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Journal articles on the topic 'Amplitude and frequency modulation'

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Published: 5 June 2025

Last updated: 15 July 2025

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Nagaraj, Naveen K. "Amplitude modulation detection with concurrent frequency modulation." Journal of the Acoustical Society of America 140, no. 3 (2016): EL251—EL255. http://dx.doi.org/10.1121/1.4962374.

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King, Andrew J., and Christian Lorenzi. "Amplitude modulation masking for frequency modulation detection." Journal of the Acoustical Society of America 140, no. 4 (2016): 3389. http://dx.doi.org/10.1121/1.4970847.

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Shantha Selva Kumari, R., and K. Seyatha. "Performance evaluation of hybrid modulation techniques for high speed radio over fiber communication system." International Journal of Modern Physics C 30, no. 09 (2019): 1950070. http://dx.doi.org/10.1142/s0129183119500700.

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In Radio over Fiber (RoF) technology, the optical network capacity is integrated with the wireless network. The main objective of this work is to enhance the performance behavior of optical fiber communication system in terms of BER, Received Power and Q-Factor. The proposed combined modulation technologies, such as Pulse Amplitude Frequency Modulation (PAFM), Differential Phase Shift Keying Amplitude Modulation (DPSKA), Offset Quadrature Phase Shift Keying Amplitude Modulation (OQPSKA), Quadrature Amplitude Frequency Modulation (QAFM), Frequency Phase Modulation (FPM) and Pulse Amplitude Phase Modulation (PAPM), are used to meet this objective. The input data are used for modulating the electrical carrier signal with a frequency of 250 and 255[Formula: see text]GHz. This hybrid modulation technique obtained the minimum BER of about [Formula: see text] in FPM technique. The maximum Q-Factor of 33 is obtained in QAFM technique. The obtained maximum received power is 0.79[Formula: see text]mW in OQPSKA technique.

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Marsh, Donald J., Olga V. Sosnovtseva, Alexey N. Pavlov, Kay-Pong Yip, and Niels-Henrik Holstein-Rathlou. "Frequency encoding in renal blood flow regulation." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 288, no. 5 (2005): R1160—R1167. http://dx.doi.org/10.1152/ajpregu.00540.2004.

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With a model of renal blood flow regulation, we examined consequences of tubuloglomerular feedback (TGF) coupling to the myogenic mechanism via voltage-gated Ca channels. The model reproduces the characteristic oscillations of the two mechanisms and predicts frequency and amplitude modulation of the myogenic oscillation by TGF. Analysis by wavelet transforms of single-nephron blood flow confirms that both amplitude and frequency of the myogenic oscillation are modulated by TGF. We developed a double-wavelet transform technique to estimate modulation frequency. Median value of the ratio of modulation frequency to TGF frequency in measurements from 10 rats was 0.95 for amplitude modulation and 0.97 for frequency modulation, a result consistent with TGF as the modulating signal. The simulation predicted that the modulation was regular, while the experimental data showed much greater variability from one TGF cycle to the next. We used a blood pressure signal recorded by telemetry from a conscious rat as the input to the model. Blood pressure fluctuations induced variability in the modulation records similar to those found in the nephron blood flow results. Frequency and amplitude modulation can provide robust communication between TGF and the myogenic mechanism.

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Krebs, Bjarne, Nicholas A. Lesica, and Benedikt Grothe. "The Representation of Amplitude Modulations in the Mammalian Auditory Midbrain." Journal of Neurophysiology 100, no. 3 (2008): 1602–9. http://dx.doi.org/10.1152/jn.90374.2008.

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Temporal modulations in stimulus amplitude are essential for recognizing and categorizing behaviorally relevant acoustic signals such as speech. Despite this behavioral importance, it remains unclear how amplitude modulations (AMs) are represented in the responses of neurons at higher levels of the auditory system. Studies using stimuli with sinusoidal amplitude modulations (SAMs) have shown that the responses of many neurons are strongly tuned to modulation frequency, leading to the hypothesis that AMs are represented by their periodicity in the auditory midbrain. However, AMs in general are defined not only by their modulation frequency, but also by a number of other parameters (duration, duty cycle, etc.), which covary with modulation frequency in SAM stimuli. Thus the relationship between modulation frequency and neural responses as characterized with SAM stimuli alone is ambiguous. In this study, we characterize the representation of AMs in the gerbil inferior colliculus by analyzing neural responses to a series of pulse trains in which duration and interpulse interval are systematically varied to quantify the importance of duration, interpulse interval, duty cycle, and modulation frequency independently. We find that, although modulation frequency is indeed an important parameter for some neurons, the responses of many neurons are also strongly influenced by other AM parameters, typically duration and duty cycle. These results suggest that AMs are represented in the auditory midbrain not only by their periodicity, but by a complex combination of several important parameters.

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Sakamoto, Hirokazu, Takeji Takui, and Koichi Itoh. "General description of multiple-modulation effects and sideband production in magnetic resonance." Canadian Journal of Chemistry 66, no. 12 (1988): 3077–82. http://dx.doi.org/10.1139/v88-476.

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A theory is presented for the sideband structure produced by a general multiple-modulation scheme with arbitrary combination of p-tuple field modulation, q-tuple frequency modulation, and r-tuple amplitude modulation for integral p, q, and r. A general formula describing the multiple-modulation effects is analytically derived using a density matrix formalism under the assumption of negligible saturation; an equivalent result is obtained from the phenomenological Bloch equation. The general formula reveals that field and frequency modulations are equivalent for the sideband production, even in the presence of amplitude modulation. Two particular cases, viz., r-tuple amplitude modulation and double field modulation are dealt with to show the validity and applicability of the general formula.

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Kotenko, V., V. Dzyubenko, Yu Kudriashov, O. Samoniuk, and V. Prokopovych. "ANALYSIS OF SPECTRA OF MULTI-FREQUENCY AMPLITUDE MODULATED RADIO SIGNALS." Проблеми створення, випробування, застосування та експлуатації складних інформаційних систем, no. 26 (I) (August 8, 2024): 30–39. http://dx.doi.org/10.46972/2076-1546.2024.26.03.

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The article presents the results of modeling the spectra of multi-frequency radio signals formed by phase modulation of a high-frequency pulsed amplitude-modulated radio signal by harmonic oscillation of an intermediate frequency in a phase modulator. Based on the obtained expression for the spectrum of the complex contour of the multi-frequency amplitude-modulated signal at the output of the phase modulator, the components of its spectrum were analyzed depending on the modulation parameters. It was established that the amplitude of these components of the spectrum and their number in the spectrum is uniquely determined by the values of the Bessel function of the first kind from the real argument - the phase modulation index. The value of the phase modulation index is directly proportional to the amplitude of the harmonic oscillation of the intermediate frequency and the steepness of the phase modulation characteristic. Frequency differences between adjacent components of the multi-frequency spectrum are uniquely determined by the frequency of the harmonic oscillation of the intermediate frequency. Each spectral component is a function of the form sinc (x), and the width of the spectrum is inversely proportional to the duration of the initial pulse amplitude-modulated radio signal. The initial phase of the central component of the spectrum corresponds to the initial phase of the high-frequency pulse amplitude-modulated radio signal. The initial phases of the side components of the spectrum depend on the nature of the change in the Bessel functions by the given phase modulation index. According to the nature of the change of the spectrum parameters according to the modulation parameters, the multi-frequency amplitude-modulated signal can be classified as a family of noise-like signals. The formation of multi-frequency amplitude-modulated signals is carried out by single-channel devices, and no strict linearity restrictions are imposed on power amplification stages. The practical application of the studied signals provides an opportunity to potentially increase the energy and structural stealth of radio communication and radar systems.

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Hörpel, Stephen Gareth, and Uwe Firzlaff. "Processing of fast amplitude modulations in bat auditory cortex matches communication call-specific sound features." Journal of Neurophysiology 121, no. 4 (2019): 1501–12. http://dx.doi.org/10.1152/jn.00748.2018.

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Bats use a large repertoire of calls for social communication. In the bat Phyllostomus discolor, social communication calls are often characterized by sinusoidal amplitude and frequency modulations with modulation frequencies in the range of 100–130 Hz. However, peaks in mammalian auditory cortical modulation transfer functions are typically limited to modulation frequencies below 100 Hz. We investigated the coding of sinusoidally amplitude modulated sounds in auditory cortical neurons in P. discolor by constructing rate and temporal modulation transfer functions. Neuronal responses to playbacks of various communication calls were additionally recorded and compared with the neurons’ responses to sinusoidally amplitude-modulated sounds. Cortical neurons in the posterior dorsal field of the auditory cortex were tuned to unusually high modulation frequencies: rate modulation transfer functions often peaked around 130 Hz (median: 87 Hz), and the median of the highest modulation frequency that evoked significant phase-locking was also 130 Hz. Both values are much higher than reported from the auditory cortex of other mammals, with more than 51% of the units preferring modulation frequencies exceeding 100 Hz. Conspicuously, the fast modulations preferred by the neurons match the fast amplitude and frequency modulations of prosocial, and mostly of aggressive, communication calls in P. discolor. We suggest that the preference for fast amplitude modulations in the P. discolor dorsal auditory cortex serves to reliably encode the fast modulations seen in their communication calls. NEW & NOTEWORTHY Neural processing of temporal sound features is crucial for the analysis of communication calls. In bats, these calls are often characterized by fast temporal envelope modulations. Because auditory cortex neurons typically encode only low modulation frequencies, it is unclear how species-specific vocalizations are cortically processed. We show that auditory cortex neurons in the bat Phyllostomus discolor encode fast temporal envelope modulations. This property improves response specificity to communication calls and thus might support species-specific communication.

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Nakano, M., and D. Rockwell. "The wake from a cylinder subjected to amplitude-modulated excitation." Journal of Fluid Mechanics 247 (February 1993): 79–110. http://dx.doi.org/10.1017/s0022112093000394.

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Controlled, amplitude-modulated excitation of a cylinder at low Reynolds number (Re equals; 136) in the cross-stream direction generates several states of response of the near wake including: a locked-in wake structure, which is periodic at the modulation frequency; a period-doubled wake structure, which is periodic at a frequency half the modulation frequency; and a destabilized structure of the wake, which is periodic at the modulation frequency, but involves substantial phase modulations of the vortex formation relative to the cylinder displacement. The occurrence of each of these states depends upon the dimensionless modulation frequency, as well as the nominal frequency and amplitude of excitation. Transition through states of increasing disorder can be attained by either decreasing the modulation frequency or increasing the amplitude of excitation at a constant value of nominal frequency. These states of response in the near wake are crucial in determining whether the far wake is highly organized or incoherent. Both of these extremes are attainable by proper selection of the parameters of excitation.

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Proshchenok, E. V., and A. Yu Rodionov. "Modern types of signal manipulation analysis of wireless communication systems." Herald of the Siberian State University of Telecommunications and Informatics 16, no. 4 (2023): 43–58. http://dx.doi.org/10.55648/1998-6920-2022-16-4-43-58.

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This paper presents an overview of modern types of signal manipulation such as hierarchical quadrature amplitude modulation (HQAM), circular quadrature amplitude modulation (CQAM) and parametric quadrature amplitude modulation (θ-QAM). Then follows the modeling of the above-mentioned types of modulations and quadrature amplitude modulation (QAM) using the MATLAB programming language. To compare the four selected types of modulation two types of modulation order are used: 16 and 64. To evaluate the effectiveness of using one or another type of modulation a communication channel was modeled to which additive white Gaussian noise (AWGN), Doppler frequency distortion and inaccurate frame synchronization were added.

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Grant, Ken W. "Frequency Modulation Detection by Normally Hearing and Profoundly Hearing-Impaired Listeners." Journal of Speech, Language, and Hearing Research 30, no. 4 (1987): 558–63. http://dx.doi.org/10.1044/jshr.3004.558.

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The ability of normally hearing and profoundly hearing-impaired subjects to detect frequency modulations was evaluated under conditions where the amplitudes of the test signals were either constant (CA), sinusoidally modulated (SAM), or randomly modulated (RAM). Results for hearing-impaired listeners showed larger frequency difference limens (DLFM) than those for normally hearing listeners for all test frequencies (100 to 1000 Hz) and for all amplitude conditions. For both normal-hearing and hearing-impaired subjects, the DFLM was smallest for the constant amplitude condition and largest for the randomly modulated condition. Differences in performance between the RAM and CA conditions were generally much larger for impaired listeners than for normally hearing listeners. With random amplitude modulation, DLFMs for the hearing-impaired subjects were approximately 36 times larger than those for normally hearing subjects.

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Yang, Kai, Zhanshan Sun, Ruiqi Mao, et al. "Wideband Rydberg atom-based receiver for amplitude modulation radio frequency communication." Chinese Optics Letters 20, no. 8 (2022): 081203. http://dx.doi.org/10.3788/col202220.081203.

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Regev, Jonathan, Johannes Zaar, Helia Relaño-Iborra, and Torsten Dau. "Age-related reduction of amplitude modulation frequency selectivity." Journal of the Acoustical Society of America 153, no. 4 (2023): 2298–311. http://dx.doi.org/10.1121/10.0017835.

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The perception of amplitude modulations (AMs) has been characterized by a frequency-selective process in the temporal envelope domain and simulated in computational auditory processing and perception models using a modulation filterbank. Such AM frequency-selective processing has been argued to be critical for the perception of complex sounds, including speech. This study aimed at investigating the effects of age on behavioral AM frequency selectivity in young (n = 11, 22–29 years) versus older (n = 10, 57–77 years) listeners with normal hearing, using a simultaneous AM masking paradigm with a sinusoidal carrier (2.8 kHz), target modulation frequencies of 4, 16, 64, and 128 Hz, and narrowband-noise modulation maskers. A reduction of AM frequency selectivity by a factor of up to 2 was found in the older listeners. While the observed AM selectivity co-varied with the unmasked AM detection sensitivity, the age-related broadening of the masked threshold patterns remained stable even when AM sensitivity was similar across groups for an extended stimulus duration. The results from the present study might provide a valuable basis for further investigations exploring the effects of age and reduced AM frequency selectivity on complex sound perception as well as the interaction of age and hearing impairment on AM processing and perception.

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Zhanabaev, Z. Zh. "COHERENT AMPLITUDE MODULATION IN A LASER GAS SENSOR." Eurasian Physical Technical Journal 20, no. 4 (46) (2023): 111–15. http://dx.doi.org/10.31489/2023no4/111-115.

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The article is devoted to a current topic in science and technology -determining the type and concentration of gas using a laser. At close values of green laser radiation intensity and bias voltage, interference patterns of the time series of the photodiode output signal were obtained. The degree of coherence (more than ~0.1) made it possible to distinguish between the types of gases and their concentrations. Signal coherence was controlled by Allan deviation values.The novelty of the research method is the choice of the harmonic of the electrical network asthe main modulation frequency. It is shown that the correlation functions and the corresponding power spectra are sensitive to low-frequency fluctuations of molecules and their clumps. This allows the results and methods of this work to be used in specific cases instead of large-sized and expensive complexes of optical instruments at room pressure and temperature.

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Houtgast, T. "Frequency selectivity in amplitude‐modulation detection." Journal of the Acoustical Society of America 85, no. 4 (1989): 1676–80. http://dx.doi.org/10.1121/1.397956.

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Ewert, Stephan, and Torsten Dau. "Frequency selectivity in amplitude‐modulation processing." Journal of the Acoustical Society of America 105, no. 2 (1999): 1234. http://dx.doi.org/10.1121/1.425936.

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Wei, Junxiong, and Changshui Chen. "Efficient frequency conversion by amplitude modulation." Optics Communications 311 (January 2013): 380–84. http://dx.doi.org/10.1016/j.optcom.2013.08.044.

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Ge, Qian, Qian Wang, Xiao Yan, and Ling He. "Algorithms for Automatic Modulation Recognition in Wireless Monitoring Applications." Applied Mechanics and Materials 241-244 (December 2012): 1772–78. http://dx.doi.org/10.4028/www.scientific.net/amm.241-244.1772.

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The paper proposes an automatic modulation recognition scheme based on instantaneous features of intercepted signals. The modulation classifier can discriminate modulations such as Amplitude Modulation (AM), Double Side Band (DSB), Single Side Band (SSB), Frequency Modulation (FM), M-ary Amplitude Shift Keying (M-ASK), M-ary Frequency Shift Keying (M-FSK), M-ary Phase Shift Keying (M-PSK) and M-ary Quadrature Amplitude Modulation (M-QAM) without any prior information. The scheme is with simple structure, computationally simpler, and suitable for real-time processing. And the recognition parameters are anti-noise, and insensitive to frequency offset, phase offset and timing error. To evaluate the performance of the scheme, several experiments with signals in Additive White Gaussian Noise (AWGN) channel were carried out in the MATLAB by varying the values of both the main modulation parameters and the signal-to-noise ratios (SNRs). The results show that the approach can achieve high recognition accuracy even at low SNR.

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Hamdi, Mustapha, and Mohamed Belhaq. "Quasi-periodic vibrations in a delayed van der Pol oscillator with time-periodic delay amplitude." Journal of Vibration and Control 24, no. 24 (2015): 5726–34. http://dx.doi.org/10.1177/1077546315597821.

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Quasi-periodic vibrations in a delayed van der Pol oscillator with time-periodic delay amplitude is investigated in this paper. The case where the delay amplitude in the position is modulated with a certain amplitude and a resonant frequency is considered. Application of the double perturbation method enables approximation of the amplitudes of quasi-periodic vibrations of the oscillator near a parametric resonance for which the frequency of the delay amplitude modulation is near twice the natural frequency of the oscillator. Analytical approximations supported by numerical simulations provide the regions in parameter space where quasi-periodic vibrations exist. Results show that the modulation of the delay amplitude in the position not only gives birth to quasi-periodic vibrations in a large range of parameters, but also with broadband large-amplitude covering a wide range of excitation frequency.

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Kreiman, Jody, Brian Gabelman, and Bruce R. Gerratt. "Perception of Vocal Tremor." Journal of Speech, Language, and Hearing Research 46, no. 1 (2003): 203–14. http://dx.doi.org/10.1044/1092-4388(2003/016).

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Vocal tremors characterize many pathological voices, but acoustic-perceptual aspects of tremor are poorly understood. To investigate this relationship, 2 tremor models were implemented in a custom voice synthesizer. The first modulated fundamental frequency (F0) with a sine wave. The second provided irregular modulation. Control parameters in both models were the frequency and amplitude of the F0 modulating waveform. Thirty-two 1-s samples of /a/, produced by speakers with vocal pathology, were modeled in the synthesizer. Synthetic copies of each vowel were created by using tremor parameters derived from different features of F0 versus time plots of the natural stimuli or by using parameters chosen to match the original stimuli perceptually. Listeners compared synthetic and original stimuli in 3 experiments. Sine wave and irregular tremor models both provided excellent matches to subsets of the voices. The perceptual importance of the shape of the modulating waveform depended on the severity of the tremor, with the choice of tremor model increasing in importance as the tremor increased in severity. The average frequency deviation from the mean F0 proved a good predictor of the perceived amplitude of a tremor. Differences in tremor rates were easiest to hear when the tremor was sinusoidal and of small amplitude. Differences in tremor rate were difficult to judge for tremors of large amplitude or in the context of irregularities in the pattern of frequency modulation. These results suggest that difference limens are larger for modulation rates and amplitudes when the tremor pattern is complex. Further, tremor rate, regularity, and amplitude interact, so that the perceptual importance of any one dimension depends on values of the others.

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Friedrich, Björn, Holger Joost, Thomas Fedtke, and Jesko L. Verhey. "Effects of infrasound on the perception of a low-frequency sound." Acta Acustica 7 (2023): 60. http://dx.doi.org/10.1051/aacus/2023061.

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The study investigated the effects of an 8 Hz infrasound sinusoid, presented at a sensation level (SL) of 9 decibels (dB), on the detection of i) a 64 Hz pure tone and ii) an 8 Hz sinusoidal amplitude modulation imposed on a 64 Hz sinusoidal carrier, presented at an SL of 25 dB. Two phase relations between infrasound and amplitude modulation were used: 0° (in phase) and 180° (in antiphase). Detection thresholds of the 64 Hz pure tone were, on average across 19 normal-hearing listeners, 4.6 dB higher in the presence than in the absence of the infrasound. Modulation detection thresholds also increased in the presence of the infrasound, on average by about 3 dB. Large individual differences in modulation detection thresholds were observed with respect to the two phase relations. On average across all listeners, however, the difference in modulation detection thresholds between in-phase and antiphase infrasound was not significant. The study shows that supra-threshold infrasound masks frequency components in the low audio-frequency range and affects the perception of amplitude modulations imposed on them.

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Edwards, Brent W., and Neal F. Viemeister. "Frequency modulation versus amplitude modulation discrimination: Evidence for a second frequency modulation encoding mechanism." Journal of the Acoustical Society of America 96, no. 2 (1994): 733–40. http://dx.doi.org/10.1121/1.411440.

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Whittaker, Edward A., Haim Grebel, Haim Lotem, and Chi Man Shum. "Reduction of residual amplitude modulation in frequency-modulation spectroscopy by using harmonic frequency modulation." Journal of the Optical Society of America B 5, no. 6 (1988): 1253. http://dx.doi.org/10.1364/josab.5.001253.

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Abdulkarem, Ahmed Mohammed, Firas Abedi, Hayder M. A. Ghanimi, et al. "Robust Automatic Modulation Classification Using Convolutional Deep Neural Network Based on Scalogram Information." Computers 11, no. 11 (2022): 162. http://dx.doi.org/10.3390/computers11110162.

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This study proposed a two-stage method, which combines a convolutional neural network (CNN) with the continuous wavelet transform (CWT) for multiclass modulation classification. The modulation signals’ time-frequency information was first extracted using CWT as a data source. The convolutional neural network was fed input from 2D pictures. The second step included feeding the proposed algorithm the 2D time-frequency information it had obtained in order to classify the different kinds of modulations. Six different types of modulations, including amplitude-shift keying (ASK), phase-shift keying (PSK), frequency-shift keying (FSK), quadrature amplitude-shift keying (QASK), quadrature phase-shift keying (QPSK), and quadrature frequency-shift keying (QFSK), are automatically recognized using a new digital modulation classification model between 0 and 25 dB SNRs. Modulation types are used in satellite communication, underwater communication, and military communication. In comparison with earlier research, the recommended convolutional neural network learning model performs better in the presence of varying noise levels.

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Ganapathisubramani, B., N. Hutchins, J. P. Monty, D. Chung, and I. Marusic. "Amplitude and frequency modulation in wall turbulence." Journal of Fluid Mechanics 712 (September 27, 2012): 61–91. http://dx.doi.org/10.1017/jfm.2012.398.

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AbstractIn this study we examine the impact of the strength of the large-scale motions on the amplitude and frequency of the small scales in high-Reynolds-number turbulent boundary layers. Time series of hot-wire data are decomposed into large- and small-scale components, and the impact of the large scale on the amplitude and frequency of the small scales is considered. The amplitude modulation effect is examined by conditionally averaging the small-scale intensity (${ u}_{S}^{2} $) for various values of the large-scale fluctuation (${u}_{L} $). It is shown that ${ u}_{S}^{2} $ increases with increasing value of ${u}_{L} $ in the near-wall region, whereas, farther away from the wall, ${ u}_{S}^{2} $ decreases with increasing ${u}_{L} $. The rate of increase in small-scale intensity with the strength of the large-scale signal is neither symmetric (about ${u}_{L} = 0$) nor linear. The extent of the frequency modulation is examined by counting the number of occurrences of local maxima or minima in the small-scale signal. It is shown that the frequency modulation effect is confined to the near-wall region and its extent diminishes rapidly beyond ${y}^{+ } = 100$. A phase lag between the large- and small-scale fluctuations, in terms of amplitude modulation, has also been identified, which is in agreement with previous studies. The phase lag between large- and small-scale fluctuations for frequency modulation is comparable to that of amplitude modulation in the near-wall region. The combined effect of both amplitude and frequency modulation is also examined by computing conditional spectra of the small-scale signal conditioned on the large scales. In the near-wall region, the results indicate that the peak value of pre-multiplied spectra increases with increasing value of ${u}_{L} $, indicating amplitude modulation, while the frequency at which this peak occurs also increases with increasing value of ${u}_{L} $, revealing frequency modulation. The overall trends observed from the conditional spectra are consistent with the results obtained through statistical analyses. Finally, a physical mechanism that can capture most of the above observations is also presented.

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Hocquet, Steve, Geoffrey Lacroix, and Denis Penninckx. "Compensation of frequency modulation to amplitude modulation conversion in frequency conversion systems." Applied Optics 48, no. 13 (2009): 2515. http://dx.doi.org/10.1364/ao.48.002515.

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Tryba, Andrew K., Fernando Peña, Steven P. Lieske, Jean-Charles Viemari, Muriel Thoby-Brisson, and Jan-Marino Ramirez. "Differential Modulation of Neural Network and Pacemaker Activity Underlying Eupnea and Sigh-Breathing Activities." Journal of Neurophysiology 99, no. 5 (2008): 2114–25. http://dx.doi.org/10.1152/jn.01192.2007.

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Many networks generate distinct rhythms with multiple frequency and amplitude characteristics. The respiratory network in the pre-Bötzinger complex (pre-Böt) generates both the low-frequency, large-amplitude sigh rhythm and a faster, smaller-amplitude eupneic rhythm. Could the same set of pacemakers generate both rhythms? Here we used an in vitro respiratory brainslice preparation. We describe a subset of synaptically isolated pacemakers that spontaneously generate two distinct bursting patterns. These two patterns resemble network activity including sigh-like bursts that occur at low frequencies and have large amplitudes and eupneic-like bursts with higher frequency and smaller amplitudes. Cholinergic neuromodulation altered the network and pacemaker bursting: fictive sigh frequency is increased dramatically, whereas fictive eupneic frequency is drastically lowered. The data suggest that timing and amplitude characteristics of fictive eupneic and sigh rhythms are set by the same set of pacemakers that are tuned by changes in the neuromodulatory state.

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Liu, Bin, Zhiwei Luo, and Tie Gang. "Influence of low-frequency parameter changes on nonlinear vibro-acoustic wave modulations used for crack detection." Structural Health Monitoring 17, no. 2 (2017): 218–26. http://dx.doi.org/10.1177/1475921716689385.

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The use of vibro-acoustic modulation is an effective nonlinear and nondestructive approach to the detection and monitoring of cracks in fatigued, defective, and fractured materials. However, the vibro-acoustic modulation results strongly depend on choice of the testing parameters. To implement this technique for additional applications, the effect of variation in the test parameters must be well understood. This study investigates the influence of variation in the amplitude and frequency of pumping (low-frequency vibration) signals on the modulation. We apply two kinds of probing excitations, sine-wave and swept-signal excitations, and we measure the modulation intensity variation with changes in the relevant parameters to observe their influence on the modulations. Dynamic strain measurement of the crack area is utilized to analyze the relation between the degree of crack opening/closing and the modulation on the crack interface. The results indicate that the probing amplitude has little effect on the modulation, and furthermore, the sweep-signal excitation technique can be used to select the proper probing frequency. The results also indicate that there is a critical pumping strain value ( εc) for the crack samples. When the pumping strain reaches this critical value, the modulation reaches a maximum. However, the opening/closing area cannot increase any more even if the pumping amplitude further increases, and thus, the modulation does not change. The extent of the crack opening/closing also varies with the pumping frequency. Our results suggest that increased sensitivity to crack detection can be achieved with the use of the resonance frequency as the pumping frequency in vibro-acoustic modulation tests.

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Cho, Chihyun, Hyunji Koo, Jae-Yong Kwon, Joo-Gwang Lee, and Tae-Weon Kang. "Measurement of Analog Modulation Index with a Calibrated Radio Frequency Attenuator." Journal of Electromagnetic Engineering and Science 21, no. 2 (2021): 87–94. http://dx.doi.org/10.26866/jees.2021.21.2.87.

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This paper presents a method for the accurate and traceable measurement of the analog modulation index. A calibrated step attenuator was used as the main apparatus because it has a higher dynamic range and lower uncertainty than a spectrum analyzer or an oscilloscope. In amplitude modulation (AM), the modulation index is obtained from the amplitude difference between the carrier and the first sideband, as in the conventional method. The resolution and calibration uncertainties of the step attenuator were propagated to the measurement uncertainty of the modulation index. The uncertainty produced by the impedance mismatch and repeatability was also included. For frequency modulation (FM) and phase modulation (PM), the modulation index, β, was estimated (with the step attenuator) from the spectrum of each sideband through the nonlinear fitting of the Bessel function. Thus, the uncertainty of the fitting process was added to the uncertainty of the measurement. The three modulations, AM, FM, and PM, exhibited an expanded uncertainty (approximately 95% confidence level, k = 2) of 0.372% for 50% nominal depth of the AM, 88.8 Hz for the peak frequency deviation of 10 kHz, and 0.88 mrad for a 0.1 radian modulation index, respectively.

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Moore, Brian C. J., and Aleksander Sek. "Detection of combined frequency and amplitude modulation." Journal of the Acoustical Society of America 91, no. 4 (1992): 2332. http://dx.doi.org/10.1121/1.403516.

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Moore, Brian C. J., and Aleksander Sek. "Detection of combined frequency and amplitude modulation." Journal of the Acoustical Society of America 92, no. 6 (1992): 3119–31. http://dx.doi.org/10.1121/1.404208.

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Bellomonte, L., I. Guastella, and R. M. Sperandeo-Mineo. "Mechanical models of amplitude and frequency modulation." European Journal of Physics 26, no. 3 (2005): 409–22. http://dx.doi.org/10.1088/0143-0807/26/3/008.

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Bunnell, H. T., and J. M. Pickett. "Amplitude versus frequency modulation in speech perception." Journal of the Acoustical Society of America 80, S1 (1986): S124. http://dx.doi.org/10.1121/1.2023635.

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Chaari, Fakher, Walter Bartelmus, Radoslaw Zimroz, Tahar Fakhfakh, and Mohamed Haddar. "Gearbox Vibration Signal Amplitude and Frequency Modulation." Shock and Vibration 19, no. 4 (2012): 635–52. http://dx.doi.org/10.1155/2012/839420.

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Gearboxes usually run under fluctuating load conditions during service, however most of papers available in the literature describe models of gearboxes under stationary load conditions. Main task of published papers is fault modeling for their detection. Considering real situation from industry, the assumption of stationarity of load conditions cannot be longer kept. Vibration signals issued from monitoring in maintenance operations differ from mentioned models (due to load non-stationarity) and may be difficult to analyze which lead to erroneous diagnosis of the system. The objective of this paper is to study the influence of time varying load conditions on a gearbox dynamic behavior. To investigate this, a simple spur gear system without defects is modeled. It is subjected to a time varying load. The speed-torque characteristic of the driving motor is considered. The load variation induces speed variation, which causes a variation in the gearmesh stiffness period. Computer simulation shows deep amplitude modulations with sidebands that don't differ from those obtained when there is a defective tooth. In order to put in evidence the time varying load effects, Short Time Fourier Transform and then Smoothed Wigner-Ville distribution are used. Results show that the last one is well suited for the studied case.The experimental validation presented at the end of the paper confirms the obtained results. Such results offer useful information when diagnosing gear transmissions by avoiding confusing conclusions from vibration signals.

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Sek, Aleksander, and Brian C. J. Moore. "Detection of quasitrapezoidal frequency and amplitude modulation." Journal of the Acoustical Society of America 107, no. 3 (2000): 1598–604. http://dx.doi.org/10.1121/1.428444.

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FAVILL, Guy, and Krispian LOWE. "Measurement and rating of amplitude modulation in low frequency wind turbine noise." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 270, no. 8 (2024): 3629–40. http://dx.doi.org/10.3397/in_2024_3350.

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Amplitude modulation in wind turbine noise refers to the distinct periodic variation in amplitude which can be perceived more than a constant level. A method for rating amplitude modulation in wind turbine noise, intended for noise in 1/3 octave bands between 50 and 800 Hz, is described in Final Report A Method for Rating Amplitude Modulation in Wind Turbine Noise 9 Aug 2016 Version 1, Institute of Acoustics IOA Noise Working Group (Wind Turbine Noise) Amplitude Modulation Working Group. This paper examines the measurement and rating of amplitude modulation in wind turbine noise below 50 Hz, below the intended range of the method described in the Institute of Acoustics report. A tonal analysis as per ETSU-R-97 is also made, and the results compared.

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Winholtz, William S., and Lorraine Olson Ramig. "Vocal Tremor Analysis With the Vocal Demodulator." Journal of Speech, Language, and Hearing Research 35, no. 3 (1992): 562–73. http://dx.doi.org/10.1044/jshr.3503.562.

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Acoustic analysis of vocal tremor has the potential to make significant quantitative and diagnostic contributions to the study of vocal disorders. This paper presents a new device for analysis of vocal tremor. The Vocal Demodulator produces amplitude- and frequency-demodulated outputs and measures the frequency and level (percent) of low-frequency tremor components in sustained phonation. A standard microphone is used to transduce the voice signal for input to the demodulator. The input fundamental frequency (F o ) range is 70–1200 Hz, and frequency response of the amplitude and frequency demodulation is 2.5–25 Hz. Five parameters are displayed in real time: F o , amplitude-modulation frequency, amplitude-modulation level, frequency-modulation frequency, and frequency-modulation level. Validation, calibration, and reliability data from synthesized test signals with modulation, as well as phonation from subjects with vocal tremor, subjects producing vibrato, and subjects with normal voice are presented. Research and clinical applications of this device are suggested.

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Bensmaïa, S. J., J. C. Craig, T. Yoshioka, and K. O. Johnson. "SA1 and RA Afferent Responses to Static and Vibrating Gratings." Journal of Neurophysiology 95, no. 3 (2006): 1771–82. http://dx.doi.org/10.1152/jn.00877.2005.

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SA1 and RA afferent fibers differ both in their ability to convey information about the fine spatial structure of tactile stimuli and in their frequency sensitivity profiles. In the present study, we investigated the extent to which the spatial resolution of the signal conveyed by SA1 and RA fibers depends on the temporal properties of the stimulus. To that end, we recorded the responses evoked in SA1 and RA fibers of macaques by static and vibrating gratings that varied in spatial period, vibratory frequency, and amplitude. Gratings were oriented either parallel to the long axis of the finger (vertical) or perpendicular to it (horizontal). We examined the degree to which afferent responses were dependent on the spatial period, vibratory frequency, amplitude, and orientation of the gratings. We found that the spatial modulation of the afferent responses increased as the spatial period of the gratings increased; the spatial modulation was the same for static and vibrating gratings, despite large differences in evoked spike rates; the spatial modulation in SA1 responses was independent of stimulus amplitude over the range of amplitudes tested, whereas RA modulation decreased slightly as the stimulus amplitude increased; vertical gratings evoked stronger and more highly modulated responses than horizontal gratings; the modulation in SA1 responses was higher than that in RA responses at all frequencies and amplitudes. The behavioral consequences of these neurophysiological findings are examined in a companion paper.

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Sek, Aleksander. "Modulation thresholds and critical modulation frequency based on random amplitude and frequency changes." Journal of the Acoustical Society of Japan (E) 15, no. 2 (1994): 67–75. http://dx.doi.org/10.1250/ast.15.67.

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Sheriff, Alimi, D. Alao Olujimi, and A. Mumuni Quadri. "An overview of orthogonal frequency division multiplexing principles, architecture, and its application." Global Journal of Engineering and Technology Advances 12, no. 1 (2022): 120–30. https://doi.org/10.5281/zenodo.6962373.

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In this work, Orthogonal Frequency Division Multiplexing’s (OFDM) principles, implementation design or high-level system architecture and application were reviewed. The condition for orthogonality, frequency spacing between consecutive subcarriers (called frequency spacing) was established analytically with practical instance highlighted. The review also covers Fast Fourier Transform (FFT) which serves as a bank of demodulators while Inverse Fast Fourier Transform (IFFT) serves as a bank of modulators in an OFDM system, advancement in OFDM, Quadrature modulation types (Binary Phase Shift Keying, 4-Quadrature Amplitude Modulation, 8-Quadrature Amplitude Modulation, 16-Quadrature Amplitude Modulation, and 64-Quadrature Amplitude Modulation QAM) and spectrum efficiency was also covered. Several technologies that use OFDM were mentioned but attention was given to its usage in Wireless LAN 802.11a.

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Campo-Valera, María, and Ivan Felis. "Underwater Acoustic Communication for The Marine Environment’s Monitoring." Proceedings 42, no. 1 (2019): 51. http://dx.doi.org/10.3390/ecsa-6-06642.

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Within the possibilities of non-linear acoustics, the parametric effect offers a range of acoustic applications that are currently being exploited in different areas. In underwater acoustics, environmental monitoring and security are one of the applications that can benefit from these technologies, allowing the transmission of information in a directivity controlled and efficient manner. An essential aspect for the optimal functioning of these technologies is the choice of the modulation that best suits the needs of communication. In the present work, different modulation techniques are explained, through their non-linear propagation, that allows generating the signals to be propagated. Among the modulations presented in this work, we have Amplitude Modulation (AM), Continuous Phase Frequency Shift Keying (CPFSK), and Linear Frequency Modulation (LFM) modulations normally used in communications. These modulations are performed with a modulating signal (sine and sine-sweeps type) whose non-linear demodulation determines the shape of the 1 and 0 bits, through the transmission of a bit string. With all this, comparisons are made between each technique, to obtain a more precise detection and discrimination of the bits.

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Abdullah, M. F. L., and Hafez Rachwan Abd Rahman. "Amplitude and Frequency Shift Keying Infrared Transmitter." Journal of Applied Engineering & Technology (JAET) 1, no. 1 (2017): 16–21. http://dx.doi.org/10.55447/jaet.01.01.5.

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In this paper, an infrared transmitter is designed using Amplitude and Frequency Shift Keying using the direct modulation where this transmitter give an opportunity for users to select the modulation signal that need to be transmitted. This transmitter is capable of transmitting signal to 353.498MHz with gain bandwidth of 12.010dB. The performance of the designed system is enhanced compared to existing transmitters. The designed can be used in existing communication system to improve the transmission of the signals for long haul communication.

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Cooper, Steven. "Wind Farm Noise—Modulation of the Amplitude." Acoustics 3, no. 2 (2021): 364–90. http://dx.doi.org/10.3390/acoustics3020025.

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The operation of a wind turbine results in a series of pulses where there is a significant instantaneous increase in the amplitude of the pressure signal, dependent upon the wind speed at the turbine blades. The variations in the amplitude of the sound being emitted can be significant at receiver locations both as an audible and inaudible sound. The modulation of the A-weighted amplitude of the acoustic signature for wind turbines is often referred to as “amplitude modulation”. Criteria have been proposed in the UK to define “excessive amplitude modulation”. In a technical sense, the general descriptor for wind turbine amplitude modulation is incorrect. The correct term for the variation of the A-weighted level is modulation of the amplitude. The rate of the modulation of the dB(A) level occurs at the blade pass frequency, which is in the infrasound region. Turbines can exhibit amplitude modulation in the low frequency region. The differences between amplitude modulation and modulation of the amplitude occurring at an infrasound rate are discussed in the context for an environmental assessment of a wind farm with respect to permit conditions and a simplified method of assessment with respect to the Modulation Index.

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Noskov, Vladislav, Rinat Galeev, Evgeniy Bogatyrev, Kirill Ignatkov, and Kirill Shaidurov. "Autodyne Sensor Signals with Amplitude-Frequency Modulation of Radiation." Sensors 20, no. 24 (2020): 7077. http://dx.doi.org/10.3390/s20247077.

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A mathematical model of an autodyne oscillator with a combined amplitude-frequency modulation, which is under the influence of its own radiation reflected from the target, is developed. The main relations are obtained for analyzing the autodyne response of a single-circuit oscillator depending on the delay time of the radiation reflected from the target with an arbitrary law of simultaneous amplitude and frequency modulation. The characteristics of the amplitude selection of signals, as well as their temporal and spectral characteristics, are calculated for harmonic amplitude-frequency modulation. The features of signal formation are established for various values of the amplitude and frequency modulation parameters and the feedback parameter of the “oscillator—target” autoparametric system. The results of experimental studies, performed on a Tigel-0.8M hybrid-integrated Ka-band oscillator module with a Gann mesa-planar diode, confirmed the findings of the theoretical analysis.

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Peshori, Kavita R., William F. Collins, and Lorne M. Mendell. "EPSP Amplitude Modulation at the Rat Ia-Alpha Motoneuron Synapse: Effects of GABAB Receptor Agonists and Antagonists." Journal of Neurophysiology 79, no. 1 (1998): 181–89. http://dx.doi.org/10.1152/jn.1998.79.1.181.

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Peshori, Kavita R., William F. Collins III, and Lorne M. Mendell. EPSP amplitude modulation at the rat Ia-alpha motoneuron synapse: effects of GABAB receptor agonists and antagonists. J. Neurophysiol. 79: 181–189, 1998. The object of this study was to examine the relationship between excitatory postsynaptic potential (EPSP) amplitude, posttetanic potentiation, and EPSP amplitude modulation at synapses made by group Ia afferents on motoneurons in the rat. These relationships were evaluated in cells in untreated rats and in cells in rats treated with the γ-aminobutyric acid-B (GABAB) receptor agonist baclofen and antagonist CGP-35348, which were used to manipulate Ca2+ entry into presynaptic terminals and consequently probability of transmitter release from them. There was no evidence for postsynaptic action of these drugs from measurement of their effects on motoneuron properties. During high-frequency stimulation (32 shock bursts at 167 Hz), EPSP amplitude either decreased (negative modulation) or increased (positive modulation) in response to successive stimuli at different connections. In untreated rats this frequency-dependent amplitude modulation behavior was inversely but weakly correlated with EPSP amplitude measured at low frequency. Intravenous (iv) administration of the GABAB agonist, baclofen, produced a marked and progressive decrease in EPSP amplitude measured at low frequency coincident with a change in frequency-dependent EPSP amplitude modulation toward more positive values (synaptic facilitation). In contrast, an increase in EPSP amplitude occurred after iv administration of the GABAB antagonist CGP-35348 that was accompanied by a negative shift in EPSP amplitude modulation during high-frequency stimulation. The negative shift in EPSP amplitude modulation (synaptic depression) after CGP-35348 application was much smaller than the positive shift induced by baclofen when normalized to the change in EPSP amplitude. Posttetanic potentiation decreased after baclofen but did not increase after CGP-35348. The relationship between modulation and EPSP amplitude was much steeper after GABAB receptor manipulation in either direction than that observed in the population of motoneurons in untreated preparations. This suggests that in the rat differences in probability of release play at most a small role in determining EPSP amplitude across the motoneuron pool.

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Manju, Venugopal, Kizhakke Kodiyath Gopika, and Pitchai Muthu Arivudai Nambi. "Association of Auditory Steady State Responses with Perception of Temporal Modulations and Speech in Noise." ISRN Otolaryngology 2014 (April 14, 2014): 1–8. http://dx.doi.org/10.1155/2014/374035.

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Amplitude modulations in the speech convey important acoustic information for speech perception. Auditory steady state response (ASSR) is thought to be physiological correlate of amplitude modulation perception. Limited research is available exploring association between ASSR and modulation detection ability as well as speech perception. Correlation of modulation detection thresholds (MDT) and speech perception in noise with ASSR was investigated in twofold experiments. 30 normal hearing individuals and 11 normal hearing individuals within age range of 18–24 years participated in experiments 1 and 2, respectively. MDTs were measured using ASSR and behavioral method at 60 Hz, 80 Hz, and 120 Hz modulation frequencies in the first experiment. ASSR threshold was obtained by estimating the minimum modulation depth required to elicit ASSR (ASSR-MDT). There was a positive correlation between behavioral MDT and ASSR-MDT at all modulation frequencies. In the second experiment, ASSR for amplitude modulation (AM) sweeps at four different frequency ranges (30–40 Hz, 40–50 Hz, 50–60 Hz, and 60–70 Hz) was recorded. Speech recognition threshold in noise (SRTn) was estimated using staircase procedure. There was a positive correlation between amplitude of ASSR for AM sweep with frequency range of 30–40 Hz and SRTn. Results of the current study suggest that ASSR provides substantial information about temporal modulation and speech perception.

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Ding, Nai, and Jonathan Z. Simon. "Neural Representations of Complex Temporal Modulations in the Human Auditory Cortex." Journal of Neurophysiology 102, no. 5 (2009): 2731–43. http://dx.doi.org/10.1152/jn.00523.2009.

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Natural sounds such as speech contain multiple levels and multiple types of temporal modulations. Because of nonlinearities of the auditory system, however, the neural response to multiple, simultaneous temporal modulations cannot be predicted from the neural responses to single modulations. Here we show the cortical neural representation of an auditory stimulus simultaneously frequency modulated (FM) at a high rate, fFM ≈ 40 Hz, and amplitude modulation (AM) at a slow rate, fAM <15 Hz. Magnetoencephalography recordings show fast FM and slow AM stimulus features evoke two separate but not independent auditory steady-state responses (aSSR) at fFM and fAM, respectively. The power, rather than phase locking, of the aSSR of both decreases with increasing stimulus fAM. The aSSR at fFM is itself simultaneously amplitude modulated and phase modulated with fundamental frequency fAM, showing that the slow stimulus AM is not only encoded in the neural response at fAM but also encoded in the instantaneous amplitude and phase of the neural response at fFM. Both the amplitude modulation and phase modulation of the aSSR at fFM are most salient for low stimulus fAM but remain observable at the highest tested fAM (13.8 Hz). The instantaneous amplitude of the aSSR at fFM is successfully predicted by a model containing temporal integration on two time scales, ∼25 and ∼200 ms, followed by a static compression nonlinearity.

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Manjula, S. H., P. Suresh, and M. G. Rao. "The Effect of Thermal Modulation on Double Diffusive Convection in the Presence of Applied Magnetic Field and Internal Heat Source." International Journal of Applied Mechanics and Engineering 26, no. 1 (2021): 135–55. http://dx.doi.org/10.2478/ijame-2021-0009.

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Abstract The investigation of thermal modulation on double-diffusive stationary convection in the presence of an applied magnetic field and internal heating is carried out. A weakly nonlinear stability analysis has been performed using the finite-amplitude Ginzburg-Landau model. This finite amplitude of convection is obtained at the third order of the system. The study considers three different forms of temperature modulations. OPM-out of phase modulation, LBMO-lower boundary modulation, IPM-in phase modulation. The finite-amplitude is a function of amplitude δ T , frequency ω and the phase difference θ. The effects of δ T and ω on heat/mass transports have been analyzed and depicted graphically. The study shows that heat/mass transports can be controlled effectively by thermal modulation. Further, it is found that the internal Rayleigh number Ri enhances heat transfer and reduces the mass transfer in the system.

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Sheriff Alimi, Olujimi D Alao, and Quadri A Mumuni. "An overview of orthogonal frequency division multiplexing principles, architecture, and its application." Global Journal of Engineering and Technology Advances 12, no. 1 (2022): 120–30. http://dx.doi.org/10.30574/gjeta.2022.12.1.0118.

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Magonov, Sergei, Sergey Belikov, John Alexander, and Marko Surtchev. "Synergy of Resonant Oscillatory Modes in Atomic Force Microscopy of Polymers." MRS Advances 1, no. 25 (2016): 1853–58. http://dx.doi.org/10.1557/adv.2016.364.

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ABSTRACTThe set of oscillatory resonance AFM modes is expanded with frequency modulation mode and frequency imaging in amplitude modulation mode. The backgrounds of these modes are discussed and their capabilities are compared on the practical examples. The data show how these techniques complement the amplitude modulation with phase imaging. The frequency imaging enhances the compositional mapping of heterogeneous samples. Frequency modulation mode provides a superior capability in imaging at low tip-sample forces.

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