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Öğe 4G C-Shaped compact microstrip antenna design and production(Pamukkale Univ, 2017) Yuzer, Ahmet Hayrettin; Seker, CihatIn this paper, an application for a monopole antenna which complies with worldwide interoperability for microwave access (WiMAX) is presented. The proposed antenna operates in the frequency range of 3.43-3.61 GHz applicable for WiMAX. The antenna is fabricated on FR4 plate of 33.25 x 33.25 x 1.6 mm3. The performance of the antenna is analyzed in terms of radiation pattern, gain and s-parameters. The s-parameter of the antenna are verified through measurements. The obtained results illustrate that the presented antenna has better characteristics in terms of operating band as well as return loss as compared to the antennas previously published in the literature.Öğe Association of memory terms in a power amplifier modeling functions to the circuit components(Taylor & Francis Ltd, 2018) Yuzer, Ahmet Hayrettin; Dursun, ErhanThe main purpose of this study is to find a relation between power amplifier (PA) circuit component values and delay terms of the PA model polynomial by using measurement results. A PA designer can use this relation to determine component values while designing memoryless/linear PAs. For this purpose, a behavioral model with memory is worked on; the model, modeling approach, experimental set-up and results are presented. Memory depths are determined for a 1-2GHz 10W Class AB power amplifier with parametric results. The advantages of the elaborated model are presented. Relations between the bias circuit components and the memory terms are investigated.Öğe Design and implementation of a spirometric measurement system that can measure COPD parameters(Pamukkale Univ, 2022) Sumbuli, Harun; Yuzer, Ahmet HayrettinThe importance and need for respirators has once again shown itself due to the coronavirus (Covid-19) epidemic, which has recently spread around the world and has been declared as a Pandemic (epidemic worldwide) by the world health organization. Monitoring respiratory activity plays a vital role in detecting respiratory diseases such as Chronic Obstructive Pulmonary Disease (COPD). In this study, a working group of 6 participants was formed to measure respiratory parameters. Each individual was provided to perform FVC, VC, MVV, RR and TV performance. The measurements were carried out simultaneously with the medical spirometer device. A total of 1860 data (1500 data for VC, 360 data for MVV) were sampled and all data were analyzed in Matlab program. It was observed that the results obtained were quite similar to each other (RMVV=0.998 for MVV; RVC=0.997 for VC). One of the most important contributions of this study is that the measured data can be sent to the computer and saved to the SD card. Thus, with the thermal printers in standard spirometers, paper wastage was prevented and the data was stored in digital environment. The developed system offers a practical and low cost solution. The developed device is expected to take an important place in biomedical device technology with its ability to measure COPD parameters.Öğe Design of a fuzzy input expert system visual information interface for classification of apnea and hypopnea(Springer, 2024) Sumbul, Harun; Yuzer, Ahmet HayrettinIn this study, a Fuzzy input Expert System (FES) is developed to detect the patients' PSG results to linguistic statements (apnea-hypopnea). All of the randomly selected 1318 PSG data taken from 15 patients (12 males (80%) and three females (20%)) from St. Vincent University Hospital / University College Dublin Sleep Apnea Database were studied and applied to the FES model. It is understood from the literature that three signals (airflow, SpO(2), and Rib movements) are the primary indicators of apnea and hypopnea. Thus, this study's three important parameters were chosen as input variables to classify the apnea-hypopnea in this study. The output variable DIS (disease) was defined as A (Apnea) and H (Hypopnea). A rule base (consisting of 75 rules) was created using membership functions in the light of AASM's 2012 scoring criteria and an expert's opinion. Since it is the most preferred method, this study uses the center-of-gravity/area (centroid) method for defuzzification. The limit values for each fuzzy expression were created. These parameters were symbolically classified. Membership functions and the degree of the membership function were defined. 231 apnea and 1029 hypopnea events have been successfully detected at 97.5% and 95.2%, respectively. A confusion matrix has been formed for calculating the performances of FES, and accuracy was found to be 97.5%. An interface program was developed using Matlab Graphical User Interface programming language, where some sample results were checked. Thus, results have been converted into understandable linguistic expressions. It can be said that the detection performance of the system developed is good by looking at the results of the correct detection. It is shown that detecting apnea and hypopnea using FES are reliable, consistent, and successful results and helps doctors make quick and reliable diagnoses without any risks.Öğe A different sleep apnea classification system with neural network based on the acceleration signals(Elsevier Sci Ltd, 2020) Yuzer, Ahmet Hayrettin; Sumbul, Harun; Nour, Majid; Polat, KemalBackground and objective: The apnea syndrome is characterized by an abnormal breath pause or reduction in the airflow during sleep. It is reported in the literature that it affects 2% of middle-aged women and 4% of middle-aged men, approximately. This study has vital importance, especially for the elderly, the disabled, and pediatric sleep apnea patients. Methods: In this study, a new diagnostic method is developed to detect the apnea event by using a microelectromechanical system (MEMS) based acceleration sensor. It records the value of acceleration by measuring the movements of the diaphragm in three axes during the respiratory. The measurements are carried out simultaneously, a medical spirometer (Fukuda Sangyo), to test the validity of measurement results. An artificial neural network model was designed to determine the apnea event. For the number of neurons in the hidden layer, 1-3-5-10-18-20-25 values were tried, and the network with three hidden neurons giving the most suitable result was selected. In the designed ANN, three layers were formed that three neurons in the hidden layer, the two neurons at the input, and two neurons at the output layer. Results: A study group was formed of 5 patients (having different characteristics (age, height, and body weight)). The patients in the study group have sleep apnea (SA) in different grades. Several 12.723 acceleration data (ACC) in the XYZ-axis from 5 different patients are recorded for apnea event training and detection. The measured accelerometer (ACC) data from one of the patients (called H1) are used to train an ANN. During the training phase, MSE is used to calculate the fitness value of the apnea event. Then Apnea event is detected successfully for the other patients by using ANN trained only with H1's ACC data. Conclusions: The sleep apnea event detection system is presented by using ANN from directly acceleration values. Measurements are performed by the MEMS-based accelerometer and Industrial Spirometer simultaneously. A total of 12723 acceleration data is measured from 5 different patients. The best result in 7000 iterations was reached (the number of iterations was tried up to 10.000 with 1000 steps). 605 data of only H1 measurements are used to train ANN, and then all data used to check the performance of the ANN as well as H2, H3, H4, and H5 measurement results. MSE performance benchmark shows us that trained ANN successfully detects apnea events. One of the contributions of this study to literature is that only ACC data are used in the ANN training step. After training for one patient, the ANN system can monitor the apnea event situation on-line for others. (C) 2020 Elsevier Ltd. All rights reserved.Öğe Effect of Resampling on Predistortion Linearizer Performance(Ieee, 2013) Sanli, Emine Betul; Yuzer, Ahmet HayrettinEfficiency of telecommunication system is affected by the amplifier used in it. In this study, it is investigated the deterioration effect of resampling on modeling performance of that system. Digital predistortion system is used to linearize Amplifier and Unit Delay memory modeling technique is used to model amplifier behavior. Two different amplifier responses is stored in order to determine the resampling effect on DPD performance, while the first measurement result has not been resampled the other one is resampled. While there is very good improvement in the spectral regrowth for the former measurement, the later has lower improvement on DPD performance due to resampling deterioration effect. In order to diminish distortion effect of resampling when it is necessary, a new way for measurement and resampling is developed. Measurement time is increased a bit and fft filter is applied while resampling the signal. Comparable result have been reached with this new technique with respect to the technique doesn't needn't resampling.Öğe Effect of the Base-band Measurement Setup Errors on DPD Performance and Elimination Procedure(Advanced Electromagnetics, Geeps-Supelec, 2017) Yuzer, Ahmet Hayrettin; Sanli, Emine BetulIn this study, the effect of base-band measurement setup errors on DPD performance was investigated and a calibration procedure is developed to eliminate the measurement errors. A base-band measurement setup is prepared at laboratory with instruments and then the data which is measured and the deteriorating effect of errors on Digital Predistortion (DPD) linearization performance are investigated. In order to eliminate deteriorating effect of this error a three steps calibration procedure is developed. Before and after calibration application DPD performance is measured. It is showed both in simulation and experimentally that the calibration procedure improved the DPD system linearization performance from 10 dB to 26dB and 13dB to 20dB, respectively.Öğe Electromagnetic Shielding Characterization of Conductive Knitted Fabrics(Electromagnetics Acad, 2017) Abdulla, Ruslan; Delihasanlar, Ediz; Abdulla, Fidan Gamze Kizilcay; Yuzer, Ahmet HayrettinThis paper examines the electromagnetic shielding characteristics of milano, cardigan and lacoste with respect to weft and rib type composite knitted fabrics. All of these fabrics, made of hybrid yarns containing 50 mu m diameter metal fibres such as copper, silver and stainless steel, were produced for electromagnetic shielding purposes. The shielding effectiveness (SE) of the fabrics was measured by reading S parameters from the signal when the sample was placed in the path of signal at the frequency range 1.7 to 2.6GHz inside the WR430 waveguide system. After which S parameters was converted to SE values. The variation in electromagnetic shielding effectiveness (EMSE) with the factors, such as radiant frequency, metal type, wales density and geometry, were discussed. Experimental results show that all factors, especially the geometry of the fabric, have significant effect on SE. The best EMSE values were obtained by milano type knitted fabrics which was above 20 dB. It was found that milano, cardigan and lacoste composite fabrics, uncommon in EMSE experiments found in literature, give better shielding performances than rib and weft composite fabrics, under the same conditions.Öğe A low-order nonlinear amplifier model with distributed delay terms(Tubitak Scientific & Technological Research Council Turkey, 2014) Yuzer, Ahmet Hayrettin; Demir, SimsekIn this paper, a novel behavioral modeling technique for the characterization of memory effects of amplifiers is proposed. This characterization utilizes asymmetric intermodulation distortion (IMD)components, which are the result of a 2-tone excitation of a nonlinear amplifier. These asymmetric IMD components are represented basically by a power series, where each term in the series has its own time delay term. These time delay terms successfully justify the presence of asymmetry in the intermodulation components, which leads to the prediction of amplitude-to-amplitude and amplitude-to-phase distortions. The parameters of the model are extracted using 2-tone measurements. A 100-W peak power amplifier is examined. Model predictions are verified by the measurement results of a 4-tone stimulus. The proposed model can also be used in time domain analysis with arbitrary excitation.Öğe A Novel Portable Real-Time Low-Cost Sleep Apnea Monitoring System based on the Global System for Mobile Communications (GSM) Network(Springer Heidelberg, 2022) Sumbul, Harun; Yuzer, Ahmet Hayrettin; Sekeroglu, KazimBackground and objective Continuous monitoring of breathing activity plays a vital role in the detection of respiratory-based diseases (SA, COPD, etc.). Sleep Apnea (SA) is characterized by recurrent upper airway obstruction during sleep associated with arterial blood denaturation, sympathetic nervous system activation, and cardiovascular impairment. Untreated patients with SA have increased mortality rates compared to the general population. This study aims to design a remote monitoring system for sleep apnea to ensure patient safety and ease the workload of doctors in the Covid-19 era. Methods This study aims to design a remote monitoring system for sleep apnea to ensure patient safety and ease the workload of doctors. Our study focuses on a novel portable real-time low-cost sleep apnea monitoring system utilizing the GSM network (GSM Shield Sim900a). Proposed system is a remote monitoring and patient tracking system to detect the apnea event in real time, and to provide information of the sleep position, pulse, and respiratory and oxygen saturation to the medical specialists (SpO(2)) by establishing a direct contact. As soon as an abnormal condition is detected in the light of these parameters, the condition is reported (instant or in the form of short reports after sleep) to the patient relatives, the doctor's mobile telephone or to the emergency medical centers (EMCs) through a GSM network to handle the case depending on the patient's emergency condition. Results A study group was formed of six patients for monitoring apnea events (three males and three females) between the ages of 20 and 60. The patients in the study group have sleep apnea (SA) in different grades. All the apnea events were detected, and all the patients were successfully alerted. Also, the patient parameters were successfully sent to all patient relatives. Patients who could not get out of apnea were called through the CALL feature, and they were informed about their ongoing apnea event and told that intervention was necessary. The proposed system is tested on six patients. The beginning moment of apnea was successfully detected and the SMS/CALL feature was successfully activated without delay. During the testing, it has been observed that while some of the patients start breathing after the first SMS, some others needed the second or the third SMS. According to the measurement result, the maximum breathless time is 46 s among the patients, and a SMS is sent every 15 s. In addition, in cases where the patient was breathless for a long time, the CALL feature was actively sought from the relatives of the patient and enabled him to intervene. The proposed monitoring system could be used in both clinical and home settings. Conclusions The monitoring of a patient in real time allows to intervene in any unexpected circumstances about the patient. The proposed work uses an acceleration sensor as a reliable method of the sleep apnea for monitoring and prevention. The developed device is more economical, comfortable, and convenient than existing systems not only for the patients but also for the doctors. The patients can easily use this device in their home environment, so which could yield a more comfortable, easy to use, cost-effective, and long-term breathing monitoring system for healthcare applications.Öğe Simulation modelling and calculation of dielectric permittivity of Opuntia at 1.7-2.6 GHz(Taylor & Francis Inc, 2017) Delihasanlar, Ediz; Yuzer, Ahmet HayrettinIn this study, dielectric permittivity of Opuntia were calculated and modelled in simulation program at 1.7-2.6 GHz. Waveguide measurement method was utilized to measure the scattering parameters of Opuntia in order to calculate dielectric constant in the predefined frequency range. The measurement system was set up with two waveguide adaptors WR430, an Anritsu network analyser (MS4624B), sample holder and a computer. The error coefficients were identified by Through-Reflect-Line (TRL) calibration technique and the accuracy of the system was checked. New Non-Iterative Method was used to calculate the dielectric constant from measured S parameters. Furthermore, according to the variation of humidity and frequencies, the dielectric constant and loss tangent of Opuntia was examined. Opuntia simulation model is defined in the Computer Simulation Technology (CST) program.Öğe Textile-based 3D metamaterial absorber design for X-band application(Taylor & Francis Ltd, 2022) Erdem, Ediz; Yuzer, Ahmet HayrettinIn this paper, a textile-based metamaterial absorber (MMA) with a wearable, flexible and 3D structure was designed, manufactured, and measured at X-band. The designed MMA consists of three layers as weft-knitted fabric (as the periodic resonator layer), double-sided bonding tape (as the dielectric layer), and plain weave fabric (as the conductive layer). The textile structures were designed using the 'Computer-Aided Design Software' and then imported to the 'Computer Simulation Technology' for simulation. For experimental measurements, textile products were produced by choosing the best method and measurements were completed in the X-band (8-12 GHz). The simulation, experimental results were compared, and the state of polarization angle independency was examined. In the TE10 polarization, while the maximum absorption ratio occurred at 9.61 GHz as 98.25% for simulation, it was at 94.25% at 9.69 GHz for experimental measurement. In the TE10 with 90 degrees polarization angle, while the maximum absorption ratio occurred at 9.81 GHz as 99.53% for simulation, it was at 94.55% at 9.52 GHz for experimental measurement. It is thought that the designed MMA can be used in military applications due to its textile-based properties and its perfect absorption.Öğe A Wide-band and Good Gain Flatness Class AB Power Amplifier Design for Mobile Communication(Ieee, 2017) Kaplan, Aysegul; Yuzer, Ahmet HayrettinIn this study, Class AB power amplifier was designed for use 3G and 4G mobile communication systems. Agilennt EEsof ADS(Advanced Design System) program was used for the design. BLF621-10G model transistor of NXP company was used as active element and Murata brand of coils and capacitors was used as passive elements. As a result of the design, a power amplifier design and simulation with 200 MHz bandwidth at 2.1 GHz was realized. When the designed power amplifier is exited with 17.5 dBm input power, a stable and good gain flatness(+/- 0.36dBm swing in the 20dB dynamic range) was obtained by obtaining 38 dBm oputput power.
