磁場解析を用いた電波腕時計用アンテナにおける副磁路の設計

抄録

  Radio-controlled watches that automatically adjust the time by using standard frequency and time signals becoming popular with consumers. To evaluate the receiving sensitivity of the antenna, we calculated the antenna output voltage by combining a magnetic field simulation and a circuit simulation. The output voltage of an antenna in a metal case is much smaller than that of an antenna in a non-conductive material case, because the leakage field induces an eddy current in the metal case. We present an example in which the sub-core increased the output voltage suppressing the leakage field. This effect of the sub-core depends on the size and arrangement of the sub-core in an antenna system, and thus optimization is essential. It is important to evaluate the quality factor (Q factor) of antennas, because the Q factor has a close relation to the receiving sensitivity. However, we show that an antenna with a higher Q factor might not always have a higher output voltage.