Thermal loss and soldering effect study of high-Q antennas in handheld devices

High-Q antennas are attractive because, besides being narrow-band, they have the advantage of being more compact and therefore occupy less volume in a mobile device. However, they can become very lossy especially at lower frequencies. In this paper it is investigated how low a thermal loss, in a very good conductor as copper, may be achieved. The effect from solderings on the antenna efficiency is also investigated and the effect has shown to be small. The resistance value, based on the extra loss due to the solderings, is estimated to be 0.25 Ohm. It is also shown that two different high-Q antennas, having the same Q value, can have difference in efficiency. Furthermore, it is discussed why it is so difficult to compare the electrical size and volume of different antenna types.