Patent ID: 7535429
Filing Date: 2009-05-19
Classification: H01Q

Abstract:
1. A variable directivity slot antenna comprising: a dielectric substrate; and a ground conductor and a slot region formed on a rear face of the dielectric substrate, the ground conductor having a finite area, wherein, the slot region divides the ground conductor into a first ground conductor and a second ground conductor; both leading ends of the slot region are open ends; at least two selective conduction paths are further provided on the rear face of the dielectric substrate, the at least two selective conduction paths traversing the slot region to connect the first ground conductor and the second ground conductor; a feed line intersecting the slot region at a feeding site near a center of the slot region along a longitudinal direction thereof is provided on a front face of the dielectric substrate; the at least two selective conduction paths include a first selective conduction path and a second selective conduction path; a slot resonator length Ls is defined as a distance between the first selective conduction path and the open end of the slot region located at the leading end in an −X direction; a slot width Ws is defined as a distance between the first ground conductor and the second ground conductor; a distance between the second selective conduction path and the open end of the slot region located at the leading end in an X direction is equal to the slot resonator length Ls; when Ws is equal to or less than (Ls/8), Ls is prescribed equal to a ¼ effective wavelength at a center frequency f0 of an operating band; when Ws exceeds (Ls/8), (2Ls+Ws) is prescribed equal to a ½ effective wavelength at the center frequency f0 of the operating band; in a see-through plan view in which the variable directivity slot antenna is seen through from a normal direction of the dielectric substrate, the feed line appears interposed between the first selective conduction path and the second selective conduction path; the X direction is defined as the longitudinal direction of the slot region, a Y direction is defined as a longitudinal direction of the feed line, and a Z direction is defined as the normal direction of the dielectric substrate; the first selective conduction path is disposed between the open end of the slot region located at the leading end in the X direction and the feeding site, and the second selective conduction path is disposed between the open end of the slot region located at the leading end in the −X direction and the feeding site; in a first state, the first selective conduction path is selected to be in a conducting state and the second selective conduction path is selected to be in an open state, thus causing a main beam to be emitted in the −X direction; in a second state, the first selective conduction path is selected to be in an open state and the second selective conduction path is selected to be in a conducting state, thus causing a main beam to be emitted in the X direction; the feed line once branches into a group of branch lines including two or more branch lines at a first point near the feeding site, and two or more branch lines in the group of branch lines become again connected at a second point near the slot, thus forming a loop line in the feed line; and a maximum value of a loop length of the entire loop line is prescribed to be a length less than 1×effective wavelength at an upper limit frequency of the operating band.