International Journal of Electronics and Telecommunications

This paper presents frequency reconfigurable dual band antenna for WiMAX and LTE 2500 band applications using four PIN diode switches. The antenna is compact in size with dimensions of 30 x 30 x 0.8 mm3 and designed on FR-4 dielectric substrate with a partial ground plane. The fabricated antenna operates in the frequency range of LTE and WiMAX (2.5-2.69 GHz and 3.4-3.6 GHz) respectively. The frequencies can be controlled by using PIN diodes and antenna attained the gain ranging of 3.34-4.46 dBi. This designed antenna resonating at 2.52 and 3.49 GHz when the PIN diodes are in ON state and resonating at 2.68 and 3.58 GHz when PIN diodes are in OFF state. The proposed antenna has bidirectional radiation at upper frequency bands and unidirectional at lower frequency bands. The proposed split ring structured antenna has the radiation efficiency of 94.12% at 2.52 GHz and 90.34% at 3.49 GHz in ON state. Antenna providing good agreement between the measured (Antenna measurement setup with VNA) and simulated results (Ansys-HFSS).

In this paper, a conventional mushroom-type EBG unit cell is made compact by etching a C-slot at its conducting surface. Further, the C-slotted mushroom-type EBG unit cell is coupled with a microstrip line using a novel groove-coupling technique to design a notch filter. The arrangement has achieved in the reduction of the electrical size of the mushroom type EBG unit cell by 46:15% and create a stop band suppression of -12 dB. The proposed EBG is applied to notch a narrow band centered at 5:2 GHz along with an ultra-wideband antenna. The far field gain of the antenna is suppressed by -5:8 dBi along the direction of its major lobe at 5:2 GHz. The overall size of the antenna system is 19x27x1:6mm3 which is compact. The performance of the antenna is validated from the simulation and measured results.

In this paper, an autonomous wearable sensor node is developed for long-term continuous healthcare monitoring. This node is used to monitor the body temperature and heart rate of a human through a mobile application. Thus, it includes a temperature sensor, a heart pulse sensor, a low-power microcontroller, and a Bluetooth low energy (BLE) module. The power supply of the node is a lithium-ion rechargeable battery, but this battery has a limited lifetime. Therefore, a photovoltaic (PV) energy harvesting system is proposed to prolong the battery lifetime of the sensor node. The PV energy harvesting system consists of a flexible photovoltaic panel, and a charging controller. This PV energy harvesting system is practically tested outdoor under lighting intensity of 1000 W/m2. Experimentally, the overall power consumption of the node is 4.97 mW and its lifetime about 246 hours in active-sleep mode. Finally, the experimental results demonstrate long-term and sustainable operation for the wearable sensor node.

The article considers information technology for the realization of human communication using residual human capabilities, obtained by organizing text entry using mobile and auxiliary devices. The components of the proposed technology are described in detail: the method for entering text information to realize the possibility of introducing a limited number of controls and the method of predicting words that are most often encountered after words already entered in the sentence. A generalized representation of the process of entering text is described with the aid of an ambiguous virtual keyboard and the representation of control signals for the selection of control elements. The approaches to finding the optimal distribution of the set of alphabet characters for different numbers of control signals are given. The method of word prediction is generalized and improved, the statistical language model with "back-off" is used, and the approach to the formation of the training corpus of the spoken Ukrainian language is proposed.

In this paper the new synthesis method for reversible networks is proposed. The method is suitable to generate optimal circuits. The examples will be shown for three variables reversible functions but the method is scalable to larger number of variables. The algorithm could be easily implemented with high speed execution and without big consuming storage software. Section 1 contains general concepts about the reversible functions. In Section 2 there are presented various descriptions of reversible functions. One of them is the description using partitions. In Section 3 there are introduced the cascade of the reversible gates as the target of the synthesis algorithm. In order to achieve this target the definitions of the rest and remain functions will be helpful. Section 4 contains the proposed algorithm. There is introduced a classification of minterms distribution for a given function. To select the successive gates in the cascade the condition of the improvement the minterms distribution must be fulfilled. Section 4 describes the algorithm how to improve the minterms distributions in order to find the optimal cascade. Section 5 shows the one example of this algorithm.

Operational amplifies (op amps) are an integral part of many analog and mixed-signal systems. Op amps with vastly different levels of complexity are used to realize functions ranging from DC bias generation to high-speed amplification or filtering. The design of op amps continues to pose a challenge as the supply voltage and transistor channel lengths scale down with each generation of CMOS technologies. The thesis deals with the analysis, design and layout optimization of CMOS op amps in deep Submicron (DSM) from a study case. Finally, layout optimizations of op amps will be given, in which propose optimization techniques to mitigate these DSM effects in the place-and-route stage of VLSI physical design.

A design of microwave installation for energy concentration on a surface of a heated object is proposed. In the installation a dipole lattice on the basis of a single-wire transmission line is used which is located inside of reflector in a form of specular parabolic conducting cylinder. The heated object is placed in the area of microwave energy concentration.

In the article a waveguide field of a surface wave in a reradiation mode is explored. The surface wave is reradiated by a group of vibrators coaxial with the waveguide wire. Results of experimental studies of field distribution along the waveguide operating in various modes are presented. The possibility of efficiency increase in reradiated field and its adjustment by contactless movement of reflector is shown.

We present here a few thoughts regarding topological aspects of transferring a signal of a continuous time into its discrete counterpart and recovering an analog signal from its discrete-time equivalent. In our view, the observations presented here highlight the essence of the above transformations. Moreover, they enable deeper understanding of the reconstruction formula and of the sampling theorem. We also interpret here these two borderline cases that are associated with a time quantization step going to zero, on the one hand, and approaching its greatest value provided by the sampling theorem, on the other

In this paper, it has been shown that any measuring process can be modeled as a process of sampling of signals. Also, a notion of a special kind of functions, called here functions with attributes, has been introduced. The starting point here, in the first of the above themes, is an observation that in fact we are not able to measure and record truly continuously in time any physical quantity. The measuring process can be viewed as going stepwise that is in steps from one instant to another, similarly as a sampling of signals proceeds. Therefore, it can be modeled as the latter one. We discuss this in more detail here. And, the notion of functions with attributes, we introduced here, follows in a natural way from the interpretation of both the measuring process as well as the sampling of signals that we present in this paper. It turns out to be useful.

It is proposed to modernize the DVB-S2 standard by using AMMC (amplitude modulation of many components) signals instead of 8PSK (8-phase shift keying) and APSK (amplitude-phase shift keying) signals, and to modernize the DVB-S2 standard equipment by using the AMMC modulator and AMMC demodulator. Usage of AMMC makes it possible to reduce the symbol error rate in communication channel up to 52 times. The satellite digital video broadcast systems that apply signal-code constructions based on AMMC are characterized by a higher energy efficiency from 1 to 2.6 dB compared with signalcode constructions based on 8PSK and APSK.

The paper depicts a complex, distributed information system aimed at promoting cybersecurity awareness at the national level. The system, that is built in accordance with the Act on National Cybersecurity, passed by the Polish Parliament, enables collecting and processing in near-real time available information on the security status of essential services and digital services and, also, provides for assessment of negative impact of the identified threats concerned with the provision of those services. Advanced access control and dissemination mechanisms, for secure information sharing within the system, are provided in order to aggregate distributed knowledge and use this information for online security risk analysis and for generation and distribution of early warnings.

Underwater Acoustic Communications (UWAC) is an emerging technology in the field of underwater communications, and it is challenging because of the signal attenuation of the sound waves. Multiple Input and Multiple- Output (MIMO) is introduced in UWAC because of its support in enhancing the data throughput even under the conditions of interference, signal fading, and multipath. The paper presents the concept and analysis of 2× 2 MIMO UWAC systems that uses a 4- QAM spatial modulation scheme thus minimizing the decoding complexity and overcoming the Inter Channel Interference (IChI). Bit Error Rate (BER) investigation is carried out over different link distances under acoustic Line of Sight (LOS). The utilization of Zero Forcing (ZF) and Vertical-Bell Laboratories Layered Space-Time (VBLAST) equalizers, which estimates the transmitted data proves a success of removing Inter Symbol Interference (ISI). The ISI caused due to multipath effect and scattering in UWAC can be reduced by iterative process considered in VBLAST. A study is made on how the distance between the transmitter and the receiver and the Doppler Effect has its impact on the performance of the system.

Covering a wide area by a large number of WiFi networks is anticipated to become very popular with Internet-of-things (IoT) and initiatives such as smart cities. Such network configuration is normally realized through deploying a large number of access points (APs) with overlapped coverage. However, the imbalanced traffic load distribution among different APs affects the energy consumption of a WiFi device if it is associated to a loaded AP. This research work aims at predicting the communication-related energy that shall be consumed by a WiFi device if it transferred some amount of data through a certain selected AP. In this paper, a forecast of the energy consumption is proposed to be obtained using an algorithm that is supported by a mathematical model. Consequently, the proposed algorithm can automatically select the best WiFi network (best AP) that the WiFi device can connect to in order to minimize energy consumption. The proposed algorithm is experimentally validated in a realistic lab setting. The observed performance indicates that the algorithm can provide an accurate forecast to the energy that shall be consumed by a WiFi transceiver in sending some amount of data via a specific AP.

Single Image Super-Resolution (SISR) through sparse representation has received much attention in the past decade due to significant development in sparse coding algorithms. However, recovering high-frequency textures is a major bottleneck of existing SISR algorithms. Considering this, dictionary learning approaches are to be utilized to extract high-frequency textures which improve SISR performance significantly. In this paper, we have proposed the SISR algorithm through sparse representation which involves learning of Low Resolution (LR) and High Resolution (HR) dictionaries simultaneously from the training set. The idea of training coupled dictionaries preserves correlation between HR and LR patches to enhance the Super-resolved image. To demonstrate the effectiveness of the proposed algorithm, a visual comparison is made with popular SISR algorithms and also quantified through quality metrics. The proposed algorithm outperforms compared to existing SISR algorithms qualitatively and quantitatively as shown in experimental results. Furthermore, the performance of our algorithm is remarkable for a smaller training set which involves lesser computational complexity. Therefore, the proposed approach is proven to be superior based upon visual comparisons and quality metrics and have noticeable results at reduced computational complexity.

This paper is devoted to some problems that appear in derivations of the discrete time Fourier transform from a formula for its continuous time counterpart for transformation from the time into the frequency domain as well as to those regarding transformation in the inverse direction. In particular, the latter ones remained so far an unresolved problem. It is solved for the first time here. Many detailed explanations accompanying the solution found are presented. Finally, it is also worth noting that our derivations do not exploit any of such sophisticated mathematical tools as the so-called Dirac delta and Dirac comb.

VTT Technical Research Centre of Finland Ltd. has developed and utilized Low Temperature Co-fired Ceramic (LTCC) technology for about 25 years. This paper presents our activities related to photonics and millimetre-waves, including also a relevant literature survey. First a short summary of the technology is given. Especially, the unique features of LTCC technology are described in more details. In addition, several examples have been given to show the validity of LTCC technology in these high-performance fields.

An useful electrochemical sensing approach was developed for norepinephrine (NE) detection based on semiconducting polymer (9-nonyl-2,7-di(selenophen-2-yl)- 9H-carbazole) and laccase modified platinum electrode (Pt). The miniature Pt biosensor was designed and constructed via the immobilization of laccase in an electroactive layer of the electrode coated with thin polymeric film. This sensing arrangement utilized the catalytic oxidation of NE to norepinephrine quinone. The detection process was based on the oxidation of catecholamine in the presence of enzyme – laccase. With the optimized conditions, the analytical performance demonstrated selectivity in a wide linear range (0.1–200x10-6 M) with a detection limit of 240 nM and a quantification limit of 365 nM. Moreover, the method was successfully applied for selective NE determination in the presence of interfering substances.

The paper contains a short literature review on the subject of special type of thin film structures with resistiveswitching memory effect. In the literature, such structures are commonly labeled as "memristors". The word "memristor" originates from two words: "memory" and "resistor". For the first time, the memristor was theoretically described in 1971 by Leon Chua as the 4th fundamental passive electronics element with a non-linear current-voltage behavior. The reported area of potential usage of memristor is enormous. It is predicted that the memristor could find application, for example in the domain of nonvolatile random access memory, flash memory, neuromorphic systems and so forth. However, in spite of the fact that plenty of papers have been published in the subject literature to date, the memristor still behaves as a "mysterious" electronic element. It seems that, one of the important reasons that such structures are not yet in practical use, is unsufficient knowledge of physical phenomena determining occurrence of the switching effect. The present paper contains a literature review of available descriptions of theoretical basis of the memristor structures, used materials, structure configurations and discussion about future prospects and limitations.

This paper presents some construction analysis and test results of a Free Space Optics system operating at the wavelength of 9.35 μm. In the system, a quantum cascade laser and a photoreceiver with mercury cadmium telluride photodetectors were used. The main parameters of these elements were discussed taking into account a data link operation. It also provides to determine a data range for various weather conditions related to scattering and scintillation. The results of numerical analyses defined the properties of currently available FSO technologies working in the near infrared or in the short infrared range of spectrum versus the performances of the developed system. The operation of this system was verified in three different test environments. The obtained results may also contain important issues related to the practical application of any FSO system.

Quantum cascade laser is one of the most sophisticated semiconductor devices. Its technology requires extremely high precision and layers quality. Device performance is limited by thermal extraction form laser core. One of solutions is to apply highly resistivity epitaxial material acting as insulating layer on top of the QCL. Present work describes consequent steps of elaboration of MOVPE technology of Fe-compensated InP layers for further applications in quantum cascade lasers.