Planar inverted F antenna with improved feeding line connection
A planar inverted F antenna has a ground conductive plate and a main conductive plate that are short-circuited by a short circuit member. The main conductive plate connects to a feeding line for feeding power to the antenna and includes opposite side ends, a base extending from one side end to a prescribed position in the direction toward the other side end, and a slit extending from the other side end of the main conductive plate up to the prescribed position to form a microstrip line that is connected to the feeding line and at least one excitation conductive plate spaced apart from the microstrip line. The prescribed position includes a feeding point to which power is supplied from the feeding line via the microstrip line having a width such that an input impedance of the antenna at the feeding point and a characteristic impedance become Z.
1. A planar inverted F antenna, comprising:
a ground conductive plate configured for connection to ground,
a short circuiting member connected to the ground conductive plate, and
a main conductive plate having one end side to which the short circuiting member is connected,
wherein the main conductive plate comprises:
one or a plurality of slit(s) formed from another end side of the main conductive plate opposite to the one end side to which the short circuiting member is connected and extending up to a position where an input impedance of the antenna becomes Z;
a microstrip line to which a feeding line is configured to be connected, the microstrip line being formed between a side of the main conductive plate and the one slit, or formed between adjacent slits of the plurality of slits, and the microstrip line having a width such that a characteristic impedance becomes Z; and
one or a plurality of excitation conductive plate(s) formed on a side of the slit to which the microstrip line is not adjacent.
2. The planar inverted F antenna according to claim 1 , wherein the ground conductive plate, the short circuiting member and the main conductive plate are integrally formed from one mutually contiguous conductive plate by being folded in the same direction at a connection part of said the ground conductive plate with the short circuiting member and a connection part of the short circuiting member with the main conductive plate.
3. The planar inverted F antenna according to claim 2 , wherein the one or the plurality of slits comprises two slits formed at positions equally spaced from both sides of a width-wise center of the main conductive plate, the microstrip line is formed on the center of the main conductive plate, and the one or the plurality of excitation conductive plates comprises a first excitation conductive plate and a second excitation conductive plate formed on the both sides of the main conductive plate.
4. The planar inverted F antenna according to claim 3 , wherein the first excitation conductive plate and the second excitation conductive plate have different lengths.
5. The planar inverted F antenna according to claim 3 , wherein the first excitation conductive plate and the second excitation conductive plate are disposed at different distances from the ground conductive plate.
6. The planar inverted F antenna according to claim 1 , wherein a through-hole for a feeding line is formed in the ground conductive plate at a position corresponding to an open end of the microstrip line.
7. The planar inverted F antenna according to claim 6 , wherein the through-hole is formed into a slit-shape in a longitudinal direction of the microstrip line, and further comprising a plurality of through-holes or a slit shaped through hole formed in the microstrip line at a position facing the through-hole for the feeding line.
8. The planar inverted F antenna according to claim 6 , wherein the through-hole is formed into a slit-shape in a longitudinal direction of the microstrip line, and further comprising a plurality of grooves formed in the microstrip line at a position facing the through-hole for the feeding line.
9. The planar inverted F antenna according to claim 1 , wherein the one or the plurality of slits comprises two slits formed at positions equally spaced from both sides of a width-wise center of the main conductive plate, the microstrip line is formed on the center of the main conductive plate, and the one or the plurality of excitation conductive plates comprises a first excitation conductive plate and a second excitation conductive plate formed on the both sides of the main conductive plate.
10. The planar inverted F antenna according to claim 9 , wherein the first excitation conductive plate and the second excitation conductive plate have different lengths.
11. The planar inverted F antenna according to claim 9 , wherein the first excitation conductive plate and the second excitation conductive plate are disposed at different distances from the ground conductive plate.
12. The planar inverted F antenna according to claim 1 , wherein the microstrip line is spaced apart from the one or the plurality of excitation conductive plates by a distance corresponding to a width of the one or the plurality of slits.
13. The inverted F antenna according to claim 1 , wherein the plurality of slits comprises a pair of slits between which the microstrip line is disposed; and wherein the plurality of excitation plates comprises a pair of excitation plates spaced apart from the microstrip line by the respective pair of slits.
14. The planar inverted F antenna according to claim 1 , wherein the position where the input impedance of the antenna becomes Z includes a feeding point to which power is supplied from the feeding line via the microstrip line without requiring direct connection of the feeding line to the feeding point.
15. A planar inverted F antenna comprising:
a ground conductive plate configured for connection to ground;
a main conductive plate having opposite side ends and being configured for connection to a feeding line for feeding power to the antenna; and
a short circuit member for short-circuiting the main conductive plate and the ground conductive plate, the short circuit member having one end connected to the ground conductive plate and another end connected to one of the side ends of the main conductive plate;
wherein the main conductive plate comprises a base extending from the one side end to a prescribed position disposed at a preselected distance in the direction toward the other side end of the main conductive plate, and at least one slit extending from the other side end of the main conductive plate up to the prescribed position to form a microstrip line as a transmission line and to which the feeding line is connected
and at least one excitation conductive plate spaced apart from the microstrip line; and
wherein the prescribed position includes a feeding point to which power is supplied from the feeding line via the microstrip line which has a width selected so that both an input impedance of the antenna at the feeding point and a characteristic impedance of the transmission line become Z.
16. The planar inverted F antenna according to claim 15 , wherein the microstrip line is configured for connection to the feeding line so that power is supplied to the feeding point without requiring direct connection of the feeding line to the feeding point.
17. The inverted F antenna according to claim 15 , wherein the preselected distance at which the prescribed position is disposed is equal to a distance between the prescribed position and a position of the connection between the short circuit member and the ground conductive plate.
18. The planar inverted F antenna according to claim 15 , wherein the microstrip line is spaced apart from the at least one excitation conductive plate by a distance corresponding to a width of the at least one slit.
19. The inverted F antenna according to claim 15 , wherein the at least one slit comprises a pair of slits between which the microstrip line is disposed, and the at least one excitation conductive plate comprises first and second excitation conductive plates spaced apart from the microstrip line by the respective pair of slits.
20. The planar inverted F antenna according to claim 19 , wherein the first excitation conductive plate and the second excitation conductive plate have different lengths; and wherein the first excitation conductive plate and the second excitation conductive plate are disposed at different distances from the ground conductive plate.