US-12620718-B2 - MIMO antenna device

US12620718B2US 12620718 B2US12620718 B2US 12620718B2US-12620718-B2

Abstract

A MIMO antenna device includes a front-side dipole antenna and a back-side dipole antenna. Long-side feed parts for hot element are connected respectively to feed points at their long sides. Long-side feed parts for ground element are connected respectively to the feed points at their long sides, and the long sides thereof face the long sides of the long-side feed parts for hot element in parallel with a predetermined interval. Ground elements are respectively arranged point-symmetric to hot elements with respect to the feed points in an offset manner. The front-side dipole antenna and the back-side dipole antenna are arranged such that the front-side feed point and the back-side feed point substantially overlap each other in a top view and that the long-side feed part for front-side is arranged perpendicular to the long-side feed part for back-side.

Inventors

Jun Ito

Assignees

HARADA INDUSTRY CO., LTD.

Dates

Publication Date: 20260505
Application Date: 20230217
Priority Date: 20220328

Claims (10)

1 . A MIMO antenna device that performs spatial multiplex transmission, the MIMO antenna device comprising: a front-side dipole antenna disposed on a front-side surface; and a back-side dipole antenna which is an antenna for the same frequency band as the front-side dipole antenna and which is disposed on a back-side surface opposite to the front-side surface, the front-side dipole antenna including: a front-side feed point; a long-side feed part for front-side hot element connected at its long side to the front-side feed point; a front-side hot element extending from the long-side feed part for front-side hot element; a long-side feed part for front-side ground element connected at its long side to the front-side feed point, the long side facing in parallel the long side of the long-side feed part for front-side hot element with a predetermined interval; and a front-side ground element extending from the long-side feed part for front-side ground element and disposed point-symmetric to the front-side hot element with respect to the front-side feed point in an offset manner, the back-side dipole antenna including: a back-side feed point; a long-side feed part for back-side hot element connected at its long side to the back-side feed point; a back-side hot element extending from the long-side feed part for back-side hot element; a long-side feed part for back-side ground element connected at its long side to the back-side feed point, the long side facing in parallel the long side of the long-side feed part for back-side hot element with a predetermined interval; and a back-side ground element extending from the long-side feed part for back-side ground element and disposed point-symmetric to the back-side hot element with respect to the back-side feed point in an offset manner, wherein the front-side dipole antenna and the back-side dipole antenna are arranged such that the front-side feed point and the back-side feed point substantially overlap each other in a top view and that the long-side feed part for front-side hot element and the long-side feed part for front-side ground element are arranged perpendicular to the long-side feed part for back-side hot element and the long-side feed part for back-side ground element.
2 . The MIMO antenna device according to claim 1 , wherein the front-side dipole antenna achieves impedance matching by changing the lengths of the facing long sides of the feed part for front-side hot element and the feed part for front-side ground element, and the back-side dipole antenna achieves impedance matching by changing the lengths of the facing long sides of the feed part for back-side hot element and the feed part for back-side ground element.
3 . The MIMO antenna device according to claim 1 , wherein the front-side dipole antenna is constituted by a front-side bowtie antenna, and the back-side dipole antenna is constituted by a back-side bowtie antenna.
4 . The MIMO antenna device according to claim 3 , wherein the front-side bowtie antenna and/or the back-side bowtie antenna has, at side surfaces of an area between the front-side surface and the back-side surface, a side element part for antenna performance adjustment extending from the front-side bowtie antenna and/or the back-side bowtie antenna.
5 . The MIMO antenna device according to claim 1 , wherein the front-side dipole antenna has a front-side folded element extending from the front-side surface to the back-side surface, the back-side dipole antenna has a back-side folded element extending from the back-side surface to the front-side surface, the front-side folded element is disposed in an area within the back-side surface where the back-side dipole antenna is absent, and the back-side folded element is disposed in an area within the front-side surface where the front-side dipole antenna is absent.
6 . The MIMO antenna device according to claim 1 , wherein coaxial cables connected respectively to the front-side feed point and the back-side feed point are wired in a space between the front-side surface and the back-side surface.
7 . The MIMO antenna device according to claim 1 , further comprising a front-side substrate having the front-side feed point and a back-side substrate having the back-side feed point, the front-side and back-side substrates being disposed between the front-side surface and the back-side surface.
8 . The MIMO antenna device according to claim 7 , wherein the front-side substrate and the back-side substrate are constituted as front and back surfaces of a single substrate.
9 . The MIMO antenna device according to claim 1 , wherein the front-side dipole antenna and the back-side dipole antenna are respectively arranged on crossing diagonal lines of a rectangular parallelepiped case.
10 . The MIMO antenna device according to claim 1 , further comprising a second front-side dipole antenna being disposed on the front-side surface, including a second front-side hot element extending from the long-side feed part for front-side hot element and a second front-side ground element extending from the long-side feed part for front-side ground element, having a different target frequency as that of the front-side dipole antenna, and disposed so as to cross the front-side dipole antenna, and a second back-side dipole antenna being disposed on the back-side surface, including a second back-side hot element extending from the long-side feed part for back-side hot element and a second back-side ground element extending from the long-side feed part for back-side ground element, having the same target frequency as that of the second front-side dipole antenna, and disposed so as to cross the back-side dipole antenna.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a U.S. national stage application of International Application No. PCT/JP2023/005775, filed on Feb. 17, 2023. This application claims priority to Japanese Patent Application No. 2022-052402 filed on Mar. 28, 2022. BACKGROUND Technical Field The present invention relates to a MIMO antenna device, and more particularly to a small-sized and broadband MIMO antenna device. Background Information Recently, a wide area communication network in which automobiles to actualize automatic driving utilize a mobile phone network has been promoted to increase the capacity of information to be communicated and the transmission speed thereof. For example, MIMO (Multiple-Input Multiple-Output) is known as a technology for performing spatial multiplex transmission in order to increase the information capacity and information transmission speed. In a MIMO antenna device using a plurality of antenna elements, there are many design restrictions such that it is generally necessary to ensure isolation by installing the antenna elements apart from each other. Further, in recent years, antenna mounting space inside an automobile tends to be restricted by other devices such as an airbag, and it is therefore difficult to reduce the antenna size to a level that can be mounted inside a vehicle. Japanese Laid-Open Patent Application No. 2021-072626A (hereinafter referred to as Patent Document 1) by the same applicant as the present application is known as a MIMO antenna device capable of being mounted in such vehicles. Patent Document 1 discloses a MIMO antenna device capable of reducing interference between antennas over a wide band and being miniaturized by making first and second dipole antennas arranged front and back crossed each other. SUMMARY A reduction in correlation coefficient is one of the requirements required for MIMO antenna devices used for high-speed and large-capacity transmission of 5G communications. To achieve this, it is important to ensure the mutual coupling (isolation) between two antennas. While a sufficient isolation is achieved in this MIMO antenna device of Patent Document 1, a further improvement is desired for some antenna arrangement conditions. The present invention has been made in view of the above situations, and an object thereof is to provide a MIMO antenna device capable of reducing interference between antennas over a wide band and being miniaturized. To achieve the above object of the present invention, a MIMO antenna device according to the present invention may include: a front-side dipole antenna disposed on a front-side surface; and a back-side dipole antenna which is an antenna for the same frequency band as the front-side dipole antenna and which is disposed on a back-side surface opposite to the front-side surface. The front-side dipole antenna may include: a front-side feed point; a long-side feed part for front-side hot element connected at its long side to the front-side feed point; a front-side hot element extending from the long-side feed part for front-side hot element; a long-side feed part for front-side ground element connected at its long side to the front-side feed point, the long side facing in parallel the long side of the long-side feed part for front-side hot element with a predetermined interval; and a front-side ground element extending from the long-side feed part for front-side ground element and disposed point-symmetric to the front-side hot element with respect to the front-side feed point in an offset manner. The back-side dipole antenna may include: a back-side feed point; a long-side feed part for back-side hot element connected at its long side to the back-side feed point; a back-side hot element extending from the long-side feed part for back-side hot element; a long-side feed part for back-side ground element connected at its long side to the back-side feed point, the long side facing in parallel the long side of the long-side feed part for back-side hot element with a predetermined interval; and a back-side ground element extending from the long-side feed part for back-side ground element and disposed point-symmetric to the back-side hot element with respect to the back-side feed point in an offset manner. The front-side dipole antenna and the back-side dipole antenna may be arranged such that the front-side feed point and the back-side feed point substantially overlap each other in a top view and that the long-side feed part for front-side hot element and the long-side feed part for front-side ground element are arranged perpendicular to the long-side feed part for back-side hot element and the long-side feed part for back-side ground element. The front-side dipole antenna may achieve impedance matching by changing the lengths of the facing long sides of the feed part for front-side hot element and the feed part for front-side ground element, and the back-side dipole antenna may achieve impedance matchi