Multi-element Antenna Arrays Research Articles

Role of Antennas and Propagation for the Wireless Systems Beyond 2000

By using laws like Shannon's, Friis' and experimental propagation results it is shown that from a theoretical point of view it is possible to overcome the problems of going to higher bandwidths and higher carrier frequencies. Multi-element antenna arrays at both ends can give the required gains even in highly scattering environments. The basic joint antenna gain is that of one channel. In many cases multiple channels with similar properties may be obtained.

A Low Complexity Downlink Beamforming Scheme for DS-CDMA System

The downlink capacity of frequency division duplex (FDD) based DS-CDMA system can be improved if multielement antenna array is equipped at the base station. In this paper, a novel two-path downlink...

Simplified processing for high spectral efficiency wireless communication employing multi-element arrays

We investigate robust wireless communication in high-scattering propagation environments using multi-element antenna arrays (MEAs) at both transmit and receive sites. A simplified, but highly spectrally efficient space-time communication processing method is presented. The user's bit stream is mapped to a vector of independently modulated equal bit-rate signal components that are simultaneously transmitted in the same band. A detection algorithm similar to multiuser detection is employed to detect the signal components in white Gaussian noise (WGN). For a large number of antennas, a more efficient architecture can offer no more than about 40% more capacity than the simple architecture presented. A testbed that is now being completed operates at 1.9 GHz with up to 16 quadrature amplitude modulation (QAM) transmitters and 16 receive antennas. Under ideal operation at 18 dB signal-to-noise ratio (SNR), using 12 transmit antennas and 16 receive antennas (even with uncoded communication), the theoretical spectral efficiency is 36 bit/s/Hz, whereas the Shannon capacity is 71.1 bit/s/Hz. The 36 bits per vector symbol, which corresponds to over 200 billion constellation points, assumes a 5% block error rate (BLER) for 100 vector symbol bursts.

On the theory of a multielement array of echosonde antennas

There is an ever‐increasing interest in the use of the multielement antenna array in acoustic‐radar work particularly when a single element cannot provide adequate directivity, gain and control. Specifying the following parameters: number of elements, element‐spacing, and amplitude‐phase excitations previously discussed [S. A. Adekola et.al., Radio Sci. 12, 11–12 (1977)], we discuss the radiation characteristics of the array. Conditions for suppressing grating lobes and secondary lobes are outlined for both end‐fire and broadside acoustic arrays. Transmitting‐aperture diameters of practical interest are 1.84 and 2.44 m [S. A. Adekola, J. Acoust. Soc. Am. 62, 524–542 (1977)]. For nonoverlapping array elements with one‐half wavelength separation between antenna‐rims, the effective distances between centres of adjacent array‐elements using 1.84‐m‐diam apertures are 1.9 and 1.89 m for 2‐ and 3‐kHz carrier‐frequencies respectively. The corresponding values for the 2.44‐m‐diam. apertures are 2.61 and 2.55 m for 1‐ and 1.5‐kHz carrier‐frequencies respectively. Improved directivity for n end‐fire discrete‐elements is achieved by increasing the phase‐lag α = 2.94/(n−1) between sources [Hansen‐Woodyard, IRE, 26(3), 333–345 (1938)]. For example, the 10‐ and 12‐array elements considered here have increased phase lags of 19° and 15° for improved‐directivity respectively. Other criteria treated include: conditions for overlapping and non‐overlapping array‐elements, and variations of 3‐dB beamwidth with the number of elements and with effective separation between elements.