Next, the Friis power transmission formula  was used to calculate the maximum antenna power gain (in the central forward direction of the antenna):
By substituting the measured [absolute value of [S.sub.21]] into (9), the measured maximum antenna power gain was plotted against frequencies ranging from 36.0 to 40 GHz to compare with simulation data (Figure 10); they indicated an acceptable agreement.
The measured antenna power gains
are approximately -4 and -6 dB at 1040 and 1900 MHz, respectively, which are lower than the simulated results by approximately 2 to 3 dB.
Above experimental results indicate that the maximum antenna power gains
at 2.4 and 5.5 GHz band are 1.99 and 3.71 dBi; in addition, antenna efficiencies are 49.33 and 55.23%, respectively.