Patent ID: 7315287

Claim:
An antenna device comprising: a rectangular parallelepiped base member made of a dielectric or magnetic material; a band-shaped first radiation conductor, including a plurality of divided first radiation conductor portions, spirally wound around the base member; variable capacitance elements connected in series between adjacent pairs of the divided first radiation conductor portions and disposed on an upper surface of the base member; and a feeding conductor for supplying a timing voltage to the variable capacitance elements, wherein the first radiation conductor has first radiation conductor parts respectively formed on upper, lower, and rear side surfaces of the base member and first connecting through-holes passing through the upper and lower surfaces are provided in the base member; the first radiation conductor part on the upper surface and the first radiation conductor part on the lower surface are connected to each another by the first through-holes, and the feeding conductor is disposed on a front surface of the base member; the variable capacitance elements includes varactor diodes, the adjacent divided first radiation conductor portions are alternately connected between pairs of anodes of the varactor diodes and between pairs of cathodes of the varactor diodes, and a ground conductor formed at least on the lower and front surfaces is provided at one end of the base member; second through-holes passing through the upper and lower surfaces are provided and connected to the ground conductor on the lower surface, and are connected between the varactor diodes on the upper surface by a first resistor; and the first radiation conductor portions, which are connected between the pairs of cathodes of the varactor diodes, are connected to the feeding conductor by a second resistor, and the first and second resistors are disposed on the upper surface of the base member.