Patent ID: 9748917
Date: 2017-08-29
CPC Classifications: H01Q,H03H

Claim:
1. An antenna device comprising an antenna element, an antenna matching circuit connected between the antenna element and a feeder unit, a capacitance detection circuit connected to the antenna element and detecting a stray capacitance of the antenna element, a feedback control circuit controlling the antenna matching circuit in accordance with an output signal of the capacitance detection circuit, a first reactance element connected to a wireless communication signal path, which is a transmission path between the antenna element and the antenna matching circuit, that allows a wireless communication signal to pass there through and that blocks a direct current, and a second reactance element that is shunt-connected to the wireless communication signal path between the antenna matching circuit and the first reactance element to form a parallel connection of the first reactance element and the stray capacitance of the antenna element when direct current charges the first reactance element and the stray capacitance, the capacitance detection circuit including a constant current source and a timing circuit measuring a time taken to charge an antenna from the constant current source and for a voltage to reach a predetermined voltage.