Les superpositions d'ondes modulées en amplitude et en fréquence (modes AM--FM) sont couramment utilisées pour modéliser de nombreux signaux du monde réel : cela inclut des signaux audio (musique, parole), médicaux (ECG), ou diverses séries temporelles (températures, consommation électrique). L'objectif de ce travail est l'analyse et la compréhension fine de tels signaux, dits "multicomposantes" car ils contiennent plusieurs modes. Les méthodes mises en oeuvre vont permettre de les représenter efficacement, d'identifier les différents modes puis de les démoduler (c'est-à-dire déterminer leur amplitude et fréquence instantanée), et enfin de les reconstruire. On se place pour cela dans le cadre bien établi de l'analyse temps-fréquence (avec la transformée de Fourier à court terme) ou temps-échelle (transformée en ondelettes continue). On s'intéressera également à une méthode plus algorithmique et moins fondée mathématiquement, basée sur la notion de symétrie des enveloppes des modes : la décomposition modale empirique. La première contribution de la thèse propose une alternative au processus dit ``de tamisage'' dans la décomposition modale empirique, dont la convergence et la stabilité ne sont pas garanties. \`A la place, une étape d'optimisation sous contraintes ainsi qu'une meilleure détection des extrema locaux du mode haute fréquence garantissent l'existence mathématique du mode, tout en donnant de bons résultats empiriques. La deuxième contribution concerne l'analyse des signaux multicomposantes par la transformée de Fourier à court terme et à la transformée en ondelettes continues, en exploitant leur structure particulière ``en ridge'' dans le plan temps-fréquence. Plus précisément, nous proposons une nouvelle méthode de reconstruction des modes par intégration locale, adaptée à la modulation fréquentielle, avec des garanties théoriques. Cette technique donne lieu à une nouvelle méthode de débruitage des signaux multicomposantes. La troisième contribution concerne l'amélioration de la qualité de la représentation au moyen de la ``réallocation'' et du ``synchrosqueezing''. Nous prolongeons le synchrosqueezing à la transformée de Fourier à court terme, et en proposons deux extensions inversibles et adaptées à des modulations fréquentielles importantes, que nous comparons aux méthodes originelles. Une généralisation du synchrosqueezing à la dimension 2 est enfin proposée, qui utilise le cadre de la transformée en ondelettes monogène. / Many signals from the physical world can be modeled accurately as a superposition of amplitude- and frequency-modulated waves. This includes audio signals (speech, music), medical data (ECG) as well as temporal series (temperature or electric consumption). This thesis deals with the analysis of such signals, called multicomponent because they contain several modes. The techniques involved allow for the detection of the different modes, their demodulation (ie, determination of their instantaneous amplitude and frequency) and reconstruction. The thesis uses the well-known framework of time-frequency and time-scale analysis through the use of the short-time Fourier and the continuous wavelet transforms. We will also consider a more recent algorithmic method based on the symmetry of the enveloppes : the empirical mode decomposition. The first contribution proposes a new way to avoid the iterative ``Sifting Process'' in the empirical mode decomposition, whose convergence and stability are not guaranteed. Instead, one uses a constrained optimization step together with an enhanced detection of the local extrema of the high-frequency mode. The second contribution analyses multicomponent signals through the short-time Fourier transform and the continuous wavelet transform, taking advantage of the ``ridge'' structure of such signals in the time-frequency or time-scale planes. More precisely, we propose a new reconstruction method based on local integration, adapted to the local frequency modulation. Some theoretical guarantees for this reconstruction are provided, as well as an application to multicomponent signal denoising. The third contribution deals with the quality of the time-frequency representation, using the reassignment method and the synchrosqueezing transform: we propose two extensions of the synchrosqueezing, that enable mode reconstruction while remaining efficient for strongly modulated waves. A generalization of the synchrosqueezing in dimension 2 is also proposed, based on the so-called monogenic wavelet transform.

Made available in DSpace on 2016-08-17T14:53:06Z (GMT). No. of bitstreams: 1 Fausto Lucena de Oliveira.pdf: 744487 bytes, checksum: 189e44c92f58b262f0b8901410cec223 (MD5) Previous issue date: 2006-02-23 / The estimation of heart rate variability (HRV) makes use of the RR intervals obtained from the electrocardiogram (ECG) and prevails as a standard procedure to analyze the modulation regulated by the autonomous nervous system. Moreover, many works have been trying to show that is possible to obtain the HRV from the systolic blood pressure (SBP). Those works often present results of the comparison in the time and frequency domains between the HRV calculated from the RR intervals and the discrete series composed by the maximum values of SBP. However, these comparisons were shown to be reliable only over time domain, for they exhibit disparities on the high frequency bands. In this work we show that the reported disparities on high frequencies could be related to many procedures adopted during the processing of these signals to extract the intervals referred to the cardiac cycles. Here, we use a recent technique called heart instantaneous frequency, proposed to calculate the HRV from both ECG and blood pressure (BP) signals, with the benefit of being more robust to undesired artifacts than the usual peak detectors. Then, we present temporal and spectral results with nonsignificant statistical differences between the HRV extracted from both ECG signals using peak detectors and BP waveforms using the HIF algorithm. / O calculo da variabilidade de frequencia cardıaca (HRV) se utiliza dos intervalos RR obtidos a partir do eletrocardiograma (ECG) e prevalece como um procedimento padrão para se analisar a modulação do sistema nervoso autonomo. Apesar disso, um grande numero de trabalhos tem tentado mostrar que é potencialmente útil obter a HRV a partir da pressão sanguinea sistólica (PSS). Estes estudos geralmente apresentam resultados da comparação no domınio do tempo e frequencia entre a HRV obtida a partir dos intervalos RR com a serie discreta formada pelos valores maximos da PSS. Entretanto, essas comparações mostraram haver apenas confiabilidade nos parametros temporais, pois apresentam disparidades nas bandas de alta frequencia. Neste trabalho, nós mostramos que as diferenças apresentadas nas altas frequencias podem estar relacionadas com os vários procedimentos adotados durante o processamento desses sinais ao se extrair os intervalos referentes aos ciclos cardıacos. Aqui, nós usamos uma técnica recente denominada de frequencia instantanea cardıaca (HIF, do inglês heart instantaneous frequency), que foi proposta para se calcular a HRV tanto com sinais de ECG quanto de pressão sanguınea (PS), com a vantagem de ser mais robusta aos artefatos indesejados que os usuais detectores de pico. Assim, nós mostramos resultados temporais e espectrais com diferenças estatısticas insignificantes entre a HRV extraıda a partir do ECG usando detectores de pico com os obtidos pelas formas de onda de PS usando o algoritmo HIF.

The study concerns the analysis of vocal cycle length perturbations in normophonic and dysphonic speakers.A method for tracking cycle lengths in voiced speech is proposed. The speech cycles are detected via the saliences of the speech signal samples, defined as the length of the temporal interval over which a sample is a maximum. The tracking of the cycle lengths is based on a dynamic programming algorithm that does not request that the signal is locally periodic and the average period length known a priori.The method is validated on a corpus of synthetic stimuli. The results show a good agreement between the extracted and the synthetic reference length time series. The method is able to track accurately low-frequency modulations and ast cycle-to-cycle perturbations of up to 10% and 4% respectively over the whole range of vocal frequencies. Robustness with regard to the background noise has lso been tested. The results indicate that the tracking is reliable for signal-to-noise ratios higher than 15dB.A method for analyzing the size of the cycle length perturbations as well as their frequency is proposed. The cycle length time series is decomposed into a sum of oscillating components by empirical mode decomposition the instantaneous envelopes and frequencies of which are obtained via AM-FM decomposition. Based on their average instantaneous frequencies, the empirical modes are then assigned to four categories (declination, physiological tremor, neurological tremor as well as cycle length jitter) and added within each. The within-category size of the cycle length perturbations is estimated via the standard deviation of the empirical mode sum divided by the average cycle length. The neurological tremor modulation frequency and bandwidth are obtained via the instantaneous frequencies and amplitudes of empirical modes in the neurological tremor category and summarized via a weighted instantaneous frequency probability density, compensating for the effects of mode mixing.The method is applied to two corpora of vowels comprising 123 and 74 control and 456 and 205 Parkinson speaker recordings respectively. The results indicate that the neurological tremor modulation depth is statistically significantly higher for female Parkinson speakers than for female control speakers. Neurological tremor frequency differs statistically significantly between male and female speakers and increases statistically significantly for the pooled Parkinson speakers compared to the pooled control speakers. Finally, the average vocal frequency increases for male Parkinson speakers and decreases for female Parkinson speakers, compared to the control speakers. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

[EN] Microwave photonics (MWP) is a well-established research field that investigates the use of photonic technologies to generate, distribute, process and analyze RF waveforms in the optical domain. Despite its great potential to solve long-standing problems faced by both the microwave and electronics industries, MWP systems are bulky, expensive and consume a lot of power. Integrated microwave photonics (IMWP) is an emerging area of research that promises to alleviate most of these drawbacks through the use of photonic integrated circuits (PIC). In this work, we have aimed at further closing the gap between the worlds of MWP and integrated optics. In particular, we have focused on the design and experimental characterization of PICs with reconfigurable, ring-assisted Mach-Zehnder interferometer filters (RAMZI), and demonstrated its potential use in different IMWP applications. These filters consist of a symmetric MZI loaded with ring resonators, which are coupled to the MZI branches by different optical couplers. The contributions of this thesis can be split into two sections. In the first one, we demonstrate integrated optical couplers and reflectors with variable power splitting and reflections ratios. These exploit the well-known properties of tapered multimode interference couplers (MMI), and their inherent robustness makes them highly suitable for the implementation of both RAMZI and reflective filters. Besides, we study in detail the impact of manufacturing deviations in the performance of a 4x4 MMI-based 90º hybrid, which is a fundamental building block in coherent optical communication systems. In the second section, we demonstrate the use of integrated RAMZI filters for three different IMWP applications, including instantaneous frequency measurement (IFM), direct detection of frequency-modulated signals in a MWP link, as well as in tunable, coherent MWP filters. A theoretical analysis of the limits and trade-offs that exist in photonics-based IFM systems is also provided. Even though these are early proof-of-concept experiments, we hope that further technological developments in the field will finally turn MWP into a commercial reality. / [ES] La fotónica de microondas (MWP) es un campo de investigación que estudia el uso de tecnologías ópticas para generar, distribuir, procesar y analizar señales de RF. A pesar de su gran potencial para resolver algunos de los problemas a los que se enfrentan las industrias electrónica y de microondas, estos sistemas son voluminosos, caros y consumen mucha potencia. La fotónica de microondas integrada (IMWP) es un área emergente que promete solucionar todos estos inconvenientes a través de la utilización de circuitos ópticos integrados (PIC). En esta tesis, hemos pretendido avanzar un poco más en el acercamiento entre estas dos disciplinas. En concreto, nos hemos centrado en el diseño y caracterización experimental de PICs con filtros reconfigurables basados en interferómetros Mach-Zehnder cargados con anillos (RAMZI), y demostrado su potencial uso en diferentes aplicaciones de IMWP. Los filtros RAMZI están hecho básicamente de un MZI simétrico cargado con anillos, los cuales a su vez se acoplan a las ramas del interferómetro a través de distintos acopladores ópticos. Las contribuciones de este trabajo se pueden dividir en dos partes. En la primera, hemos demostrado acopladores y reflectores ópticos integrados con coeficientes de acoplo y reflexión variables. Éstos explotan las propiedades de los acopladores por interferencia multimodal (MMI), y su robustez les hace muy atractivos para la implementación de filtros RAMZI y de tipo reflectivo. Además, hemos analizado el impacto que las tolerancias de fabricación tienen en el rendimiento de un híbrido óptico de 90º basado en un MMI 4x4, el cual es un elemento fundamental en los sistemas de comunicaciones ópticas coherentes. En la segunda parte, hemos demostrado el uso de filtros RAMZI en tres aplicaciones distintas de IMWP. En concreto, hemos utilizado dichos filtros para implementar sistemas de medida de frecuencia instantánea (IFM), detección directa de señales moduladas en frecuencia para enlaces fotónicos, así como en filtros coherentes y sintonizables de MWP. También hemos desarrollado un análisis teórico de las limitaciones y problemas que existen en los sistemas IFM. A pesar de que todos los experimentos realizados han consistido en prototipos para una prueba de concepto, esperamos que futuros avances tecnológicos permitan que la fotónica de microondas se convierta algún día en una realidad comercial. / [CA] La fotònica de microones (MWP) és un camp d'investigació que estudia l'ús de tecnologies òptiques per a generar, distribuir, processar y analitzar senyals de radiofreqüència. A pesar del seu gran potencial per a resoldre alguns dels problemes als que s'enfronten les indústries electrònica i de microones, estos sistemes son voluminosos, cars i consumixen molta potència. La fotònica de microones integrada (IMWP) és un àrea emergent que promet solucionar tots estos inconvenients a través de la utilització de circuits òptics integrats (PIC). En esta tesi, hem pretés avançar un poc més en l'acostament entre estes dos disciplines. En concret, ens hem centrat en el disseny i caracterització experimental de PICs amb filtres reconfigurables basats en interferòmetres Mach-Zehnder carregats amb anells (RAMZI), i demostrat el seu potencial en diferents aplicacions d' IMWP. Els filtres RAMZI estan fets bàsicament d'un MZI simètric carregat amb anells, els quals, al seu torn, s'acoblen a les branques del interferòmetre a través de distints acobladors òptics. Les contribucions d'este treball es poden dividir en dos parts. En la primera, hem demostrat acobladors i reflectors òptics integrats amb coeficients de transmissió i reflexió variables. Estos exploten les propietats dels acobladors per interferència multimodal (MMI), i la seua robustesa els fa molt atractius per a la implementació de filtres RAMZI i de tipo reflectiu. A més a més, hem analitzat l'impacte que les toleràncies de fabricació tenen en el rendiment d'un híbrid òptic de 90 graus basat en un MMI 4x4, el qual és un element fonamental en els sistemes de comunicacions òptiques coherents. En la segona part, hem demostrat l'ús de filtres RAMZI en tres aplicacions diferents de IMWP. En concret, hem utilitzat estos filtres per a implementar sistemes de mesura de freqüència instantània (IFM), detecció directa de senyals modulades en freqüència per a enllaços fotònics, així com en filtres coherents i sintonitzables de MWP. També hem desenvolupat una anàlisi teòrica de les limitacions i problemes que existixen en els sistemes IFM. A pesar de que tots els experiments realitzats han consistit en prototips per a una prova de concepte, esperem que futurs avanços tecnològics permeten que la fotònica de microones es convertisca algun dia en una realitat comercial. / Sánchez Fandiño, JA. (2016). Integrated Optical Filters for Microwave Photonic Applications [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/67690

This thesis deals with the problem of estimating the velocity of a mobile station (MS)in a mobile communication system using the instantaneous frequency (IF) of the received signal at the MS antenna. This estimate is essential for satisfactory handover performance, effective dynamic channel assignment, and optimisation of adaptive multiple access wireless receivers. Conventional methods for estimating the MS velocity are based either on the statistics of the envelope or quadrature components of the received signal. In chapter 4 of the thesis, we show that their performance deteriorates in the presence of shadowing. Other velocity estimators have also been proposed which require prior estimation of the channel or the average received power. These are generally difficult to obtain due to the non-stationary nature of the received signal. An appropriate window which depends on the unknown MS velocity must first be applied in order to accurately estimate the required quantities. Using the statistics of the IF of the received signal at the MS antenna given in chapter 3, new velocity estimators are proposed in chapter 4 of this thesis. The proposed estimators are based on the moments, zero-crossing rate, and covariance of the received IF. Since the IF of the received signal is not affected by any amplitude distortion, the proposed IF-based estimators are robust to shadowing and propagation path-loss. The estimators for the MS velocity in a macro- and micro-cellular system are presented separately. A macro-cell system can be considered as a special case of a micro-cell in which there is no line-of-sight component at the receiver antenna. It follows that those estimators which are derived for micro-cells can be used in a macro-cell as well. In chapter 4, we analyse the performance of the proposed velocity estimators in the presence of additive noise, non-isotropic scattering, and shadowing. We also prove analytically that the proposed velocity estimators outperform the existing methods in the presence of shadowing and additive noise. The proposed IF-based estimators need prior estimation of both the IF of the received signal and Ricean K-factor. The IF estimation in a typical wireless environment, can be considered as a special case of a general problem of IF estimation in the presence of multiplicative and additive noise. In chapter 5, we show that current time-frequency approaches to this problem which are based on the peak of a time-frequency distribution (TFD) of the signal, fail because of the special shape of the power spectral density of the multiplicative noise in a wireless environment. To overcome this drawback, the use of the first-order moment of a TFD is studied in chapter 5. Theoretical analysis and simulations show that the IF estimator based on the first-order moment of a TFD exhibits negligible bias when the signal-to-additive noise ratio is more than 10 dB. The Ricean K-factor is not only necessary for velocity estimation in micro-cells, but also is a measure of the severity of fading and a good indicator of the channel quality. Two new methods for estimating the Ricean K-factor based on the first two moments of the envelope of the received signal, are proposed in chapter 6. Performance analysis presented in chapter 6, prove that the proposed K estimators are robust to non-isotropic scattering. Theoretical analysis and simulations which are presented in chapters 4 and 7 of this thesis, prove that the proposed velocity and K estimators outperform existing estimators in the presence of shadowing and additive noise.

Submitted by CAMILO CARRANZA (carranzacamilo@gmail.com) on 2017-07-25T19:58:22Z No. of bitstreams: 1 Camilo_PhD_Thesis.pdf: 11035322 bytes, checksum: efe400c07b13cabff41e927078789c59 (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-07-26T18:31:30Z (GMT) No. of bitstreams: 1 carranzalopez_jc_dr_ilha.pdf: 11035322 bytes, checksum: efe400c07b13cabff41e927078789c59 (MD5) / Made available in DSpace on 2017-07-26T18:31:30Z (GMT). No. of bitstreams: 1 carranzalopez_jc_dr_ilha.pdf: 11035322 bytes, checksum: efe400c07b13cabff41e927078789c59 (MD5) Previous issue date: 2017-06-05 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Nesta tese são investigadas, teórica e experimentalmente, a sincronização em fase e a sincronização em anti-fase de dois metrônomos oscilando sobre uma base móvel, a partir de um modelo aqui proposto. Uma descrição do funcionamento do mecanismo de escapamento dos metrônomos é feita, junto a um estudo da relação entre este e o oscilador de van der Pol. Também uma aproximação experimental do valor do amortecimento do metrônomo é fornecida. A frequência instantânea das respostas, numérica e experimental, do sistema é usada na analise. A diferença de outros trabalhos prévios, os dados experimentais têm sido adquiridos usando vídeos dos experimentos e extraídos com ajuda do software Tracker. Para investigar a relação entre as condições iniciais do sistema e seu estado final de sincronização, foram usados mapas bidimensionais chamados ‘basins of attraction’. A relação entre o modelo proposto e um modelo prévio também é mostrada. Encontrou-se que os parâmetros relevantes em relação a ambos os tipos de sincronização são a razão entre a massa do metrônomo e a massa da base, e o amortecimento do sistema. Tem-se encontrado, tanto experimental quanto teoricamente, que a frequência de oscilação dos metrônomos aumenta quando o sistema sincroniza-se em fase, e se mantém a mesma de um metrônomo isolado quando o sistema sincroniza-se em anti-fase. A partir de simulações numéricas encontrou-se que, em geral, incrementos no amortecimento do sistema levam ao sistema se sincronizar mais em fase do que em anti-fase. Adicionalmente se encontrou que, para dado valor de amortecimento, diminuir a massa da base leva a uma situação em que a sincronização em anti-fase é mais comum do que a sincronização em fase. / This thesis concerns a theoretical and experimental investigation into the synchronization of two coupled metronomes. A simplified model is proposed to study in-phase and anti-phase synchronization of two metronomes oscillating on a mobile base. A description of the escapement mechanism driving metronomes is given and its relationship with the van der Pol oscillator is discussed. Also an experimental value for the damping in the metronome is determined. The instantaneous frequency of the responses from both numerical and experimental data is used in the analysis. Unlike previous studies, measurements are made using videos and the time domain responses of the metronomes extracted by means of tracker software. Basins of attraction are used to investigate the relationship between initial conditions, parameters and both final synchronization states. The relationship between the model and a previous pendulum model is also shown. The key parameters concerning both kind of synchronization have been found to be the mass ratio between the metronome mass and the base mass, and the damping in the system. It has been shown, both theoretically and experimentally, that the frequency of oscillation of the metronomes increases when the system reaches in-phase synchronization, and is the same as an isolated metronome when the system synchronizes in anti-phase. From numerical simulations, it has been found that, in general, increasing damping leads the system to synchronize more in-phase than in anti-phase. It has also been found that, for a given damping value, decreasing the mass of the base results in the situation where anti-phase synchronization is more common than in-phase synchronization.

No description available.

We analyzed long-term temperature trends in Utah using a relatively new signal processing method called Empirical Mode Decomposition (EMD). We evaluated the available weather records in Utah and selected 52 stations, which had records longer than 60 years, for analysis. We analyzed daily temperature data, both minimum and maximums, using the EMD method that decomposes non-stationary data (data with a trend) into periodic components and the underlying trend. Most decomposition algorithms require stationary data (no trend) with constant periods and temperature data do not meet these constraints. In addition to identifying the long-term trend, we also identified other periodic processes in the data. While the immediate goal of this research is to characterize long-term temperature trends and identify periodic processes and anomalies, these techniques can be applied to any time series data to characterize trends and identify anomalies. For example, this approach could be used to evaluate flow data in a river to separate the effects of dams or other regulatory structures from natural flow or to look at other water quality data over time to characterize the underlying trends and identify anomalies, and also identify periodic fluctuations in the data. If these periodic fluctuations can be associated with physical processes, the causes or drivers might be discovered helping to better understand the system. We used EMD to separate and analyze long-term temperature trends. This provides awareness and support to better evaluate the extremities of climate change. Using these methods we will be able to define many new aspects of nonlinear and nonstationary data. This research was successful and identified several areas in which it could be extended including data reconstruction for time periods missing data. This analysis tool can be applied to various other time series records.

No description available.

Signal processing has been playing a key role in providing solutions to key problems encountered in communications, in general, and in wireless communications, in particular. Time-Frequency Signal Processing (TFSP) provides eective tools for analyzing nonstationary signals where the frequency content of signals varies in time as well as for analyzing linear time-varying systems. This research aimed at exploiting the advantages of TFSP, in dealing with nonstationary signals, into the fundamental issues of signal processing, namely the signal estimation and signal separation. In particular, it has investigated the problems of (i) the Instantaneous Frequency (IF) estimation of Linear Frequency-Modulated (LFM) signals corrupted in complex-valued zero-mean Multiplicative Noise (MN), and (ii) the Underdetermined Blind Source Separation (UBSS) of LFM signals, while focusing onto the fast-growing area of Wireless Communications (WCom). A common problem in the issue of signal estimation is the estimation of the frequency of Frequency-Modulated signals which are seen in many engineering and real-life applications. Accurate frequency estimation leads to accurate recovery of the true information. In some applications, the random amplitude modulation shows up when the medium is dispersive and/or when the assumption of point target is not valid; the original signal is considered to be corrupted by an MN process thus seriously aecting the recovery of the information-bearing frequency. The IF estimation of nonstationary signals corrupted by complex-valued zero-mean MN was investigated in this research. We have proposed a Second-Order Statistics approach, rather than a Higher-Order Statistics approach, for IF estimation using Time-Frequency Distributions (TFDs). The main assumption was that the autocorrelation function of the MN is real-valued but not necessarily positive (i.e. the spectrum of the MN is symmetric but does not necessary has the highest peak at zero frequency). The estimation performance was analyzed in terms of bias and variance, and compared between four dierent TFDs: Wigner-Ville Distribution, Spectrogram, Choi-Williams Distribution and Modified B Distribution. To further improve the estimation, we proposed to use the Multiple Signal Classification algorithm and showed its better performance. It was shown that the Modified B Distribution performance was the best for Signal-to-Noise Ratio less than 10dB. In the issue of signal separation, a new research direction called Blind Source Separation (BSS) has emerged over the last decade. BSS is a fundamental technique in array signal processing aiming at recovering unobserved signals or sources from observed mixtures exploiting only the assumption of mutual independence between the signals. The term "blind" indicates that neither the structure of the mixtures nor the source signals are known to the receivers. Applications of BSS are seen in, for example, radar and sonar, communications, speech processing, biomedical signal processing. In the case of nonstationary signals, a TF structure forcing approach was introduced by Belouchrani and Amin by defining the Spatial Time- Frequency Distribution (STFD), which combines both TF diversity and spatial diversity. The benefit of STFD in an environment of nonstationary signals is the direct exploitation of the information brought by the nonstationarity of the signals. A drawback of most BSS algorithms is that they fail to separate sources in situations where there are more sources than sensors, referred to as UBSS. The UBSS of nonstationary signals was investigated in this research. We have presented a new approach for blind separation of nonstationary sources using their TFDs. The separation algorithm is based on a vector clustering procedure that estimates the source TFDs by grouping together the TF points corresponding to "closely spaced" spatial directions. Simulations illustrate the performances of the proposed method for the underdetermined blind separation of FM signals. The method developed in this research represents a new research direction for solving the UBSS problem. The successful results obtained in the research development of the above two problems has led to a conclusion that TFSP is useful for WCom. Future research directions were also proposed.