251 research outputs found
From Chirps to Random-FM Excitations in Pulse Compression Ultrasound Systems
Pulse compression is often practiced in ultrasound Non Destructive Testing
(NDT) systems using chirps. However, chirps are inadequate for setups where
multiple probes need to operate concurrently in Multiple Input Multiple Output
(MIMO) arrangements. Conversely, many coded excitation systems designed for
MIMO miss some chirp advantages (constant envelope excitation, easiness of
bandwidth control, etc.) and may not be easily implemented on hardware
originally conceived for chirp excitations. Here, we propose a system based on
random-FM excitations, capable of enabling MIMO with minimal changes with
respect to a chirp-based setup. Following recent results, we show that
random-FM excitations retain many advantages of chirps and provide the ability
to frequency-shape the excitations matching the transducers features.Comment: 4 pages, 4 figures. Post-print from conference proceedings. Note that
paper in conference proceedings at http://dx.doi.org/10.1109/ULTSYM.2012.0117
has some rendering issue
Multi Detector Fusion of Dynamic TOA Estimation using Kalman Filter
In this paper, we propose fusion of dynamic TOA (time of arrival) from
multiple non-coherent detectors like energy detectors operating at sub-Nyquist
rate through Kalman filtering. We also show that by using multiple of these
energy detectors, we can achieve the performance of a digital matched filter
implementation in the AWGN (additive white Gaussian noise) setting. We derive
analytical expression for number of energy detectors needed to achieve the
matched filter performance. We demonstrate in simulation the validity of our
analytical approach. Results indicate that number of energy detectors needed
will be high at low SNRs and converge to a constant number as the SNR
increases. We also study the performance of the strategy proposed using IEEE
802.15.4a CM1 channel model and show in simulation that two sub-Nyquist
detectors are sufficient to match the performance of digital matched filter
Adaptive Investment Strategies For Periodic Environments
In this paper, we present an adaptive investment strategy for environments
with periodic returns on investment. In our approach, we consider an investment
model where the agent decides at every time step the proportion of wealth to
invest in a risky asset, keeping the rest of the budget in a risk-free asset.
Every investment is evaluated in the market via a stylized return on investment
function (RoI), which is modeled by a stochastic process with unknown
periodicities and levels of noise. For comparison reasons, we present two
reference strategies which represent the case of agents with zero-knowledge and
complete-knowledge of the dynamics of the returns. We consider also an
investment strategy based on technical analysis to forecast the next return by
fitting a trend line to previous received returns. To account for the
performance of the different strategies, we perform some computer experiments
to calculate the average budget that can be obtained with them over a certain
number of time steps. To assure for fair comparisons, we first tune the
parameters of each strategy. Afterwards, we compare the performance of these
strategies for RoIs with different periodicities and levels of noise.Comment: Paper submitted to Advances in Complex Systems (November, 2007) 22
pages, 9 figure
The bistatic continuous-wave radar method for the study of planetary surfaces Scientific report no. 13
Bistatic continuous-wave radar for mapping surface of planet
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