Antenna device

A device comprising:

• a first metal plate that is arranged to cover at least part of a first side surface in a longitudinal direction of an antenna module having a main radiation unit of substantially rectangular shape;
• and
• a second metal plate that is arranged to cover at least part of a second side surface in the longitudinal direction of the antenna module, the second side surface being different from the first side surface, wherein
• the antenna module is arranged such that the main radiation unit faces a high dielectric constant member of a housing,
• a first distance between an end side of the first metal plate and the high dielectric constant member is smaller than a distance between the main radiation unit and the high dielectric constant member, and
• a second distance between an end side of the second metal plate and the high dielectric constant member is smaller than the distance between the main radiation unit and the high dielectric constant member.