Antenna module and electronic device

According to one embodiment, an antenna module includes a substrate, a first antenna, an array antenna, and a radio frequency (RF) module. The first antenna includes a first radiation element arranged on the substrate and a first ground plane arranged on the substrate. The array antenna includes a plurality of second radiation elements arranged on the substrate. The substrate includes a first surface and a second surface. The first ground plane is arranged on at least the first surface of the substrate. The plurality of second radiation elements are arranged on the second surface of the substrate and opposed to the first ground plane via the substrate.

FIELD

Embodiments described herein relate generally to technology for wireless communication using an antenna for a lower frequency band and an antenna for higher frequency bands.

BACKGROUND

Recently, a fifth-generation cellular system has been reviewed as a successor to the fourth-generation cellular systems such as Long Term Evolution (LTE).

The adoption of a new radio access technology (RAT) in addition to the existing LTE system has been reviewed in the fifth-generation cellular system. A frequency band higher than the frequency bands (cellular frequency bands) used in the LTE system will be used to implement high-speed wireless communication in the new radio access technology.

Antennas of two different types, i.e., an antenna for a lower frequency band (cellular frequency band) and an antenna for higher frequency bands are therefore required for a wireless device conforming to the fifth-generation cellular system. This matter may be a cause for increasing antenna implementation space which should be secured in the wireless device.

Thus, a new antenna structure which can suppress increase in antenna implementation space is required.

DETAILED DESCRIPTION

In general, according to one embodiment, an antenna module comprises a substrate, a first antenna, an array antenna, and a radio frequency (RF) module. The first antenna comprises a first radiation element arranged on the substrate and a first ground plane arranged on the substrate, and transmits and receives electromagnetic waves of a first frequency band. The array antenna comprises a plurality of second radiation elements arranged on the substrate, and transmits and receives electromagnetic waves of a second frequency band higher than the first electromagnetic wave. The radio frequency (RF) module is connected to the array antenna, and feeds radio frequency (RF) signals of the second frequency band to the array antenna. The substrate includes a first surface and a second surface. The first ground plane is arranged on at least the first surface of the substrate. The plurality of second radiation elements are arranged on the second surface of the substrate and opposed to the first ground plane via the substrate. The first ground plane and the plurality of second radiation elements function as a plurality of patch antennas.

First, a structure of an antenna module1of the embodiment will be explained with reference toFIG. 1,FIG. 2andFIG. 3.FIG. 1is a perspective view showing the antenna module1seen from a surface side thereof,FIG. 2is a side view showing the antenna module1, andFIG. 3is a perspective view showing the antenna module1seen from a back surface side thereof.

The antenna module1may be installed in an electronic device (wireless device) configured to execute wireless communication with a cellular communication system such as a fifth-generation cellular system. The antenna module1is implemented as an integrated antenna module in which an antenna for a lower frequency band and an antenna for a higher frequency band are integrated on the same substrate.

Use of not only existing macro-cells, but also a plurality of small-cells additionally arranged in each of the macro-cells, in the cellular communication system such as a fifth-generation cellular system has been reviewed.

The antenna for a lower frequency band in the integrated antenna module1may be used for wireless communication with a macro-cell base station and the antenna for a higher frequency band in the integrated antenna module1may be used for wireless communication with a small-cell base station.

The lower frequency band may include a frequency band (cellular frequency band) used in an existing LTE system such as LTE or LTE-Advanced. In contrast, the higher frequency band may include a frequency band higher than the cellular frequency, for example, a millimeter-wave frequency band (for example, higher than or equal to 30 GHz).

The lower frequency band may be used for communication using control signals (control plane: C-Plane) of the cellular communication system and the higher frequency band may used for communication using data signals (user plane: U-Plane) of the cellular communication system.

The integrated antenna module1comprises a substrate (antenna substrate)2. The antenna for a lower frequency band used for wireless connection with the LTE system (macro-cell) and the antenna for the higher frequency band used for wireless connection with the new RAT (small-cell) such as the millimeter-wave radio system, are mounted on the same substrate (antenna substrate)2.

The substrate2is a dielectric substrate. The substrate2may be configured by, for example, a printed circuit board (PCB). The substrate2is in the form of a plate having two planar surfaces (a top surface and a back surface). The substrate2may be in the form of a rectangle having four edges21,22,23and24.

The antenna for a lower frequency band functions as an LTE antenna configured to execute wireless communication with a macro-cell base station in a lower frequency band (cellular frequency band). The LTE antenna is configured to transmit and receive electromagnetic waves in the existing lower frequency band (cellular frequency band) used in the cellular communication system.

The LTE antenna may be a monopole type antenna such as an inverted-F antenna or an inverted-L antenna. The LTE antenna comprises an LTE antenna element3which is a line-shaped radiation element arranged on the substrate2, and a ground plane5arranged on the substrate2.

The LTE antenna element3and the ground plane5may be arranged on the same surface of the substrate2or arranged on two different surfaces (top surface2A and back surface2B) of the substrate2, respectively.

In the antenna structure shown inFIG. 1toFIG. 3, the LTE antenna element3and the ground plane5are arranged on the same surface of the substrate2, for example, the top surface (first surface)2A of the substrate2.

The LTE antenna element3is formed of a conductor. The LTE antenna element3may be formed in a conductor pattern on the top surface (first surface)2A of the substrate2. The LTE antenna element3may comprise at least a conductor31and a conductor32. The conductor31is in an elongated shape and is extended parallel to an extending direction (X-direction) of the upper edge21of the substrate2. The conductor32is in an elongated shape and is extended in a perpendicular direction from an end portion of the conductor31to make connection between the end portion of the conductor31and a feed point4.

The feed point4is arranged between the LTE antenna element3and the ground plane5. The feed point4can be implemented by a coaxial connector connected to a coaxial cable. In this case, an inner conductor of the coaxial cable is electrically connected to the LTE antenna element3(i.e., the conductor32of the LTE antenna element3) via the coaxial connector. In contrast, the outer conductor of the coaxial cable is electrically connected to the ground plane5via the coaxial connector.

The ground plane5may be formed in a conductor pattern on the top surface (first surface)2A of the substrate2. The ground plane5is a conductor having a planar surface. The ground plane5may be in the form of a rectangle having four edges151,152,153and154. The edge151of the ground plane5is extended parallel to an extending direction (X direction) of the conductor31of the LTE antenna element3, and is opposed to the conductor31of the LTE antenna element3with a gap therebetween.

The ground plane5plays a role of improving the radiation property of the LTE antenna element3. The ground plane5has an area predetermined in accordance with the frequency band corresponding to the LTE antenna. Typically, the top surface (first surface)2A of the substrate2includes a first region in which the LTE antenna element3is arranged and a second region in which the ground plane5is arranged, and the second region is set to be larger than the first region. The ground plane5may be large enough to cover a substantially entire surface of the second region.

As explained above, the LTE antenna is a monopole type antenna, and the current flows to not only the LTE antenna element3, but also the ground plane5. At the ground plane5, a large amount of current flows along each edge (151,152,153and154) on the periphery of the ground plane5.

The antenna for the higher frequency band is an array antenna configured to execute wireless communication with a small-cell base station in the higher frequency band (including the millimeter-wave frequency band). In general, as the used frequency is higher, the linearity of the electromagnetic wave becomes higher and the reach range of the electromagnetic wave becomes shorter. For this reason, the antenna for the higher frequency band is implemented as an array antenna6capable of executing beam forming to cover a wider range.

The array antenna6(hereinafter called a millimeter-wave array antenna) is configured to execute transmission and reception of the electromagnetic wave in the higher frequency band (including the millimeter-wave frequency band).

The millimeter-wave array antenna6comprises a plurality of radiation elements (hereinafter called millimeter-wave antenna elements)7. Each of the millimeter-wave antenna elements7may be a flat conductor.

In the present embodiment, each of the millimeter-wave antenna elements7of the millimeter-wave array antenna6is implemented as a patch antenna. In other words, the plurality of millimeter-wave antenna elements7of the millimeter-wave array antenna6are arranged on a back surface (second surface)2B of the second substrate2and are opposed to the ground plane5of the LTE antenna via the substrate2. Each of the millimeter-wave antenna elements7may be formed in a conductor pattern on the back surface (second surface)2B of the substrate2. The ground plane5and the plurality of millimeter-wave antenna elements7function as a plurality of patch antennas. In other words, the ground plane5serves as a ground of the LTE antenna and a ground of the millimeter-wave array antenna6(a plurality of patch antennas).

In the present embodiment, the ground plane5of the LTE antenna and the plurality of millimeter-wave antenna elements7are arranged to be superposed on each other on the both surfaces of the substrate2but, as explained above, the millimeter-wave array antenna6is implemented as the plurality of patch antennas composed of the ground plane5and the plurality of millimeter-wave antenna elements7(planar radiation elements). The performance of the millimeter-wave array antenna6can be thereby prevented from being deteriorated by the ground plane7.

In the present embodiment, the millimeter-wave antenna elements7are opposed to a region of part of the ground plane5via the substrate2.

The region may be set at a position remote from the periphery of the ground plane5(i.e., a central region of the ground plane5), in the ground plane5. In this constitution, an influence of the current of the LTE antenna flowing on the ground plane5to the millimeter-wave array antenna6can be reduced. This is because, since most of the current on the LTE antenna flows along each edge of the periphery of the ground plane5as explained above, the amount of the current flowing in the central region remote from the periphery of the ground plane5is small.

The millimeter-wave radio frequency (RF) module8configured to feed the radio frequency (RF) signals of the millimeter-wave frequency band to the plurality of millimeter-wave antenna elements7may also be arranged on the substrate2.

The position on the substrate2at which the millimeter-wave radio frequency (RF) module8should be arranged is not particularly limited. In the antenna structure shown inFIG. 1toFIG. 3, the millimeter-wave radio frequency (RF) module8is arranged on the top surface (first surface)2A of the substrate2.

To set a distance between the millimeter-wave radio frequency (RF) module8and each millimeter-wave antenna element7to be sufficiently short, the millimeter-wave radio frequency (RF) module8may be arranged at a position opposed to the plurality of millimeter-wave antenna elements7via the ground plane5and the substrate2. In this case, terminals of the millimeter-wave radio frequency (RF) module8may be connected to the millimeter-wave antenna elements7via, for example, a via pattern penetrating the ground plane5and the substrate2.

The integrated antenna module1comprising the LTE antenna and the array antenna6can be implemented in the same size as the size of the LTE antenna (i.e., the LTE antenna element3and the ground plane5), in the above-explained antenna structure.

Thus, the antennas of two different types, i.e., the millimeter-wave array antenna6and the LTE antenna, can be provided inside the wireless device without increasing the antenna incorporation space which should be secured inside the wireless device.

As explained above, millimeter-wave radio frequency (RF) module8may be arranged on the surface (top surface)2A opposed to the surface (back surface)2B on which the plurality of millimeter-wave antenna elements7are arranged.

Each of the millimeter-wave antenna elements7is electrically connected to the millimeter-wave radio frequency (RF) module8through via51in the substrate2. The millimeter-wave radio frequency (RF) module8comprises an IC8A and a plurality of terminals8B connected to the vias51. On the ground plane5, a periphery of each of the vias51may be removed. In other words, each of the vias51is electrically insulated from the ground plane5.

In another embodiment, as shown inFIG. 5, in the substrate2, a ground plane9may be provided in a layer between the plurality of millimeter-wave antenna elements7and the millimeter-wave radio frequency (RF) module8.

Each of the millimeter-wave antenna elements7is electrically connected to the millimeter-wave radio frequency (RF) module8through the via51in the substrate2. The millimeter-wave radio frequency (RF) module8comprises an IC8A and a plurality of terminals8B connected to the vias51. On the ground plane9, a periphery of each of the vias51may be removed. In other words, each of the vias51is electrically insulated from the ground plane9. The ground plane5and the ground9are electrically connected to each other through a via52. The ground plane5may comprise an opening through which a part of the top surface2A of the substrate2is exposed. In this case, the millimeter-wave radio frequency (RF) module8may be arranged on the exposed portion of the top surface2A of the substrate2.

FIG. 6toFIG. 10are side views showing another structure of the integrated antenna module1.

In the antenna structure shown inFIG. 6, the LTE antenna element3, and the plurality of millimeter-wave antenna elements7of the millimeter-wave array antenna6are arranged on the second surface2B of the second substrate2and the ground plane5of the LTE antenna is arranged on the first surface2A of the substrate2. The feed point4shown inFIG. 1may be arranged on the first surface2A or the second surface2B of the substrate2.

In the antenna structure shown inFIG. 7, the LTE antenna element3, the plurality of millimeter-wave antenna elements7and the ground plane5are arranged on the second surface2B of the substrate2. The ground plane5on the second surface2B includes an opening, and the plurality of millimeter-wave antenna elements7are arranged on a region of the second surface2B which is exposed through the opening. On the first surface2A of the substrate2, the ground plane5is left on the only region opposed to the plurality of millimeter-wave antenna elements7. The ground plane5on the first surface2A may be electrically connected to the ground plane5on the second surface2B through a via53.

In the antenna structure shown inFIG. 8, the LTE antenna element3is arranged on the first surface2A of the substrate2, and the plurality of millimeter-wave antenna elements7and the ground plane5are arranged on the second surface2B of the substrate2. The ground plane5includes an opening, and the plurality of millimeter-wave antenna elements7are arranged on a region of the second surface2B which is exposed through the opening. On the first surface2A of the substrate2, the ground plane5is left on the only region opposed to the plurality of millimeter-wave antenna elements7. The ground plane5on the first surface2A may be electrically connected to the ground plane5on the second surface2B through the via53.

In the antenna structure shown inFIG. 9, the LTE antenna element3is arranged on the first surface2A of the substrate2, and the plurality of millimeter-wave antenna elements7are arranged on the second surface2B of the substrate2. Furthermore, the ground plane5is arranged on each of the first surface2A and the second surface2B. The ground plane5on the second surface2B includes an opening, and the plurality of millimeter-wave antenna elements7are arranged on a region of the second surface2B which is exposed through the opening. The ground plane5on the first surface2A may be electrically connected to the ground plane5on the second surface2B through the via53.

In the antenna structure shown inFIG. 10, the LTE antenna element3and the plurality of millimeter-wave antenna elements7are arranged on the second surface2B of the substrate2. Furthermore, the ground plane5is arranged on each of the first surface2A and the second surface2B. The ground plane5on the second surface2B includes an opening, and the plurality of millimeter-wave antenna elements7are arranged on a region of the second surface2B which is exposed through the opening. The ground plane5on the first surface2A may be electrically connected to the ground plane5on the second surface2B through the via53.

FIG. 11shows arrangement of the ground plane5and the plurality of millimeter-wave antenna elements7on the back surface side of the antenna module1shown inFIG. 7toFIG. 10.

As shown inFIG. 11, the ground plane5on the second surface2B of the substrate2includes an opening5A in a rectangular shape. A second region2B′ on the second surface2B is exposed through the opening5A of the ground plane5. The plurality of millimeter-wave antenna elements7of the millimeter-wave array antenna6are arranged on the second surface2B′. A certain distance is secured between an outer periphery of the plurality of millimeter-wave antenna elements7and an outer periphery of the opening5A of the ground plane5. Deterioration of the performance of the millimeter-wave array antenna6caused by the ground plane5on the second surface2B can be thereby suppressed.

FIG. 12andFIG. 13show a heat radiation structure applied to the antenna module1. The heat radiation structure is used to eliminate the heat generated from the millimeter-wave radio frequency (RF) module8via the ground plane5.

At least a part of the ground plane5is arranged on the same surface (for example, first surface2A) as the surface of the substrate2on which the millimeter-wave radio frequency (RF) module8is mounted.

A thermally conductive sheet60is applied onto the millimeter-wave radio frequency (RF) module8and the ground plane5. The thermally conductive sheet60is a thermally conductive member which transfers the heat of the millimeter-wave radio frequency (RF) module8to the ground plane5.

In the heat radiation structure, the heat generated inside the millimeter-wave radio frequency (RF) module8by operating the millimeter-wave radio frequency (RF) module8is transferred to the ground plane5via the thermally conductive sheet60and eliminated via the ground plane5.

FIG. 14shows an example of the configuration of the millimeter-wave radio frequency (RF) module8and the millimeter-wave array antenna6.

The millimeter-wave array antenna6comprises a plurality of millimeter-wave antenna elements7arranged on the substrate2. The millimeter-wave antenna elements7may be two-dimensionally spaced apart from each other with regular intervals. Each of the millimeter-wave antenna elements7may be formed in a conductor pattern on the substrate2.

Each of the millimeter-wave antenna elements7is connected to the millimeter-wave radio frequency (RF) module8. The millimeter-wave radio frequency (RF) module8is connected to a millimeter-wave baseband module111. The millimeter-wave baseband module111is connected to a host CPU (processor) in the above-explained wireless device.

The millimeter-wave radio frequency (RF) module8is composed of a frequency converter, an amplifier, a phase shifter, a switch, etc. The frequency converter executes conversion between a millimeter-wave radio frequency (RF) signal and a baseband signal.

The switch changes combination of the millimeter-wave antenna elements7which should be used for radiation of the electromagnetic wave and thereby varies an angle of radiation of the radio wave emitted from the millimeter-wave array antenna6(beam-forming function).

The millimeter-wave baseband module111is configured to execute conversion between the baseband signal and the data signal. The millimeter-wave radio frequency (RF) module8and the millimeter-wave baseband module111function as millimeter-wave transceivers configured to execute wireless communication in the millimeter-wave frequency band.

FIG. 15shows a circuit example of the millimeter-wave radio frequency (RF) module8.

The millimeter-wave radio frequency (RF) module8comprises a power amplifier (PA)121, a low noise amplifier (LNA)122, a switch (SW)123configured to change transmission and reception, a switch (SW)124configured to change combination of the millimeter-wave antenna elements7which should be used, a plurality of phase shifters125, etc. For example, the phase shifters125produce signals having phases different from each other. The switch (SW)124changes combination of the millimeter-wave antenna elements7which should be used for radiation of the electromagnetic wave. A plurality of millimeter-wave antenna elements7may be included in each combination and, for example, each combination may include two millimeter-wave antenna elements7or at least three millimeter-wave antenna elements7.

InFIG. 15, each combination includes two millimeter-wave antenna elements7. In this case, for example, six combinations denoted by numbers 71 to 76 may be selectively used. The combination of the millimeter-wave antenna elements7which should be used for radiation of the electromagnetic wave is changed by the switch (SW)124, and the angle of radiation of the radio wave emitted from the millimeter-wave array antenna6can be thereby changed.

FIG. 15shows a circuit example, and various circuits capable of executing beam-forming can be applied to the millimeter-wave radio frequency (RF) module8.

FIG. 16is a perspective view showing an electronic device incorporating the integrated antenna module1.

The electronic device is the wireless device, and may be implemented as notebook personal computers, tablet computers, smartphones, PDA, or the like or may be implemented as various Internet of Things (IoT) terminals such as vending machines, sensor devices, etc.

It is hereinafter assumed that the electronic device is implemented as a notebook-type personal computer10.

The computer10comprises a computer main body11and a display unit12. A display device such as a liquid crystal display (LCD)15is incorporated in the display unit12.

The display unit12is attached to the computer main body11so as to be rotatable between an opened position at which the top surface of the computer main body11is exposed and a closed position at which the top surface of the computer main body11is covered with the display unit12. A lower end portion of the display unit12is coupled to a rear end portion of the computer main body11via rotatable hinges16A and16B.

The computer main body11comprises a housing shaped in a thin box, and a keyboard13and a touch pad (pointing device)14are arranged on the top surface of the housing.

The integrated antenna module1may be arranged inside the housing of the display unit12. The integrated antenna module1may be arranged on, for example, the back surface side of the LCD15, inside the housing of the display unit12. The integrated antenna module1may be arranged near an upper end portion of the display unit12.

If the electronic device is a tablet computer or a smartphone, the integrated antenna module1is arranged inside the housing of the tablet computer or the housing of the smartphone.

FIG. 17shows a system configuration of the computer10.

The computer10comprises a CPU101, a main memory102, a storage device103, a BIOS-ROM104, an embedded controller (EC)105, a card interface106and an LTE transceiver112, besides the LCD15, the integrated antenna module1, and the millimeter-wave baseband module111.

The CPU101is a processor configured to process the data, and controls the operations of each of the components in the computer10. The CPU101includes a circuit (processing circuit). The CPU101loads software and user data from the storage device103such as an HDD or SDD on the main memory102. Then, the CPU101executes software300. The software includes an operating system (OS), various driver programs and various application programs. The driver programs include a communication control program. The communication control program controls transmission and reception of control signals (control-plane) using the LTE frequency band (i.e., the cellular frequency band) and transmission and reception of data signals (user-plane) using the millimeter-wave frequency band.

In addition, the CPU101also executes a Basic Input/Output System (BIOS) stored in the BIOS-ROM104which is a nonvolatile memory. The BIOS is a system program for hardware control.

The EC105functions as a system controller configured to execute power management of the computer10. The EC105has a function of powering on and off the computer10in response to user operations of the power switch. At power-on of the computer10, the EC105controls a power-on sequence (control of reset timing and control of reset cancellation timing) of each component in the computer10. The EC105is implemented as a processing circuit such as a single-chip microcomputer. The EC105may incorporate a keyboard controller configured to control input devices such as the keyboard (KB)13and the touch pad14.

The card interface106interfaces with a Subscriber Identity Module (SIM) card200. The SIM card200is a storage device which stores at least subscriber information. The subscriber information is intrinsic identification information preliminarily allocated to identify the wireless device (computer10).

Each of the LTE transceiver112and the millimeter-wave baseband module111is electrically connected to the CPU101via a bus. The LTE transceiver112and the millimeter-wave baseband module111function as a transceiver configured to execute wireless communication using the lower frequency band and the higher frequency band.

The LTE transceiver112comprises an LTE baseband module113and an LTE radio frequency (RE) module114. The LTE radio frequency (RE) module114is connected to the integrated antenna module1via a feeder115such as a coaxial cable. More specifically, the coaxial cable is connected to the feed point (coaxial connector)4explained with reference toFIG. 1.

The millimeter-wave baseband module111is connected to the integrated antenna module1via a signal line116. More specifically, the signal line116is connected to the millimeter-wave radio frequency (RF) module8in the integrated antenna module1.

The LTE transceiver112and the millimeter-wave baseband module111may be implemented as devices different from each other or may be integrated inside the same device.

FIG. 18shows a relationship between the computer10and the wireless communication network.

The wireless communication network is a mobile network such as a fifth-generation cellular system. The wireless communication network includes a plurality of macro-cells201. Each macro-cell201includes a macro-cell base station as a base station having a large transmission power.

The lower frequency band such as the LTE frequency band is used for wireless communication between a macro-cell base station201A and the computer10. In other words, the computer10executes transmission and reception of the control signals (control-plane) to and from the macro-cell base station201A by using the LTE antenna in the integrated antenna module1.

A plurality of small-cells301are additionally arranged in each macro-cell201. Each small-cell301includes a small-cell base station301A as a base station having a small transmission power. The macro-cell base station201A and each small-cell base station301A are interconnected to each other via a cable transmission path.

The lower frequency band such as the millimeter-wave frequency band is used for wireless communication between the small-cell base stations301A and the computer10. In other words, the computer10executes transmission and reception of the data signals (user-plane) to and from each small-cell base station301A by using the millimeter-wave array antenna6in the integrated antenna module1.

In the present embodiment, as explained above, the antenna for lower frequency band (LTE antenna) comprising the LTE antenna element3and the ground plane5, and the millimeter-wave array antenna6comprising the plurality of millimeter-wave antenna elements7are arranged on the single substrate2. The plurality of millimeter-wave antenna elements7of the millimeter-wave array antenna6are arranged on the surface opposed to the surface of the substrate2on which the ground plane5is arranged, and are opposed to the ground plane5via the substrate2. Thus, the ground plane5and the plurality of millimeter-wave antenna elements7function as a plurality of patch antennas, and the ground plane5serves as a ground of the LTE antenna and a ground of the millimeter-wave array antenna6(a plurality of patch antennas).

In this antenna structure, the integrated antenna module1comprising the millimeter-wave array antenna6corresponding to the millimeter-wave frequency band connected to the new radio system, and the LTE antenna corresponding to the LTE frequency band connected to the LTE system, can be implemented in the same size as the size of the LTE antenna (i.e., the LTE antenna element3and the ground plane5). The millimeter-wave array antenna6and the LTE antenna can be therefore provided inside the wireless device without increasing the antenna incorporation space which should be secured inside the wireless device.