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1
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Fading Statistics in Communications - a Random Matrix Approach

100%
Yeh J., Ott E., Antonsen T., Anlage S.
Acta Physica Polonica A
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2011
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vol. 120
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issue 6A
A-85-A-88
EN
Fading is the time-dependent variations in signal strength measured at a receiver, due to temporally evolving multipath scattering and interference. In our previous work we introduced a statistical fading model for the time-reversal invariant case by combining the predictions of random matrix theory with the random coupling model that includes system-specific properties such as the radiation impedance of the ports and short-orbit effects. In the high-loss limit this random matrix theory model reduced to the most common fading models in the wireless communication field. In this paper we discuss the theoretical model in more detail and extend it to the case of broken time-reversal invariance.
2
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Aspects of the Scattering and Impedance Properties of Chaotic Microwave Cavities

88%
Hemmady S., Zheng X., Antonsen T., Ott E., Anlage S.
Acta Physica Polonica A
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2006
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vol. 109
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issue 1
65-71
EN
We consider the statistics of the impedance Z of a chaotic microwave cavity coupled to a single port. We remove the non-universal effects of the coupling from the experimental Z data using the radiation impedance obtained directly from the experiments. We thus obtain the normalized impedance whose probability density function is predicted to be universal in that it depends only on the loss (quality factor) of the cavity. We find that impedance fluctuations decrease with increasing loss. The results apply to scattering measurements on any wave chaotic system.
3
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Experimental Study of Quantum Graphs with Simple Microwave Networks: Non-Universal Features

88%
Fu Z., Koch T., Antonsen T., Ott E., Anlage S.
Acta Physica Polonica A
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2017
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vol. 132
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issue 6
1655-1660
EN
Quantum graphs provide a setting to test the hypothesis that all ray-chaotic systems show universal wave chaotic properties. Here, an experimental setup consisting of a microwave coaxial cable network is used to simulate quantum graphs. The networks which are large compared to the wavelength, are constructed from coaxial cables connected by T junctions. The distributions of impedance statistics are obtained from experiments on an ensemble of tetrahedral networks. The random coupling model (RCM) is applied in an attempt to uncover the universal statistical properties of the system. Deviations from RCM predictions have been observed in that the statistics of diagonal and off-diagonal impedance elements are different. It is argued that because of the small finite-size quantum graphs utilized here there will be non-universal results.
4
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Chaotic Time-Reversed Acoustics: Sensitivity οf the Loschmidt Echo to Perturbations

76%
Taddese B., Johnson M., Hart J., Antonsen T., Ott E., Anlage S.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
729-732
EN
We experimentally demonstrate a new acoustic sensor based on the concept of quantum mechanical scattering fidelity and the Loschmidt echo applied to classical acoustic waves in air. The sensor employs a one-recording-channel time-reversal mirror that exploits spatial reciprocity to sensitively measure the classical analog of the scattering fidelity of an enclosed region. The experiments are carried out in a stairwell using a simple speaker and microphone. The input is a 7.0 kHz signal that is amplitude modulated with a 1 ms long pulse. We examine the sensitivity of the time-reversed reconstructed pulse to phase noise, long term drift, and to typical perturbations caused by the rotation of an object in the scattering environment.
5
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New Results in Chaotic Time-Reversed Electromagnetics: High Frequency One-Recording-Channel Time-Reversal Mirror

76%
Anlage S., Rodgers J., Hemmady S., Hart J., Antonsen T., Ott E.
Acta Physica Polonica A
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2007
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vol. 112
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issue 4
569-574
EN
We experimentally demonstrate a new electromagnetic one-recording-channel time-reversal mirror that can operate at high frequencies and high bandwidths. The experiments are carried out in a 1 m^3 ray-chaotic enclosure using two simple antennas. The input is a 7.0 GHz signal that is amplitude modulated with a 60 ns long pulse. The time-reversal focused signal has a peak-signal-to-noise ratio of about 9 dB, and is very sensitive to small perturbations to the ray-chaotic enclosure. The results are consistent with expectations for single-recording-channel time-reversal mirrors, and establish a new platform for study of fundamental issues in time-domain wave chaos, as well as novel applications.
6
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Impedance and Scattering Variance Ratios of Complicated Wave Scattering Systems in the Low Loss Regime

64%
Yeh J., Drikas Z., Gil Gil J., Hong S., Taddese B., Ott E., Antonsen T., Andreadis T., Anlage S.
Acta Physica Polonica A
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2013
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vol. 124
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issue 6
1045-1052
EN
Random matrix theory successfully predicts universal statistical properties of complicated wave scattering systems in the semiclassical limit, while the random coupling model offers a complete statistical model with a simple additive formula in terms of impedance to combine the predictions of random matrix theory and nonuniversal system-specific features. The statistics of measured wave properties generally have nonuniversal features. However, ratios of the variances of elements of the impedance matrix are predicted to be independent of such nonuniversal features and thus should be universal functions of the overall system loss. In contrast with impedance variance ratios, scattering variance ratios depend on nonuniversal features unless the system is in the high loss regime. In this paper, we present numerical tests of the predicted universal impedance variance ratios and show that an insufficient sample size can lead to apparent deviation from the theory, particularly in the low loss regime. Experimental tests are carried out in three two-port microwave cavities with varied loss parameters, including a novel experimental system with a superconducting microwave billiard, to test the variance-ratio predictions in the low loss time-reversal-invariant regime. It is found that the experimental results agree with the theoretical predictions to the extent permitted by the finite sample size.
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