Summary
International Symposium on Antennas and Propagation
2008
Session Number:3C24
Session:
Number:3C24-5
Characterization Of Multi-Port Eleven Antenna For Use In MIMO System
Jungang Yin, Daniel Nyberg, Xiaoming Chen, Per-Simon Kildal,
pp.-
Publication Date:2008/10/27
Online ISSN:2188-5079
Summary:
MIMO (multiple-input multiple-output) is the use of multiple antennas (diversity antennas) at both the receiving and the transmitting sides of a radio communication link to enhance performance in a multi-path fading environment. MIMO systems are characterized by their maximum available capacity, and the multi-port antennas can be characterized by a diversity gain for a certain combination algorithm. Considering a two-antenna diversity receiver, the so-called diversity gain can be defined as the increase in SNR (signal-to-noise ratio) due to an appropriate combination (selection, maximal-ratio or equal-gain combining scheme, etc.) of the two received signals, and can be distinguished as apparent and effective diversity gain, depending on whether we use as a reference one of the two elements of the diversity antenna or an ideal single antenna (with radiation efficiency of 100%), respectively [1]. The reverberation chamber is basically a metal cavity that is large enough to support many resonant modes at the frequency of operation, and all modes can be stirred by a number of means inside the chamber in order to create a Rayleigh distributed transfer function between the transmitting and receiving antennas [2], which represents an isotropic multipath environment of a similar type as can be found in urban and indoor scenarios, but with a uniform elevation distribution of the incoming waves [3]. The antenna performance in such an isotropic multi-path environment is characterized by its radiation efficiency, which can be measured fast and accurately in a relatively small reverberation chamber [4]. The diversity gain of multi-port antennas can also be measured in a straight forward manner inside it [5]-[6]. Besides, measurements in BluetestR reverberation chamber are even fast, accurate and repeatable when compared with anechoic chambers of equal or larger size, provided the chamber has efficient stirring methods [1]. This reverberation chamber has been used to characterize a number of different antennas for MIMO and diversity systems, as described in [7]-[8]. The Eleven antenna is a new coaxially-fed wideband feed that can cover a decade bandwidth, and it has been developed as feed for reflector antennas and in particular for radio telescopes. The fourport (1x4 model: 1 polarization times 4 ports, as shown in Fig.1 left) version of an L-band Eleven antenna has been studied in [9], showing that the mono-pulse tracking is an intrinsic capability of this single-polarized multi-port antenna. Further more, this capability can readily be extended to its dual-polarization counterpart by adding an extra orthogonal Eleven antenna, resulting in an eightport antenna (2x4 model: 2 polarizations times 4 ports, as shown in Fig.1 right).