Antenna Device

Abstract

The antenna device includes a housing (10) in which an antenna (12) is provided, a control board (20) provided in the housing (10), a signal ground (22) that constitutes a reference ground for a circuit in the control board (20) and on which a wireless module (21) is mounted and that is connected to the antenna (12) by a coaxial cable (11), a frame ground (23) that constitutes a ground for the housing (10), a capacitor (24) that connects between the signal ground (22) and the frame ground (23), a housing-side grounding part 13 that grounds the coaxial cable 11, and a board-side grounding part (26) that grounds the coaxial cable (11). The loop length of a closed loop (30) that passes through the housing-side grounding part (13), the board-side grounding part (26), the capacitor (24), and the connection part between the housing (10) and the frame ground (23) is less than a wavelength corresponding to the maximum transmission and reception frequency of the wireless module (21).