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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.

To estimate OIP3 of low power RF amplifiers from DC power operating conditions is of a good help at the beginning of the design work. We introduce a simple formula intended for estimation of OIP3 of Bipolar Junctions Transistors. Harmonic balance simulations and measurements were carried out to validate usability of this formula. The results show that there is more relation between OIP3 and the collector current than between OIP3 and the collector emitter-voltage. The proposed formula is applicable for collector currents in the range of 2 mA to 8 mA and for collector-emitter voltages in the range of 2 V to 3 V.

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