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EP-3748770-B1 - ANTENNA DEVICE

EP3748770B1EP 3748770 B1EP3748770 B1EP 3748770B1EP-3748770-B1

Inventors

  • YOSHIOKA, HIROKI

Dates

Publication Date
20260506
Application Date
20200605

Claims (5)

  1. An antenna device (1) configured to be installed on a vehicle, comprising: a stacked dipole antenna unit (40) that has a plurality of dipole antennas (d1, d2) configured to be arranged to a plane perpendicular to a front-back direction of the vehicle, wherein the stacked dipole antenna unit (40) includes a flat antenna substrate (41) that has a front surface and a back surface provided with respective antenna element units (42, 43), each of the antenna element units (42, 43) includes antenna elements (421 to 425, 431 to 435), and one of the antenna elements (423, 425) on the front surface and one of the antenna elements (433, 435) on the back surface function as one of the dipole antennas (d1, d2), characterized by further comprising: a wave director (60A) that is arranged at a front position or at a back position of the stacked dipole antenna unit (40), wherein the wave director (60A) has a flat wave director substrate (61A, 61B) and a conducting unit (62A, 62B), and the conducting unit (62A, 62B) is formed on the wave director substrate (61A, 61B) and extends in a direction that is parallel to an extending direction of the dipole antennas (d1, d2).
  2. The antenna device (1) according to claim 1, further comprising: a second antenna unit (30), wherein the stacked dipole antenna unit (40) and the second antenna unit (30) are configured to perform wireless communication different from each other.
  3. The antenna device (1) according to claim 1 or 2, wherein the stacked dipole antenna unit (40) is configured to perform wireless communication between vehicles.
  4. The antenna device (1) according to any one of claims 1 to 3, further comprising: an antenna base (10) which is a base of the antenna device (1) and which has a base body (11) which is a flat base unit, said base unit comprising a ground surface, wherein a height (h) of a feeding point of each of the dipole antennas (d1, d2) from the ground surface of the base body (11) is 0.25λ or more and 1.0λ or less, where λ represents a wavelength corresponding to the wavelength of operation of the dipole antennas.
  5. The antenna device (1) according to any one of claims 1 to 4, wherein a distance (D) between the dipole antennas (d1, d2) is 0.4λ or less, where λ represents a wavelength corresponding to the wavelength of operation of the dipole antennas.

Description

BACKGROUND Technological Field The present invention relates to an antenna device. Description of the Related Art US 9 300 053 B2 proposes a wideband embedded armor antenna composed of the following elements: an armor layer mounted to a vehicle; a driven dipole between said armor layer and said vehicle; a first parasitically driven dipole to the outside of said armor layer; a second parasitically driven dipole between said driven dipole and said vehicle; and, a feed for said driven dipole which does not pierce said armor layer, whereby the antenna structure is embedded in the armor layer without altering the characteristics of said armor layer. A dual-band antenna described in US 2010/103050 A1 includes a first element that is formed into a planar shape in one of surfaces of an insulating board, a second element that is formed in the other surface of the board so as not to overlap the first element, power feeding means for feeding power to the lower end of the first element, and a through-hole that is made in an end portion of a power feeding line and connected to a middle of the first element in one of surfaces of the board. EP 2 833 479 A1 discloses an antenna system combining two directional antennas with opposite radiation directions. At least one of the antennas comprises a dipole disposed on a dielectric substrate of a printed circuit board (PCB), connected to a reflector plane through transmission lines. In order to provide the desired radiation pattern, the reflector plane is arranged perpendicularly to the PCB plane in which the dipole is disposed. This design prevents radiated power to be diverted into side lobes, enhancing overall system performance. JP 2007 142988 A proposes an antenna which includes half wavelength dipole antenna elements. The dipole antenna elements are vertically arranged in such a manner that longitudinal axes of those are aligned in a vertical line and the dipole antenna elements are not to contact each other. A coaxial cable can be inserted between the upper dipole antenna element and the lower dipole antenna element. The element conductors constituting the dipole antenna elements are formed of a metal foil adhered to a dielectric substrate. One element conductor is formed on a top face of the dielectric substrate and the other element conductor is formed on a back face of the dielectric substrate. Conventionally, there is known an in-vehicle antenna device installed on a roof of a vehicle such as a motor vehicle and receiving radio waves of a wireless communication system (standard) such as GPS (Global Positioning System), satellite radio broadcasting, and AM/FM radio broadcasting. A fixing unit provided on a bottom surface of the antenna device is inserted into a roof hole for fixing (fixing opening) formed on an installation surface of a roof of the vehicle, such that the antenna device is appropriately fixed on the installation surface. As a wireless communication system of the above in-vehicle antenna device, V2X (Vehicle to everything) is known to perform communication between a motor vehicle and an object. The V2X is a general term incorporating the followings as communication systems: V2N (Vehicle to cellular Network) that uses a communication standard such as 3G (Generation) and LTE (Long Term Evolution); V2V (Vehicle to Vehicle) that performs communication between motor vehicles (inter - vehicle communication); and V2I (Vehicle to roadside Infrastructure) that performs communication between the motor vehicle and a corresponding device(s) on the road (road-to-vehicle communication). There is known an antenna device including a monopole antenna for V2X communication as the in-vehicle antenna device. The monopole antenna can reduce the size (height) of the antenna device and can be used in combination with other media antennas for satellite radio broadcasting (such as a patch antenna) and the like. However, a monopole antenna is susceptible to other media antennas. Therefore, according to the technique in JP 2018-182722 A, a V2X antenna device includes a sleeve antenna having an erected antenna substrate with patterned conductive wire, an antenna for satellite radio broadcasting, and an antenna for GPS. In V2X communication, communication in the front and back directions of the vehicle are important for V2V communication. For example, a vehicle appropriately performs processing to prevent an accident in response to receiving information on sudden braking of a vehicle in front in V2V communication. However, since a monopole antenna tends to have directivity pointing upward from the horizontal plane, its gain in the front-rear direction of the vehicle is likely to be reduced when the monopole antenna is installed in a vehicle. Furthermore, a sleeve antenna is hardly susceptible to other media antennas, but is desired to have more gain in the front-rear direction of the vehicle. SUMMARY An object of the present invention is to increase the gain in the front-rear direct