Patent ID: 7649497
Filing Date: 2010-01-19
Classification: H01Q

Abstract:
1. An antenna device comprising: a first wire antenna element having a length about half a wavelength of a radio wave in use; a second wire antenna element which is in a same plane as the first wire antenna element and substantially perpendicular to the first wire antenna element, and which is connected to the first wire antenna element at one end; a third wire antenna element which is in the same plane as the first wire antenna element and substantially in parallel with the first wire antenna element; and a feed point provided on the second wire antenna element, wherein the length of the third wire antenna element is longer than the length of the first wire antenna element, and wherein a sum (a+c+h) of a length (a) of one side of the first wire antenna element seen from a first connection point of the first wire antenna element and the second wire antenna element, a length (c) of the one side of the third wire antenna element seen from a second connection point of the second wire antenna element and the third wire antenna element, and a length (h) of the second wire antenna element, is different from a sum (b+d+h) of a length (b) of the other side of the first wire antenna element seen from the first connection point, a length (d) of the other side of the third wire antenna element seen from the second connection point, and the length (h) of the second wire antenna element, and the sum (a+c+h) and the sum (b+d+h) each are lengths effecting frequencies of two series resonances, the antenna device operating at a frequency of parallel resonance being used as the frequency of the radio wave in use, wherein the frequency of parallel resonance is between the frequencies of two series resonances, and the first connection point is offset from a center point of the first wire antenna element, the offset being larger than or equal to (0.013×the wavelength of the radio wave in use) and smaller than or equal to (0.03×the wavelength of the radio wave in use).