Function Of Signal Frequency Research Articles

Motion speed control of magnetic microsphere robot under alternating signals

Gradient magnetic field driving method does not have strict structural requirements for micro robots, making processing convenient. However, the speed control parameter of micro robots under gradient magnetic fields is single, which limits the practical application of this type of robots. Therefore, this article proposes to use alternating signals to control the motion speed of magnetic microsphere robots. Here, a motion analysis model of a magnetic microsphere robot driven by alternating signals is established, and a formula for calculating the movement speed of the magnetic microsphere robot is provided. The special motion mode of the magnetic microsphere robot driven by alternating signals is considered, and the correctness of the theoretical calculation is verified by experiments. The mechanisms and conditions for the different motion modes of magnetic microsphere robots are revealed. The movement speed of the magnetic microsphere robot under the alternating voltage signals is determined as a function of signal frequency, signal duty cycle, and bias voltage value. The results show that under the alternating voltage signals, the magnetic microsphere robot has three different motion states, namely rotation -movement alternation, swing-movement alternation, and pure movement. There are three control parameters of the speed, which are signal change frequency, duty cycle, and bias voltage.

Analysis and Reduction of Nonlinear Distortion in AC-Coupled CMOS Neural Amplifiers with Tunable Cutoff Frequencies

Integrated CMOS neural amplifiers are key elements of modern large-scale neuroelectronic interfaces. The neural amplifiers are routinely AC-coupled to electrodes to remove the DC voltage. The large resistances required for the AC coupling circuit are usually realized using MOSFETs that are nonlinear. Specifically, designs with tunable cutoff frequency of the input high‑pass filter may suffer from excessive nonlinearity, since the gate-source voltages of the transistors forming the pseudoresistors vary following the signal being amplified. Consequently, the nonlinear distortion in such circuits may be high for signal frequencies close to the cutoff frequency of the input filter. Here we propose a simple modification of the architecture of a tunable AC-coupled amplifier, in which the bias voltages Vgs of the transistors forming the pseudoresistor are kept constant independently of the signal levels, what results in significantly improved linearity. Based on numerical simulations of the proposed circuit designed in 180 nm technology we analyze the Total Harmonic Distortion levels as a function of signal frequency and amplitude. We also investigate the impact of basic amplifier parameters—gain, cutoff frequency of the AC coupling circuit, and silicon area—on the distortion and noise performance. The post-layout simulations of the complete test ASIC show that the distortion is very significantly reduced at frequencies near the cutoff frequency, when compared to the commonly used circuits. The THD values are below 1.17% for signal frequencies 1 Hz–10 kHz and signal amplitudes up to 10 mV peak-to-peak. The preamplifier area is only 0.0046 mm2 and the noise is 8.3 µVrms in the 1 Hz–10 kHz range. To our knowledge this is the first report on a CMOS neural amplifier with systematic characterization of THD across complete range of frequencies and amplitudes of neuronal signals recorded by extracellular electrodes.

Detailed study on effects of gate voltage, frequency and temperature on dielectric properties of Cu/PAr/n-CdS/SnO2 MIS Schottky diode

In this paper, CdS based metal–insulator–semiconductor (MIS) diode was fabricated by using the Polyarylate (PAr) film as insulator dielectric on transparent conductive glass substrate. The dielectric parameters such as dielectric constant (), loss (ϵ), loss tangent (tan δ), ac conduc-tivity (σ AC ) and complex modulus (, ) of the MIS Schottky diode were examined as a function of signal frequency, gate voltage and temperature. The detailed analysis revealed the interface states at the CdS/PAr junction and the characteristics of these interface states in the examined frequency range. The value of the angular frequency exponent (S) and the corres-ponding temperature dependence of σ ac indicate the hopping mechanism which agrees with the CBH model. The barrier height between the neighbouring states is determined as 47 meV for the temperature range studied. The temperature dependence of ΔV FB verifies the thermally active behaviour of interface states which decrease from 117 to 41 meV with increasing temperature.

Effect of age, test frequency and level on thresholds for the TEN(HL) test for people with normal hearing

Objective The objective was to assess the effect of age on thresholds for the TEN(HL) test for diagnosing dead regions in the cochlea, as a function of signal frequency and TEN(HL) level. Design The TEN(HL) test was administered twice for each ear of each participant (in two separate sessions) using signal frequencies from 0.5 to 4 kHz and TEN(HL) levels of 30, 50 and 70 dB HL/ERBN. Study sample 19 young participants (mean age 24 years) and 17 older participants (mean age 65 years). All had near-normal audiograms with no history of hearing problems. Results There was no systematic change from session 1 to session 2 and repeatability was good. There was no significant effect of ear or gender. The average signal-to-TEN(HL) ratio at threshold was greater for the older than for the young group, especially for the highest level at high frequencies. An equation is presented that can be used to predict the “normal” threshold as a function of age, TEN(HL) level and signal frequency. Conclusions Thresholds for the TEN(HL) test were greater for the older group and increased at high frequencies and high TEN levels. The results can be used to give a more accurate diagnosis of dead regions.

Fabrication of the Impedance-Matched Josephson Parametric Amplifier and the Study of the Gain Profile

We designed and fabricated an impedance-matched Josephson parametric amplifier (JPA) working in the flux-pump mode for the broadband amplification of microwave signals. A simple fabrication method suitable for a small cleanroom was developed. We also studied the phase response, as well as the gain, as a function of signal frequency and pump power at various pump frequencies. The phase response can be explained with the behavior of the nonlinear Duffing oscillator. The observed decrease of the resonance frequency as the pump power increases, as well as the emergence of an unstable bifurcation zone, are the characteristic nonlinear behavior of the Duffing oscillator. The features of the gain profile in the stable zone can be explained with a model adapted from the theoretical model for the two-dimensional gain profile of an impedance-matched, current-pumped JPA. Over 17 dB gain with a bandwidth more than 300 MHz (centered around 6.45 GHz) was observed. Our impedance-matched JPA is used for improving the fast readout fidelity of transmon qubits.

Nonlinear feature of phase matched Lamb waves in solid plate

The measurement of second harmonic Lamb waves is investigated as a promising feature extraction technique to characterize material nonlinearity in plate-like structures. In general, the effect of second harmonic generation can be weak, due to the dispersive nature of Lamb waves. The phase matched Lamb modes are explored to generate the second harmonics with a cumulative growth effect. Among all phase matched Lamb modes, it is of particular interest to find the most suitable Lamb modes for improving the efficiency of second harmonic generation and reception. Analytical expressions and experimental observations of second harmonic generation of Lamb waves in an isotropic plate with weak nonlinearity, are presented in this paper. Nonlinear parameters of Lamb waves are derived in this paper for the first time as a function of signal frequency, wave mode and geometric parameters of waveguides. Nonlinear features of various phase matched Lamb modes are discussed for the comparison of efficiency of second harmonic generation. The experimental results are found to be consistent with the theoretical predictions in a qualitative manner. This study shows that physics based feature selection is essential for efficient generation and reception of second harmonic Lamb waves.

Loosely coherent search in LIGO O1 data for continuous gravitational waves from Terzan 5 and the Galactic Center

We report results of a search for continuous gravitational waves from a region covering the globular cluster Terzan 5 and the galactic center. Continuous gravitational waves are expected from fast-spinning, slightly non-axisymmetric isolated neutron stars as well as more exotic objects. The regions that we target are believed to be unusually abundant in neutron stars. We use a new loosely coherent search method that allows to reach unprecedented levels of sensitivity for this type of search. The search covers the frequency band 475-1500 Hz and frequency time derivatives in the range of [-3e-8, +1e-9] Hz/s, which is a parameter range not explored before with the depth reached by this search. As to be expected with only a few months of data from the same observing run, it is very difficult to make a confident detection of a continuous signal over such a large parameter space. A list of parameter space points that passed all the thresholds of this search is provided. We follow-up the most significant outlier on the newly released O2 data and cannot confirm it. We provide upper limits on the gravitational wave strength of signals as a function of signal frequency.

Localization of broadband sounds carrying interaural time differences: Effects of frequency, reference location, and interaural coherence.

The auditory processes involved in the localization of sounds in rooms are still poorly understood. The present study investigated the auditory system's across-frequency processing of interaural time differences (ITDs) and the impact of the interaural coherence (IC) of the stimuli in ITD discrimination and localization. First, ITD discrimination thresholds were measured as a function of signal frequency, reference ITD, and IC using critical-band wide noises. The resulting data were fitted with a set of analytical functions and ITD weights were derived using concepts from signal detection theory. Inspired by the weighted-image model [Stern, Zeiberg, and Trahiotis. (1988). J. Acoust. Soc. Am. 84, 156-165], the derived ITD weights were then integrated in a simplified localization model using an optimal combination of ITD information across frequency. To verify this model, a series of localization experiments were conducted using broadband noise in which ITD and IC were varied across frequency. The model predictions were in good agreement with the experimental data, supporting the assumption that the auditory system performs a weighted integration of ITD information across frequency to localize a sound source. The results could be valuable for the design of new paradigms to measure localization in more complex acoustic conditions and may provide constraints for future localization models.

Psychoacoustic measurements of ipsilateral cochlear gain reduction as a function of signal frequency.

Forward masking experiments at 4 kHz have demonstrated that preceding sound can elicit changes in masking patterns consistent with a change in cochlear gain. However, the acoustic environment is filled with complex sounds, often dominated by lower frequencies, and ipsilateral cochlear gain reduction at frequencies below 4 kHz is largely unstudied in the forward masking literature. In this experiment, the magnitude of ipsilateral cochlear gain reduction was explored at 1, 2, and 4 kHz using forward masking techniques in an effort to evaluate a range of frequencies in listeners with normal hearing. Gain reduction estimates were not significantly different at 2 and 4 kHz using two forward masking measurements. Although the frequency was a significant factor in the analysis, post hoc testing supported the interpretation that gain reduction estimates measured without a masker were not significantly different at 1, 2, and 4 kHz. A second experiment provided evidence that forward masking in this paradigm at 1 kHz cannot be explained by excitation alone. This study provides evidence of ipsilateral cochlear gain reduction in humans at frequencies below the 4 kHz region.

Reference thresholds for the TEN(HL) test for people with normal hearing

Objective: To estimate normative values and repeatability of thresholds for the TEN(HL) test for diagnosing dead regions in the cochlea, as a function of signal frequency, TEN(HL) level, age and gender. Design: The TEN(HL) test was administered twice for each ear of each participant using signal frequencies from 0.5 to 4 kHz and TEN(HL) levels of 30, 50 and 70 dB HL/ERBN. Study sample: In all, 29 young participants and 8 older participants were tested. All had normal audiograms with no history of hearing problems. Results: There was good repeatability across sessions. There was no significant effect of ear, gender or age group. The average signal-to-TEN ratio (STR) at threshold was close to 0 dB. For low signal frequencies, the STR at threshold varied only slightly with TEN(HL) level, but for the signal frequencies of 3 and 4 kHz the STR at threshold increased to about +2.7 dB for the TEN(HL) level of 70 dB/ERBN. Conclusions: For a high TEN(HL) level, the “normal” STR at threshold at 3 and 4 kHz is closer to +2 dB than to 0 dB. Further research is needed to assess whether the TEN(HL)-test criteria need to be modified when testing at high frequencies and high levels.

(Invited) A 1-mG MEMS Sensor

MEMS (microelectromechanical systems) technology has contributed substantially to the miniaturization of inertial sensors, such as accelerometers and gyroscopes [1]. Nowadays, MEMS inertial sensors have been widely used in a variety of application in our daily life. In recent years, accurate sensing of low acceleration, specifically below 1 G ( G = 9.8 m/s2, gravitational acceleration), has been one of the major interests for MEMS accelerometer development; those highly-sensitive accelerometers are to be used for possible applications such as healthcare and medical use, navigation systems, and micro-gravity monitoring in space [2]. According to the background, we have proposed a design approach of sub-1G MEMS accelerometer with a gold proof mass [3]. The high-density of gold has enabled us to suppress the thermo-mechanical noise, as it is called Brownian noise (BN ), when compared with typical proof mass material such as silicon; as the magnitude of BN is inversely proportional to the proof mass [4], the increase of proof-mass density would be an effective method to have low BN with a minimum proof-mass footprint. In this paper, we present a 1mG MEMS sensor that was designed to be an extension of our previous work. A proof-of-concept device has been developed with a proof mass made of electroplated gold. The target BN was set to be below 1 μG/Hz1/2, which has potential of acceleration sensing with a resolution of 1 mG or even lower. The proof mass was designed to be 2.4 mm × 2.1 mm in area with the thickness of 12 μm, which was nearly four times larger than that of our previous sensor. To reduce the metal warpage, the proof mass was segmented into a number of sub-blocks that were cross-linked by the additional metal layer. The device was fabricated by the post-CMOS (complementary metal-oxide semiconductor) process [6] utilizing gold electroplating; the sensor can be implemented on to CMOS-LSI (large-scale integration). Thus, MEMS structures and sensing circuitry could be integrated as a single chip with a minimum footprint and parasitic elements. Fig. 1(a) shows a top view of the fabricated MEMS device. The proof mass consists of the array of 18 × 21 sub-blocks. Each proof mass corner is suspended by micromechanical spring. A close-up SEM (scanning electron microscope image) is shown in Fig. 1(b). The stopper is used to limit the displacement of the proof mass, which would prevent the self-destruction of the MEMS structure at the input of excess acceleration. The fundamental characteristics of the MEMS device were experimentally obtained by the frequency response, where we measured capacitance and phase as a function of signal frequency; the actual BN was estimated to be 0.16 μG/Hz1/2 [5] that was sufficiently lower than the target value of 1 μG/Hz1/2. Also, we measured the capacitance change between the proof mass and the fixed counter electrode as a function of input acceleration. The experimental results indicate that the MEMS device was capable of capacitive sensing input acceleration below 1G. The evaluation results show that the proposed sensor design could further improve the sensing resolution of MEMS accelerometers, which would be required for possible future applications. The presentation will cover the design, fabrication process, and measurement results of the proof-of-concept device. [1] N. Yazdi, F. Ayazi, and K. Najafi, “Micromachined Inertial Sensors”, Proc. IEEE, Vol. 86, pp.1640-1659, 1998. [2] G. Krishnan, C. U. Kshirsagar, G. K. Ananthasuresh, and N. Bhat, “Micromachined High-Resolution Accelerometers,” J. Indian Inst. Sci., vol. 87, pp. 333-361, 2007. [3] D. Yamane et al., “Design of sub-1g microelectromechanical systems accelerometers” Appl. Phys. Lett., vol. 104, issue 7, pp. 074102, 2014. [4] M. Lemkin, and B. E. Boser, “A Three-Axis Micromachined Accelerometer with a CMOS Position-Sense Interface and Digital Offset-Trim Electronis,” IEEE J. Solid-State Circuits, vol. 34, pp. 456-468, 1999. [5] D. Yamane, T. Konishi, T. Matsushima, H. Toshiyoshi, K. Machida, and K. Masu, "A Sub-1G Capacitive Sensor for Integrated CMOS-MEMS Accelerometers," in Proc. 7th Asia-Pacific Conference on Transducers and Micro/Nano Technologies (APCOT2014), EXCO, Daegu, Korea. June 29 - July 2, 2014, P2-55. [6] K. Machida, T. Konishi, D. Yamane, H. Toshiyoshi, and K. Masu, “Integrated CMOS-MEMS Technology and Its Applications,” ECS Trans., vol. 61, pp. 21-39, 2014. Figure 1

Insights into environmental drivers of acoustic angular response using a self-organising map and hierarchical clustering

Acoustic backscatter from the seafloor is a complex function of signal frequency, seabed roughness, grain size distribution, benthos, bioturbation, volume reverberation, and other factors. Angular response is the variation in acoustic backscatter with incident angle and is considered be an intrinsic property of the seabed. An unsupervised classification technique combining a self-organising map (SOM) and hierarchical clustering was used to create an angular response facies map and explore the relationships between acoustic facies and ground truth data. Cluster validation routines indicated that a two cluster solution was optimal and separated sediment dominated environments from mixtures of sediment and hard ground. Low cluster separation limited cluster validation routines from identifying fine cluster structure visible with an AR density plot. Cluster validation, aided by a visual comparison with an AR density plot, indicated that a 14 cluster solution was also a suitable representation of the input dataset. Clusters that were a mixture of hard and unconsolidated substrates displayed an increase in backscatter with an increase in the occurrence of hard ground and highlighted the sensitivity of AR curves to the presence of even modest amounts of hard ground. Remapping video observations and sediment data onto the SOM matrix is innovative and depicts the relationship between ground truth data and cluster structure. Mapping environmental variables onto the SOM matrix can show broad trends and localised peaks and troughs and display the variability of ground truth data within designated clusters. These variables, when linked to AR curves via clusters, can indicate how environmental factors influence the shape of the curves. Once these links are established they can be incorporated into improved geoacoustic models that replicate field observations.

Why longer song elements are easier to detect: threshold level-duration functions in the Great Tit and comparison with human data

Our study estimates detection thresholds for tones of different durations and frequencies in Great Tits (Parus major) with operant procedures. We employ signals covering the duration and frequency range of communication signals of this species (40-1,010 ms; 2, 4, 6.3 kHz), and we measure threshold level-duration (TLD) function (relating threshold level to signal duration) in silence as well as under behaviorally relevant environmental noise conditions (urban noise, woodland noise). Detection thresholds decreased with increasing signal duration. Thresholds at any given duration were a function of signal frequency and were elevated in background noise, but the shape of Great Tit TLD functions was independent of signal frequency and background condition. To enable comparisons of our Great Tit data to those from other species, TLD functions were first fitted with a traditional leaky-integrator model. We then applied a probabilistic model to interpret the trade-off between signal amplitude and duration at threshold. Great Tit TLD functions exhibit features that are similar across species. The current results, however, cannot explain why Great Tits in noisy urban environments produce shorter song elements or faster songs than those in quieter woodland environments, as detection thresholds are lower for longer elements also under noisy conditions.

A Physics-Based Causal Bond-Wire Model for RF Applications

A predictive causal physics-based compact model that describes the electrical behavior of multiple bond wires as a function of signal frequency and geometry of the wires is presented. It takes into account the inductive coupling between the wires, the frequency-dependent losses, and the capacitance between the wires and the ground plane. The model does not require any fitting parameters and places no restriction on the shape of the bond wires. Model predictions of resistance, of capacitance to the ground plane, and of self and mutual inductances of bond wires with different shapes were compared to the corresponding measured quantities. All inductive calculations use closed formulas that give a better approximations than the state-of-the-art. Furthermore, the causal nature of this model implies that it may be used for time-domain simulations.

Ionospheric bending correction for GNSS radio occultation signals

Ionospheric propagation effects on Global Navigation Satellite Systems (GNSS) signals are the most pronounced during radio occultation due to long ionospheric travel paths of the received signal on low Earth orbiting satellites. Inhomogeneous plasma distribution and anisotropy cause higher‐order nonlinear refraction effects on GNSS signals which cannot be fully removed through a linear combination of dual‐frequency observables. In this paper, higher‐order ionospheric effects due to straight line of sight (LOS) propagation assumption such as the excess path length of the signal in addition to the LOS path and the total electron content difference between the curved path and the LOS path have been investigated for selected GPS‐CHAMP occultation events. Based on simulation studies we have derived correction formulas for computing raypath bending effects as functions of signal frequency, tangential height of the raypath, ionospheric parameters such as the maximum ionization and total electron content. If these parameters are known, the proposed correction method is able to correct on an average about 65–80% bending errors of GNSS occultation signals.

Determining Electromagnetic Energy Loss Through a Radio-Frequency Transmission Line by Infrared Thermal Imaging

This paper presents a technique for measuring local electromagnetic energy loss through a transmission line by infrared thermal imaging. The technique offers an attractive route to investigate solid-state radio-frequency (RF) structures with different sizes and an arbitrary layout of lines by achieving an electromagnetic energy mapping over a wide frequency range between 300 MHz and 6 GHz. The measurement setup and the microstrip RF transmission line test device are described. An analytical model expressing the dissipated power profile as a function of signal frequency, transmission line features, and impedance mismatch is presented. Electromagnetic loss and temperature increase induced by dissipation are numerically studied. Experimental results are presented and discussed.

Diffusion in a linear oscillator driven by colored noises with white cross-correlation

The diffusion in a linear oscillator driven by white cross-correlation colored noises in which one of the noises is modulated by a biased period signal is studied. Effects on d versus Q curve, d versus D curve, and d versus Ω curve by multiplicative colored noise self-correlation time τ1 as well as additive colored noise self-correlation time τ2 are revealed. Here d, Q, D, and Ω denote the diffusion coefficient of the oscillator, the intensity of the signal modulated noise, the intensity of the pure additive noise, and the signal frequency, respectively. It is found that a minimum exists in the d versus Q curve and the d versus D curve respectirely. The diffusion coefficient as a function of signal frequency Ω exhibits a pronounced maximum at Ω=Ω, here Ω is the oscillator frequency. The condition of diffusion coefficient d=0 is derived.

Breakdown characteristics of helium and nitrogen at kHz frequency range in partial vacuum for point-to-point electrode configuration

Power devices operating in partial vacuum, such as aerospace systems or space environment are susceptible to partial discharges, corona, or volume discharges due to the partial vacuum conditions. These power systems also operate under frequencies and waveforms quite different from those studied and developed for earthbound power distribution systems. In this paper, we present our studies on the breakdown characteristics of helium and nitrogen gases under positive square-pulsed voltage at frequencies varying from 50 kHz to 200 kHz in partial vacuum, for a point-to-point electrode configuration. It is observed that high frequency breakdown voltage is lower than the dc breakdown voltage under the same experimental conditions and electrode geometry. Also, breakdown voltage versus pressure curves exhibited a Pashcen like behavior. Breakdown voltages of helium and nitrogen as a function of signal frequency are also presented.

Effects of activation of the efferent system on psychophysical tuning curves as a function of signal frequency

It has been shown that electrical stimulation of the efferent auditory system can influence neural tuning curves in animals. Here, we examined a psychophysical analog of this effect in humans. All of the 19 normally hearing subjects showed a reduction in the amplitude of otoacoustic emissions in one ear when contralateral broadband noise was presented, indicating a functioning efferent system. Psychophysical tuning curves (PTCs) were measured in simultaneous masking in the absence and presence of contralateral stimulation (CS). The CS was a continuous narrowband noise centered at the signal frequency and presented at a level of 50 or 60 dB SL. The CS had no consistent effect on the masker level at the tips of the PTCs. For the two highest signal frequencies (2000 and 4000 Hz), the CS reduced the masker level required for threshold on both the low- and high-frequency sides of the PTCs, and the sharpness of tuning, as measured by Q10, decreased significantly. For the two lowest signal frequencies (500 and 1000 Hz), the masker level required for threshold on the low-frequency sides of the PTCs increased with CS, and the Q10 values increased significantly. The general pattern of the results was consistent with that observed for electrical stimulation of the efferent system in animals.

Genetic algorithm based inversion of neural networks applied to optimised design of UWB planar antennas

An inversion of artificial neural networks using a genetic algorithm is presented for a novel concept of optimisation applied to UWB planar antennas of bow-tie type with respect to specified values of antenna performance in the frequency range 3.1–10.6 GHz. This efficient concept is shown to achieve significant reduction in computing time for optimisation. The multidimensional inversion is characterised by a simple composite fitness or target function that includes antenna parameters as a function of signal frequency or/and angle dependence. Good impedance matching and gain performance is achieved over the whole frequency range by adequately modifying the radiating contour profile of the conventional triangular bow-tie antenna.