Patent ID: 8681063

Claim:
An antenna device comprising: a loop-shaped element radiating a radio wave of at least wavelength λ and having an electrical length of m×λ; a first power feeder exciting the loop-shaped element via voltage or current coupling by using a first electrical signal for radiating the radio wave; and a second power feeder exciting the loop-shaped element via a coupling method that is the same type as the first power feeder by using a second electrical signal for radiating a radio wave of wavelength λ/(2×p−1) at a portion that becomes a node of a standing wave that is formed with the first power feeder as an anti-node and that is based on the first electrical signal, here, “m” and “p” are natural numbers, wherein power feeders of the first power feeder and the second power feeder that perform the voltage coupling have capacitive coupling electrodes arranged opposing the loop-shaped element and are power-fed from central parts of the capacitive coupling electrodes.