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Databases : Web of Science Core ... ✕Researcher : Mehmet ERTUĞRUL ✕
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Prof. Dr. Mehmet ERTUĞRULMühendislik Fakültesi
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Broadband, Stable, and Noniterative Dielectric Constant Measurement of Low-Loss Dielectric Slabs Using a Frequency-Domain Free-Space Method

Mehmet ERTUĞRUL

A broadband, stable, and noniterative free-space method is proposed for dielectric constant ε′r determination of low-loss dielectric slabs from reflection-only measurements through simple calibration standards (reflect and air). It is applicable for dispersive samples and does not require thickness information. Simulations of nondisperive and dispersive samples are performed to validate our method. Dielectric constant measurements of polyethylene and polyoxymethylene samples (9–11 GHz) are carried out to examine the accuracy of our method.

Article 2022 Mühendislik Fakültesi IEEE Transactions on Antennas and Propagation70 ( 12 ) 65 Views
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Artificial Neural Network Model for Evaluating Parameters of Reflection-Asymmetric Samples From Reference-Plane-Invariant Measurements

Mehmet ERTUĞRUL

A technique based on artificial neural network (ANN) is proposed to extract the electromagnetic properties of reflection-asymmetric samples from reference-plane-invariant (RPI) scattering parameter measurements. It first determines reference plane transformation distances and then extracts the material properties. The number of neurons in the hidden layer of the ANN model was evaluated subject to accuracy and time constraints. We examined the conformity of the dataset of the ANN model and the required time for the training process by considering different numbers of neurons in the selected hid ...More

Article 2023 Mühendislik Fakültesi IEEE Transactions on Instrumentation and Measurement72 62 Views
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Excitation wavelength dependent triple-mode photoluminescence of copper-based halides for advanced anti-counterfeiting

Mehmet ERTUĞRUL

New fluorescent materials with a low cost, hypotoxicity, and concealment are desired for the application of anti-counterfeiting. Herein, we report a CsCu2I3@Cs3Cu2I5 composite with a triple-mode photoluminescence (PL) feature by simply adjusting the excitation wavelengths, which are ascribed to the multiple excited states of different phases in the CsCu2I3@Cs3Cu2I5 composite. The broadband emission and high quantum yield (∼51) of the composite originate from the structure-oriented self-trapped excitons effect of Cs3Cu2I5 and CsCu2I3 phases. Moreover, the incorporation of polyethylene oxide (PE ...More

Article 2023 Mühendislik Fakültesi APL Materials11 ( 7 ) 38 Views
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Temporal Reflection Response of Plane Waves Within an N-Layer Structure Involving Bianisotropy

Mehmet ERTUĞRUL

The temporal reflection response of an N -layer composite structure involving bianisotropic behavior is examined for the first time in the literature. Toward this goal, the wave matrix (WM) method, which is fundamental, relatively easier to apply, and compact and iterative suitable for analysis of multilayer structures, is first extended to the analysis of an interface separating two different media involving bianisotropy. Next, the reflection response of the whole structure is derived in terms of series form to better analyze its temporal behavior. Then, frequency-domain and time-domain respo ...More

Article 2023 Mühendislik Fakültesi IEEE Transactions on Antennas and Propagation71 ( 7 ) 46 Views
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Extraction Method for Unique Determination of Complex Permittivity from Graphical Analysis of Natural Frequencies

Mehmet ERTUĞRUL

A time-domain free-space extraction procedure is proposed to uniquely determine the relative complex permittivity ϵr (ω) based on two sets of natural frequencies of the metal-and air-backed dielectric samples. A graphical analysis is applied for evaluating whether unique ϵr (ω) can be extracted using such natural frequencies. The method is numerically validated using two dielectric samples with different ϵ (ω) for the ideal case (no noise) and under the influence of noise with different signal-to-noise ratios (SNRs). Keyword: graphical method; natural modes; parameter extraction; unique soluti ...More

Article 2023 Mühendislik Fakültesi IEEE Transactions on Antennas and Propagation71 ( 9 ) 19 Views
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Easy-to-Implement Ultra-Thin, Wide-Band, and Multi-Functional Polarization Converter for K and Ka Band Applications

Mehmet ERTUĞRUL

This article presents an ultrathin, broadband, and multipurpose polarization converter design utilizing an anisotropic metasurface for K and Ka band. The proposed polarization converter, which has a single layer F4B as a substrate material with hexagonal-shaped metallic solid structure along with hexagonal ring with diagonal splits on its front surface and a background (a completely metallic surface) on its back, works as not only a circular polarization converter but also a linear polarization to circular polarization (LP to CP) converter. Its polarization conversion rate (PCR) is more than 9 ...More

Article 2022 Mühendislik Fakültesi Advanced Theory and Simulations5 ( 4 ) 128 Views
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Determination of Propagation Constants and Wave Impedance of Non-Reciprocal Networks From Position-Insensitive Waveguide Measurements

Mehmet ERTUĞRUL

A microwave method is proposed to determine the forward and backward propagation constants (gamma ⁺ and gamma ⁻) and the wave impedance ( z_w ) of reciprocal and non-reciprocal microwave networks whose positions are not known within their measurement cells (position-insensitive). The proposed method relies purely on analytical expressions and can also evaluate the reference plane transformation distances. Scattering parameter measurements at the X-band (8.2-12.4 GHz) of a reciprocal network (a waveguide straight) and a non-reciprocal network (a microwave phase shifter) arbitrarily positioned i ...More

Article 2022 Mühendislik Fakültesi IEEE Transactions on Microwave Theory and Techniques70 ( 5 ) 59 Views
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Improved Method for Permittivity Determination of Dielectric Samples by Free-Space Measurements

Mehmet ERTUĞRUL

A new deembedding technique is proposed for relative complex permittivity epsilon(r) determination of dielectric materials using gated free-space measurements. Its three main features are 1) it does not require any formal calibration procedure (calibration-free); 2) it is position-insensitive; and 3) it extracts ripple-free epsilon(r) due to gating process. The objective function derived to determine epsilon(r) by the proposed method is validated by free-space measurements of three dielectric samples (polypropylene, polyethylene, and polyoxymethylene). Besides, the accuracy of our method is co ...More

Article 2022 Mühendislik Fakültesi IEEE Transactions on Instrumentation and Measurement71 86 Views
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Thermally Processed Quantum-Dot Polypropylene Composite Color Converter Film for Displays

Mehmet ERTUĞRUL

Quantum dots (QDs) have attracted much attention as one of the most promising candidates for next-generation display materials. However, stability is still a big challenge for QDs. Herein, we encapsulated QDs in a thermoplastic polypropylene (PP) matrix by thermal processing technology to prepare a stabler color conversion film for the first time. Thermal processing technology expands the packaging materials of QDs from traditional soluble polymers to thermoplastic polymers such as PP with easy processing and a low cost. We showed that the QDs in the PP film exhibited longerlasting stability t ...More

Article 2022 Mühendislik Fakültesi ACS Applied Materials & Interfaces14 ( 27 ) 73 Views
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Enhancing the stability of environmental resistance of alloyed CdZnSeS@ZnS quantum dots by doping Ti ions into shell layer

Mehmet ERTUĞRUL

Colloidal quantum dots (QDs) are promising luminescent materials for display and lighting, but their stability has long been an issue. Here, we designed a passivation strategy of doping Ti ions into the shell of alloyed CdZnSeS@ZnS QDs. The results showed that Ti ions were successfully doped into the ZnS shell and the stability of QDs was improved. In the aging test, the Ti ions doped QDs maintained 51.4 of the initial performance after 90 h of aging, while the pristine QDs decreased to less than 25 of the initial value. In addition, we discuss the reasons why Ti ions doping improves the stabi ...More

Article 2022 Mühendislik Fakültesi Nanotechnology33 ( 50 ) 45 Views
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Self-filtering narrowband perovskite photodetector with ultra-narrowband and high spectral rejection ratio

Mehmet ERTUĞRUL

Narrowband photodetectors have broad application prospects in many fields where only a range of specific wavelengths of light needs tobe detected. However, the current narrowband detectors have some disadvantages, such as the integration is difficult, the full width at half-maximum is not narrow enough, and the spectral rejection ratio is not ideal (< 20). Here, we present a self-filtering photodetector basedon MAPbX3single crystals with a very narrow spectral response and a full width of 15 nm at half maximum. It also shows a high responsivity (similar to 100 mA/W) and a high spectral rejecti ...More

Article 2022 Mühendislik Fakültesi APL Materials10 ( 10 ) 41 Views
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Graphical Method for Examining Complex Natural Frequencies of Dispersive Materials

Mehmet ERTUĞRUL

A graphical method is extended to and applied for visual inspection of solution patterns (region of complex natural frequencies sn) in the complex s-plane for dispersive materials characterized by the Debye and Lorentz models. These patterns are in the form of exponential decay and C-shaped profiles for the Debye and Lorentz models, respectively. Their forms are observed to be affected (e.g., moving left/right) in different manners with a variation of dispersion parameters. This method, thanks to its visual inspection capability, can help in analyzing/synthesizing filters and frequency-selecti ...More

Article 2021 Mühendislik Fakültesi IEEE Microwave and Wireless Components Letters31 ( 5 ) 132 Views
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