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Journal Details
Format
Journal
eISSN
1339-309X
First Published
07 Jun 2011
Publication timeframe
6 times per year
Languages
English

Search

Volume 73 (2022): Issue 3 (June 2022)

Journal Details
Format
Journal
eISSN
1339-309X
First Published
07 Jun 2011
Publication timeframe
6 times per year
Languages
English

Search

10 Articles
Open Access

Differential STBC NOMA: A new approach to downlink cooperative NOMA

Published Online: 11 Jul 2022
Page range: 158 - 165

Abstract

Abstract

Due to the ability of massive connectivity, large bandwidth, and low latency, the non-orthogonal multiple access (NOMA) is considered the best approach for the 5th generation and beyond. However, the system performance is declined when the number of users is increased as each user will experience a great number of successive interface cancelations (SIC) in the downlink. To improve system performance, the NOMA is combined with cooperative communication which gives more spectral efficiency and fairness as compared to non-cooperative NOMA. Furthermore, space-time block code (STBC)- cooperative NOMA-based users experienced less SIC as compared to conventional CNOMA. This paper evaluates the performance of differential STBC-CNOMA with keeping in mind the imperfect SIC, channel state information (CSI), and timing synchronization between distributed cooperating users. The simulations results show that differential STBC-CNOMA gives high performance in terms of outage probability and sum rate analysis as compared to simple STBC-NOMA and conventional CNOMA. Hence, the differential STBC-CNOMA seems to be a better and more effective solution to enhance system performance.

Keywords

  • CNOMA
  • differential STBC
  • SIC
  • STBC
Open Access

Compact triple-band implantable antenna for multitasking medical devices

Published Online: 11 Jul 2022
Page range: 166 - 173

Abstract

Abstract

This paper presents a compact implantable antenna’s design, fabrication, and measurement for biotelemetry applications. The proposed design with the size of 255 mm3 provides a triple-band operation that covers all the Medical Implant Communication Service (MICS: 402 MHz), Medical Device Radiocommunications Service (MedRadio: 405 MHz), and Industrial, Scientific, and Medical (ISM: 433, 915 and 2450 MHz) bands simultaneously. The compact structure with triple- band performance is essentially achieved by using a spiral-like radiator loaded with meandered and internal gear-shaped elements excited by a vertical coaxial probe feed. Also, the slots-loaded partial ground plane is utilized to improve impedance matching at the desired frequency bands. The design and analysis of the antenna were carried out using the Ansoft HFSS software in a homogenous skin model and the CST Microwave Studio in a realistic human model. The proposed antenna was fabricated to validate the simulated results, and characteristics of its return loss and radiation patterns were measured in minced pork meat. Moreover, realized gains and specific absorption rate (SAR) values of the antenna were numerically computed using the simulators. Based on the simulated and measured results, the proposed antenna performance was found to be comparable to the limited number of multiband implantable antenna designs reported in the recent literature.

Keywords

  • biotelemetry applications
  • implantable antennas
  • ISM bands
  • MedRadio bands
  • triple-band antennas
Open Access

Influence of nanofiller concentration on polypropylene nanocomposites for high voltage cables

Published Online: 11 Jul 2022
Page range: 174 - 181

Abstract

Abstract

Polymeric insulation for HVDC cable is attracting more attention in the modern power transmission system. Especially, the thermoplastic material is desirable for power cable insulation because of its recyclability and ease of processing. Thermoplastic material development is a good alternative to cross-linked polyethylene in the future. Polypropylene has the advantage of avoiding by-products during cable production, which can minimize space accumulation and degassing costs. Therefore, this study investigates the influence of nanofillers on the structural properties of isotactic polypropylene. In addition, the proposed composite material’s morphology, melting, dielectric permittivity, and breakdown strength are examined. Different weight percentages of inorganic nanofillers such as TiO2 and ZnO are used to make nanocomposite thin films. With increasing filler concentration, the dielectric constant of the nanocomposite thin film increases. Apart from that, the dielectric loss of the TiO2 nanocomposite thin film increases with weight percentage initially and it falls nearer to virgin material at a higher frequency. The breakdown strength of the nanocomposite materials shows a similar variation with filler concentration. TiO2 is more resistant to deterioration than ZnO composite. Based on the results of the complete investigation, the TiO2 nanocomposite is better suited for the insulation of HVDC cables.

Keywords

  • isotactic polypropylene
  • breakdown strength
  • titanium oxide
  • zinc oxide
  • thermoplastic
  • HF and superim-posed AC
Open Access

Analysing the shielding effectiveness of rectangular enclosure by determining aperture dimensions with particle swarm optimization

Published Online: 11 Jul 2022
Page range: 182 - 189

Abstract

Abstract

Electromagnetic shielding enclosure is used to protect electronic circuits against external EMI. Aperture on the enclosure, which is necessary for various reasons such as mounting connector, ventilation attenuates shielding effectiveness (SE) of the enclosure. Enlarging enclosure dimensions makes SE get better. Yet, they canot be designed so large due to weight and dimension considerations for EV. When the dimensions of the shielding enclosure remain fixed and the aperture is to have a particular area, it is essential to optimize aperture dimensions to increase SE. In this paper, an optimization methodology based on PSO is designed to obtain the optimal SE for a particular dimension range. The study also provides a comparative analysis between designed optimization methodology and the one based on genetic algorithm in the literature. Obtained SE results indicate that the optimization methodology establishes a very good agreement with the results in the literature. Moreover, it has faster convergence and higher calculation accuracy than GA and it utilizes a smaller number of parameters thanks to its simplicity. Finally, it is concluded that through designed optimization methodology in this study, SE of the enclosure can be raised by optimizing aperture dimensions when the dimensions of shielding enclosure remain fixed.

Keywords

  • electromagnetic shielding
  • shielding effectiveness
  • particle swarm optimization
  • genetic algorithm
  • electric vehicles
Open Access

Flawed implemented cryptographic algorithm in the Microsoft ecosystem

Published Online: 11 Jul 2022
Page range: 190 - 196

Abstract

Abstract

With the continuous development in the electronic chip field, the requirements for the security of IT infrastructures are also increasing. The need for ever-increasing key lengths in cryptography to maintain security cannot grow indefinitely. One of the solutions in the field of cryptography for using shorter keys while maintaining security is cryptography based on the principle of elliptic curves. Asymmetric elliptic curve cryptosystems lies in solving the discrete logarithm problem on an elliptic curve. However, not only secure algorithm but also its correct implementation is important. In this paper, we discuss an incorrect implementation of the ECC algorithm in the crypt32.dll library (Microsoft Windows) and the possibilities of its misuse.

Keywords

  • ECC
  • cryptographic
  • security
  • crypt32. dll
  • ECCDSA
Open Access

Quadrant-based contour features for accelerated shape retrieval system

Published Online: 11 Jul 2022
Page range: 197 - 202

Abstract

Abstract

Shape representation and retrieval are essential research topics of computer vision. This paper proposes a novel feature set to be used in content-based image retrieval systems. The proposed method is an extended version of our previous study which uses contour information of shapes. The previous study calculated the center of mass (CoM) of the shape. By taking the CoM as origin, we created imaginary vectors in every angular direction. From each vector, we extracted three features which are the number of intersections between vector and contour, average distance of intersection points to CoM, and standard deviation of these points. In this method, we extract novel features and decrease the size of the feature set to decrease the computation time. We divide the shape into quadrants and represent each quadrant by nine features. Each shape image is represented by a 4x9 feature vector. We tested the proposed method on MPEG-7 and ETH-80 datasets and compared it with the state-of-art. According to the results, our method decreased the computation time dramatically while giving a state-of-art level retrieval accuracy.

Keywords

  • image retrieval
  • shape representation
  • contour-based feature
Open Access

Pixel level vacuum packaging for single layer microbolometer detectors with on pixel lens

Published Online: 11 Jul 2022
Page range: 203 - 208

Abstract

Abstract

This paper presents a new approach for fabrication of single layer microbolometer detectors featuring pixel level vacuum packaging together with a lens on the pixel. The proposed lens structure can be used to increase the fill factor of the detector so that the pixel size can be decreased without decreasing the minimum feature size in the detector which is a problem in single layer microbolometers. The designs of the lens and the fabrication process of pixel level vacuum packaged microbolometer detector together with this lens are given in the framework of this study. The optical and mechanical simulations of the structure are performed. The radius of curvature of the lens is optimized to be 25 μm and it is shown that the condensing efficiency is 100% for 3 μm lens-detector distance. The deflection in the lens structure is found approximately as 0.8 nm in 1 atm environment pressure, showing that the proposed structure is durable. The proposed structure increases the fill factor to twice of the original value without decreasing the minimum feature size in the fabrication processes, resulting in the same amount of improvement in the performance of the detector. This approach can also be used to increase the yield and decrease the fabrication cost of single layer and also standard microbolometers with small pixel sizes, as it integrates the vacuum packaging in the fabrication steps.

Keywords

  • pixel level packaging
  • lens on pixel
  • single layer microbolometer
Open Access

Robust boundary of stability and design of robust controller in uncertain polytopic linear systems

Published Online: 11 Jul 2022
Page range: 209 - 214

Abstract

Abstract

This paper is devoted to design of a robust controller for an uncertain continuous-time linear polytopic system. The design procedure will take place in two steps. In the first step, we calculate the robust stability boundary of a closed loop system. Then on the basis of the result obtained in this way, we select a robust controller design method that accepts the calculated stability boundary. This procedure allows better implementation of the second step of the designed robust controller. Two examples of application of the proposed method follow finally, which illustrate its effectiveness.

Keywords

  • robust control
  • uncertain polytopic system
  • output feedback
  • PID controller
  • regional pole
Open Access

Waveguide power phase shifter with a ferrite circulator in S-band

Published Online: 11 Jul 2022
Page range: 215 - 220

Abstract

Abstract

This paper presents the application of a phase shifter with a ferrite Y-circulator in band S. Global literature addresses primarily the basic types of power waveguide phase shifters, however, there has been minimal literature on a phase shifter that uses a ferrite circulator for phase shifting. The paper describes theoretical and practical results where a ferrite circulator is used to shift the phase. A power phase shifter utilizing a ferrite circulator could be used in power applications where high demands are placed on the phase shift accuracy with minimal power losses. The phase shift is handled by a tunable waveguide short circuit that is connected to the port 2 of the ferrite circulator. By changing the waveguide length, the phase is changed. The measured results are compared with theoretical calculations and evaluated. The proposed phase shifter utilizing the ferrite circulator has its advantages in its simple design, in the accuracy of the phase adjustment and in the speed of the tuning. Another great advantage is its quite low cost due to its simple design.

Keywords

  • ferrite circulator
  • s-parameters
  • rectangular waveguide
  • dielectric
  • port
  • phase
Open Access

An efficient approach for sub-carrier allocation in MIMO MC-CDMA systems

Published Online: 11 Jul 2022
Page range: 221 - 225

Abstract

Abstract

Sub-carrier allocation is an important process that directly affects users data and bit error rates for multi-user multi-carrier systems. The most important feature of the allocation process is to assign the sub-carriers to the active users in proportion to their needs to provide high-speed data transmission and reduce the bit error rates. In this study, an efficient subcarrier allocation algorithm has been proposed based on both capacity and fairness criteria for a MIMO MC-CDMA system, which is preferred as the multiplexing scheme in high data rate communication systems. The proposed algorithm achieves not only better error rate performance but also increases the total data rate compared to other algorithms

Keywords

  • MIMO MC-CDMA
  • subcarrier allocation
  • fairness
  • capacity
10 Articles
Open Access

Differential STBC NOMA: A new approach to downlink cooperative NOMA

Published Online: 11 Jul 2022
Page range: 158 - 165

Abstract

Abstract

Due to the ability of massive connectivity, large bandwidth, and low latency, the non-orthogonal multiple access (NOMA) is considered the best approach for the 5th generation and beyond. However, the system performance is declined when the number of users is increased as each user will experience a great number of successive interface cancelations (SIC) in the downlink. To improve system performance, the NOMA is combined with cooperative communication which gives more spectral efficiency and fairness as compared to non-cooperative NOMA. Furthermore, space-time block code (STBC)- cooperative NOMA-based users experienced less SIC as compared to conventional CNOMA. This paper evaluates the performance of differential STBC-CNOMA with keeping in mind the imperfect SIC, channel state information (CSI), and timing synchronization between distributed cooperating users. The simulations results show that differential STBC-CNOMA gives high performance in terms of outage probability and sum rate analysis as compared to simple STBC-NOMA and conventional CNOMA. Hence, the differential STBC-CNOMA seems to be a better and more effective solution to enhance system performance.

Keywords

  • CNOMA
  • differential STBC
  • SIC
  • STBC
Open Access

Compact triple-band implantable antenna for multitasking medical devices

Published Online: 11 Jul 2022
Page range: 166 - 173

Abstract

Abstract

This paper presents a compact implantable antenna’s design, fabrication, and measurement for biotelemetry applications. The proposed design with the size of 255 mm3 provides a triple-band operation that covers all the Medical Implant Communication Service (MICS: 402 MHz), Medical Device Radiocommunications Service (MedRadio: 405 MHz), and Industrial, Scientific, and Medical (ISM: 433, 915 and 2450 MHz) bands simultaneously. The compact structure with triple- band performance is essentially achieved by using a spiral-like radiator loaded with meandered and internal gear-shaped elements excited by a vertical coaxial probe feed. Also, the slots-loaded partial ground plane is utilized to improve impedance matching at the desired frequency bands. The design and analysis of the antenna were carried out using the Ansoft HFSS software in a homogenous skin model and the CST Microwave Studio in a realistic human model. The proposed antenna was fabricated to validate the simulated results, and characteristics of its return loss and radiation patterns were measured in minced pork meat. Moreover, realized gains and specific absorption rate (SAR) values of the antenna were numerically computed using the simulators. Based on the simulated and measured results, the proposed antenna performance was found to be comparable to the limited number of multiband implantable antenna designs reported in the recent literature.

Keywords

  • biotelemetry applications
  • implantable antennas
  • ISM bands
  • MedRadio bands
  • triple-band antennas
Open Access

Influence of nanofiller concentration on polypropylene nanocomposites for high voltage cables

Published Online: 11 Jul 2022
Page range: 174 - 181

Abstract

Abstract

Polymeric insulation for HVDC cable is attracting more attention in the modern power transmission system. Especially, the thermoplastic material is desirable for power cable insulation because of its recyclability and ease of processing. Thermoplastic material development is a good alternative to cross-linked polyethylene in the future. Polypropylene has the advantage of avoiding by-products during cable production, which can minimize space accumulation and degassing costs. Therefore, this study investigates the influence of nanofillers on the structural properties of isotactic polypropylene. In addition, the proposed composite material’s morphology, melting, dielectric permittivity, and breakdown strength are examined. Different weight percentages of inorganic nanofillers such as TiO2 and ZnO are used to make nanocomposite thin films. With increasing filler concentration, the dielectric constant of the nanocomposite thin film increases. Apart from that, the dielectric loss of the TiO2 nanocomposite thin film increases with weight percentage initially and it falls nearer to virgin material at a higher frequency. The breakdown strength of the nanocomposite materials shows a similar variation with filler concentration. TiO2 is more resistant to deterioration than ZnO composite. Based on the results of the complete investigation, the TiO2 nanocomposite is better suited for the insulation of HVDC cables.

Keywords

  • isotactic polypropylene
  • breakdown strength
  • titanium oxide
  • zinc oxide
  • thermoplastic
  • HF and superim-posed AC
Open Access

Analysing the shielding effectiveness of rectangular enclosure by determining aperture dimensions with particle swarm optimization

Published Online: 11 Jul 2022
Page range: 182 - 189

Abstract

Abstract

Electromagnetic shielding enclosure is used to protect electronic circuits against external EMI. Aperture on the enclosure, which is necessary for various reasons such as mounting connector, ventilation attenuates shielding effectiveness (SE) of the enclosure. Enlarging enclosure dimensions makes SE get better. Yet, they canot be designed so large due to weight and dimension considerations for EV. When the dimensions of the shielding enclosure remain fixed and the aperture is to have a particular area, it is essential to optimize aperture dimensions to increase SE. In this paper, an optimization methodology based on PSO is designed to obtain the optimal SE for a particular dimension range. The study also provides a comparative analysis between designed optimization methodology and the one based on genetic algorithm in the literature. Obtained SE results indicate that the optimization methodology establishes a very good agreement with the results in the literature. Moreover, it has faster convergence and higher calculation accuracy than GA and it utilizes a smaller number of parameters thanks to its simplicity. Finally, it is concluded that through designed optimization methodology in this study, SE of the enclosure can be raised by optimizing aperture dimensions when the dimensions of shielding enclosure remain fixed.

Keywords

  • electromagnetic shielding
  • shielding effectiveness
  • particle swarm optimization
  • genetic algorithm
  • electric vehicles
Open Access

Flawed implemented cryptographic algorithm in the Microsoft ecosystem

Published Online: 11 Jul 2022
Page range: 190 - 196

Abstract

Abstract

With the continuous development in the electronic chip field, the requirements for the security of IT infrastructures are also increasing. The need for ever-increasing key lengths in cryptography to maintain security cannot grow indefinitely. One of the solutions in the field of cryptography for using shorter keys while maintaining security is cryptography based on the principle of elliptic curves. Asymmetric elliptic curve cryptosystems lies in solving the discrete logarithm problem on an elliptic curve. However, not only secure algorithm but also its correct implementation is important. In this paper, we discuss an incorrect implementation of the ECC algorithm in the crypt32.dll library (Microsoft Windows) and the possibilities of its misuse.

Keywords

  • ECC
  • cryptographic
  • security
  • crypt32. dll
  • ECCDSA
Open Access

Quadrant-based contour features for accelerated shape retrieval system

Published Online: 11 Jul 2022
Page range: 197 - 202

Abstract

Abstract

Shape representation and retrieval are essential research topics of computer vision. This paper proposes a novel feature set to be used in content-based image retrieval systems. The proposed method is an extended version of our previous study which uses contour information of shapes. The previous study calculated the center of mass (CoM) of the shape. By taking the CoM as origin, we created imaginary vectors in every angular direction. From each vector, we extracted three features which are the number of intersections between vector and contour, average distance of intersection points to CoM, and standard deviation of these points. In this method, we extract novel features and decrease the size of the feature set to decrease the computation time. We divide the shape into quadrants and represent each quadrant by nine features. Each shape image is represented by a 4x9 feature vector. We tested the proposed method on MPEG-7 and ETH-80 datasets and compared it with the state-of-art. According to the results, our method decreased the computation time dramatically while giving a state-of-art level retrieval accuracy.

Keywords

  • image retrieval
  • shape representation
  • contour-based feature
Open Access

Pixel level vacuum packaging for single layer microbolometer detectors with on pixel lens

Published Online: 11 Jul 2022
Page range: 203 - 208

Abstract

Abstract

This paper presents a new approach for fabrication of single layer microbolometer detectors featuring pixel level vacuum packaging together with a lens on the pixel. The proposed lens structure can be used to increase the fill factor of the detector so that the pixel size can be decreased without decreasing the minimum feature size in the detector which is a problem in single layer microbolometers. The designs of the lens and the fabrication process of pixel level vacuum packaged microbolometer detector together with this lens are given in the framework of this study. The optical and mechanical simulations of the structure are performed. The radius of curvature of the lens is optimized to be 25 μm and it is shown that the condensing efficiency is 100% for 3 μm lens-detector distance. The deflection in the lens structure is found approximately as 0.8 nm in 1 atm environment pressure, showing that the proposed structure is durable. The proposed structure increases the fill factor to twice of the original value without decreasing the minimum feature size in the fabrication processes, resulting in the same amount of improvement in the performance of the detector. This approach can also be used to increase the yield and decrease the fabrication cost of single layer and also standard microbolometers with small pixel sizes, as it integrates the vacuum packaging in the fabrication steps.

Keywords

  • pixel level packaging
  • lens on pixel
  • single layer microbolometer
Open Access

Robust boundary of stability and design of robust controller in uncertain polytopic linear systems

Published Online: 11 Jul 2022
Page range: 209 - 214

Abstract

Abstract

This paper is devoted to design of a robust controller for an uncertain continuous-time linear polytopic system. The design procedure will take place in two steps. In the first step, we calculate the robust stability boundary of a closed loop system. Then on the basis of the result obtained in this way, we select a robust controller design method that accepts the calculated stability boundary. This procedure allows better implementation of the second step of the designed robust controller. Two examples of application of the proposed method follow finally, which illustrate its effectiveness.

Keywords

  • robust control
  • uncertain polytopic system
  • output feedback
  • PID controller
  • regional pole
Open Access

Waveguide power phase shifter with a ferrite circulator in S-band

Published Online: 11 Jul 2022
Page range: 215 - 220

Abstract

Abstract

This paper presents the application of a phase shifter with a ferrite Y-circulator in band S. Global literature addresses primarily the basic types of power waveguide phase shifters, however, there has been minimal literature on a phase shifter that uses a ferrite circulator for phase shifting. The paper describes theoretical and practical results where a ferrite circulator is used to shift the phase. A power phase shifter utilizing a ferrite circulator could be used in power applications where high demands are placed on the phase shift accuracy with minimal power losses. The phase shift is handled by a tunable waveguide short circuit that is connected to the port 2 of the ferrite circulator. By changing the waveguide length, the phase is changed. The measured results are compared with theoretical calculations and evaluated. The proposed phase shifter utilizing the ferrite circulator has its advantages in its simple design, in the accuracy of the phase adjustment and in the speed of the tuning. Another great advantage is its quite low cost due to its simple design.

Keywords

  • ferrite circulator
  • s-parameters
  • rectangular waveguide
  • dielectric
  • port
  • phase
Open Access

An efficient approach for sub-carrier allocation in MIMO MC-CDMA systems

Published Online: 11 Jul 2022
Page range: 221 - 225

Abstract

Abstract

Sub-carrier allocation is an important process that directly affects users data and bit error rates for multi-user multi-carrier systems. The most important feature of the allocation process is to assign the sub-carriers to the active users in proportion to their needs to provide high-speed data transmission and reduce the bit error rates. In this study, an efficient subcarrier allocation algorithm has been proposed based on both capacity and fairness criteria for a MIMO MC-CDMA system, which is preferred as the multiplexing scheme in high data rate communication systems. The proposed algorithm achieves not only better error rate performance but also increases the total data rate compared to other algorithms

Keywords

  • MIMO MC-CDMA
  • subcarrier allocation
  • fairness
  • capacity

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