| 摘要 |
A multifrequency antenna, which may be used as a built-in antenna of a small and thin radio communication terminal, such as a mobile telephone, is able to receive radio waves of multifrequency bands without enlarging the shape thereof. The antenna is structured using a main mode resonance frequency and a high-order mode resonance frequency of a single-frequency plane antenna with a short-circuit plate. Specifically, a radiator conductor plate in an optional shape is arranged on a ground plate, and the radiator conductor plate is connected to the ground plate via the short-circuit plate. Power is supplied to the radiator conductor plate from a power-feeding source via a feeder cable. In the radiator conductor plate, a cut portion for shifting the high-order mode resonance frequency to the location at a predetermined distance from the short-circuit plate is formed, and the high-order mode resonance frequency is shifted into a desired band by this cut portion. Consequently, the multifrequency antenna operates at least at two frequencies: the main mode resonance frequency, and at least one high-order mode resonance frequency shifted by the cut portion. Thus, a small and thin multifrequency antenna can be realized at a low cost without a concomitant increase in both the mounting area and the mounting volume of the multifrequency antenna.
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