Coupling degree adjustment circuit, antenna device, and wireless communication device

#1. Field of the Invention

#The present invention relates to a coupling degree adjustment circuit, an antenna device for multiband, and a communication terminal apparatus equipped with the antenna device.

#2. Description of the Related Art

#FIG. 1A is a view illustrating a typical configuration of a conventional multiple resonant antenna. FIG. 1B is a view illustrating a return loss characteristic of the multiple resonant antenna.

#FIG. 2A and FIG. 2B are circuit diagrams of an antenna device 101 of a first preferred embodiment of the present invention.

#FIG. 3 is a view illustrating a configuration of the antenna device of the first preferred embodiment of the present invention.

#FIG. 2A and FIG. 2B are circuit diagrams of an antenna device 101 of a first preferred embodiment of the present invention. In FIG. 2A, a portion of a coupling degree adjustment circuit 21 is simplified and illustrated. In FIG. 2B, the configuration of the coupling degree adjustment circuit 21 is more specifically illustrated. This antenna device 101 includes the coupling degree adjustment circuit 21, a first radiating element 11, and a second radiating element 12. The first radiating element 11 is connected to a first port (a feeding port) P1 of the coupling degree adjustment circuit 21. The second radiating element 12 is connected to a second port P2 of the coupling degree adjustment circuit 21.

#The coupling degree adjustment circuit 21 includes a primary side circuit including a first coil element L1, and a secondary side circuit including a second coil element L2. The first coil element L1 is connected to a first radiating element 11, and the second coil element L2 is connected to a second radiating element 12.

#The coupling degree adjustment circuit 21 includes the first coil element L1 and the second coil element L2 that are electromagnetically coupled to each other. Thus, the first radiating element 11 and the second radiating element 12 are coupled through the coupling degree adjustment circuit 21. Then, a degree of coupling of the first radiating element 11 and the second radiating element 12 can be defined by a degree of coupling of the coupling degree adjustment circuit 21. The degree of coupling of the coupling degree adjustment circuit 21 can be defined by, for example, a coil distance between the first coil element L1 and the second coil element L2. While the electromagnetic field coupling of each coil element is coupling that is mainly performed through a magnetic field, electric field coupling may be partially included.