89,280 research outputs found
Shot Noise Current-Current Correlations in Multi-Terminal Diffusive Conductors
We investigate the correlations in the current fluctuations at different
terminals of metallic diffusive conductors. We start from scattering matrix
expressions for the shot noise and use the Fisher-Lee relation in combination
with diagram technique to evaluate the noise correlations. Of particular
interest are exchange (interference) effects analogous to the Hanbury
Brown--Twiss effect in optics. We find that the exchange effect exists in the
ensemble averaged current correlations. Depending on the geometry, it might
have the same magnitude as the mean square current fluctuations of the shot
noise. The approach which we use is first applied to present a novel derivation
of the 1/3-suppression of shot noise in a two-terminal geometry, valid for an
arbitrary relation between the length and wire width. We find that in all
geometries correlations are insensitive to dephasing.Comment: 10 pages, two-column Revtex, 7 figures include
Joint Design of Multi-Tap Analog Cancellation and Digital Beamforming for Reduced Complexity Full Duplex MIMO Systems
Incorporating full duplex operation in Multiple Input Multiple Output (MIMO)
systems provides the potential of boosting throughput performance. However, the
hardware complexity of the analog self-interference canceller scales with the
number of transmit and receive antennas, thus exploiting the benefits of analog
cancellation becomes impractical for full duplex MIMO transceivers. In this
paper, we present a novel architecture for the analog canceller comprising of
reduced number of taps (tap refers to a line of fixed delay and variable phase
shifter and attenuator) and simple multiplexers for efficient signal routing
among the transmit and receive radio frequency chains. In contrast to the
available analog cancellation architectures, the values for each tap and the
configuration of the multiplexers are jointly designed with the digital
beamforming filters according to certain performance objectives. Focusing on a
narrowband flat fading channel model as an example, we present a general
optimization framework for the joint design of analog cancellation and digital
beamforming. We also detail a particular optimization objective together with
its derived solution for the latter architectural components. Representative
computer simulation results demonstrate the superiority of the proposed low
complexity full duplex MIMO system over lately available ones.Comment: 8 pages, 4 figures, IEEE ICC 201
Breaking the challenge of signal integrity using time-domain spoof surface plasmon polaritons
In modern integrated circuits and wireless communication systems/devices,
three key features need to be solved simultaneously to reach higher performance
and more compact size: signal integrity, interference suppression, and
miniaturization. However, the above-mentioned requests are almost contradictory
using the traditional techniques. To overcome this challenge, here we propose
time-domain spoof surface plasmon polaritons (SPPs) as the carrier of signals.
By designing a special plasmonic waveguide constructed by printing two narrow
corrugated metallic strips on the top and bottom surfaces of a dielectric
substrate with mirror symmetry, we show that spoof SPPs are supported from very
low frequency to the cutoff frequency with strong subwavelength effects, which
can be converted to the time-domain SPPs. When two such plasmonic waveguides
are tightly packed with deep-subwavelength separation, which commonly happens
in the integrated circuits and wireless communications due to limited space, we
demonstrate theoretically and experimentally that SPP signals on such two
plasmonic waveguides have better propagation performance and much less mutual
coupling than the conventional signals on two traditional microstrip lines with
the same size and separation. Hence the proposed method can achieve significant
interference suppression in very compact space, providing a potential solution
to break the challenge of signal integrity
Modulation parameter estimation of LFM interference for direct sequence spread spectrum communication system in alpha-stable noise
The linear frequency modulation (LFM) interference is one of the typical broadband interferences in direct sequence spread spectrum (DSSS) communication system. In this article, a novel modulation parameter estimation method of LFM interference is proposed for the DSSS communication system in alpha-stable noise. To accurately estimate the modulation parameters, the alpha-stable noise should be eliminated first. Thus, we formulate a new generalized extended linear chirplet transform to suppress the alpha-stable noise, for a robust time-frequency, transformation of LFM interference is realized. Then, using the Radon transform, the maximum value after transformation and the chirp rate according to the angle related to the maximum value are estimated. In addition, a generalized Fourier transform is introduced to estimate the initial frequency of the LFM interference. For the performance analysis, the Cramér-Rao lower bounds of the estimated chirp rate and the initial frequency of the LFM interference in the presence of alpha-stable noise are derived. Moreover, the asymptotic properties of the modulation parameter estimator are analyzed. Simulation results demonstrate that the performance of the proposed parameter estimation method significantly outperforms existing methods, especially in a low SNR regime
Serial Position Effects in Short-term Visual Memory: A SIMPLE Explanation?
A version of Sternberg’s (1966) short-term, visual memory recognition paradigm with pictures of unfamiliar faces as stimuli was used in three experiments to assess the applicability of the distinctiveness based SIMPLE model proposed by Brown, Neath & Chater (2002). Initial simulations indicated that the amount of recency predicted increased as the parameter measuring the psychological distinctiveness of the stimulus material (c) increased, and that the amount of primacy was dependent on the extent of proactive interference from previously presented stimuli. The data from experiment 1, which used memory lists of four and five faces varying in visual similarity confirmed the predicted, extended recency effect. However, changes in visual similarity were not found to produce changes in c. In Experiments 2 and 3, the conditions that influence the magnitude of c were explored. These revealed that both the familiarity of the stimulus class before testing, and changes in familiarity due to perceptual learning, influenced distinctiveness as indexed by the parameter c. Overall the empirical data from all three experiments were well-fit by SIMPLE
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