614 research outputs found
Some Advances in Nonlinear Speech Modeling Using Modulations, Fractals, and Chaos
In this paper we briefly summarize our on-going work on modeling nonlinear structures in speech signals, caused by modulation and turbulence phenomena, using the theories of modulation, fractals, and chaos as well as suitable nonlinear signal analysis methods. Further, we focus on two advances: i) AM-FM modeling of fricative sounds with random modulation signals of the 1/f-noise type and ii) improved methods for speech analysis and prediction on reconstructed multidimensional attractors. 1
Digital Demodulator for BFSK waveform based upon Correlator and Differentiator Systems
The present article relates in general to digital demodulation of Binary Frequency Shift Keying (BFSK waveform) . New processing methods for demodulating the BFSK-signals are proposed here. Based on Sampler Correlator, the hardware consumption for the proposed techniques is reduced in comparison with other reported. Theoretical details concerning limits of applicability are also given by closed-form expressions. Simulation experiments are illustrated to validate the overall performance
Traffic control system and method Patent
Traffic control system for supersonic transports using synchronous satellite for data relay between vehicles and ground statio
A radio-paging receiver architecture and demodulator
Imperial Users onl
Multirate Frequency Transformations: Wideband AM-FM Demodulation with Applications to Signal Processing and Communications
The AM-FM (amplitude & frequency modulation) signal model finds numerous applications in image processing, communications, and speech processing. The traditional approaches towards demodulation of signals in this category are the analytic signal approach, frequency tracking, or the energy operator approach. These approaches however, assume that the amplitude and frequency components are slowly time-varying, e.g., narrowband and incur significant demodulation error in the wideband scenarios. In this thesis, we extend a two-stage approach towards wideband AM-FM demodulation that combines multirate frequency transformations (MFT) enacted through a combination of multirate systems with traditional demodulation techniques, e.g., the Teager-Kasiser energy operator demodulation (ESA) approach to large wideband to narrowband conversion factors.
The MFT module comprises of multirate interpolation and heterodyning and converts the wideband AM-FM signal into a narrowband signal, while the demodulation module such as ESA demodulates the narrowband signal into constituent amplitude and frequency components that are then transformed back to yield estimates for the wideband signal.
This MFT-ESA approach is then applied to the various problems of: (a) wideband image demodulation and fingerprint demodulation, where multidimensional energy separation is employed, (b) wideband first-formant demodulation in vowels, and (c) wideband CPM demodulation with partial response signaling, to demonstrate its validity in both monocomponent and multicomponent scenarios as an effective multicomponent AM-FM signal demodulation and analysis technique for image processing, speech processing, and communications based applications
Closed-Loop Control of a Piezo-Fluidic Amplifier
Fluidic valves based on the Coand\u{a} effect are increasingly being
considered for use in aerodynamic flow control applications. A limiting factor
is their variation in switching time, which often precludes their use. The
purpose of this paper is to demonstrate the closed-loop control of a recently
developed, novel piezo-fluidic valve that reduces response time uncertainty at
the expense of operating bandwidth. Use is made of the fact that a fluidic jet
responds to a piezo tone by deflecting away from its steady state position. A
control signal used to vary this deflection is amplitude modulated onto the
piezo tone. Using only a pressure measurement from one of the device output
channels, an output-based LQG regulator was designed to follow a desired
reference deflection, achieving control of a 90 m/s jet. Finally, the
controller's performance in terms of disturbance rejection and response time
predictability is demonstrated.Comment: 31 pages, 23 figures. Published in AIAA Journal, 4th May 202
Range-resolved interferometric signal processing using sinusoidal optical frequency modulation
A novel signal processing technique using sinusoidal optical frequency modulation of an inexpensive continuous-wave laser diode source is proposed that allows highly linear interferometric phase measurements in a simple, self-referencing setup. Here, the use of a smooth window function is key to suppress unwanted signal components in the demodulation process. Signals from several interferometers with unequal optical path differences can be multiplexed, and, in contrast to prior work, the optical path differences are continuously variable, greatly increasing the practicality of the scheme. In this paper, the theory of the technique is presented, an experimental implementation using three multiplexed interferometers is demonstrated, and detailed investigations quantifying issues such as linearity and robustness against instrument drift are performed
Prediction of motion induced magnetic fields for human brain MRI at 3T
Objective Maps of B0 field inhomogeneities are often used to improve MRI
image quality, even in a retrospective fashion. These field inhomogeneities
depend on the exact head position within the static field but acquiring field
maps (FM) at every position is time consuming. Here we explore different ways
to obtain B0 predictions at different head positions. Methods FM were predicted
from iterative simulations with four field factors: 1) sample induced B0 field,
2) system's spherical harmonic shim field, 3) perturbing field originating
outside the field of view, 4) sequence phase errors. The simulation was
improved by including local susceptibility sources estimated from UTE scans and
position-specific masks. The estimation performance of the simulated FMs and a
transformed FM, obtained from the measured reference FM, were compared with the
actual FM at different head positions. Results The transformed FM provided
inconsistent results for large head movements (>5 degree rotation), while the
simulation strategy had a superior prediction accuracy for all positions. The
simulated FM was used to optimize B0 shims with up to 22.2% improvement with
respect to the transformed FM approach. Conclusion The proposed simulation
strategy is able to predict movement induced B0 field inhomogeneities yielding
more precise estimates of the ground truth field homogeneity than the
transformed FM
Simultaneous Digital Demodulation and RDS Extraction of FM Radio Signals
FM radio plays a large part in many peoples\u27 lives. A digital stream of information known as the Radio Data System (RDS) can be transmitted alongside the audio signal in an FM radio broadcast. This digital signal may contain information such as the current song, traffic alerts, and emergency notices. Using MATLAB, a method is presented by which the RDS data may be digitally extracted from multiple FM broadcasts simultaneously. This method\u27s parallel nature makes Digital Signal Processing (DSP) technology, such as a Field Programmable Gate Array (FPGA), an ideal platform for implementation
Statistical models for natural sounds
It is important to understand the rich structure of natural sounds in order to solve important
tasks, like automatic speech recognition, and to understand auditory processing
in the brain. This thesis takes a step in this direction by characterising the statistics of
simple natural sounds. We focus on the statistics because perception often appears to
depend on them, rather than on the raw waveform. For example the perception of auditory
textures, like running water, wind, fire and rain, depends on summary-statistics,
like the rate of falling rain droplets, rather than on the exact details of the physical
source.
In order to analyse the statistics of sounds accurately it is necessary to improve a
number of traditional signal processing methods, including those for amplitude demodulation,
time-frequency analysis, and sub-band demodulation. These estimation tasks
are ill-posed and therefore it is natural to treat them as Bayesian inference problems.
The new probabilistic versions of these methods have several advantages. For example,
they perform more accurately on natural signals and are more robust to noise,
they can also fill-in missing sections of data, and provide error-bars. Furthermore,
free-parameters can be learned from the signal. Using these new algorithms we demonstrate
that the energy, sparsity, modulation depth and modulation time-scale in each
sub-band of a signal are critical statistics, together with the dependencies between the
sub-band modulators. In order to validate this claim, a model containing co-modulated
coloured noise carriers is shown to be capable of generating a range of realistic sounding
auditory textures.
Finally, we explored the connection between the statistics of natural sounds and perception.
We demonstrate that inference in the model for auditory textures qualitatively
replicates the primitive grouping rules that listeners use to understand simple acoustic
scenes. This suggests that the auditory system is optimised for the statistics of natural
sounds
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