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The relationship between antenna loss and superdirectivity in MIMO systems
 IEEE Transactions on Wireless Communications
"... The relationship between antenna loss and superdirectivity in MIMO systems ..."
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The relationship between antenna loss and superdirectivity in MIMO systems
Using parasitic elements for implementing the rotating antenna for MIMO receivers
 IEEE Trans. on Wireless Communications
, 2008
"... Abstract—We consider a new concept of a MultipleInputMultipleOutput (MIMO) receiver which uses one active receiving antenna and multiple parasitic elements. The parasitic elements give the possibility of creating a directive antenna beam which is rotated 360 degrees around within the duration of ..."
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Abstract—We consider a new concept of a MultipleInputMultipleOutput (MIMO) receiver which uses one active receiving antenna and multiple parasitic elements. The parasitic elements give the possibility of creating a directive antenna beam which is rotated 360 degrees around within the duration of a symbol period. The received signal which is accessed at the antenna connector of the active antenna is expanded in frequency bandwidth compared to the transmitted signal. We show that each subband of the received signal consists of linearly independent combinations of the transmitted signals, and thus we have obtained a MIMO receiver. We give a few examples on how to implement this receiver and also explain the effects of sampling the wavefield at discrete angular directions. Index Terms—MIMO systems, transmission technology, transceiver design.
New aspects of electromagnetic information theory for wireless and antenna systems
 IEEE Trans. Antennas Propag
, 2008
"... Abstract—This paper investigates informationtheoretic characterization, via Shannon’s information capacity and number of degrees of freedom, of wave radiation (antenna) and wireless propagation systems. Specifically, the paper derives, from the fundamental physical point of view of Maxwell’s equati ..."
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Abstract—This paper investigates informationtheoretic characterization, via Shannon’s information capacity and number of degrees of freedom, of wave radiation (antenna) and wireless propagation systems. Specifically, the paper derives, from the fundamental physical point of view of Maxwell’s equations describing electromagnetic fields, the Shannon information capacity of spacetime wireless channels formed by electromagnetic sources and receivers in a known background medium. The theory is developed first for the case of sources working at a fixed frequency (timeharmonic case) and is expanded later to the more general case of temporally bandlimited systems (timedomain fields). In the bandlimited case we consider separately the two cases of timelimited and essentially bandlimited systems and of purely bandlimited systems. The developments take into account the physical radiated power constraint in addition to a constraint in the source L 2 norm which acts to avoid antenna superdirectivity. Based on such radiated power and current L 2 norm constraints we derive the Shannon information capacity of canonical wireless and antenna systems in free space, for a given additive Gaussian noise level, as well as an associated number of degrees of freedom resulting from such capacity calculations. The derived results also illustrate, from a new informationtheoretic point of view, the transition from near to far fields. Index Terms—Antenna, degrees of freedom, electromagnetic information, information capacity, wave information, wireless. I.
MODELING ANTENNA COUPLING AND CORRELATION IN RAPIDLY FADING MIMO CHANNELS
"... Node mobility in rich multipath environments limits the quality of attainable channel state information (CSI) due to wavelengthscale fading, leading to effectively lower channel capacities. Recent work on the capacity of blockfading MIMO channels considers the impact of antenna correlation at the ..."
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Node mobility in rich multipath environments limits the quality of attainable channel state information (CSI) due to wavelengthscale fading, leading to effectively lower channel capacities. Recent work on the capacity of blockfading MIMO channels considers the impact of antenna correlation at the transmitter [1], proving that correlation guarantees capacity growth with additional antennas and suggests that for rapidly fading channels, antennas should be paced as close together as possible. This work augments the MIMO modeling strategy in [1] to include the effects of electromagnetic coupling of the antennas. Constraining the radiated power of the transmit array reveals that the reported gains result from simple beamforming mechanisms, and that capacity growth only comes from increased channel correlation, not antenna correlation whose gain is offset by increased coupling. The new model also predicts that optimal antenna placement for rapidly fading channels is not arbitrarily close, but rather on the order of 0.3 to 0.6 wavelengths. Key words: MIMO; correlation; coupling; antenna placement. 1.
ABSTRACT MIMO COMMUNICATION CAPACITY: ANTENNA COUPLING AND PRECODING FOR INCOHERENT DETECTION
, 2006
"... of a dissertation submitted by ..."
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IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION 1 New Aspects of Electromagnetic Information Theory for Wireless and Antenna Systems
"... This paper investigates certain fundamental aspects not fully covered by previous work on informationtheoretic characterization, via Shannon’s information capacity and number of degrees of freedom, of wave radiation (antenna) and wireless propagation systems. Specifically, the paper derives, from t ..."
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This paper investigates certain fundamental aspects not fully covered by previous work on informationtheoretic characterization, via Shannon’s information capacity and number of degrees of freedom, of wave radiation (antenna) and wireless propagation systems. Specifically, the paper derives, from the fundamental physical point of view of Maxwell’s equations describing electromagnetic fields, the Shannon information capacity of spacetime wireless channels formed by electromagnetic sources and receivers in a known background medium. The theory is developed for both the case of sources working at a fixed frequency (timeharmonic case) and for the more general situation of temporally bandlimited systems. In the bandlimited case we consider separately the two cases of essentially bandlimited and timelimited systems and of purely bandlimited systems. The developments take into account the physical radiated power constraint in addition to the more usual constraint in the source L 2 norm. Based on such radiated power and/or current L 2 norm constraints we derive the Shannon information capacity of canonical wireless and antenna systems in free space, for a given additive Gaussian noise level, as well as an associated number of degrees of freedom resulting from such capacity calculations. This approach constitutes a rigorous, informationtheoretic method to define under given noise the dimensionality of the field. The derived results illustrate, from a new informationtheoretic point of view, the transition from near to far fields. The paper also examines how some of the capacity results for a known background also apply under certain conditions to more general propagation environments having additional multipathing scatterers.
Communicating on MIMO channels with covariance information: antenna correlation and coupling
"... Abstract—A recent study on correlated blockfading MIMO channels with transmit covariance information indicates guaranteed capacity growth with additional transmit elements, in contrast to previous results for uncorrelated channels. Also, for very rapidly fading channels, the results indicate the o ..."
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Abstract—A recent study on correlated blockfading MIMO channels with transmit covariance information indicates guaranteed capacity growth with additional transmit elements, in contrast to previous results for uncorrelated channels. Also, for very rapidly fading channels, the results indicate the optimality of placing antenna elements as close together as possible. In this work, application of radiated power considerations indicates that transmit beamforming only increases capacity when this gain results from correlation inherent in the channel, not correlation that is simply offset by increased antenna coupling. The new analysis reveals that when multipath is directionally biased, antenna spacings of 0.3 to 0.6 wavelengths are optimal, and that when no such bias is present, antennas should be placed as far apart as possible. As expected, the electromagnetic analysis shows that at zero element separation, the array yields no capacity gain over a single antenna. I.