To reduce a high frequency current, which flows to a printed circuit board, and to improve a diversity effect while reducing the amount of coupling between two antennas by making one antenna into helical antenna, for which a conductor wire for the length of 1/2 wavelength of a used frequency is wound into the shape of coil, and arranging it so as to make directional characteristics or polarization characteristics mutually different from the other antenna.
A diversity antenna for portable telephone set uses a helical antenna 3 as a built-in antenna, is arranged in an attitude so as to have a radiation component in the breadthwise direction of a casing and has sensitivity not only in the component of vertical polarization due to a whip antenna 2 but also in the component of horizontal polarization due to the helical antenna. As the built-in antenna, the helical antenna 3 is arranged horizontal at the lower end of a printed circuit board 1, where the lower end part of the whip antenna 2 is located, and further, the winding length of the helical antenna 3 is set for almost the 1/2 wavelength of the used frequency. This length is determined so as not to let a high frequency flow to the printed circuit board 1.
MURAMOTO MITSURU
SASAKI KANEMI
ONISHI NAOKI
Next Patent: OSCILLATION CIRCUIT OF VOLTAGE CONTROLLING TYPE