ical devices [7]. The reverberation chamber is usually a metal-box cavity, with different sizes in its three dimensions and with some type of mode-stirrer mecha- nism. When one excites one or several antennas in the chamber at a suitable fre- quency, a number of standing wave modes will be generated. By placing the device under test (DUT) in the cavity, one makes sure that all the radiation generated stays in the cavity. By changing the boundary conditions for the modes in the cav- ity using a movable metal plate (often in the form of a propeller), it is possible to ensure that the radiated power can be detected regardless of the direction in which it is sent. Traditional reverberation chambers for EMC usually have an accuracy of not better than 3 dB in standard deviation (STD). This is much too high an uncertainty to measure antenna efficiency, radiated power, or receiver sensitivity, although it is quite sufficient for EMC measurements. At the end of the 1990s, Professor Per-Simon Kildal at the antenna group at Chalmers University of Technology, Gothenburg, Sweden, had an idea of how to improve the accuracy of reverberation chambers SO that they could be used to mea- sure antenna efficiency, radiated power, and receiver sensitivity of small antennas and wireless terminals with small antennas [8]. The origin of the idea was the com- prehension that the traditional way of measuring antennas in anechoic chambers was not at all suited for small antennas or wireless terminals with small antennas (e.g., mobile phones) because they are normally used in environments with multiple paths (i.e., indoors or in urban areas). It also opened up the possibility to develop a very small test chamber that the antenna engineer could use at his desk (see Figure 12.1). The vision of a very small measurement facility that would give future antenna engineers the possibility to design antennas at their desks led to the creation of the company Bluetest AB in 2000 [9]. Bluetest AB and Chalmers University of Technology worked very closely