Abstract: A small antenna for portable radios and the like in which two planar conductive boards are disposed in parallel relationship at a spaced interval which is small when compared with received radio wavelengths. A dielectric frame is disposed between the two planar conductive boards keeping them at the preselected spaced interval. Arbitrary feeding points are selected along the edges of the two conductive boards and at least one conductor is positioned at an arbitrary selected feeding point to short-circuit the two conductive boards. In some cases a plurality of arbitrary feeding points may be selected along the edges of the two conductive boards and a plurality of conductors positioned at the plurality of arbitary selected feeding points which short-circuits the conductive boards. The positions of the plurality of conductors which short-circuit the conductive boards may be automatically changed at will to provide the most desirable condition responsive to the direction of the radio waves.

Abstract: A miniature antenna, in which a pair of square conductor plates disposed in parallel with a spacing sufficiently smaller than the wavelength used are fixed to each other to an insulating frame to form an antenna structure which is used also as a case. Feeding terminals are provided at a desired position on one side of each of the conductor plates. High-frequency-wise short-circuit elements are provided at a plurality of positions on other sides of the conductor plates. A gravity-direction sensor, which produces an output in accordance with the direction of gravity, is provided in the case. The plurality of short-circuit elements are selectively short-circuited by the output of the gravity-direction sensor so that the plane of polarization of the antenna is brought into agreement with the direction of gravity.