Frequency Modulation

This paper outlines the applicative environment and sketches the technical details of an FM subcarrier technology called multipurpose radio communication channel (MPRC). This technology delivers data at maximum data rate of around 40 kbs using a proprietary codec algorithm, subsidiary communication channel (SCC). As a result it is possible to obtain video transmission in QCIF format at roughly 8/12 fps using 35 kHz of the 100 kHz available for a commercial FM radio station in Europe. In this way, it is possible to transmit video on FM radio together with the usual radio broadcasting. SCC is briefly described in its main characteristics

Among the family of pulse time modulation (PTM) techniques, square wave frequency modulation (SWFM) is particularly well suited to the transmission of high-quality wideband instrumentation and video signals such as MAC and high definition TV over optical fibres due to its attractive combination of performance and simplicity. This paper discusses aspects of SWFM and describes two experimental systems employing novel demodulators suitable for 5.5 MHz (PAL) and 12 MHz wide format MAC bandwidth systems respectively. >

An approach to watermarking digital signals using frequency modulation-'Chirp Coding'-is considered. The principles underlying this approach are based on the use of a matched filter to reconstruct a 'chirp stream'code that is uniquely robust. The method is generic in the sense that it can, in principle, be used for a variety of different signal (the authentication of speech and biomedical signals, for example). Further, by generating a bit stream that is signal dependent, chirp coding provides a method of self-authentication, ...

In this work, we present an analytical study of aliasing image spurs problem in digital-RF modulators. The inherent finite image rejection ratio of this types modulators is conceptually discussed. A pulse amplitude modulation (PAM) model of the converter is used in the theoretical discussion. Behavioral level simulation of the digital-RF converter model is included. Finite image rejection is a limiting issue in this architecture, and Digital-IF mixing is used to alleviate the problem which is also reviewed and simulated.

In this paper, the AM–FM modulation model is applied to speech analysis, synthesis and coding. The AM–FM model represents the speech signal as the sum of formant resonance signals each of which contains amplitude and frequency modulation. Multiband filtering and demodulation using the energy separation algorithm are the basic tools used for speech analysis. First, multiband demodulation analysis (MDA) is

A novel Empirical Mode Decomposition (EMD) algorithm, called 2T-EMD, for both mono-and multivariate signals is proposed in this paper. It differs from the other approaches by its computational lightness and its algorithmic simplicity. The method is essentially based on a redefinition of the signal mean envelope, computed thanks to new characteristic points, which offers the possibility to decompose multivariate signals without any projection. The scope of application of the novel algorithm is specified, and a comparison of the 2T-EMD technique with classical methods is performed on various simulated mono-and multivariate signals. The monovariate behaviour of the proposed method on noisy signals is then validated by decomposing a fractional Gaussian noise and an application to real life EEG data is finally presented.

We present a theoretical model developed for estimating the power, the optical signal to noise ratio and the number of generated carriers in a comb generator, having as a reference the minimum optical signal do noise ratio at the receiver input, for a given fiber link. Based on the recirculating frequency shifting technique, the generator relies on the use of coherent and orthogonal multi-carriers (Coherent WDM) that makes use of a single laser source (seed) for feeding high capacity (above 100 Gb/s) systems. The theoretical model has been validated by an experimental demonstration, where 23 comb lines with an optical signal to noise ratio ranging from 25 to 33 dB, in a spectral window of ~ 3.5 nm, are obtained.

The Case I, Case II, and Case III distributions for the phase angle between two vectors perturbed by Gaussian noise are restated in terms of integrals with integrands containing only exponentials. Added to these are a Case IV distribution in which one of the vectors is noise free; and Case V, Case VI, and Case VII distributions for the instantaneous radian frequency that results when the time between the two vectors goes to zero. In addition, existing and new forms for the probability density functions corresponding to each of the distributions are given. The results are applied to digital FM with a limiter/discriminator receiver to easily obtain the bit error probability without coding and the corresponding probability density function needed in a Chernoff bound approach to study the bit error probability with coding.

Background: Language comprehension requires decoding of complex, rapidly changing speech streams. Detecting changes of frequency modulation (FM) within speech is hypothesized as essential for accurate phoneme detection, and thus, for spoken word comprehension. Despite past demonstration of FM auditory evoked response (FMAER) utility in language disorder investigations, it is seldom utilized clinically. This report's purpose is to facilitate clinical use by explaining analytic pitfalls, demonstrating sites of cortical origin, and illustrating potential utility. Results: FMAERs collected from children with language disorders, including Developmental Dysphasia, Landau-Kleffner syndrome (LKS), and autism spectrum disorder (ASD) and also normal controls-utilizing multi-channel reference-free recordings assisted by discrete source analysis-provided demonstratrions of cortical origin and examples of clinical utility. Recordings from inpatient epileptics with indwelling cortical electrodes provided direct assessment of FMAER origin. The FMAER is shown to normally arise from bilateral posterior superior temporal gyri and immediate temporal lobe surround. Childhood language disorders associated with prominent receptive deficits demonstrate absent left or bilateral FMAER temporal lobe responses. When receptive language is spared, the FMAER may remain present bilaterally. Analyses based upon mastoid or ear reference electrodes are shown to result in erroneous conclusions. Serial FMAER studies may dynamically track status of underlying language processing in LKS. FMAERs in ASD with language impairment may be normal or abnormal. Cortical FMAERs can locate language cortex when conventional cortical stimulation does not. Conclusion: The FMAER measures the processing by the superior temporal gyri and adjacent cortex of rapid frequency modulation within an auditory stream. Clinical disorders associated with receptive deficits are shown to demonstrate absent left or bilateral responses. Serial FMAERs may be useful for tracking language change in LKS. Cortical FMAERs may augment invasive cortical language testing in epilepsy surgical patients. The FMAER may be normal in ASD and other language disorders when pathology spares the superior temporal gyrus and surround but presumably involves other brain regions. Ear/mastoid reference electrodes should be avoided and multichannel, reference free recordings utilized. Source analysis may assist in better understanding of complex FMAER findings.

A technique is presented for determining the frequency modulation transfer function of a laser. The method is based on a Mach-Zehnder interferometer, with a significant difference in the optical path lengths of the two arms. A frequency-modulated laser beam incident on the interferometer produces a phase-modulated photocurrent signal with an effective modulation index that is related to the amplitude of the optical frequency modulation. Techniques for determining both the amplitude and the phase of the optical frequency modulation from the photocurrent signal are described. PACS 42.60.Fc; 42.55.Px; 07.60.Ly

This paper discusses a new implementation of a Gaussian minimum-shift keying (GMSK) modulator and demodulator on the European Space Agency (ESA)'s common deep-space receiver-the Intermediate Frequency Modem System (IFMS), which is a software radio based platform. The GMSK demodulator is needed for ESA's deep-space and near-Earth missions, starting with the Herschel-Planck satellites in 2008. The implementation requirements and hardware restrictions from the IFMS lead to the need for a significant simplification versus the optimum demodulation approach. In part, this can be achieved by using a demodulator based on the Laurent decomposition, yet further simplifications and changes to obtain a feasible implementation were necessary. The presented GMSK demodulator was directly implemented on the existing IFMS receiver without requiring any hardware changes. Measurements with the demodulator showed only a marginal technical degradation in the order of 0.1-0.3 dB for the chosen approach. Furthermore, for testing purposes, a GMSK modulator was implemented on the same platform.

The literature describes tracking devices that allow a single detector coupled to a spinning FM reticle to determine target location. The spinning FM reticles presented were limited to single parameter reticles of frequency vs angle, frequency vs radius, or phase. This study presents these parameters with their capabilities and limitations and shows that multiple parameters can be integrated into a single reticle. Also, a general equation is developed that describes any FM reticle of the spinning type.

Developmental dyslexia is characterized by a phonological processing deficit and impaired low-level auditory processing may contribute to this problem. However, this remains controversial because not all dyslexic individuals show psychophysical deficits on auditory processing tasks; hence it has been argued that auditory processing deficits are not a causal factor in dyslexia. Because behavioral psychophysical tasks include both bottom-up processing and top-down strategies, dyslexics' successful coping strategies may positively influence their performance on auditory behavioral measures. Therefore we have studied whether dyslexics who perform adequately on auditory psychophysical tasks nevertheless show electrophysiological evidence of impaired auditory processing. We compared auditory event-related mismatch negativity (MMN) potentials to frequency modulated (FM) tones at 5, 20 and 240 Hz between dyslexic adults and controls. Groups were matched for age, cognitive ability and psychophysical FM detection thresholds. The dyslexic group showed significantly smaller MMNs in the 20 Hz FM condition in both the early (150-300 ms, P = 0.010) and late (300-500 ms, P = 0.049) time frames. A 2-way ANOVA showed a significant group by FM rate interaction (P = 0.012). There were no significant differences between the groups in the 5 Hz or 240 Hz conditions. The magnitude of the 20 Hz FM MMN correlated with the degree of discrepancy between cognitive and literacy skills (0.66, P = 0.003) in the entire group. Thus, even among compensated dyslexics with above-average cognitive abilities and adequate performance on auditory psychophysical tasks, the MMN responses of some dyslexic adults were found to be abnormal. ava i l a b l e a t w w w. s c i e n c e d i r e c t . c o m w w w. e l s ev i e r. c o m / l o c a t e / b r a i n r e s ARTICLE IN PRESS Please cite this article as: Catherine J. Stoodley et al., Auditory event-related potentials differ in dyslexics even when auditory psychophysical performance is normal, Brain Research (2006),

Frequency-modulation techniques have been used to reduce electromagnetic interference (EMI) produced by the clock of digital systems working in the range of hundreds of megahertz. The working principle consists of modulating the original constant clock frequency in order to spread the energy of each single harmonic into a certain frequency band, thus reducing the peak amplitude of EMI at harmonic frequencies. Nowadays, the switching frequency of power converters has increased up to values that make interesting the application of such techniques to reduce EMI emissions due to switching of power circuits. This paper presents the theoretical principles of frequency modulation using deterministic profiles for the modulating function. It shows the effectiveness of such methods in terms of EMI reduction for different modulation profiles and other parameters. The method is compared with other methods using random modulation. Tests carried out on a buck converter are presented for experimental validation of the method. A short discussion on optimal modulation profiles and parameters is also included.

ABSTRACT The Full Bridge converter topology modulated in phase shift is one of the most popular converters used to obtain high efficiency conversion, especially in high power and high voltage applications. This converter topology combines the simplicity of fixed frequency modulations with the soft switching characteristic of resonant converters but, if a diode rectifier is used as output stage, it suffers of severe overshoot voltage spikes and ringing across the rectifier. In this paper, a new regenerative active snubber is widely studied and developed to reduce this drawback. The proposed snubber is based on a combination of an active clamp with a buck converter used to discharge the snubber capacitor. The snubber gate signal is obtained by using those of the phase shift modulation.

Selecting the proper warehouse location has been always one of the most important and strategic challenges in the optimization process of a logistics system. Such decisions have a great importance for companies because they are costly and difficult to reverse, and entail a long term commitment. Many quantitative and qualitative factors affect the selection of the warehouse location as a long term decision. A new balancing and ranking method combined with an interval data approach has been presented in this paper for solving a warehouse location selection problem. This method involves a three-step procedure to derive an overall complete final order of the warehouses which are already selected for the decision making. The procedure involves the definition of an outranking matrix based on the criteria values for all the available warehouse locations while taking into account the frequency of superiority of one location over others. The ordering of the warehouse locations has been performed based on the information of an advantagesdisadvantages table, the distance travelled after final balancing, and the provisional order of locations. This is referred to as the triangularisation. It should be noted that unlike other MCDM models, the proposed method does not require weights for the decision making criteria. In addition, the proposed approach is much more flexible than the conventional methods in some other aspects. To demonstrate the procedural implementation of the proposed method and illustrate its effectiveness, it was applied to a case study and the results are evaluated and verified.

John Chowningè una delle figure più rilevanti e influenti a livello mondiale nel campo della computer music, tanto come compositore che come ricercatore. Le sue opere negli anni settanta significarono un grande progresso nella maturazione e controllo dei mezzi di composizione elettroacustici digitali. Turenas, in particolare rappresenta un punto di grande importanza storica nel repertorio. La prima parte di questa analisiè la traduzione dello scritto Escuchando Turenas de John Chowning di Luis Jure. 1

The phase vocoder is a well established tool for time scaling and pitch shifting speech and audio signals via modification of their short-time Fourier transforms (STFTs). In contrast to time-domain time-scaling and pitch-shifting techniques, the phase vocoder is generally considered to yield high quality results, especially for large modification factors and/or polyphonic signals. However, the phase vocoder is also known

This report gives a brief discussion of the frequency modulation (FM).It highlights significant basics of the telecommunications and signal processing which revolves around modulation and demodulation. The modulator and demodulator circuits were designed and simulated later on using Multisim. After that, the circuits were implemented and the results were examined. As given, the message signal has a frequency of 15 kHz while the carrier frequency has 125 kHz of frequency.

In this paper, a low power, low flicker noise and high IIP3 I/Q mixer for 76-108MHz EURO/US/Korea/Japan FM radio receiver applications is presented. The proposed mixer includes a transconductance (Gm) stage, a current mode passive switching stage driven by a 25% duty cycle LO, a transimpedance amplifier (TIA), and a 25% duty cycle LO generator. Simulation results show a 9.2dB DSB noise figure at 50kHz, 13dBm IIP3, and 23dB voltage gain, respectively, while drawing only 800uA including a LO generator from a 1.2-V supply in a standard 65nm CMOS technology.

vii viii Preface Part I defines and explains the basic concepts of TFSAP, intuitively derives a variety of well-known time-frequency distributions (TFDs), and then reduces them to a common form. This leads to the general treatment of quadratic TFDs in Chapter 3, which should be regarded as the core of the book and as a prerequisite for the later chapters.

This work focuses on presenting a novel high efficiency channel encoding for transmitting acoustical signals in the hope of improving wireless underwater communication. Yet, water puts a damper on communication capacity, slowing down the signal propagation and creating background noise and echoes. For thus systems and methods for implementing a control channel, e.g., in underwater communication system, are presented below. Aspects of the channel structures used to implement the control channel described herein, can improve error detection capabilities, reduce decoding complexity, and increase transmission efficiency. In certain aspects, transmission efficiency can be increased through using CRC encoding. A circular trellis check and Viterbi decoding can also be used to increase efficiency and maintain error detection capabilities. Symbol Error Rate (SER) can be reduced in embodiments described herein over that of tail-biting convolutional coding with a CRC. Furthermore, error detection offered by Reed Solomon encoder can well compensate underwater noise. Additionally, the encoder packet size can be fixed in order to facilitate decoding and reducing receiver complexity.

A novel switched excitation method for linear frequency modulated excitation of ultrasonic transducers in pulse compression systems is presented that is simple to realise, yet provides reduced signal sidelobes at the output of the matched filter compared to bipolar pseudochirp excitation. Pulse compression signal sidelobes are reduced through the use of simple amplitude tapering at the beginning and end of the excitation duration. Amplitude tapering using switched excitation is realised through the use of intermediate voltage switching levels, half that of the main excitation voltages. In total five excitation voltages are used creating a quinary excitation system. The absence of analogue signal generation and power amplifiers renders the excitation method attractive for applications with requirements such as a high channel count or low cost per channel. A systematic study of switched linear frequency modulated excitation methods with simulated and laboratory based experimental verification is presented for 2.25 MHz non-destructive testing immersion transducers. The signal to sidelobe noise level of compressed waveforms generated using quinary and bipolar pseudo-chirp excitation are investigated for transmission through a 0.5 m water and kaolin slurry channel. Quinary linear frequency modulated excitation consistently reduces signal sidelobe power compared to bipolar excitation methods. Experimental results for transmission between two 2.25 MHz transducers separated by a 0.5 m channel of water and 5% kaolin suspension shows improvements in signal to sidelobe noise power in the order of 7-8 dB. The reported quinary switched method for linear frequency modulated excitation provides improved performance compared to pseudo-chirp excitation without the need for high performance excitation amplifiers.

Pulse compression is used in radar systems to improve range resolution while maintaining a high duty cycle. In addition to practical implementation constraints, the key issues for the selection of a pulse-compression waveform are mismatch loss, peak / integrated range sidelobes, and Doppler tolerance. While much progress has been made in the design of nonlinear frequency modulated (FM) chirp waveforms satisfying these requirements, the corresponding performance for binary phase-coded waveforms is often inadequate. In order to improve the range sidelobes achieved with phase-coded waveforms, specially designed mismatched pulse compression filters can be used. Several such approaches have been described in the literature since 1959. This paper review these techniques and highlight a particular approach using infinite impulse response (IIR) filters, which has received little attention in the past. Using this technique the performance for a number of binary phase codes of different length have been determined and their Doppler tolerance is investigated.

We present the design, fabrication, and results from the first monolithically integrated optical phase-locked loop (OPLL) photonic integrated circuit (PIC) suitable for a variety of homodyne and offset phase locking applications. This InP-based PIC contains two sampled-grating distributed reflector (SG-DBR) lasers, semiconductor optical amplifiers (SOAs), phase modulators, balanced photodetectors, and multimode interference (MMI)-couplers and splitters. The SG-DBR lasers have more than 5 THz of frequency tuning range and can generate a coherent beat for a wide spectrum of frequencies. In addition, the SG-DBR lasers have large tuning sensitivities and do not exhibit any phase inversion over the frequency modulation bandwidths making them ideal for use as current controlled oscillators in feedback loops. These SG-DBR lasers have wide linewidths and require high feedback loop bandwidths in order to be used in OPLLs. This is made possible using photonic integration which provides low cost, easy to package compact loops with low feedback latencies. In this paper, we present two experiments to demonstrate proof-of-concept operation of the OPLL-PIC: homodyne locking and offset locking of the SG-DBR lasers.

Signal isolation is needed in power electronics systems that include separate primary and secondary 'grounds'. The feasibility of using a piezoelectric transformer (PT) as a galvanic barrier was investigated in this study theoretically and experimentally. The research included the issues of drive, demodulation, bandwidth, and common mode rejection. In particular, two types of excitation signals were compared: amplitude modulated and frequency modulated. The frequency response of the piezoelectric isolator was studied both by small signal envelope simulation using ORCAD/PSPICE and experimentally. It is concluded that the FM approach offers a larger BW but the AM scheme seems to be easier to implement.

Using the techniques of microelectromechanical systems, we have constructed a small low-power magnetic sensor based on alkali atoms. We use a coherent population trapping resonance to probe the interaction of the atoms' magnetic moment with a magnetic field, and we detect changes in the magnetic flux density with a sensitivity of 50 pT Hz −1/2 at 10 Hz. The magnetic sensor has a size of 12 mm 3 and dissipates 195 mW of power. Further improvements in size, power dissipation, and magnetic field sensitivity are immediately foreseeable, and such a device could provide a hand-held battery-operated magnetometer with an atom shot-noise limited sensitivity of 0.05 pT Hz −1/2 . Measurement of magnetic fields with picotesla sensitivity is critical to many applications including underground and underwater ordinance detection, 1 geophysical mapping, 2 navigation, and even the detection and mapping of the human heart beat. 3 Sensitive magnetometers often weigh several kilograms, are quite bulky, and dissipate substantial power while operating. In addition, as the sensitivity increases so does the size and power consumption. Large-scale optical magnetometers 4 that use alkali metal vapors achieve sensitivities 5,6 of ϳ1 fT Hz −1/2 , and rival superconducting quantum interference devices 7 in this regard without the need for cryogenic cooling. Depending on the design of an atomoptical magnetometer, it can operate in a magnetic flux density ranging from 10 −15 to Ͼ 10 −3 T. An optical magnetometer measures the absolute field, thereby needing no external calibration, since the measured spin precession frequency of the alkali atom has a known direct relation to the magnetic flux density. By miniaturizing an optical magnetometer based on the coherent population trapping (CPT) effect 8 by a factor of 10 4 , we demonstrate a highly sensitive magnetic sensor that is millimeters in size, and has the potential to enable, for example, long-range remote sensing of magnetic fields based on battery-operated disposable devices.

GHz. The fully integrated FM transceiver design in standard 0.18 m CMOS process incorporates a transmit/receive switch, a single-ended input differential output low noise amplifier, differential input single-ended output power amplifier, an LC tuned quadrature voltage controlled oscillator, mixer, IF amplifier, a g m -C based oscillator and a chopper stabilized amplifier used for wireless sensor applications. The power output is about 50mW.

We propose and demonstrate two configurations for optical millimeter-wave (mm-wave) generation and transmission of 3-Gb/s downstream data based on a gain-switched laser (GSL). The first configuration generates an optical comb spectrum from a GSL that can be appropriately filtered to generate two optical sidebands with 60-GHz separation. These sidebands are modulated with baseband data by using an external intensity modulator and then transmitted via optical fiber to the remote antenna unit (RAU). The second configuration produces a modulated optical frequency comb by driving the laser with both RF local oscillator and data streams coupled together and then followed by the same optical filters to generate two modulated optical sidebands. At the RAU, these two sidebands are heterodyned using a photodetector to generate the electrical modulated mm-wave signal. We investigate the distribution of these two methods over 3-km fiber with 2-m wireless link and demonstrate the system simplicity and cost efficiency for mm-wave over fiber systems. Both configurations are simulated to verify our obtained results and show system performance at higher bit rates.

The multilevel inverters (MLIs) are classified into three topologies such as Diode Clamped, Flying Capacitor and Cascade Multilevel Inverter (CMLI). CMLI topologies include two kind of structure that is named symmetric and asymmetric topologies. Asymmetric Cascade MLI (ACMLI) topologies consist of unequal DC sources. Many modulation techniques have been used in ACMLI topology such as Multi-Carrier PWM (MC-PWM), Space Vector PWM and Selective Harmonic PWM. The MC-PWM technique is achieved by four different types. In this study, MC-PWM techniques which are named Phase Disposition PWM, Phase Opposition Disposition PWM, Alternate Phase Opposition Disposition PWM and Phase Shifted PWM have been compared. It is uncovered that Phase Opposition Disposition PWM technique is more convenient in terms of Total Harmonic Distortion of output voltage and current signals and in terms of the quality of power factor in ACMLI which is performed in this study.

In this study, Auditory Steady State Responses (ASSR) to 100 μsec clicks and 4 msec cochlear chirps are recorded in adult subjects at repetition rates of 20 to 100 Hz in 10 Hz increments. Response characteristics of ASSRs are compared in the frequency domain. Results show that response amplitudes to both stimuli peak in the proximity of 40 Hz and 80 Hz, but chirps generate responses with larger amplitudes at all repetition rates. The responses at 40 Hz repetition rates for both clicks and chirps are larger than the corresponding responses at 80 Hz stimuli in awake adults. The 40 Hz responses, however, show greater variability than the 80 Hz responses depending on the subject's state of consciousness. The predictions of the ASSR waveforms at each repetition rate were then synthesized by superimposing the suitably shifted Middle Latency Response (MLR) waveforms that were recorded during the same session with a stimulus repetition rate of 10 Hz for both click and chirp recordings. ...

Series compensation of transmission lines using fixed series capacitors can cause sub-synchronous resonance (SSR) between electrical and mechanical systems. This phenomenon leads to severe damages to turbine generator shafts. Thyristor controlled series compensator (TCSC) is one of the FACTS devices which can be utilized to damp electromechanical and sub-synchronous oscillations. This device can perform flexible series compensation and SSR damping. The effect of different parameters of the TCSC is studied using complex torque coefficient method. Open loop and closed-loop constant current and constant power control methods are simulated using PSCAD/EMTDC software package. First IEEE benchmark model for sub-synchronous resonance studies and a complete model of TCSC is used to analyze the effect of different parameters and control structure on the SSR damping capability of the TCSC.

https://ieeexplore.ieee.org/document/9021056/

......................................................................................................................................................................In this paper, we investigate the use of chirp spread spectrum signaling over air-ground channels. This includes evaluation of not only the traditional linear chirp, but also of a new chirp signal format we have devised for multiple access applications. This new format is more practical than prior multiuser chirp systems in the literature, because we allow for imperfect synchronism. Specifically we evaluate multiuser chirp signaling over air-ground channels in a quasi-synchronous condition. The air-ground channels we employ are models based upon an extensive NASA measurement campaign. We show that our new signaling scheme outperforms the classic linear chirp in these air-ground settings.

Stimulated Brillouin Scattering (SBS) imposes a limitation on the transmitted power in radioover-fiber (RoF) distribution systems. By employing an optical filter at the transmitter that converts the optical microwave signal to Single Side Band (SSB) format, in order to overcome dispersive fading, it is also possible to reduce the effect of SBS on system performance. In this paper the authors compare the cases of filtering the optical microwave signal at the transmitter or the remote site of a radio-over-fibre system, in terms of the effect of SBS on system performance. The authors also investigate and demonstrate how the modulation depth of the optical-microwave data signal influences the Brillouin threshold in RoF distribution systems.

In many wireless applications, it is necessary to demodulate and digitize frequency or phase modulated signals. Most commonly, this is done using separate frequency discrimination and analog-to-digital (A/D) conversion. In low-cost IC technologies, such as CMOS, precise analog frequency discrimination is not practical, so the A/D conversion is usually performed in quadrature or at a nonzero intermediate frequency (IF) with digital frequency discrimination. While practical, the approach tends to require complicated A/D converters, and accuracy is usually limited by the quality of the A/D conversion. This paper presents an alternative structure, referred to as a delta-sigma frequency-to-digital converter (16FDC), that simultaneously performs frequency demodulation and digitization.

In this paper, we propose a method for characterizing a musical signal by extracting a set of sinusoidal descriptors reflecting the maximum information contained in this signal. We focus our study on a signal of oriental music characterized by its richness in tone that can be extended to tone, taking into account the frequency and time characteristics of this type of music. To do so, the descriptors are extracted from the original signal which is framed and analyzed on a window of short duration. This signal is viewed as the result of a combined modulation of amplitude and frequency. For this result, we apply shortterm the non-stationary sinusoidal modeling technique. In each segment, the signal is represented by a set of sinusoids characterized by their intrinsic parameters: amplitudes, frequencies and phases. The extraction technique adopted is closely related to the slot window; therefore great importance is devoted to the study and the choice of the kind of the window and its width. It must be of variable length in order to get better results in the practical implementation of our method. For this purpose, evaluation tests were carried out by synthesizing the signal from the estimated parameters. Interesting results have been identified concerning the comparison of the synthesized signal with the original one.

A synchronization scheme enabling the use of orthogonal frequency division multiplexing OFDM/FM over a mobile radio channel in a pure ALOHA environment is proposed. The scheme encodes synchronization information in parallel with data in the same manner in which data is encoded in the OFDM/FM frame. The synchronization information is in the form of tones, centered in certain reserved frequency sub-channels of the OFDM signal. The receiver uses a correlation detector, implemented in the frequency domain, to acquire synchronization accurately on a packet-by-packet basis. Experimental results indicate that the bit-error-rate performance achievable with the proposed scheme is within 1.5 dB of the performance obtained with ideal synchronization.

Objective: To test a common assumption underlying the clinical use of electroencephalographic (EEG) biofeedback training (neurofeedback), that the modulation of discreet frequency bands is associated with frequency-specific effects. Specifically, the proposal was assessed that enhancement of the low beta components sensorimotor rhythm (SMR: 12 -15 Hz) and beta1 (15-18 Hz) affect different aspects of attentional processing.