Multiple Element Antenna System Research Articles

Performance Study of Pattern Reconfigurable Antennas in MIMO Communication Systems

We explore the potential benefits of using pattern reconfigurable antennas in multiple-input multiple-output (MIMO) communication systems. First, theoretical capacity increases are calculated in a typical indoor multipath environment assuming ideal, fully reconfigurable antennas and compared to cases using theoretical isotropic antennas. Next, a real reconfigurable antenna built into a multiple element antenna system for MIMO use is described and analyzed to investigate the possible effects of beam tilts on capacity. Finally, this system is used to quantify the possible capacity improvements due to both antenna diversity and antenna gain that are enabled by antenna pattern reconfigurability in a scientifically reproducible environment that includes antenna coupling.

On the asymptotic capacity of MIMO systems with antenna arrays of fixed length

Previous authors have shown that the asymptotic capacity of a multiple-element-antenna (MEA) system with N transmit and N receive antennas [termed an (N,N) MEA] grows linearly with N if, for all l, the correlation of the fading for two antenna elements whose indices differ by l remains fixed as antennas are added to the array. However, in practice, the total size of the array is often fixed, and thus the correlation of the fading for two elements separated in index by some value l will change as the number of antenna elements is increased. In this paper, under the condition that the size of an array of antennas is fixed, and assuming that the transmitter does not have access to the channel state information (CSI) while the receiver has perfect CSI, the asymptotic properties of the instantaneous mutual information I/sub N,N/ of an (N,N) MEA wireless system employing uniform linear arrays in a quasi-static fading channel are derived analytically and tested for accuracy for finite N through simulations. For many channel correlation structures, it is demonstrated that the asymptotic performance converges almost surely, implying that such MEA systems have a certain strong robustness to the instantiation of the channel fading values.

Optimization of Antenna Array Structures in Mobile Handsets

A study of the capacity of multiple-element antenna systems is presented with particular emphasis on the effects of mutual coupling between the antenna elements. As the total size of the array is often fixed and limited, the correlation of fading as well as the mutual coupling of two elements separated in index by some value l increases. In this paper, at first with the assumption that the length of the linear array of antenna elements and the number of antenna elements at the receiver are fixed, the capacity with coding, without coding, and the symbol error rate (SER) of space-time coding are investigated. The results obtained show that for the mean signal to noise ratio at the receiver of /spl rho/=20 dB, the linear array of three antenna elements is the optimum choice if the total length of the array is in the range of 0.3/spl lambda/-0.86/spl lambda/, while in the case of channel state information (CSI), this range is 0.25/spl lambda/-0.6/spl lambda/. The effects of the signal-to-noise ratio (SNR) and number of the base station antenna elements on the capacity of the fixed-length linear arrays are also discussed. Next, it is assumed that the number of antenna elements at the transmitter and receiver are equal. Simulation results show the number of antenna elements for maximizing the capacity.

The potential use of time reversal techniques in multiple element antenna systems

Based on outdoor measurements we study the feasibility of applying the time reversal techniques (TR) in multiple element antenna (MEA) wireless communication systems. It is demonstrated that the use of TR in wireless communication has a promising potential in mitigating the effect of channel dispersion and especially in reducing the cochannel interference where a margin of 18 dB interference reduction has been obtained.

The potential use of time reversal techniques in multiple element antenna systems

Based on outdoor measurements we study the feasibility of applying the time reversal techniques (TR) in multiple element antenna (MEA) wireless communication systems. It is demonstrated that the use of TR in wireless communication has a promising potential in mitigating the effect of channel dispersion and especially in reducing the cochannel interference where a margin of 18 dB interference reduction has been obtained.

Effect of antenna polarization on the capacity of a multiple element system in an indoor environment

We analyze the behavior of a multiple element antenna system in an indoor environment based on the measurements taken in the Lucent Bell Labs building in Crawford Hill, NJ, with a system of 12 transmitters and 15 receivers. In particular, we investigate the capacity behavior with respect to the polarization of the transmitting/receiving elements and the distance between the transmitting and the receiving arrays. The analysis of the power rolloff versus distance clearly demonstrates the different propagation characteristics of the horizontally versus the vertically polarized electric fields. Under strong line-of-sight (LOS) conditions (hallway environment), the power of the horizontally polarized waves falls off faster with distance than that of the vertically polarized fields. Also, the cross-polarization coupling is about -15 dB. Under nonline-of-sight (NLOS) conditions (labs), both polarizations display similar rolloff behavior with distance and the cross-polarization coupling is about 0 dB. There is a power loss of at least 15 dB under NLOS conditions relative to LOS conditions. The average received signal power affects the system capacity. In the hallway, horizontally polarized systems achieve lower capacities than their vertically polarized counterparts. Also the achievable capacity in the labs is much lower than that in the hallway, because of the lower average received power. The comparison of single polarization systems to hybrid polarization systems shows that combined polarization systems perform better in terms of achievable capacity. Therefore, there lies an advantage in using both electric field polarizations. However, under strong LOS conditions the channel itself inherently limits the capacity behavior of the system.