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In this communication, based upon a squeezed-state trial wave function, we have performed a simple variational study of the spectral collapse of the two-photon Rabi model. Our analysis indicates that the light-matter interaction and the spin-flipping effectively constitute two competing impacts upon the radiation mode. Whilst the former tries to decrease the radiation mode frequency, the latter may counteract or reinforce it, contingent upon the state of the atomic system. The light–matter interaction appears to dominate the frequency modulation as its coupling strength goes beyond the critical value, leading to the emergence of the spectral collapse. However, at the critical coupling the dominance of the light–matter interaction is not complete, and incomplete spectral collapse appears. The extent of incomplete spectral collapse is found to depend upon the energy difference between the two atomic levels as well. [ABSTRACT FROM AUTHOR]

Continuous-time frequency modulation (CTFM) technique is extensively used in Sonar signal processing to estimate the range of received echoes. In this, the range resolution is inversely proportional to the bandwidth of the probe signal. A dual-demodulator continuous-time frequency modulation (DD-CTFM) technique that was proposed to improve the range resolution does not offer any significant improvement in range resolution over CTFM in practice. The super-resolution based analysis techniques for CTFM also offer limited improvement over the conventional CTFM technique. This paper describes a new method for CTFM analysis that has the potential to make the range resolution independent of the probe signal bandwidth. The proposed enhanced range resolution dual-demodulator continuous-time frequency modulation (ER-DD-CTFM) algorithm has two phases; one is the training phase and other is the test phase. In the training phase the complex weights are calculated in frequency domain due to all the possible echoes from the range of interest, while in the test phase the information of the echoes that are actually present in the received signal is estimated by solving a set of linear equations. The ER-DD-CTFM algorithm has been analyzed in simulation studies and in experiments conducted in an acoustic anechoic chamber. Both the studies and experiments demonstrate that up-to ten times better range resolution can be obtained using the proposed ER-DD-CTFM algorithm over DFT analysis based CTFM. Further, the improvements in the range resolution compared to Root-MUSIC analysis based CTFM are 2.8 times and 2.35 times for the simulation and experimental study respectively. [ABSTRACT FROM AUTHOR]

This work proposes a unified framework for linear system identification in frequency subbands using wavelet packets. To that end, a previous wavelet-packet technique is extended to allow for the use of general model structures and standard identification procedures. The technique can be straightforwardly applied to the identification of models with different structures, such as subspace models, provided that their parameters can be identified using a least-squares approach. Models with autoregressive structures are used here for means of illustration. The proposed technique is illustrated with the examples of the longitudinal dynamics of a flexible aircraft and with the model of a cantilever beam. The proposed wavelet-packet approach is favorably compared with the technique on which it was based and with a recently proposed wavelet-based subspace identification technique. [ABSTRACT FROM AUTHOR]

In this paper, the bimodal amplitude-and frequency modulation method of atomic force microscopy (AFM) is applied to investigate the residual oil film on KDP crystal surface after polishing and surface cleaning. The thickness map of residual oil film is obtained based on the relationship between the cantilever resonant frequency shift and the surface stiffness. The thickness maps measured by AFM and spectroscopic imaging ellipsometry methods are compared, and the results obtained by two methods are consistent. The measurement scheme extends the application of AFM technology to characterize the residual oil on the KDP surface quality quantitatively after polishing and surface cleaning. [ABSTRACT FROM AUTHOR]

A wideband dipole signal is required for dipole dispersion correction and near-borehole imaging. To obtain the broadband flexural wave dispersion, we use a nonlinear frequency modulation (NLFM) signal and propose a segment linear frequency modulation (SLFM) signal as the dipole excitation signal to compensate for the excitation intensity. The signal-to-noise ratio (SNR) of the signal over the entire frequency band is increased. The finite-difference method is used to simulate the responses from a Ricker wavelet, a linear frequency modulation (LFM) signal, an NLFM signal, and an SLFM signal in two borehole models of a homogeneously hard formation and a radially stratified formation. The dispersion and radial tomography results at low SNR of the sound source signals are compared. Numerical modeling suggests that the energy of the flexural waves excited by the Ricker wavelet source is concentrated near the Airy phase. In this case, the dispersion is incomplete and information regarding the formation near or far from the borehole cannot be obtained. The LFM signal yields dispersion information near the Airy phase and the high-frequency range but not in the low-frequency range. Moreover, the information regarding the formation far from the borehole is not accurate. The NLFM signal extends the frequency range of the flexural waves by compensating for the excitation intensity and yields information regarding the formation information, but it is not easy to obtain. The SLFM signal yields the same results as the NLFM signal and is easier to implement. Consequently, the dipole detection range expands and the S-wave velocity calculation accuracy improves. [ABSTRACT FROM AUTHOR]

A method of processing microwave sensor signals is proposed. Application of this method allows substantially improving the accuracy of determination of Doppler frequency and associated information parameters. Here, frequency modulation changing by the symmetric saw-tooth law is used with spectral processing of the output signal on rising and falling sections. The Doppler frequency is calculated from the cross-correlation function of the spectral envelope, which makes it possible to eliminate error caused by the spectral structure of the Doppler signal. [ABSTRACT FROM AUTHOR]

Single-channel speech separation is a challenging problem that has been of particular interest in recent years. Here the goal is to separate the target speech signal from the interference signals, with high accuracy. We propose a new hybrid single-channel speech separation system that applies adaptive coherent modulation filtering for low-frequency subbands and iterative incoherent speech separation technique for high-frequency subbands. In the adaptive coherent modulation filtering, an affine projection filter is applied to subband envelope in order to eliminate the interference signal. The subband envelope is determined via demodulation of the subband signal using a coherently detected subband carrier based on the time-dependent spectral center-of-gravity demodulation. The adaptive affine projection filter uses the separated target signal obtained from the iterative incoherent speech separation system as a reference signal. This system first obtains a rough estimate of target fundamental frequency range and then uses this estimate to segregate target speech. It then improves both fundamental frequency range estimation and voiced speech separation iteratively. Perceptual evaluation of speech quality, as one of the evaluation indices investigated in this paper, indicates that the proposed system extracts the majority of target speech segments with minimal interference and outperforms previous systems in voiced speech separation. [ABSTRACT FROM AUTHOR]

In this article, we investigate the plasmon-dielectric spectral interaction in the Ag/InSe and Al/InSe thin-film interfaces. The mechanism is explored by means of optical absorbance and reflectance at terahertz frequencies and by the impedance spectroscopy at gigahertz frequencies. It was observed that the interfacing of the InSe with Ag and Al metals with a film thickness of 250 nm causes an energy band gap shift that suits the production of thin-film optoelectronic devices. The reflectance and dielectric constant and optical conductivity spectral analysis of these devices displayed the properties of wireless band stop filters at 390 THz. The physical parameters which are computed from the conductivity spectra revealed higher mobility of charge carriers at the Al/InSe interface over that of Ag/InSe. The respective electron-bounded plasmon frequencies are found to be 2.61 and 2.13 GHz. On the other hand, the impedance spectral analysis displayed a microwave resonator feature with series resonance peak position at 1.68 GHz for the Al/InSe/Ag interface. In addition, the temperature-dependent impedance spectra, which were recorded in the temperature range of 300-420 K, revealed no significant effect of temperature on the wave trapping properties of the Al/InSe/Ag interface. The sensitivity of the interfaces to terahertz and gigahertz frequencies nominates it as laser light/microwave traps, which are used in fibers and communications. [ABSTRACT FROM AUTHOR]

A mono-component AM-FM signal decomposition method is proposed using discrete second-order generalized integrator and phase-locking scheme. A discrete second-order generalized integrator (SOGI) is employed in the algorithm as a quadrature signal generator for a center carrier frequency. The outputs from SOGI are in-phase and quadrature components of the AM-FM signal. These components are processed in the discrete phase-locked loop to estimate instantaneous frequency variation and instantaneous amplitude variation. The estimated instantaneous frequency variation is fed back to SOGI to adjust the center frequency. Proposed mono-component AM-FM demodulator is implemented in FPGA platform. The algorithm offers good acquisition time, accuracy, and operating range. Experimental investigations performed on the algorithm prove the efficacy and suitability of the algorithm for mono-component AM-FM demodulation. [ABSTRACT FROM AUTHOR]

The problem of increasing the precision with which the pitch frequency of speech signals is measured is considered. Existing algorithms for determining this frequency are presented and a new algorithm based on complementary ensemble empirical mode decomposition is developed. The results of the investigations confirm the robustness of the algorithm in the presence of frequency modulation of the pitch of speech signals. [ABSTRACT FROM AUTHOR]

In the conventional 2D-FFT based target detection method, all range-Doppler cells are computed by FFT (Fast Fourier Transform) and scanned by CA-CFAR (Cell-Averaging Constant False Alarm Rate) detection. This results in high computational complexity and long processing time. In this paper, we developed an automotive 24 GHz BSD (Blind Spot Detection) FMCW (Frequency Modulated Continuous Wave) radar with a low complexity target detection architecture based on a ROI (Region Of Interest) pre-processing scheme. In the real BSD zone, because the number of cars to be detected is limited, the designed method only extracts their velocities corresponding to the range ROIs in which real targets exist. Moreover, the presence probability of vehicles with the same range-bin but different velocities is very low. Thus, in the designed method, some Doppler ROIs cells with a high magnitude are only applied for CA-CFAR detection. This architecture can dramatically reduce the amount of data to be processed compared to that of the conventional 2D FFT based method, resulting in enhanced processing time. We developed a 24 GHz FMCW radar system composed a transceiver, antennas, and signal processing module. The designed algorithm was implemented in a tiny micro-processor of the signal processing module. By implementing our proposed algorithm in the developed 24 GHz FMCW radar system in an anechoic chamber and a real road, we verified that the range and velocity of a car occupying the BSD zone were detected. Compared to that of the conventional method, the reduction ratio of the total processing time was measured to be 52.4 %. [ABSTRACT FROM AUTHOR]

Features of propagation of low-frequency electromagnetic waves in the low-latitude ionosphere are considered in the case when such waves are generated by means of demodulation of the radiation of a high-power short-wave ground transmitter in the lower ionosphere. Calculations are performed in the ray approximation based on a simplified model (developed specially for the case under study) of the anomaly of the low-latitude equatorial electron density. It is demonstrated that latitude gradients of the equatorial anomaly may result in both additional focusing and defocusing of the beam of demodulated low-frequency waves. [ABSTRACT FROM AUTHOR]

Lowpass continuous-time Delta-Sigma modulators are very sensitive to clock jitter effects and various techniques have been proposed to cope with them in the past years. While three major techniques, switched-capacitor-resistor, switched-shaped-current and fixed-width pulse, are very effective to reduced clock jitter effects in theory, intrinsic device noise and external power supply noise may still limit their effectiveness in practice. In this paper, we perform detailed noise analysis of the three techniques to study their limits under external power supply noise as it is typically dominant and also to make a quantitative and practical comparison. It is found that the fixed-width pulse feedback technique may have a favorable edge among them for high frequency modulator designs, whereas switched-capacitor-resistor and switched-shaped-current techniques are more preferable in low to medium frequency modulator designs. [ABSTRACT FROM AUTHOR]

It is very interesting to measure the bistatic characteristics of sound scattering by the ocean bottom and surface for the development of present-day hydrolocation net-centric schemes. Possible methods for measuring scattering bistatic characteristics are evaluated. The angular characteristics of reverberation related to illumination of a water area by active linearly frequency-modulated signals are studied using linear passive arrays to test a measuring scheme in a shallow water area with a depth of ~20 m in the 1-3 kHz frequency range. The bistatic sound-scattering characteristics in the water area are calculated based on the measurements. The obtained characteristics are compared with the known data on the backscattering of sound. [ABSTRACT FROM AUTHOR]

Non-orthogonal multiple access (NOMA) can share the same frequency band with multiple mobile devices. In the conventional NOMA scheme, the possible pairs of users are limited and this limitation restricts the amount of capacity improvement. This is because the receiver only for the near user cancels the signal of the other user and then detect the desired signal. In this paper, the effect of joint detection in the far user of the NOMA downlink is evaluated through constellation constrained capacity. It allows the pairing of users with the difference of the propagation losses of less than 8 dB. The possible number of user pairs in the NOMA system then increases and a larger total capacity may be achievable. [ABSTRACT FROM AUTHOR]

Noise equivalent temperature difference (NETD) is the critical parameter for passive imaging detection. A modelling of the sensitivity performance including the f-type low flicker noise (1/ f-noise) influence is presented, specifically investigated on the 1/ f-noise to the sensitivity performance and the trade-offs between the low-noise amplifier (LNA)'s gain and the video frequency bandwidth. Measurement bench is set up, and results confirm that low-frequency modulation to the signal helps in improving the sensitivity performance. Based on the measurement results, it is concluded that signal power influences the 1/ f-noise properties in detection diode. The amplifier's output power is suggested to be lower than −30 dBm at least. This level is much lower than the point of P (1 dB compressed point of the LNA). [ABSTRACT FROM AUTHOR]

We consider a new signal processing method for the difference frequency of an FM microwave distance sensor, based on a sinusoidal signal model with three independent parameters - amplitude, frequency, and phase, which avoids the discretization error in spectral processing. [ABSTRACT FROM AUTHOR]

The main problems for ultrasonic inspection of austenitic stainless steel welds are low signal to noise ratio (SNR) and detection accuracy, caused by anisotropic and heterogeneous material structure with bulky columnar crystal. In order to overcome the problems mentioned above, a linear frequency modulated (LFM) pulse with a large time-bandwidth product can be used as the exciting signal in the ultrasonic inspection of the austenitic stainless steel welds, which can both enhance the average transmitted power and increase the SNR and time resolution by pulse compression process. Therefore, the ultrasonic time-of-flight diffraction (TOFD) technique with the LFM excitation was carried out to realize an accurate sizing and locating detection in austenitic stainless steel welds. Compared with the conventional TOFD testing, the SNR can be increased 12-15 dB, and the measured accuracy is also enhanced obviously. Accordingly the measured depth error is less than 0.81 % and the length error is less than 2.5 %. The proposed method can both enhance the capabilities of the ultrasonic inspection of austenitic welds and the measurement accuracy of ultrasonic TOFD testing. [ABSTRACT FROM AUTHOR]

The Sine Non-linear Chirp Keying (SNCK) is one kind of the SFM schemes, which play an important role as the commonly useful signals in sonar, radar and wireless communication systems. By adjusting its time-bandwidth product, the SNCK can satisfy different requirements of the quality of service and has better ability in Doppler shift inhibition than the ordinary MSK. However, no mathematical analysis for the time-bandwidth product (modulation factor) estimation of the SNCK scheme has been available. In this paper, a SCD-based estimation algorithm for the modulation factor of the SNCK scheme has been proposed. The mathematical model and diagrams of the three-dimensional SCD and the corresponding bi-frequency plane make it easy to understand how the SCD-based algorithm localizes the center frequency and the keying rate, as well as estimates the modulation factor. The simulation results show that the proposed estimation algorithm is useful under different SNR conditions. The corresponding Cramer-Rao lower bound are derived and used as the reference of the estimation algorithm. Moreover, we improve the estimation algorithm when the modulation factor varies, by using a set of the local ratio data, which compensates the differences between the simulation ratio values and the theoretical ratio results. This algorithm can be effective for the communication system with the SNCK scheme to synchronize the carrier and the symbol, as well as to demodulate the transmitted signals with unknown parameters. It is concluded that the obvious features of the SCD can be extracted for other similar signals with high reliability. [ABSTRACT FROM AUTHOR]

A transformer LC oscillator utilizing the low phase noise of spiral LC oscillator and the large frequency tuning range of active inductors is proposed to yield both a large frequency range and low phase noise. The oscillator is a passive transformer LC oscillator with the primary winding of the transformer connected to the oscillating nodes of the oscillator and the secondary winding loaded with an active inductor. The contribution of the noise of the active inductor is minimized by adjusting the coupling of the transformer such that the overall phase noise of the oscillator is much lower as compared with that of corresponding active inductor oscillators while the frequency tuning range of the oscillator is much larger than that of passive transformer oscillators. The VCO has been designed in an IBM 130 nm 1.2V CMOS technology and analyzed using Spectre from Cadence Design Systems with BSIM3 device models. For purpose of comparison, an active inductor LC oscillator and a spiral inductor LC oscillator have also been designed and analyzed. The phase noise of the active inductor, spiral transformer, and hybrid oscillators at 1 MHz frequency offset from their nominal oscillation frequency is $$-$$ 80.18, $$-$$ 106.9, and $$-$$ 100.5 dBc/Hz, respectively. The power consumption of the spiral inductor, active inductor, and hybrid oscillators is 4.8, 30, and 34.8 mW, respectively. [ABSTRACT FROM AUTHOR]

Frequency pulling of an oscillator integrated in a quadrature phase-shift keying wireless transmitter degrades the performance of the wireless system. This paper analyses the behavior of an oscillator in the presence of coupling between the oscillator and a power amplifier or antenna. Symbol switching in the modulator will cause frequency shifts in the oscillator at the modulation frequency. A new architecture for a 120 GHz quadrature frequency generator with large tuning range and immunity against PA-VCO coupling is presented. Combining the output signals of two independent oscillators, the pulling effect is removed and the frequency generator can be integrated with a PA and an antenna on the same chip. This architecture also makes quadrature generation with large tuning range feasible at 120 GHz. The chip is fabricated in a 45 nm CMOS technology and shows a tuning range of 16.2 GHz (13.5 $$\%$$ ), a phase noise of $$-$$ 112 dBc/Hz @ 10 MHz offset and a phase error of 5 $$^\circ$$ (Volkaerts et al. in: IEEE Radio Frequency Integrated Circuits Symposium (RFIC), ). [ABSTRACT FROM AUTHOR]

The results of investigations and the characteristics of a calibrator based on a vector generator are described. The application of the calibrator in the State checking schemes is considered. [ABSTRACT FROM AUTHOR]

In this article the affiliation "Jaypee Institute of Information Technology, Noida, India" for Author Kapil Dev Tyagi was missing. Correction to: Analog Integrated Circuits and Signal Processing (2019) 99:585-597 https://doi... The original version of this article unfortunately contained a mistake. [Extracted from the article]

The wavefunction of a moderately cold atom in a stationary near-resonant standing light wave delocalizes very fast due to wave packet splitting. However, we show that frequency modulation of the field may suppress packet splitting for some atoms having specific velocities in a narrow range. These atoms remain localized in a small space for a long time. We propose that in a real experiment with cold atomic gas this effect may decrease the velocity distribution of atoms (the field traps the atoms with such specific velocities while all other atoms leave the field). [ABSTRACT FROM AUTHOR]

In this paper, we propose an approach for the analysis and detection of acoustic events in speech signals using the Bessel series expansion. The acoustic events analyzed are the voice onset time (VOT) and the glottal closure instants (GCIs). The hypothesis is that the Bessel functions with their damped sinusoid-like basis functions are better suited for representing the speech signals than the sinusoidal basis functions used in the conventional Fourier representation. The speech signal is band-pass filtered by choosing the appropriate range of Bessel coefficients to obtain a narrow-band signal, which is decomposed further into amplitude modulated (AM) and frequency modulated (FM) components. The discrete energy separation algorithm (DESA) is used to compute the amplitude envelope (AE) of the narrow-band AM-FM signal. Events such as the consonant and vowel beginnings in an unvoiced stop consonant vowel (SCV) and the GCIs are derived by processing the AE of the signal. The proposed approach for the detection of the VOT using the Bessel expansion is shown to perform better than the conventional Fourier representation. The performance of the proposed GCI detection method using the Bessel series expansion is compared against some of the existing methods for various noise environments and signal-to-noise ratios. [ABSTRACT FROM AUTHOR]

This work is devoted to the problems of information transmission with frequency shift keying and fast frequency hopping in special channels where the signal/noise ratio is low, and a high energy interfering signal is present. We propose a demodulation algorithm that is significantly more stable to the influence of a powerful interfering signal as compared to other known algorithms. Under these conditions, we show a statistical criterion that lets one significantly reduce error probability on the demodulator's output. For the chosen criterion we prove several lemmas that let us speed up the demodulation algorithm. Computer modeling results show that the proposed demodulation algorithm has better correcting ability under a powerful interfering signal than previously known ones. [ABSTRACT FROM AUTHOR]

Artificial bee colony or ABC is one of the newest additions to the class of population based Nature Inspired Algorithms. In the present study we suggest some modifications in the structure of basic ABC to further improve its performance. The corresponding algorithms proposed in the present study are named Intermediate ABC (I-ABC) and I-ABC greedy. In I-ABC, the potential food sources are generated by using the intermediate positions between the uniformly generated random numbers and random numbers generated by opposition based learning (OBL). I-ABC greedy is a variation of I-ABC, where the search is always forced to move towards the solution vector having the best fitness value in the population. While the use of OBL provides a priori information about the search space, the component of greediness improves the convergence rate. The performance of proposed I-ABC and I-ABC greedy are investigated on a comprehensive set of 13 classical benchmark functions, 25 composite functions included in the special session of CEC 2005 and eleven shifted functions proposed in the special session of CEC 2008, ISDA 2009, CEC 2010 and SOCO 2010. Also, the efficiency of the proposed algorithms is validated on two real life problems; frequency modulation sound parameter estimation and to estimate the software cost model parameters. Numerical results and statistical analysis demonstrates that the proposed algorithms are quite competent in dealing with different types of problems. [ABSTRACT FROM AUTHOR]

Bottlenose dolphins ( Tursiops truncatus) produce individually distinctive signature whistles that broadcast the identity of the caller. Unlike voice cues that affect all calls of an animal, signature whistles are distinct whistle types carrying identity information in their frequency modulation pattern. Signature whistle development is influenced by vocal production learning. Animals use a whistle from their environment as a model, but modify it, and thus invent a novel signal. Dolphins also copy signature whistles of others, effectively addressing the whistle owner. This copying occurs at low rates and the resulting copies are recognizable as such by parameter variations in the copy. Captive dolphins can learn to associate novel whistles with objects and use these whistles to report on the presence or absence of the object. If applied to signature whistles, this ability would make the signature whistle a rare example of a learned referential signal in animals. Here, we review the history of signature whistle research, covering definitions, acoustic features, information content, contextual use, developmental aspects, and species comparisons with mammals and birds. We show how these signals stand out amongst recognition calls in animals and how they contribute to our understanding of complexity in animal communication. [ABSTRACT FROM AUTHOR]

A combination of optical feedback self-locking of a continuous-wave distributed feedback diode laser to a V-shaped high finesse cavity, laser phase modulation at a frequency equal to the free spectral range of the V-cavity and detection of the transmitted laser beam at this high modulation frequency is described for the possible application in cavity-enhanced absorption spectroscopy. In order to estimate the noise level of an absorbance baseline, the triplet of frequency modulated light, i.e. the central laser frequency and the two sidebands, were transmitted through both the V-cavity in open air and a 1.5-cm long optical cell placed behind the cavity output mirror and filled with acetylene (CH) at low pressure. The performance of the setup was evaluated from the measured relative intensity noise on the cavity output (normalised by the bandwidth) and the frequency modulation absorption signals induced by CH absorption in the 1.5-cm cell. From these data, we estimate that the noise-equivalent absorption sensitivity of 2.1 × 10 cm Hz-by a factor of 11.7 above the shot-noise limit-can be achieved for CH absorption spectra extracted from the heterodyne beat signals recorded at the transmission maxima intensity peaks of the successive TEM resonances. [ABSTRACT FROM AUTHOR]

The little destruction to the deployment site and high repeatability of the Controlled Accurate Seismic Source (CASS) shows its potential for investigating seismic wave velocities in the Earth's crust. However, the difficulty in retrieving impulsive seismic waveforms from the CASS data and identifying the seismic phases substantially prevents its wide applications. For example, identification of the seismic phases and accurate measurement of travel times are essential for resolving the spatial distribution of seismic velocities in the crust. Until now, it still remains a challenging task to estimate the accurate travel times of different seismic phases from the CASS data which features extended wave trains, unlike processing of the waveforms from impulsive events such as earthquakes or explosive sources. In this study, we introduce a time-frequency analysis method to process the CASS data, and try to retrieve the seismic waveforms and identify the major seismic phases traveling through the crust. We adopt the Wigner-Ville Distribution (WVD) approach which has been used in signal detection and parameter estimation for linear frequency modulation (LFM) signals, and proves to feature the best time-frequency convergence capability. The Wigner-Hough transform (WHT) is applied to retrieve the impulsive waveforms from multi-component LFM signals, which comprise seismic phases with different arrival times. We processed the seismic data of the 40-ton CASS in the field experiment around the Xinfengjiang reservoir with the WVD and WHT methods. The results demonstrate that these methods are effective in waveform retrieval and phase identification, especially for high frequency seismic phases such as PmP and SmS with strong amplitudes in large epicenter distance of 80-120 km. Further studies are still needed to improve the accuracy on travel time estimation, so as to further promote applicability of the CASS for and imaging the seismic velocity structure. [ABSTRACT FROM AUTHOR]

This paper presents an optimization methodology for continuous time loop-filters design applied to Class-D amplifiers. The methodology is based on an evolutionary optimization approach which integrates both the topology selection and circuit sizing by automatically generating optimal sized topologies and performance tradeoffs for the Class-D amplifier. The presented approach is demonstrated on two cases: for the design of a half-bridge amplifier and for a fully differential BTL class-D loop filter topology that achieves less than 0.003% THD at 680 mW output power in typical 0.18 μm CMOS technology. [ABSTRACT FROM AUTHOR]

A nonlinear circuit model taking into account the parasitics of the resonator connection to the measurement bench is presented; the measured data agree with the simulation results, except some undulations in the frequency dependence of the 2 f harmonic component of the reflected power. New models for the anti-series and the anti-parallel connections of two resonators are proposed. The frequency warping effect is discussed together with its elimination using the Gear methods up to the sixth order. [ABSTRACT FROM AUTHOR]

The goal of internal frequency compensation of a low dropout voltage regulator (LDO) is the selection of a small-value, ESR-independent output capacitor. Cascode compensation formed by a common-gate transistor acting as a current buffer, an optional series resistor, and a compensation capacitor creates a dominant pole and a left-half-plane (LHP) zero, allowing adequate phase margin and stable LDO design. To this end, a 1.21 V output, 100 mA, 0.1-10 μF output capacitor, ESR-independent, low voltage LDO using cascode compensation with replica bias is designed and fabricated in a 0.5 μm CMOS process with an area of 0.22 mm. A line regulation of 0.05% V/V, load regulation of 0.001% V/mA and dropout voltage of 220 mV were measured. LDO-specific pole-zero analysis is detailed. In addition to this design, two improved transient response LDO architectures using cascode compensation with split-length transistors are also explored. A Power Good feature is discussed, which enables direct interface between the LDO and a micro-processor. [ABSTRACT FROM AUTHOR]

This paper identifies the unavoidable time skew between counter and TDC inputs, if not properly compensated or corrected, as the major source of spurs in the output spectrum of an All-Digital-Phase-Locked Loops (ADPLLs). The frequency and the level of the main spur induced by the time skew are first analytically estimated. Then, an ADPLL, operating in the 3-4-GHz band, is designed in 90-nm CMOS technology and the reported simulations confirm the theoretical results. A simple glitch-removal circuit, capable of operating even in the presence of fast and large frequency drifts is proposed. The glitch corrector is demonstrated to cancel out the −24-dBc spur and its harmonics, without altering the lock transient behavior of the ADPLL. [ABSTRACT FROM AUTHOR]

This work explores the generation of a local oscillator for WCDMA band VII based on frequency multiplication of a GSM reference. The frequency multiplier is based on a PLL, which includes a compact VCO based on a ring oscillator. A proper PLL design allows to sufficiently reject the relative high VCO phase noise, complying with the WCDMA requirements. The effectiveness of the proposed approach is proved with the design of the whole multiplier in a 90 nm CMOS technology. The generated oscillation ranges from 3 to 6 GHz, while the simulated phase noise is −120 and −144 dBc/Hz at a frequency offset of 0.6 and 20 MHz, respectively, dissipating 6.3 mW. [ABSTRACT FROM AUTHOR]

A projection-type moiré topography that uses a frequency modulation technique with two liquid crystal digital gratings (LCDGs) is proposed. In this method, moiré contours are filtered to remove the image of the original grating from the moiré contours by moving the image created by the LCDGs. The frequency modulation technique can be used to analyze the fringe of step heights or other separate areas by modulating the fringe interval. The experimental results showed the possibility of measuring three-dimensional shapes and step heights. [ABSTRACT FROM AUTHOR]

The magnetically modulated saturation absorption profile is studied for a wide range of external DC magnetic field. The salient features of Doppler-free signal generated by laser frequency modulation and atomic energy level modulation are compared. The DC offset of the signal profile is found to be unstable as the external DC magnetic field is changed. The technical difficulty of tuning laser frequency under locked condition over a large frequency span is discussed along with possible solutions. [ABSTRACT FROM AUTHOR]

For the wideband nonstationary sinusoidal frequency modulation (SFM) interference in DSSS systems, the paper proposes a method to estimate partial parameters of the interference, and then an interference suppression algorithm is developed. The performance of the algorithm is analyzed. Simulations show that the algorithm can efficiently suppress the SFM interference. [ABSTRACT FROM AUTHOR]

Three methods for information transmission based on chaotic signal source modulation based on: application of adaptive observers, adaptive identification with the Implicit Adjustable Model, and frequency modulation with the adaptive demodulator are described. Application of the proposed methods for information transmission by means of chaotic Chua generator modulation is presented. [ABSTRACT FROM AUTHOR]

Detection of modulated light signals transmitted by active image markers can be used in object localization tasks and machine vision applications. The asynchronous demodulation pixel is able to detect the signal transmitted by these modulated markers. The modulated marker position in a two-dimensional pixel array can be used to identify the marker location in the field. In this paper the asynchronous demodulation pixel is analyzed and its operation is investigated in the presence of non-ideal effects such as parasitic elements, device mismatches and process variations. The effect of demodulator bias conditions and different switch pulsing techniques are examined and a modified demodulator controlling method is presented to increase the dynamic range and sensitivity of the pixel compared with the common operation schemes. The different demodulator structures are also simulated as 64 × 64 pixel array sensors using a 0.18 μm standard CMOS process and their operation is compared regarding sensitivity, filter transfer function, pixel size and power consumption. [ABSTRACT FROM AUTHOR]

The review deals largely with studies from my laboratory that were prompted by conversations I had with Gerhard Neuweiler more than 15 years ago. The studies were conducted on bats and dealt with mechanisms that enable the population of neurons in the inferior colliculus (IC) to respond selectively to the variety of signals bats emit for both communication and echolocation. The first section is concerned with how neurons in the dorsal nucleus of the lateral lemniscus (DNLL), the nucleus ventral to the IC, respond to species-specific signals and how they compare to responses of IC neurons evoked by the same signals. Those studies showed that DNLL neurons have no sideband inhibition and their responses are determined by excitation. In contrast, inhibition dominates in the IC where it carves out highly selective discharge properties. Those studies, in turn, raised questions about the quantitative features of inhibition that could only be answered with more sophisticated techniques. In the second section, results from analyses with spectrotemporal receptive fields (STRFs) are presented, and in the final section I show data derived from in vivo whole cell recordings that illustrate how features of inhibition interact with excitation to generate directionality selective responses in the IC. [ABSTRACT FROM AUTHOR]

Dual-frequency modulation (DFM) has been used to continuously track the frequency shifts of optical cavity modes in the vicinity of an optical transition of a gas inside the cavity for assessment of the gas concentration. A theoretical description of the size and lineshape of the DFM dispersion spectroscopy (DFM-DS) signal is given. Since the signal is measured in terms of a radio frequency the technique is insensitive to laser intensity fluctuations. The signal strength, which can accurately be obtained by curve fitting, only depends on fundamental parameters (including the line strength), thus enabling quantitative detection without calibration procedure. In a first demonstration, using a compact setup based on a narrowband fiber laser, the change in free spectral range around a value of 379.9 MHz due to an acetylene transition near 1531 nm was measured with a resolution of 6 Hz (i.e. with an accuracy of 1.5 parts in 10) in 12.5 s acquisition time, which corresponds to a minimum detectable integrated absorption (SNR=3) of 3×10 cm. [ABSTRACT FROM AUTHOR]

This paper describes a CMOS implementation of a Linear Voltage Regulator (LVR) used to power an implanted physiological signal system that is used to monitor the blood pressure. The topology is based on a classical structure of a Low Dropout Regulator (LDO) and receives his activation energy from a RF link characterizing a passive RFID tag. The LVR was designed to achieve important features like low power consumption, and a small silicon area without the need for any external discrete components. The low power operation represents an essential condition to avoid a high energy RF link, thus minimizing the power of the transmitter and the thermal effects on the patient tissues. The project was diffused in a 0.35 μm CMOS TSMC technology and a prototype was tested to validate the overall performance. The LVR output is regulated at 1 V and supplies a maximum load current of 0.5 mA @ 37°C. The load regulation is 13 mV/mA and the line regulation is 39 mV/V. The LVR total power consumption is 1.2 mW. [ABSTRACT FROM AUTHOR]

A spectral-representation-based algorithm is proposed to simulate non-stationary and stochastic processes with evolutionary power, according to a prescribed non-stationary cross-spectral density matrix. Non-stationary multi-point seismic ground motions at different locations on the ground surface are generated for use in engineering applications. First, a modified iterative procedure is used to generate uniformly modulated non-stationary ground motion time histories which are compatible with the prescribed power spectrum. Then, ground motion time histories are modeled as a non-stationary stochastic process with amplitude and frequency modulation. The characteristic frequency and damping ratio of the Clough-Penzien acceleration spectrum are considered as a function of time in order to study the frequency time variation. Finally, two numerical examples are presented to validate the efficiency of the proposed method, and the results show that this method can be effectively applied to the dynamic seismic analysis of long and large scale structures. [ABSTRACT FROM AUTHOR]

Electrochemical frequency modulation (EFM), a nondestructive corrosion measurement technique that can directly give values of corrosion current without prior knowledge of Tafel constants, is applied here to investigate the inhibition performance of tyrosine (Tyr) toward corrosion of low chromium alloy steel in 0.50 M HCl. Measurements were conducted under various experimental conditions in the range of temperature (20–60 °C). Results obtained from EFM were compared with other traditional corrosion monitoring techniques, namely Tafel extrapolation, impedance, and weight loss. Polarization measurements showed that Tyr acted as a mixed-type inhibitor with cathodic predominance. The inhibition process was attributed to the formation of an adsorbed film on the metal surface that protected the metal against corrosive agents. Energy dispersive X-ray spectroscopy and scanning electron microscopy examinations of the electrode surface confirmed the existence of such an adsorbed film. The inhibition efficiency increased with increase in Tyr concentration, while it decreased with solution temperature. The adsorptive behavior of Tyr on the electrode surface followed Temkin-type isotherm. Thermodynamic functions for the adsorption process were determined. The data obtained from the different methods were in good agreements, which indicated that the EFM technique was valid for monitoring the corrosion inhibition under the studied conditions. [ABSTRACT FROM AUTHOR]

Abstract  Measuring velocity spectra in turbulent flows requires methods providing a high temporal resolution and a low measurement uncertainty. Hot-wire anemometry is often used, but it is intrusive. Laser Doppler anemometry is non-intrusive, but due to the statistical arrival of individual tracers provides no constant measurement rate. We therefore propose the use of Doppler global velocimetry (DGV), which is a contactless method allowing temporally equidistant measurements of continuous signals. Additionally, 2d measurements are possible instead of single point measurements. The commonly applied slow cameras are substituted by a fibre coupled detector array consisting of 25 avalanche photo diodes, which increases temporal resolution up to 10 μs. Contrarily to conventional DGV, a sinusoidal laser frequency modulation enables omitting the reference detector array. A correction of beam splitting and image misalignment errors is thus not necessary, but disturbances due to temporal fluctuations of the scattered light can occur and have to be reduced by increasing the modulation frequency. We validate the proposed system capability of synchronously measuring velocity spectra at multiple points in turbulent flows by presenting experimental results. The acquired velocity spectra in a wind tunnel experiment show good agreement with hot-wire comparison measurements within 0.1 m/s. An uncertainty analysis is given, which allows the achievable measurement uncertainty to be estimated as a function of the desired temporal resolution. An uncertainty down to 0.2 m/s can, for example, be achieved assuming a desired temporal resolution of 1 ms. These promising results open new perspectives for turbulence and correlation studies in flows such as to investigate the turbulence characteristics behind a truncated cylinder attached to a plate or the inlet of an aircraft turbine for flow characterisation in industry. [ABSTRACT FROM AUTHOR]

The results of frequency-modulation (FM) spectroscopy of coherent dark resonances from the Zeeman sublevels of the transition F=2 ↔ F=1 of D1 line in absorption of 87Rb atoms are presented and discussed in detail. By contrast with the conventional spectroscopy of coherent dark resonances employing two laser beams, relative frequency of which can be varied, these data has been obtained with the help of a single frequency-modulated laser field. Variation of the modulation frequency plays then a similar role as the variation of the relative frequency in conventional spectroscopy. Experimental data are fit to the theoretical calculations, which are based on the theory of FM spectroscopy of coherent dark resonances recently developed by us. Feasibility of using such experimental technique for accurate measurements of magnetic fields is also discussed. [ABSTRACT FROM AUTHOR]

Abstract  We are building a long-range FM/cw nonscanning imaging lidar breadboard. This lidar system achieves ranging based on a frequency modulation/continuous wave (FM/cw) technique, implemented by an amplitude modulated mid-IR diode laser transmitter with a linear frequency modulation (LFM) of the subcarrier. Firstly, various schemes of light beam modulation are analyzed. Secondly, we put forward a laser modulation scheme whose core was formed by a 1.55 μm electro-absorption modulated laser diode (EML) and an erbium-doped optical fiber amplifier (EDFA), then a corresponding experimental system architecture and components for light beam modulation and detection are established. Finally, a corresponding experiment of laser beam modulation is completed for the first time. In our experiment, the EML amplitude is modulated by a 200 MHz to 800 MHz LFM signal, whose amplitude value is 2.05 V. The average output power of the modulated laser obtained in the experiment is 10 W, peak power is 16.4 W, and the average modulation depth is 78%. The results of tests predict that this laser modulation scheme is likely to improve the imaging range of the FM/cw lidar. [ABSTRACT FROM AUTHOR]

Electrochemical frequency modulation, EFM is a new technique for corrosion rate measurements. With the EFM technique, the corrosion rate and corrosion kinetic parameters can be obtained instantaneously without prior knowledge of Tafel slopes, which makes this method an ideal technique for application as a corrosion monitoring tool. Results obtained with the EFM technique were shown to be in agreement with chemical (weight loss) and electrochemical methods (Tafel extrapolation and electrochemical impedance spectroscopy, EIS) for corrosion rate measurements. New synthesized hydrazine carbodithioic acid derivatives namely, N′-furan-2-yl-methylene-hydrazine carbodithioic acid (A), N′-(4-dimethylamino-benzylidene)-hydrazine carbodithioic acid (B) and N′-(3-nitro-benzylidene)-hydrazine carbodithioic acid (C) were examined as corrosion inhibitors for carbon steel in 1 M perchloric acid solution. The results obtained from both chemical and electrochemical measurements show that these compounds suppressed both anodic and cathodic processes of carbon steel corrosion in 1 M HClO4 by adsorption on the electrode surface. The adsorption mode follows the Langmuir adsorption isotherm. The efficiency of the inhibitors increases in the order C > B > A. [ABSTRACT FROM AUTHOR]

Abstract  Software-defined radio (SDR) is a revolution in radio design due to the ability to create radios that can self-adapt on the fly. In SDR devices, all of the signal processing is implemented in the digital domain, mainly on DSP blocks or by DSP software. By simply downloading a new program, a SDR device is able to interoperate with different wireless protocols, incorporate new services, and upgrade to new standards. Therefore, massively parallel signal processing at higher frequencies are needed to implement a realistic SDR. Thus, FPGAs have been used extensively for implementing essential functions in SDR architectures at lower frequencies. In this paper, we explore the design of a digital FM receiver using the approach of an All-Digital Phase Locked-Loop (ADPLL). The circuit is designed in VHDL, then synthesized and simulated using LeonardoSpectrum Level 3 and ModelSim SE 6, respectively. It operates at a frequency up to 150 MHz and occupies the area of roughly 15 K logic gates. [ABSTRACT FROM AUTHOR]