Minimum Number Of Antennas Research Articles

Mutual information statistics for dual MIMO systems in correlated Rayleigh fading

In this letter, we derive very simple and exact expressions for the mutual information (MI) distributions under isotropic Gaussian input of dual multiple-input multiple-output (MIMO) systems, where the minimum number of antennas at either side of the wireless link is two, in a semicorrelated Rayleigh fading environment with correlation at the dual-antenna side only. Furthermore, exact closed-form expressions for the MI moments (mean, variance), and other higher order statistics, such as the skewness and kurtosis, are derived. The proposed methodology for evaluating the MI statistics, is easily extendable to other multielement antenna settings such as single-input multiple-output (SIMO), multiple-input single-output (MISO) and dual MIMO systems for both uncorrelated and semicorrelated Rayleigh fading, where correlation can be assumed at the side with the largest number of antennas

Mode separation and direction of arrival estimation in HF links

Estimation of arrival angles and incoming signals is a challenging problem for HF channels where the signals are correlated and the separation between the signals can be as low as a couple of degrees. In this paper, a new algorithm, Multipath Separation‐Direction of Arrival (MS‐DOA), is developed to estimate both the arrival angles in elevation and azimuth and the incoming signals at the output of the reference antenna with very high accuracy. The MS‐DOA algorithm provides reliable angle and signal estimates even with small separation of arrival angles and for low SNRs. The minimum number of antennas that are required by the algorithm is only one more than the number of incoming signals. In a narrowed down region of interest and for a few incoming signals, the computational search time for MS‐DOA is only a couple of minutes in a standard PC.

Bounds and approximations for optimum combining of signals in the presence of multiple cochannel interferers and thermal noise

We derive an upper bound and investigate some approximations on the symbol error probability (SEP) for coherent detection of M-ary phase-shift keying, using an array of antennas with optimum combining in wireless systems in the presence of multiple uncorrelated equal-power cochannel interferers and thermal noise in a Rayleigh fading environment. Our results are general and valid for an arbitrary number of antenna elements as well as an arbitrary number of interferers. In particular, the exact SEP is derived for an arbitrary number of antennas and interferers; the computational complexity of the exact solution depends on the minimum number of antennas and interferers. Moreover, closed-form approximations are provided for the cases of dual optimum combining with an arbitrary number of interferers, and of two interferers with an arbitrary number of antenna elements. We show that our bounds and approximations are close to Monte Carlo simulation results for all cases considered in this paper.

Remote sensing of hydrometeors by means of interferometric radiometry: Theory and experimental results

Spaceborne and ground‐based radiometric measurements at microwave and millimeterwave frequencies have proved able to monitor hydrometeors, but at present the angular resolution of those systems is limited by the radiometer's antenna beam width. Efforts to improve the angular resolution of such systems by applying the interferometric techniques successfully used in radio astronomy [Thompson et al, 1986; Ruf et al., 1988] have encountered two main limitations. First, imaging interferometric radiometers are extremely complex, with a very large number of antennas and correlators. Second, because of the wide field of view, the array size is restricted by spatial decorrelation effects that cannot be simply compensated for by an adjustable delay, as in radio astronomy. Bandwidth segmentation overcomes this limitation at the expense of an even higher system's complexity. To overcome these limitations, this paper presents a technique that may achieve high angular resolution with a minimum number of antennas, taking advantage of the spatial filtering due to signal decorrelation. It describes both the basic theory behind this process and the experimental results at X band with a random static distribution of rubber bits and with simulated rain. The experimental results agree well with theoretical predictions and computer simulations, showing the inevitable trade‐off between angular resolution and radiometric sensitivity.

Vulnerability of a communication network with a satellite

AbstractThe vulnerability of an integrated communication network composed of a terrestrial network and a satellite network is discussed in a graph‐theoretic manner. A ground switching station (a switch board) is abstracted as a vertex, a wire and an antenna, respectively, for a communication with a satellite as an edge of a graph. As a measure of the vulnerability of a communication network we introduce anew the concept of “S‐connectivity.” Although the concept of S‐connectivity is obtained by generalizing the conventional idea of vertex‐connectivity, since it takes into consideration the difference in the reliability between a satellite as a wireless transistor and a ground station controlled by software, it appears suitable as a means to determine the vulnerability of a communication network consisting of a terrestrial network and a satellite network.This paper discusses: (1) What is the S‐connectivity when antennas that transmit to and receive from a satellite, are used on each ground station? (2) If ground stations exist which cannot communicate through the terrestrial network, at which stations should antennas be installed to enable communications with the minimum number of antennas via satellite? (3) When the number of edges of a terrestrial network is fixed, what kind of terrestrial network maximizes the S‐connectivity? (4) What are the computation times of algorithms for solving the preceding problems (1) and (2)?

Wider Aperture Sine‐Cosine Direction Finders

Higher‐order sine‐cosine azimuth patterns for Adcock direction finding are investigated to determine spacing errors, reradiation errors, and pickup factor. The higher modes achieve wider apertures and reduced wave interference error; they exhibit comparable pickup factors but require an increase in the minimum number of antennas and different sensing methods. The 1.220λ spacing limit is appropriate only to the dipole mode, the corresponding limit for the quadrupole mode being 1.684λ and correspondingly greater for the higher modes. Reduced spacing error for the minimum number of antennas occurs at increasingly wider apertures which also tend to more closely approach the theoretical limits with increasing mode. The higher modes exhibit reduced response in the vicinity of the zenith. The resolution of the additional bearing ambiguities involves the use of one or more lower‐order patterns. Predicted sense performance as a function of reradiated field amplitude is computed for a combination of quadrupole and dipole modes.