Automatic impedance matching of a tablet type 4-branch MRC array close to the human hands

Digital broadcasting terrestrial services have been spread all over the world. A portable TV is held by the human hands when a user watches terrestrial digital broadcasting while walking. Hence, we must consider the electromagnetic interaction between the antenna and the human hand. The factors causing the performance degradation of a 4-branch MRC array have been studied. The results show that impedance mismatch loss emerging at the branch elements is the major factor among various loss factors caused by the human hands [1]. To overcome this difficulty, we proposed a method of the mitigation of impedance mismatch using a varactor diode, and the effectiveness of the method was confirmed by experiments [2]. However, the method of controlling voltages impressed at the diodes automatically was not fully examined.