 39.1 mNm(-1) for pH: 8, 9, 10 and 11 values, respectively. The optical band gaps (Egap) were calculated as 2.17, 1.82, 1.77 and 2.27 eV for pH: 8, 9, 10 and 11, respectively. PbSe deposits' electrical resistivity was measured via four-point probe technique depending on deposits thicknesses, and they were found to be 65.27, 26.21, 39.87 and 36.03 Omega cm for pH: 8, 9, 10 and 11, respectively.
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    A New Approach to Pilot Contamination in Massive MIMO Systems for 5G Communication Networks with Butterfly Optimization Algorithm
    (Gazi Univ, 2022) Altiraiki, Salah; Tezel, Necmi Serkan
    Communication technologies, in particular fifth-generation (5G) mobile phones, are currently developing around the world. Massive multi-input-multi-output (MIMO) systems are usually used in this type of communication network so that a large number of users are able to connect to the network and use its services. Massive MIMO systems are a good solution for 5G communication networks leveraging antennas to improve communication performance. To increase output communication power in 5G networks, the problem was optimized with the butterfly optimization algorithm (BOA). According to the simulation results, the proposed method outperformed other similar communication methods, such as the Random, SPRS, WGC PD and SPRS+WGC PD algorithms in terms of the signal-to-interference-plus-noise ratio (SINR) and rate of connection of users to the network.
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    A new approach to pilot contamination in massive mimo systems for 5g communication networks with butterfly optimization algorithm
    (2022) Altıraıkı, Salah; Tezel, Necmi Serkan
    Communication technologies, in particular fifth-generation (5G) mobile phones, are currently developing around the world. Massive multi-input-multi-output (MIMO) systems are usually used in this type of communication network so that a large number of users are able to connect to the network and use its services. Massive MIMO systems are a good solution for 5G communication networks leveraging antennas to improve communication performance. To increase output communication power in 5G networks, the problem was optimized with the butterfly optimization algorithm (BOA). According to the simulation results, the proposed method outperformed other similar communication methods, such as the Random, SPRS, WGC PD and SPRS+WGC PD algorithms in terms of the signal-to-interference-plus-noise ratio (SINR) and rate of connection of users to the network.
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    Radio Frequency Transient Segment Detection Based on Akaike Information Criterion
    (Gazi Univ, 2022) Ajouat, Saleh Abulgasem; Tezel, Necmi Serkan
    The precise interpreting of RF data starts from retrieving or knowing the exact time instant at which moment the sender is turned on, this challenge implies two important issues; prevent manipulating redundant information such as unavoidable background noise which speed up the processing and the other issue is to study the exact behavior of that sender. A method has been developed to automatically catch the onset in transient of Bluetooth signal using of the Akaike Information Criterion (AIC). Present method has been examined on real world data taken from the most common cellular phones brands by different ways with variation of signal to noise ratio. The AIC algorithm shows robustness in the existence of relatively a high-amplitude random noise.
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    Radio frequency transient segment detection based on akaike information criterion
    (2022) Tezel, Necmi Serkan
    The precise interpreting of RF data starts from retrieving or knowing the exact time instant at which moment the sender is turned on, this challenge implies two important issues; prevent manipulating redundant information such as unavoidable background noise which speed up the processing and the other issue is to study the exact behavior of that sender. A method has been developed to automatically catch the onset in transient of Bluetooth signal using of the Akaike Information Criterion (AIC). Present method has been examined on real world data taken from the most common cellular phones brands by different ways with variation of signal to noise ratio. The AIC algorithm shows robustness in the existence of relatively a high-amplitude random noise.
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    Surface and electro-optical properties of amorphous Sb2S3 thin films
    (Springer Heidelberg, 2019) Tezel, Necmi Serkan; Tezel, Fatma Meydaneri; Kariper, I. Afsin
    Sb2S3 thin films to be used in optoelectronic applications were produced on glass substrates, via chemical bath deposition method (CBD) at different pH values. The optical properties of these films such as T%, R%, n, k, epsilon(1) and epsilon(2) (real and imaginary) were calculated using the absorbance values measured at room temperature with UV spectrophotometer. Critical surface tension was measured by Zisman method, and found as 43.2, 97.4, 150.7 and 123.8 mN/m for pH: 9, 10, 11 and 12. Film thicknesses and surface roughness (R-q) were measured to be 125; 412; 205 and 138nm, and 1.64; 30.31; 49.49 and 19.76nm for pH: 9, 10, 11 and 12, respectively. Optical band gap (E-gap) was calculated as 2.24; 2.11; 2.25 and 2.32eV for pH: 9, 10, 11 and 12, respectively. Average electrical resistivity of the Sb2S3 thin films was calculated to be 35.41; 36.81; 36.76 and 28.72 cm for pH: 9, 10, 11 and 12, respectively. According to the results obtained, usage areas of these films in optoelectronic applications are discussed.