Electronic device including antenna device

An electronic device comprising:

• a housing including a first plate, a second plate facing away from the first plate, and a side member surrounding a space between the first plate and the second plate;
• an antenna assembly including:
• a plurality of planes disposed in parallel to the second plate, and stacked on each other, wherein the planes include:
• a first plane interposed between the first plate and the second plate;
• a second plane interposed between the first plane and the first plate;
• and
• a third plane interposed between the second plane and the first plate;
• a first conductive plate disposed in parallel to the planes and interposed between the first plane and the first plate within a first area, when viewed from above the second plate;
• conductive islands having a first repeating pattern and disposed on the first plane within a second area surrounding the first area, when viewed from above the second plate;
• conductive islands disposed on the second plane within the second area, and having a second repeating pattern partially overlapped with the first repeating pattern, when viewed from above the second plate;
• conductive islands disposed on the third plane within the second area, and having a third repeating pattern partially overlapped with the second repeating pattern, when viewed from above the second plate;
• and
• a wireless communication circuitry disposed in the space, electrically connected with the first conductive plate, and configured to supply a signal having a frequency range of 3 GHz to 300 GHz.