Showing papers on "Frequency band published in 2015"
TL;DR: A wave form feature manifold (WFM) method to extract the weak signature from waveform feature space which obtained by binary wavelet packet transform and is effective in weak signature extraction is proposed.
200 citations
TL;DR: It is shown, both theoretically and experimentally, that full-power reflection with general control over the reflected wave phase is possible with a single-layer array of deeply subwavelength inclusions, and it is proved that it is possible using electrically and magnetically polarizable inclusions.
Abstract: Conventional mirrors obey the simple reflection law that a plane wave is reflected as a plane wave, at the same angle. To engineer spatial distributions of fields reflected from a mirror, one can either shape the reflector or position some phase-correcting elements on top of a mirror surface. Here we show, both theoretically and experimentally, that full-power reflection with general control over the reflected wave phase is possible with a single-layer array of deeply subwavelength inclusions. These proposed artificial surfaces, metamirrors, provide various functions of shaped or nonuniform reflectors without utilizing any mirror. This can be achieved only if the forward and backward scattering of the inclusions in the array can be engineered independently, and we prove that it is possible using electrically and magnetically polarizable inclusions. The proposed subwavelength inclusions possess desired reflecting properties at the operational frequency band, while at other frequencies the array is practically transparent. The metamirror concept leads to a variety of applications over the entire electromagnetic spectrum, such as optically transparent focusing antennas for satellites, multifrequency reflector antennas for radio astronomy, low-profile conformal antennas for telecommunications, and nanoreflectarray antennas for integrated optics.
166 citations
Patent•
21 Jan 2015
TL;DR: In this paper, a channel optimization in half-duplex communications systems is presented, where the first terminal optimal frequency is based on the radio frequency (RF) spectral information local to the first node.
Abstract: Channel Optimization in Half Duplex Communications Systems is provided herein. Methods may include obtaining at a first terminal, radio frequency (RF) spectral information local to the first terminal, analyzing at the first terminal, RF spectral information for a second terminal that is not co-located with the first terminal, transmitting data to the second terminal on a second terminal optimal frequency band, and receiving data from the second terminal on the first terminal optimal frequency band, where the first terminal optimal frequency being based upon the RF spectral information local to the first terminal.
166 citations
TL;DR: In this paper, the Lambert W function was used to define the time-domain breadth and the frequency-domain bandwidth of the Ricker wavelet and developed quantities analytically in terms of the LambertW function.
Abstract: The Ricker wavelet is theoretically a solution of the Stokes differential equation, which takes into account the effect of Newtonian viscosity, and is applicable to seismic waves propagated through viscoelastic homogeneous media. In this paper, we defined the time-domain breadth and the frequency-domain bandwidth of the Ricker wavelet and developed quantities analytically in terms of the Lambert W function. We determined that the central frequency, the geometric center of the frequency band, is close to the mean frequency statistically evaluated using the power spectrum, rather than the amplitude spectrum used in some of the published literature. We also proved that the standard deviation from the mean frequency is not, as suggested by the literature, the half-bandwidth of the frequency spectrum of the Ricker wavelet. Moreover, we established mathematically the relationships between the theoretical frequencies (the central frequency and the half-bandwidth) and the numerical measurements (the mean frequency and its standard deviation) and produced each of these frequency quantities analytically in terms of the peak frequency of the Ricker wavelet.
150 citations
13 Sep 2015
TL;DR: In this article, side-channel attacks on RSA and ElGamal implementations that use sliding-window or fixed-window (m-ary) modular exponentiation are presented, using a very low measurement bandwidth (a frequency band of less than 100 kHz around a carrier under 2 MHz).
Abstract: We present new side-channel attacks on RSA and ElGamal implementations that use sliding-window or fixed-window (m-ary) modular exponentiation. The attacks extract decryption keys using a very low measurement bandwidth (a frequency band of less than 100 kHz around a carrier under 2 MHz) even when attacking multi-GHz CPUs.
122 citations
TL;DR: In this article, the authors explore possibilities to realize a thin absorbing layer which produces no reflected waves in a very wide frequency range, while the transmission coefficient has a narrow peak of full absorption.
Abstract: Energy of propagating electromagnetic waves can be fully absorbed in a thin lossy layer, but only in a narrow frequency band, as follows from the causality principle. On the other hand, it appears that there are no fundamental limitations on broadband matching of thin absorbing layers. However, known thin absorbers produce significant reflections outside of the resonant absorption band. In this paper we explore possibilities to realize a thin absorbing layer which produces no reflected waves in a very wide frequency range, while the transmission coefficient has a narrow peak of full absorption. Here we show, both theoretically and experimentally, that a wide-band-matched thin resonant absorber, invisible in reflection, can be realized if one and the same resonant mode of the absorbing array unit cells is utilized to create both electric and magnetic responses. We test this concept using chiral particles in each unit cells, arranged in a periodic planar racemic array, utilizing chirality coupling in each unit cell but compensating the field coupling at the macroscopic level. We prove that the concept and the proposed realization approach also can be used to create non-reflecting layers for full control of transmitted fields. Our results can have a broad range of potential applications over the entire electromagnetic spectrum including, for example, perfect ultra-compact wave filters and selective multi-frequency sensors.
120 citations
TL;DR: In this article, a single-degree-of-freedom geometrically nonlinear oscillator with stable-quasi-zero-stiffness (SQZS) is presented, which can be extensively applied in vibration isolation.
116 citations
TL;DR: The obtained results show that analysis of PSD and coherence-based functional network can be taken as a potential comprehensive measure to distinguish AD patients from the normal, which may benefit the understanding of the disease.
Abstract: In this paper, we investigate the abnormalities of electroencephalograph (EEG) signals in the Alzheimer’s disease (AD) by analyzing 16-scalp electrodes EEG signals and make a comparison with the normal controls. The power spectral density (PSD) which represents the power distribution of EEG series in the frequency domain is used to evaluate the abnormalities of AD brain. Spectrum analysis based on autoregressive Burg method shows that the relative PSD of AD group is increased in the theta frequency band while significantly reduced in the alpha2 frequency bands, particularly in parietal, temporal, and occipital areas. Furthermore, the coherence of two EEG series among different electrodes is analyzed in the alpha2 frequency band. It is demonstrated that the pair-wise coherence between different brain areas in AD group are remarkably decreased. Interestingly, this decrease of pair-wise electrodes is much more significant in inter-hemispheric areas than that in intra-hemispheric areas. Moreover, the linear cortico-cortical functional connectivity can be extracted based on coherence matrix, from which it is shown that the functional connections are obviously decreased, the same variation trend as relative PSD. In addition, we combine both features of the relative PSD and the normalized degree of functional network to discriminate AD patients from the normal controls by applying a support vector machine model in the alpha2 frequency band. It is indicated that the two groups can be clearly classified by the combined feature. Importantly, the accuracy of the classification is higher than that of any one feature. The obtained results show that analysis of PSD and coherence-based functional network can be taken as a potential comprehensive measure to distinguish AD patients from the normal, which may benefit our understanding of the disease.
114 citations
Patent•
07 Aug 2015TL;DR: In this paper, a dual-band adaptive concurrent processing method and apparatus is described, and a second coefficient of proportionality between timeslots occupied by the services at the two frequency bands in the (N+1)th adjustment period is determined.
Abstract: Embodiments of the present invention provide a dual band adaptive concurrent processing method and apparatus. In the embodiments of the present invention, by using statistical information of a service at a first frequency band and a service at a service at a second frequency band in the Nth adjustment period, service performance of the services at the frequency bands in the adjustment period may be acquired; and based on the statistical information, and a QoS requirement that the services at the two frequency bands need to meet, a second coefficient of proportionality between timeslots occupied by the services at the two frequency bands in the (N+1)th adjustment period may be determined, so that switching control on a first channel and a second channel may be performed in the (N+1)th adjustment period according to the determined second coefficient of proportionality.
112 citations
11 Oct 2015
TL;DR: Of the studied weather variables, variation in signal strength can be best explained by the variation in temperature, and frequency diversity can reduce the effects of channel-specific variation, and the difference between the transmit power levels.
Abstract: Many wireless sensor networks operating outdoors are exposed to changing weather conditions, which may cause severe degradation in system performance. Therefore, it is essential to explore the factors affecting radio link quality in order to mitigate their impact and to adapt to varying conditions. In this paper, we study the effects of temperature and humidity on radio signal strength in outdoor wireless sensor networks. Experimental measurements were performed using Atmel ZigBit 2.4GHz wireless modules, both in summer and wintertime. We employed all the radio channels specified by IEEE 802.15.4 for 2.4GHz ISM frequency band with two transmit power levels. The results show that changes in weather conditions affect received signal strength. Of the studied weather variables, variation in signal strength can be best explained by the variation in temperature. We also show that frequency diversity can reduce the effects of channel-specific variation, and the difference between the transmit power levels.
111 citations
TL;DR: In this paper, a criterion fusion approach is proposed to guide the spectral segmentation process of the bearing signal, which is first divided into initial fine segments which are then adaptively merged into different subsets using an enhanced bottom-up segmentation technique.
TL;DR: In this article, the authors proposed that the differential mode should have excellent out-of-band rejection and high selectivity for the desired frequency band, while the common mode should be suppressed over a wider frequency band.
Abstract: With the development of wireless communication technology, radiofrequency (RF) circuits and integrated circuits are becoming more complex and packing more functionality and signals into an ever closer space, with a high level of electromagnetic interaction between circuit nodes and interference/crosstalk from substrate coupling and free space [1]. Balanced/differential circuit technology has become more important in modern communication systems because of good commonmode rejection that leads to relatively high immunity to environmental noise when compared with the single-ended technology [1]-[3], as shown in Figure 1(a) and (b). For balanced circuits, the differential mode should have excellent out-of-band rejection and high selectivity for the desired frequency band, while the common mode should be suppressed over a wider frequency band. In the past few years, many microstrip balanced filters for single band and dual band with common-mode suppression have been realized [4]-[10], with different balanced networks, balanced driven antennas, balanced amplifiers, and mixers [11]-[18].
TL;DR: Findings indicate that eLORETA-ICA with EEG data can identify five RS-independent-Ns in their intrinsic frequency bands, and correct correlations within RS- independent-Ns are identified.
Abstract: Recent functional magnetic resonance imaging (fMRI) studies have shown that functional networks can be extracted even from resting state data, the so called “Resting State independent Networks” (RS-independent-Ns) by applying independent component analysis (ICA). However, compared to fMRI, electroencephalography (EEG) and magnetoencephalography (MEG) have much higher temporal resolution and provide a direct estimation of cortical activity. To date, MEG studies have applied ICA for separate frequency bands only, disregarding cross-frequency couplings. In this study, we aimed to detect EEG-RS-independent-Ns and their interactions in all frequency bands. We applied exact low resolution brain electromagnetic tomography-ICA (eLORETA-ICA) to resting-state EEG data in 80 healthy subjects using five frequency bands (delta, theta, alpha, beta and gamma band) and found five RS-independent-Ns in alpha, beta and gamma frequency bands. Next, taking into account previous neuroimaging findings, five RS-independent-Ns were identified: (1) the visual network in alpha frequency band, (2) dual-process of visual perception network, characterized by a negative correlation between the right ventral visual pathway (VVP) in alpha and beta frequency bands and left posterior dorsal visual pathway (DVP) in alpha frequency band, (3) self-referential processing network, characterized by a negative correlation between the medial prefrontal cortex (mPFC) in beta frequency band and right temporoparietal junction (TPJ) in alpha frequency band, (4) dual-process of memory perception network, functionally related to a negative correlation between the left VVP and the precuneus in alpha frequency band; and (5) sensorimotor network in beta and gamma frequency bands. We selected eLORETA-ICA which has many advantages over the other network visualization methods and overall findings indicate that eLORETA-ICA with EEG data can identify five RS-independent-Ns in their intrinsic frequency bands, and correct correlations within RS-independent-Ns.
TL;DR: In this article, a U-slot loaded single-layer half-width leaky-wave antenna (HW-MLWA) is proposed to achieve dual-band operation by periodically loading the antenna with U-shaped slots.
Abstract: Half-width microstrip leaky-wave antennas (HW-MLWAs) are generally single band. Here, we present a new method to achieve dual-band operation from an HW-MLWA by periodically loading the antenna with U-shaped slots. These dual-band MLWAs are able to steer the beam in forward directions in one band and in backward directions in the other band. One of the antenna designs was prototyped and tested, and excellent agreement between the predicted and measured results were observed. The measured 10-dB return loss bandwidth of the first and second bands are $19.5 \% $ (5.24–6.37 GHz) and $13.2 \% $ (7.9–9.02 GHz), respectively. The antenna can steer the main beam from $30^\circ $ to $65^\circ $ in the first band and from $-46^\circ $ to $-10^\circ$ in the second band by sweeping the frequency from 5.25 to 6.25 GHz and 7.75 to 9 GHz, respectively. The measured peak gain of the antenna is 12.2 and 14.1 dBi in the first and second bands, respectively. Although the antenna parameters are optimized for dual-band operation, the radiation properties in another higher frequency band (third band) are also explored. In the third band, the antenna beam continuously scans from backward to forward direction as frequency increases. Moreover, this U-slot loaded single-layer half-width LWA is easy to fabricate.
Patent•
01 Apr 2015
TL;DR: In this article, the authors proposed a channel detection method applied when an LTE system works in an unlicensed frequency band, a terminal and a base station, and when the channel is an idle state, data business transmission is performed.
Abstract: The invention provides a channel detection method applied when an LTE (long term evolution) system works in an unlicensed frequency band, a channel detection system applied when the LTE system works in the unlicensed frequency band, a terminal and a base station. The channel detection method applied when the LTE system works in the unlicensed frequency band comprises steps as follows: when data business arrives, a current subframe is determined, and channel detection time is set in the current subframe and/or a backward adjacent subframe for channel condition detection; and when the channel is an idle state, data business transmission is performed. With the adoption of the technical scheme, under the premise that normal work of the LTE system in the unlicensed frequency band is guaranteed, data business transmission delay caused by channel detection at a fixed detection period can be effectively reduced, the data business transmission efficiency is improved, and peaceful coexistence of the LTE system and other systems in the unlicensed frequency band is realized simultaneously.
TL;DR: In this article, a linear-to-circular polarizer was proposed to transform linearly polarized field to circularly polarized field over a wide frequency band. But the proposed polarizer is robust under oblique and deflected illuminations.
Abstract: A new single-layer linear-to-circular polarizer is presented in this communication. A novel hybrid meander line and loop configuration is employed to transform linearly polarized field to circularly polarized field over a wide frequency band. Numerical simulations indicate that the proposed polarizer is robust under oblique and deflected illuminations. A prototype of the proposed polarizer is designed and fabricated. Measured results show that the band of axial ratio less than 3 dB ranges from 18 to 29 GHz with about 3-dB insertion loss.
TL;DR: A novel method to achieve broadband low-scattering THz characteristics with wide-angle and polarization independence by a 2-bit flexible and nonabsorptive coding metasurface is proposed.
Abstract: Expanding bandwidths and arbitrary control of technology remain key issues in the field of electromagnetic waves, especially in terahertz (THz) wave. In this paper, we propose a novel method to achieve broadband low-scattering THz characteristics with wide-angle and polarization independence by a 2-bit flexible and nonabsorptive coding metasurface. The coding metasurface is composed of four digital elements based on double cross metallic line for “00”, “01”, “10”, and “11.” The reflection phase difference of neighboring elements is about 90° over a broad THz frequency band and wide incident angles. The low scattering coefficients below –10 dB were achieved over a wide frequency band from 0.8 THz to 1.5 THz when the incident angle is less than 50° by coding the four elements sequences. This superior property is maintained when the flexible coding metasurface is wrapped around a metallic cylinder with different dimensions. These results present a novel method to control THz waves freely and demonstrate significant scientific value in practical applications.
Patent•
14 Apr 2015
TL;DR: In this paper, a base-station apparatus is included in a communication system, in which a resource reservation signal which reserves the frequency band that is not able to be used exclusively is transmitted to the frequency bands that can be used based on a second communication scheme different from the first communication scheme.
Abstract: Provided are a base-station apparatus, a terminal apparatus, and a communication method that make it possible to realize a LTE-A system which, while suppressing interference from an existing system, improves throughput by applying CA to an unlicensed band. The base-station apparatus of the invention is a base-station apparatus which is included in a communication system, in which a first communication scheme applied to a frequency band that is able to be used exclusively is applied to a frequency band that is not able to be used exclusively, and which is able to communicate with a terminal apparatus by using the frequency band that is able to be used exclusively and the frequency band that is not able to be used exclusively, in which a resource reservation signal which reserves the frequency band that is not able to be used exclusively is transmitted to the frequency band that is not able to be used exclusively based on a second communication scheme different from the first communication scheme, and the first communication scheme is applied to the frequency band that is not able to be used exclusively after the resource reservation signal is transmitted.
TL;DR: In this paper, three frequency-domain design methods are proposed to deal with robust fractional order PID controller design via numerical optimization, which achieve robustness to the variation of some parameters by maintaining the open-loop phase quasi-constant in a pre-specified frequency band.
Abstract: This paper deals with robust fractional order PID controller design via numerical optimization. Three new frequency-domain design methods are proposed. They achieve good robustness to the variation of some parameters by maintaining the open-loop phase quasi-constant in a pre-specified frequency band, i.e., maintaining the iso-damping property of the controlled system. The two first methods are extensions of the well-known Monje-Vinagre et al. method for uncertain systems. They ameliorate the numerical optimization algorithm by imposing the open-loop phase to be flat in a frequency band not only around a single frequency. The third method is an interval-based design approach that simplifies the algorithm by reducing the constraints number and offers a more large frequency band with an iso-damping property. Several numerical examples are presented to show the efficiency of each proposed method and discuss the obtained results. Also, an application to the liquid carbon monoxide level control is presented.
Patent•
04 Feb 2015
TL;DR: In this article, a channel detection method and system of an LTE (Long Term Evolution) system working at a non-authorized frequency band as well as equipment and a terminal having functions of a base station is presented.
Abstract: The invention provides a channel detection method and system of an LTE (Long Term Evolution) system working at a non-authorized frequency band as well as equipment and a terminal having functions of a base station. The channel detection method is applicable to the LTE system of the equipment having the functions of the base station. The channel detection method comprises the following steps: dividing the non-authorized frequency band into a plurality of frequency bands; setting a judgment threshold which corresponds to each of the frequency bands and is used for detecting the busy state of channels in each frequency band; and setting a channel monitoring subframe for detecting the states of a downlink channel and/or an uplink channel in each frequency band in a frame structure of the LTE system, and detecting the busy state of the downlink channel and/or the uplink channel in each frequency band according to the judgment threshold corresponding to each frequency band. According to the technical scheme, the use ratio of a frequency spectrum of the non-authorized frequency band is increased, and furthermore, the LTE system cannot cause large interferences on other systems during normal working at the non-authorized frequency band.
TL;DR: In this paper, a piezoelectric vibratory energy harvester was developed for wideband operation at low frequencies. But the performance of the two-stage vibratory structure was not evaluated.
Abstract: This study develops a piezoelectric vibratory energy harvester intended for wideband operation at low frequencies. The harvester features a two-stage vibratory structure. The first stage picks up ambient low-frequency vibration and excites the second stage to vibrate at its resonant frequency, thereby realizing frequency upconversion and improving power-generation capability. The first stage is designed as a multimode resonator to adapt to a wide frequency band by multimode vibration coupling. Finite element simulation and lumped-element modeling indicate that the multimode coupled vibration at the first stage can excite the second stage into wideband resonance that well adapts the electric power generation to the wideband ambient vibrations. The micro harvesters are fabricated, with the testing results validating the design concept. The harvester can operate under acceleration amplitude of 1 g and frequency from 10 to 30 Hz. A peak power of 24.56 μW and a maximum average power of 3.62 μW are achieved at 1 g and 20 Hz. The harvester also exhibits power generating capability under excitation of the vibration from a running bus, where a peak power of 6.89 μW is generated.
TL;DR: In this paper, a dual-circular reflector with independent dualcircular polarizations is proposed for the first time, and the achieved bandwidth is 790 MHz (9.4% at the center frequency 8.37 GHz).
Abstract: A reflectarray with independent dual-circular polarizations is proposed for the first time. The reflector panel operates in X-band and contains 97 unit-cells. It is made with a lego-type configuration allowing change manually the phase aperture distribution and demonstrating experimentally the independence of both polarizations in the same frequency band. To this end, various beam pointing directions are selected in right-hand and left-hand polarizations. The achieved bandwidth is 790 MHz (9.4% at the center frequency 8.37 GHz) for an axial ratio lower than 3.5 dB with 1.5 dB gain variations.
TL;DR: In this paper, a predictive electrical model of the slow-wave coplanar waveguide structure (S-CPW) is presented under the assumption of Quasi-TEM propagation mode.
Abstract: In this paper, a predictive electrical model of the slow-wave coplanar waveguide structure (S-CPW) is presented. The model was developed under the assumption of Quasi-TEM propagation mode. This assumption allows treating separately the electric field from the magnetic field. Therefore, inductive and capacitive effects are processed apart. Within this context, analytical formulas, parameterized by S-CPW geometric dimensions, are given for each electric parameter in the model, including resistances that account for losses. The model was validated with electromagnetic simulations $({\rm HFSS}^{{{{\rm TM}}}})$ and measurement results on several integrated technologies. An excellent agreement was achieved over a wide frequency band from DC up to 110 GHz, with a maximum error of 10%. Consequently, the model provides a fast and powerful tool for designing circuits based on S-CPW. The developed model enables a better insight of how geometries influence the overall S-CPW performance. The model was applied to the design of a quarter-wave length transmission lines and tunable phase shifter. The transmission lines were optimized in terms of performance, minimum length or surface. The tunable phase shifter was designed by embedding varactors in the S-CPW floating shield. These designs highlight the efficiency of the model for complex optimization or complex circuits design, respectively.
TL;DR: In this article, an all-textile Louis Vuitton logo antenna is proposed for the industrial, scientific, and medical 2.45 GHz band and in the 4.5 GHz band.
Abstract: An all-textile Louis Vuitton logo antenna is proposed. For proper antenna design, the electrical properties of various leathers are measured. The crossed LV-shaped logo is composed of two longer thin arms for the lower frequency band and two shorter thick arms for the higher frequency band. The proposed logo antenna is fabricated from a conductive textile and a leather substrate, and it has an appropriate logo size for practical bag utilization. The proposed antenna operates in the industrial, scientific, and medical 2.45 GHz band and in the 4.5 GHz band. The corresponding fractional $-\hbox{10}\hbox{-dB}$ reflection coefficient bandwidths and maximum gains are 17.1% and $-\hbox{0.29}~\hbox{dBi}$ , respectively, for the lower frequency band and 13% and 3.05 dBi, respectively, for the higher frequency band.
Patent•
29 Jul 2015
TL;DR: In this article, a method for using DRX in a non-authorized frequency band is presented, which comprises the steps of configuring non-continuous received DRX parameters for UE to obtain the DRX activating time and DRX sleeping time of the UE; sending the parameters to the UE, setting information of CCA detection time of an idle channel of UE at the non-authorised frequency band; and sending the first indication information to UE to indicate the UE to wake up at the CCA time in the nonauthorized frequency band so as to monitor the channel
Abstract: The embodiment of the invention discloses a method for using DRX in a non-authorized frequency band. The method comprises the steps of configuring non-continuous received DRX parameters for UE to obtain the DRX activating time and the DRX sleeping time of the UE; sending the DRX parameters to the UE; setting information of CCA detection time of an idle channel of the UE at the non-authorized frequency band; sending the first indication information to the UE to indicate the UE to wake up at the CCA time in the non-authorized frequency band so as to monitor the channel of the non-authorized frequency band; sending the data according to the CCA time of the UE at the non-authorized frequency band, and the DRX activating time and the DRX sleep time of the UE. According to the technical scheme, the method has the advantages that the UE can effectively monitor the channel of the non-authorized frequency band while the power consumption of the UE at the non-authorized frequency band is reduced; the LTE device and the WiFi device can fairly share the resources in the non-authorized frequency band.
24 May 2015
TL;DR: New electrochemical type fractors have been developed, by coating a polymer-carbon nanotube (CNT) composite over Cu clad epoxy block and putting the block in polarizing solution, which will help to realize fractional order circuits which need to be operated in wide frequency band.
Abstract: A fractor or a fractional order element should show a constant phase (CP), between ±90° (except 0°) at any frequency, theoretically. However, all the practical realization of single component fractor have limitation in their CP zone. Not many single-component-fractors have been reported having CP zone more than a decade. In this work, new electrochemical type fractors have been developed, by coating a polymer-carbon nanotube (CNT) composite over Cu clad epoxy block and putting the block in polarizing solution. By varying the percentage of CNT in polymer-CNT composite and the nature of polarizing solution, two different types of fractor have been realized. One is a wide-band fractor having CP zone of five decades (20 Hz to 2 MHz) with a ripple of ±2° only. The other one shows two distinct CP zones at two different phase angles. Each zone is about two decade long. These fractors will help to realize fractional order circuits which need to be operated in wide frequency band.
TL;DR: The Hurst parameter provides a robust and versatile tool for quantifying FHR variability, yields better acidosis detection performance compared to the LF/HF ratio, and avoids arbitrariness in spectral band splitting and definitions.
Abstract: Background
The fetal heart rate (FHR) is commonly monitored during labor to detect early fetal acidosis. FHR variability is traditionally investigated using Fourier transform, often with adult predefined frequency band powers and the corresponding LF/HF ratio. However, fetal conditions differ from adults and modify spectrum repartition along frequencies.
Aims
This study questions the arbitrariness definition and relevance of the frequency band splitting procedure, and thus of the calculation of the underlying LF/HF ratio, as efficient tools for characterizing intrapartum FHR variability.
Study Design
The last 30 minutes before delivery of the intrapartum FHR were analyzed.
Subjects
Case-control study. A total of 45 singletons divided into two groups based on umbilical cord arterial pH: the Index group with pH ≤ 7.05 (n = 15) and Control group with pH > 7.05 (n = 30).
Outcome Measures
Frequency band-based LF/HF ratio and Hurst parameter.
Results
This study shows that the intrapartum FHR is characterized by fractal temporal dynamics and promotes the Hurst parameter as a potential marker of fetal acidosis. This parameter preserves the intuition of a power frequency balance, while avoiding the frequency band splitting procedure and thus the arbitrary choice of a frequency separating bands. The study also shows that extending the frequency range covered by the adult-based bands to higher and lower frequencies permits the Hurst parameter to achieve better performance for identifying fetal acidosis.
Conclusions
The Hurst parameter provides a robust and versatile tool for quantifying FHR variability, yields better acidosis detection performance compared to the LF/HF ratio, and avoids arbitrariness in spectral band splitting and definitions.
TL;DR: In this paper, a photonic approach to Doppler frequency shift estimation was proposed and experimentally demonstrated, providing a high-resolution and frequency-independent solution for radar, microwave/millimeter-wave, and communication systems.
Abstract: High-resolution Doppler frequency shift (DFS) estimation in a wide frequency range is essential for radar, microwave/millimeter-wave, and communication systems. In this paper, a photonic approach to DFS estimation is proposed and experimentally demonstrated, providing a high-resolution and frequency-independent solution. In the proposed approach, the DFS between the transmitted microwave signal and the received echo signal is mapped into a doubled frequency spacing between two target optical sidebands by using two cascaded electrooptic modulators. Subsequently, the DFS is then estimated through the spectrum analysis of a low-frequency electrical signal generated from the frequency beating of the two target sidebands with an improved resolution by a factor of 2. In the experiments, DFSs from ${-}{\hbox{90}}$ to 90 kHz are successfully estimated for microwave/millimeter-wave signals at 10, 15, and 30 GHz, where the estimation errors are lower than $\pm {\hbox{5}} \times {\hbox{10}}^{-10}$ Hz. For radial velocity measurement, these results reveal a range from 0 to 900 m/s and a resolution of ${\hbox{1}} \times {\hbox{10}}^{-11}$ m/s at 15-GHz frequency band, or a range from 0 to 450 m/s and a resolution of ${\hbox{5}} \times {\hbox{10}}^{-12}$ m/s at 30-GHz band. To eliminate the estimation ambiguity, a reference branch is introduced for generating an indicator frequency to discriminate the sign of DFS and the direction of radial velocity for approaching or receding motion. In addition, extended discussions on the signal-to-noise ratio, the minimum measurable DFS, and other detection features of the proposed approach are presented.
TL;DR: A new improved Kurtogram was proposed in this paper instead of Kurtosis, correlated Kurtosis of envelope signal extracted from the wavelet packet node was used as an indicator to determine the optimal frequency band Correlated Kurtosis helps to determine fault related impulse signals not affected by other unrelated signal components.
Abstract: A new improved Kurtogram was proposed in this paper Instead of Kurtosis, correlated Kurtosis of envelope signal extracted from the wavelet packet node was used as an indicator to determine the optimal frequency band Correlated Kurtosis helps to determine the fault related impulse signals not affected by other unrelated signal components Finally, two simulated and three experimental bearing fault cases are used to validate the effectiveness of proposed method and to compare with other similar methods The results demonstrate it can locate resonant frequency band with a high reliability than two previous developed methods by Lei et al and Wang et al especially for the incipient faults under low load
TL;DR: The presented source tunability of the temporal carrier frequency and spectrum expands the scope of spectrally dense THz sources to time-resolved nonlinear THz spectroscopy in the entire THz gap and opens new opportunities towards ultrafast coherent control over matter and light.
Abstract: In Terahertz (THz) science, one of the long-standing challenges has been the formation of spectrally dense, single-cycle pulses with tunable duration and spectrum across the frequency range of 0.1–15 THz (THz gap). This frequency band, lying between the electronically and optically accessible spectra hosts important molecular fingerprints and collective modes which cannot be fully controlled by present strong-field THz sources. We present a method that provides powerful single-cycle THz pulses in the THz gap with a stable absolute phase whose duration can be continuously selected between 68 fs and 1100 fs. The loss-free and chirp-free technique is based on optical rectification of a wavelength-tunable pump pulse in the organic emitter HMQ-TMS that allows for tuning of the spectral bandwidth from 1 to more than 7 octaves over the entire THz gap. The presented source tunability of the temporal carrier frequency and spectrum expands the scope of spectrally dense THz sources to time-resolved nonlinear THz spectroscopy in the entire THz gap. This opens new opportunities towards ultrafast coherent control over matter and light.