 shown with an arrow. The distance between one of the antenna branches and the line for selection combining is the "apparent" diversity gain. © 2009 by Taylor & Francis Group, LLC Measuring Performance of 3GPP LTE Terminals Table 12.1 Apparent Diversity Gain, Radiation Efficiency, and Effective Diversity Gain at 1% CDF as a Function of Relative Polarization Angle and Distance between Two Dipoles Relative Effective Apparent Radiation Angle Distance Diversity Diversity Efficiency (deg.) Gain (dB) Gain (dB) Correlation Note: At a relative angle of 0°, the dipoles are parallel, and at a relative angle of 90°, they are perpendicular. "apparent" and "effective" diversity gain, one obtains the radiation efficiency of each antenna as well as the correlation of each. Table 12.1 shows these param- eters for 10 different antenna configurations (i.e., with two dipoles at five different relative angles to each other and at a distance of 15 and 30 mm from each other, respectively). In Table 12.1, we can clearly see that although the apparent diversity gain is relatively high for all configurations, the reduced antenna efficiency makes the effective diversity gain much smaller, especially at close distance or small relative angles. It is also interesting to note that although the correlation between the diver- sity antennas is high only when they are parallel, the effective diversity gain is still affected by mutual coupling at relative angles of 45° and less. The traditional ways of measuring diversity gain using drive tests or anechoic chambers with software channel modeling are expensive and time consuming. The time spent to measure or estimate the diversity gain can easily be hours. The diver- sity measurements presented in this section have been made in 1 minute-one to two orders of magnitude faster. This kind of measurement speed will allow antenna designers of diversity antennas to work in completely new ways. They will be able to make small changes in the antenna positions or design and more or less imme- diately get fe