A new method to measure radiation efficiency of terminal antennas

Abstract

This paper considers characterization of small antennas, which operate in multipath environment, such as antennas for mobile phones and Bluetooth modules. There has been proposed a new characterization method [ I]-[2] based on measurements in a so called reverberation chamber, which is possible due to the fact that the terminals are located in a complex multipath environment, so that normal characteristics such as radiation pattern shapes are often not important. The reverberation chamber, also called mode-stirred chamber, is known in the EMC area, and is a kind of statistic multimode chamber. The present paper reports measurements of a simple test case in an existing reverberation. The test case is a dipole located at different distances from a lossy dielectric cylinder, representing human tissue. The measurements were taken in the 900 MHz-band (870-970 MHz). The results show that we can measure the radiation efficiency of the test case with a reasonably accuracy. Introduction.Mobile and wireless telephony has grown enormously the last years, and it is expected to continue to grow all over the world. In addition, more and more services are added to the mobile phones, such as access to Internet. In a mobile communication system the mobile phones are terminals, and the network is formed by wireless connection of each terminal. to the nearest fixed base station, where the base stations are connected together with other base stations in a fixed network. The next years we will also see a rapid growth of short-range microwave links, commonly referred to as Bluetooth systems. In a Bluetooth system two terminals, which are located up to 100 m apart, communicate directly with each other. Bluetooth is intended to replace all existing signal cables, e.g. the mouse, keyboard and network cables of a PC, and the headset cable of a mobile phone. Bluetooth will also open numerous new possibilities to locate and transfer signals from sensors and from and to control units in machines and factories.

Mobile handset performance evaluation using radiation pattern measurements

“…Instead attempts have been made to simulate the multipath propagation environments in so-called scattered field measurements, where a room is designed to create a multipath environment for a handset, see section 3.5.2.2 of [8]. Similar artificial propagation environments are created in the so-called stirred mode chamber [9], [10] which is a shielded chamber with metal walls and a number of moving metallic parts which change the field inside the chamber. The main problem of these methods using artificial environments is in controlling the signal distribution inside the room and that the created mobile environment is not necessarily typical for a mobile in real use [11].…”

Characterization Method of an Automotive Random-Los Ota Measurement Setup

“…We call it pure Line-Of-Sight (LOS) propagation channel, since it is useful to characterize fixed antenna installations with little or, in the limiting case, no fading at all. On the other hand, the reverberation chamber is useful to emulate the Rich Isotropic MultiPath (RIMP) propagation channel, i.e., the other limiting case [5,6]. RIMP emulates the propagation channels encountered in urban or indoor environments where scattering is the main contributing propagation mechanism leading to severe fading of the received signal [2].…”

Yet another antenna efficiency measurement method in reverberation chambers

“…[8]- [11]. The use of reverberation chambers to measure radiation efficiency was introduced by Rosengren et al [12]. Since then, several measurement procedures inside the reverberation chamber have been evaluated, e.g.…”