IP Library › Granted Patent US 12689239
Granted Patent B2
US 12689239 · App. 18/694,707 · Granted Jul 21, 2026

Antenna device, and contactless power transfer system

Inventors: Takanori Washiro (Tokyo, JP); Kazuya Akiyama (Tokyo, JP)
Assignee: NTT, Inc.
H02J50/40H02J50/05H02J50/12H02J50/20
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Quick Facts
Patent No.
US 12689239
App. No.
18/694,707
Granted
Jul 21, 2026
Kind
B2
Abstract

An antenna device used in a contactless power transmission system includes a first resonant antenna having a first impedance and a second resonant antenna having a second impedance different from the first impedance.

Claims (16)

1 . An antenna device configured to be used in a contactless power transmission system, the antenna device comprising:

a first antenna having a first impedance; and

a second resonant antenna having a second impedance different from the first impedance,

wherein the antenna device is connected to a power transmission and reception circuit in the contactless power transmission system,

wherein the first impedance is higher than an impedance of the power transmission and reception circuit, and the second impedance is lower than the impedance of the power transmission and reception circuit,

wherein the first antenna and the second resonant antenna are connected in parallel,

the first antenna is an electric field antenna using electric field coupling, and the second resonant antenna is a magnetic field antenna of an LC series resonance circuit using magnetic field coupling,

the first impedance decreases as the distance to a facing antenna decreases, and

the second impedance increases as the distance to the facing antenna decreases.

2 . The antenna device according to claim 1 , wherein the first antenna and the second resonant antenna are disposed such that a center of the first antenna and a center of the second resonant antenna are at a same position.

3 . A contactless power transmission system comprising:

two antenna devices each of which is the antenna device of claim 1 .

4 . The antenna device according to claim 1 , wherein the parallel connection of the first antenna and the second resonant antenna forms a combined impedance, and the parallel connection is configured such that the decrease in the first impedance and the increase in the second impedance mutually offset each other when the distance to the facing antenna decreases, thereby reducing a change in the combined impedance.

5 . The antenna device according to claim 4 , wherein the power transmission and reception circuit comprises a matching circuit, and wherein the reduction in the change in the combined impedance maintains an impedance matching state with the matching circuit when the distance to the facing antenna changes.

6 . The contactless power transmission system according to claim 3 , wherein the power transmission and reception circuit of the first antenna device comprises a first matching circuit and an inverter, and the power transmission and reception circuit of the second antenna device comprises a second matching circuit and a rectifier circuit.

7 . The antenna device according to claim 4 , wherein the antenna device is configured to maintain an impedance matching state with the power transmission and reception circuit without actively detecting or controlling a coupling state of the antenna device.