Antenna device, wireless communication device, and band adjustment method

A wireless communication device comprising:

• a power supply source that supplies signal used in wireless communication;
• a circuit board that includes the power supply source;
• and
• an antenna device that includes:
• a feed antenna element that is coupled electrically to the power supply source;
• and
• a parasitic antenna element that is coupled electrically to the feed antenna element,
• wherein the feed antenna element is configured in the circuit board equipped with the power supply source, and
• the parasitic antenna element includes a ground part, and the ground part is coupled electrically to a ground layer via an inductive element having inductivity, the ground layer has a reference potential and is formed in the circuit board,
• the inductive element has a circuit constant which adjusts a resonant frequency of the parasitic antenna element such that the resonant frequency of the parasitic antenna element is lower than a resonant frequency of the feed antenna element and widens a bandwidth of return-loss characteristics and radiation efficiency characteristics in wireless communication by resonance of the parasitic antenna element and the feed antenna element,
• a shape and size of the feed antenna element is at least substantially the same as a shape and size of the parasitic antenna element.

A bandwidth adjustment method comprising:

• configuring a parasitic antenna element in a circuit board in which a feed antenna element is configured, the feed antenna element being coupled electrically to a power supply source which supplies signal used in wireless communication, the parasitic antenna element being coupled electrically to the feed antenna element,
• a shape and size of the feed antenna element is is at least substantially the same as a shape and size of the parasitic antenna element;
• electrically connecting a connection part of the parasitic antenna element to a ground layer via an inductive element having inductivity, the ground layer having a reference potential and being formed in the circuit board;
• and
• adjusting a bandwidth of wireless communication by resonance of the parasitic antenna element and the feed antenna element to widen the bandwidth of return-loss characteristics and radiation efficiency characteristics in wireless communication by adjusting an inductive reactance of being a circuit constant of the inductive element such that the resonant frequency of the parasitic antenna element is lower than a resonant frequency of the feed antenna element.