Dual-Antenna RF CMOS Front-End for Interferer Removal in Ultra-Wideband Systems

Many ultra-wideband (UWB) systems are challenged by strong jammers and narrowband interferers. Using two antennas, we demonstrate a robust UWB radio frequency (RF) front-end design in a 0.25 μm mixed-signal complementary metal oxide semiconductor (CMOS) technology. The proposed realization is capable of adaptively removing a high-power, narrowband interferer early in the receiver chain avoiding front-end saturation and preserving UWB signal power. The early interferer removal resulting in interferer-free demodulation is based on the least mean squares (LMS) algorithm and achieved through a novel combiner low-noise amplifier and noise optimized filtering. Circuit level RF simulations of the proposed circuitry indicate a maximum improvement in signal-to-interference ratio of 39.6 dB.     

Familiar/unfamiliar face classification from EEG signals by utilizing pairwise distant channels and distinctive time interval

The aim of the study is to classify single trial electroencephalogram and to estimate active regions/locations on skull in unfamiliar/familiar face recognition task. For this purpose, electroencephalographic signals were acquired from ten subjects in different sessions. Sixty-one familiar and fifty-nine unfamiliar face stimuli were shown to the subjects in the experiments. Since channel responses are different for familiar and unfamiliar classes, the channels discriminating the classes were investigated. To do so, three distances and four similarity measures were employed to assess the most distant channel pairs between familiar and unfamiliar classes for a 1-s time duration; 0.6 s from the stimulus to 1.6 s in a channel selection process. It is experimentally observed that this time interval is maintaining the greatest distance between two categories. The electroencephalographic signals were classified using the determined channels and time interval to measure accuracy. The best classification accuracy was 81.30% and was obtained with the Pearson correlation as channel selection method. The most discriminative channel pairs were selected from prefrontal regions.     

Thermoelectric and Magnetic Properties of Pt-Substituted $${BaFe_{4-{x}}Pt_{{x}}Sb_{12}}$$ Compounds

\({BaFe_{4-{x}}Pt_{{x}}Sb_{12}}\) (x = 0, 0.1, 0.2) compounds were prepared by melting and annealing, followed by a spark plasma sintering method. Low-temperature thermoelectric and magnetic properties were investigated based on Seebeck coefficient, electrical and thermal conductivity and magnetization measurements. The structural properties of \({BaFe_{4-{x}}Pt_{{x}}Sb_{12}}\) (x = 0, 0.1, 0.2) compounds were ascertained by powder x-ray diffraction analysis, confirming that all samples have a main phase of a skutterudite structure with the space group Im\({\mathrm {\bar{3}}}\). The lattice parameters obtained, 9.202(5), 9.199(5) and 9.202(1) Å for x = 0, 0.1 and 0.2, respectively, were found consistent with literature. The Seebeck coefficient sign shows that holes are dominant carriers in all compounds. The local maximum Seebeck coefficient was observed around 50 K which may be a trace of paramagnon-drag effect of charge carriers. Thermal conductivity and electrical resistivity measurements were carried out between 4.2 and 300 K. Temperature dependence of electrical resistivity reflects that all samples show semi-metallic behavior in our temperature range of 4.2–300 K. Samples for x = 0.1 and x = 0.2 show Kondo-like behavior. In magnetization measurement, we observe that there are two successive magnetic transitions in Pt-substituted compounds; however, there is only one (transition from a paramagnetic state to long-range magnetic ordering) in Pt-free compounds. In Pt-substituted compounds, the first transition appears at \( T _{ {\rm c}}\) = 48 K. In addition, the second transition is observed at \( T _{ {\rm irr}}\) = 30 K where an intermediate state is observed before the magnetic ordering transforms to an irreversible ferromagnetic state. We concluded that Pt substitution on the Fe side effectual on the thermoelectric and magnetic properties of \({BaFe_{4-{x}}Pt_{{x}}Sb_{12}}\) (x = 0, 0.1, 0.2) compounds.     

On Multiple Scattering of Radiation by an Infinite Grating of Dielectric Circular Cylinders at Oblique Incidence

A rigorous analytical representation for the multiple scattering coefficients of the fields radiated by an infinite grating of dielectric circular cylinders excited by an obliquely incident plane electromagnetic wave is derived in terms of the “well-known scattering coefficients of an isolated dielectric cylinder at oblique incidence” and “Schlömilch series”. In addition, a generalized sum-integral grating equation is acquired for the multiple scattered amplitude of a cylinder at oblique incidence in the grating in terms of the scattering coefficients of the insulating dielectric circular cylinder at oblique incidence.     

Energy-efficient and fault-tolerant drone-BS placement in heterogeneous wireless sensor networks

Wireless Networks - This paper introduces a distributed and energy-aware algorithm, called Minimum Drone Placement (MDP) algorithm, to determine the minimum number of base stations mounted on...     

Quality Map Thresholding for De-noising of Complex-Valued fMRI Data and Its Application to ICA of fMRI

Although functional magnetic resonance imaging (fMRI) data are acquired as complex-valued images, traditionally most fMRI studies only use the magnitude of the data. FMRI analysis in the complex domain promises to provide more statistically significant information; however, the noisy nature of the phase poses a challenge for successful study of fMRI by complex-valued signal processing algorithms. In this paper, we introduce a physiologically motivated de-noising method that uses phase quality maps to successfully identify and eliminate noisy areas in the fMRI data so they can be used in individual and group studies. Additionally, we show how the developed de-noising method improves the results of complex-valued independent component analysis of fMRI data, a very successful tool for blind source separation of biomedical data.     

Investigation of Ionospheric Electron Density Change During Two Partial Solar Eclipses and Its Comparison with Predictions of NeQuick 2 and IRI-2016 Models

Wireless Personal Communications - In the present study, the results obtained by incoherent scatter radar (ISR) and empirical models (NeQuick2 and IRI-2016) of the variations in mid-latitude...     

Review of different classes of RFID authentication protocols

Radio-frequency identification (RFID) is an up-and-coming technology. The major limitations of RFID technology are security and privacy concerns. Many methods, including encryption, authentication and hardware techniques, have been presented to overcome security and privacy problems. This paper focuses on authentication protocols. The combination of RFID technology being popular but unsecure has led to an influx of mutual authentication protocols. Authentication protocols are classified as being fully fledged, simple, lightweight or ultra-lightweight. Since 2002, much important research and many protocols have been presented, with some of the protocols requiring further development. The present paper reviews in detail recently proposed RFID mutual authentication protocols, according to the classes of the authentication protocols. The protocols were compared mainly in terms of security, the technique that they are based on, protocols that the presented protocol has been compared with, and finally, the method of verifying the protocol. Important points of the comparisons were collected in two tables.

     

Neural Network Based Receiver for Multiuser Detection in MC-CDMA Systems

In this paper, we present a multiuser detection technique based on artificial neural network (NN) for synchronous multicarrier code division multiple access systems over Rayleigh fading channels. To test the robustness of the proposed receiver, also the effect of power control problem is studied with a comparative manner. Bit error rate (BER) performance of the NN based receiver is compared with the single user bound and conventional receivers. Although the BER performance of the conventional receiver degrades as the number of the users and power level differences among the users increase, as a decision structure, neural network based receiver gives closer BER performance to the single user bound.     

Detection of interdependent primary systems using wideband cognitive radios

Cognitive radios (CRs) may be sharing multiple frequency bands with primary systems if the CR is a wideband or an ultra wideband (UWB) system. In that case, the CR should ensure all the coexisting primary systems in these bands are detected before it can start data transmission. In this work, we study the primary system detection performance of a wideband CR assuming that there are multiple coexisting primary systems and that these primary systems may be jointly active. Accordingly, we consider the implementation of energy detection scheme in multiple bands followed by two detection methods: (i) a maximum-a-posteriori (MAP) based detection (i.e., joint detection) that takes into account the statistics of simultaneously operating systems in independent bands and (ii) a Neyman–Pearson (NP) test based detection that optimizes the threshold values independently in each band (i.e., independent detection). For a simpler implementation of the independent detection, we show that the threshold values obtained from joint detection can be used in order to achieve the optimum NP test based independent detection results. In addition to quantifying the gain of joint detection over independent detection in terms of probabilities of false alarm and detection for practical scenarios, we also present the operation capability of CRs in terms of the fractions of time the CR can access the channel without interfering with the primary systems. The results are important for the practical implementation of multiband detection when the primary systems are known to be interdependent.