A planar antenna includes first and second radiation elements. A first partial periphery of the first radiation element and a second partial periphery of the second radiation element face each other at a uniform gap equal to or less than a tenth of the length of the first partial periphery. The first radiation element includes a third partial periphery parallel to a straight line for connecting the both ends of the first partial periphery, a feeding point at a central portion of the first partial periphery, and a slit having an opened end and a closed end. A distance from the feeding point to the opened end along the slit through the closed end is longer than a sum of a half of the first partial periphery and a longer one of the other two partial peripheries.
1. A planar antenna comprising:
a first radiation element having a planar shape, the first radiation element including a first partial periphery, a third partial periphery, a fourth partial periphery, a fifth partial periphery, a feeding point positioned at a substantially center of the first partial periphery; and
a second radiation element having a planar shape, the second radiation element including a second partial periphery having a length at least substantially equal to that of the first partial periphery;
wherein the first partial periphery and the second partial periphery face each other at a substantially uniform gap that is substantially equal to or less than a tenth of the length of the first partial periphery;
wherein the third partial periphery is substantially parallel to a straight line connecting both ends of the first partial periphery;
wherein the fourth partial periphery connects one end of the first partial periphery to one end of the third partial periphery;
wherein the fifth partial periphery connects the other end of the first partial periphery to the other end of the third partial periphery;
wherein the first radiation element includes a slit having an opened end and a closed end, the opened end opening at a periphery of the first radiation element other than the first partial periphery, the closed end closed within the first radiation element; and
wherein a distance from the feeding point to the opened end along the slit through the closed end is longer than a distance obtained by adding a half of the length of the first partial periphery and a longer one of a length of the fourth partial periphery and a length of the fifth partial periphery.
2. The planar antenna according to claim 1 ,
wherein the opened end is positioned in the vicinity of the third partial periphery.
3. A planar antenna comprising:
a first radiation element having a planar shape, the first radiation element including a first partial periphery, a third partial periphery, a fourth partial periphery, a fifth partial periphery, a feeding point positioned at a substantially center of the first partial periphery; and
a second radiation element having a planar shape, the second radiation element including a second partial periphery having a length at least substantially equal to that of the first partial periphery;
wherein the first partial periphery and the second partial periphery face each other at a substantially uniform gap that is substantially equal to or less than a tenth of the length of the first partial periphery;
wherein the third partial periphery is substantially parallel to a straight line connecting both ends of the first partial periphery;
wherein the fourth partial periphery connects one end of the first partial periphery to one end of the third partial periphery;
wherein the fifth partial periphery connects the other end of the first partial periphery to the other end of the third partial periphery;
wherein the first radiation element includes a slit having an opened end and a closed end, the opened end opening at a periphery of the first radiation element other than the first partial periphery, the closed end closed within the first radiation element;
wherein a distance from the feeding point to the one end of the third partial periphery through the closed end and the opened end along the slit is longer than a distance obtained by adding a half of the first partial periphery and a longer one of a length of the fourth partial periphery and a length of the fifth partial periphery; and
wherein the one end of the third partial periphery is positioned at a side of the opened end.
4. A planar antenna comprising:
a first radiation element having a planar shape, the first radiation element including a first partial periphery, a third partial periphery, a fourth partial periphery, a fifth partial periphery, a feeding point positioned at a substantially center of the first partial periphery; and
a second radiation element having a planar shape, the second radiation element including a second partial periphery having a length at least substantially equal to that of the first partial periphery;
wherein the first partial periphery and the second partial periphery face each other at a substantially uniform gap that is substantially equal to or less than a tenth of the length of the first partial periphery;
wherein the third partial periphery is substantially parallel to a straight line connecting both ends of the first partial periphery;
wherein the fourth partial periphery connects one end of the first partial periphery to one end of the third partial periphery;
wherein the fifth partial periphery connects the other end of the first partial periphery to the other end of the third partial periphery;
wherein the first radiation element includes a first slit and a second slit provided parallel to a portion of the first slit;
wherein the first slit has an opened end and a closed end, the opened end opening at a periphery of the first radiation element other than the first partial periphery, the closed end closed within the first radiation element; and
wherein a distance from the feeding point to the opened end along the first slit through the closed end is longer than a distance obtained by adding a half of the length of the first partial periphery and a longer one of a length of the fourth partial periphery and a length of the fifth partial periphery.
5. The planar antenna according to claim 4 ,
wherein the opened end is positioned in the vicinity of the third partial periphery.