JP7804181B2 - Dual-polarized antenna - Google Patents

Description

The present invention relates to a dual-polarized antenna capable of transmitting and receiving vertically polarized waves and horizontally polarized waves.

In 5G communications using the millimeter wave band, it is possible to multiplex two information channels at a single carrier frequency using mutually orthogonal vertically and horizontally polarized waves. Conventionally, antennas using substrate integrated waveguides (SIWs) have been known as dual-polarized antennas capable of transmitting and receiving both vertically and horizontally polarized waves (see, for example, Patent Document 1).

The dual-polarized antenna using SIW, as disclosed in Patent Document 1 and elsewhere, radiates electromagnetic waves parallel to the substrate surface. This type of antenna is called an "endfire type." In contrast, antennas that radiate electromagnetic waves perpendicular to the substrate surface are called "broadside type."

Endfire dual-polarized antennas are ideal for use cases where they are installed on the roof of a vehicle, for example, and perform 360-degree beam searches for communications. From the perspective of vehicle design, a low-profile, small-sized array antenna is desirable in order to minimize protrusions on the roof. Dual-polarized antennas that use SIW are easy to manufacture and are also suitable for making antennas low-profile and small.

Special Publication No. 2021-517760

However, in dual-polarized antennas, as antennas become lower-profile and smaller, the separation between the vertically polarized and horizontally polarized transmission lines tends to become narrower. In this case, cross-polarized components are more likely to leak from one transmission line (e.g., a vertically polarized transmission line) to the other transmission line (e.g., a horizontally polarized transmission line), which could result in a decrease in communication quality.

The object of the present invention is to provide a dual-polarized antenna with high cross-polarization discrimination.

A dual-polarized antenna according to one aspect of the present invention comprises:
A dual-polarized antenna having a plurality of antenna units arranged in a row, capable of transmitting and receiving a first polarized wave oscillating in a first direction and a second polarized wave oscillating in a second direction orthogonal to the first direction,
Each of the plurality of antenna units comprises:
a first antenna element for the first polarization;
a second antenna element for the second polarization;
a transmission line that transmits an input signal to the first antenna element and the second antenna element ,
In the adjacent antenna units,
each of the first antenna elements radiates the first polarized wave with a phase delayed by a predetermined first phase with respect to the phase of a first input signal;
One of the second antenna elements radiates the second polarized wave at a phase delayed by a predetermined second phase relative to the phase of the second input signal, and the other of the second antenna elements radiates the second polarized wave at an opposite phase to the second phase delayed by the second phase relative to the phase of the second input signal.

The present invention provides a dual-polarized antenna with high cross-polarization discrimination.

FIG. 1 is a perspective view showing an external appearance of an antenna device according to an embodiment of the present invention. FIG. 2 is an exploded perspective view of the antenna device. FIG. 3 is a front view of the antenna device as viewed from the positive side in the X-axis direction. FIG. 4 is a side view of the antenna device as viewed from the negative side in the Y-axis direction. 5A and 5B are plan views showing the antenna structure of the antenna body. FIG. 6 is a perspective view showing the antenna structure of the antenna main body. FIG. 7 is a diagram showing the laminated structure of the antenna body. FIG. 8 is a diagram showing the phases of input signals to adjacent antenna units. FIG. 9 is a diagram showing the antenna output when there is no coupling between the lines. FIG. 10 is a diagram showing the horizontally polarized component in the antenna output when the horizontally polarized component is coupled to the vertically polarized input signal. FIG. 11 is a diagram showing the vertically polarized component in the antenna output when the vertically polarized component is coupled to the horizontally polarized input signal. 12A and 12B are diagrams showing the intensities of the main polarization component and the cross polarization component in the radiation direction.

An antenna device A according to an embodiment of the present invention will now be described in detail with reference to the drawings.

Antenna device A is a dual-polarized antenna capable of radiating first and second polarized waves that are orthogonal to each other. Antenna device A transmits, for example, vertically and horizontally polarized waves in the 5G millimeter wave band (28 GHz). Antenna device A is an end-fire antenna whose main radiation direction is parallel to the substrate surface.

In this disclosure, the first direction, which is the vibration direction of the first polarized wave, will be described as the "vertical direction," and the second direction, which is the vibration direction of the second polarized wave, will be described as the "horizontal direction." Furthermore, the description will be made using a right-handed Cartesian coordinate system in which the direction perpendicular to the substrate surface is the positive direction of the Z axis, and the main radiation direction of the first polarized wave and the second polarized wave is the positive direction of the X axis. Below, the terms "X-axis direction," "Y-axis direction," and "Z-axis direction" refer to the positive directions of the X axis, Y axis, and Z axis, respectively.

Figure 1 is an external perspective view showing an antenna device A according to one embodiment of the present invention. Figure 2 is an exploded perspective view of antenna device A. Figure 3 is a front view of antenna device A as viewed from the positive side in the X-axis direction. Figure 4 is a side view of antenna device A as viewed from the negative side in the Y-axis direction.

As shown in Figures 1 to 4, antenna device A comprises an antenna main body 1 and an antenna cover 5. Figures 3 and 4 show the interior of the antenna main body 1 in a see-through manner.

The antenna main body 1 is an array antenna having eight antenna units 1A-1H arranged in a row in the Y-axis direction. Control units 61 and 62 are mounted on the antenna main body 1. The control units 61 and 62 are, for example, beamforming ICs, and perform functions such as adjusting the phase and gain of each antenna connected via a transmission line and amplifying the transmission signal. The control unit 61 controls the power supply to antenna units 1A-1D, and the control unit 62 controls the power supply to antenna units 1E-1H.

The antenna cover 5 is an auxiliary member placed at the end of the antenna body 1 on the positive side in the X-axis direction. The antenna cover 5 is made of a conductive material such as metal. The antenna cover 5 has a first cover body 51, a second cover body 52, and a third cover body 53. The first cover body 51 and the second cover body 52 are positioned opposite each other in the Z-axis direction and are connected by the third cover body 53. In other words, the antenna cover 5 has a roughly U-shape in the XZ cross section, with the positive side in the X-axis direction open.

For example, the antenna cover 5 is attached to the antenna body 1 by inserting and securing the positive end of the antenna body 1 in the X-axis direction into the opening 53a provided in the third cover body 53. The antenna cover 5 is electrically connected to the ground pattern (reference number omitted) of the antenna body 1. The antenna cover 5 is secured in a manner that ensures DC conduction with the ground of the antenna body 1, for example, by soldering or a conductive adhesive. Note that the antenna cover 5 may also be secured in a manner that does not involve DC conduction, such as by screwing, as long as the opening 53a of the mounting portion is sufficiently close to the ground of the antenna body 1. Providing the antenna cover 5 improves the antenna gain of the antenna device A.

Figures 5A and 5B are plan views showing the antenna structure of the antenna main body 1. Figure 6 is a perspective view showing the antenna structure of the antenna main body 1. In Figures 5B and 6, portions of the antenna units 1A and 1B are shown enlarged. In addition, in Figure 6, the interior of the antenna structure is shown in a see-through manner.

As shown in Figures 5A and 5B, antenna units 1A to 1H each have a first antenna section 10 and a second antenna section 20. The first antenna section 10 has an antenna structure for vertical polarization. The second antenna section 20 has an antenna structure for horizontal polarization. Antenna units 1A to 1H are formed, for example, from a multilayer printed wiring board.

Antenna units 1A-1H are formed, for example, from multilayer printed wiring boards. Using printed wiring board circuit formation technology, antenna units 1A-1H can be easily manufactured. Furthermore, the size, shape, and position of the antenna elements in the first antenna section 10 and second antenna section 20 can be easily controlled, improving element precision.

The layered structure of the antenna body 1 is shown in Figure 7. For example, as shown in Figure 7, the antenna body 1 has a first conductor layer M1 to a sixth conductor layer M6. The first conductor layer M1 to the sixth conductor layer M6 are formed from metal foil such as copper foil. A dielectric layer D made of a resin material or the like is interposed between each of the first conductor layer M1 to the sixth conductor layer M6. The antenna cover 5 is electrically connected, for example, to the ground patterns (reference numerals omitted) of the first conductor layer M1 and the sixth conductor layer M6.

The first antenna section 10 includes a first transmission line 11 and a first antenna element 12. The first transmission line 11 is a section that transmits vertically polarized signals. The first antenna element 12 is a section that radiates vertically polarized waves.

The first transmission line 11 is a microstrip line formed on the surface of the substrate by the first conductor layer M1.

The first antenna element 12 includes a waveguide 30 that propagates vertically polarized waves. The waveguide 30 has, for example, a substrate integrated waveguide (SIW) structure. The waveguide 30 is formed by side via groups 31G, 32G, a rear via group 33G, an upper plate 34, and a lower plate 35.

The side via groups 31G and 32G are each formed of a plurality of side vias 31 and 32 arranged in the X-axis direction. The back via group 33G is formed of a plurality of back vias 33 arranged in the Y-axis direction. The side vias 31 and 32 and the back via 33 are through holes that connect the ground pattern (reference number omitted) formed on the first conductor layer M1 to the ground pattern (reference number omitted) on the sixth conductor layer M6, and penetrate the second conductor layer M2 to the fifth conductor layer M5. The side vias 31 and 32 and the back via 33 are electrically connected to the second conductor layer M2, the fourth conductor layer M4, and the fifth conductor layer M5, and are electrically insulated from the third conductor layer M3.

The upper plate 34 is formed by the ground plane of the second conductor layer M2. The ground plane of the second conductor layer M2 forms a return path for the transmission line (e.g., the first transmission line 11) formed on the surface layer of the board. The lower plate 35 is formed by the ground plane of the fifth conductor layer M5.

The side via groups 31G and 32G, the rear via group 33G, the top plate 34, and the bottom plate 35 form a rectangular waveguide with an opening on the positive side in the X-axis direction. A first via 36 connected to the first transmission line 11 is inserted near the rear via group 33G.

The first via 36 is a through-hole that connects the first conductor layer M1 and the sixth conductor layer M6, and penetrates the second conductor layer M2 to the fifth conductor layer M5. The first via 36 is electrically insulated from the second conductor layer M2 to the fifth conductor layer M5. An electromagnetic field is induced around the first via 36 and propagates within the waveguide 30. It is then radiated as a vertically polarized wave from the opening of the waveguide 30.

The second antenna section 20 includes a second transmission line 21 and a second antenna element 22. The second transmission line 21 is a section that transmits horizontally polarized signals. The second antenna element 22 is a section that radiates horizontally polarized waves.

The second transmission line 21 is a microstrip line formed on the surface of the substrate by the first conductor layer M1. The second transmission line 21 is arranged close to and approximately parallel to the first transmission line 11.

The second antenna element 22 includes a radiating portion 23 and a signal converting portion 24. The radiating portion 23 has, for example, a dipole antenna structure. The signal converting portion 24 converts the single-ended signal from the second transmission line 21 into a differential signal.

The radiation portion 23 is formed by the fourth conductor layer M4. The radiation portion 23 has a linear shape and extends to the positive and negative sides of the Y-axis direction, sandwiching a slot 24B formed in the fourth conductor layer M4.

The signal conversion section 24 is composed of a relay line 24A formed on the third conductor layer M3 and a slot 24B formed on the fourth conductor layer M4. The relay line 24A is a microstrip line and is connected to the second transmission line 21 via a second via 25. The second via 25 is a through hole that connects the first conductor layer M1 and the third conductor layer M3 and penetrates the second conductor layer M2. The second via 25 is electrically insulated from the second conductor layer M2.

The relay line 24A has a generally L-shape, extending from the connection with the second via 25 to the positive side in the X-axis direction and bending in the Y-axis direction. In FIG. 6, the relay line 24A of the antenna unit 1A bends to the positive side in the Y-axis direction, while the relay line 24A of the antenna unit 1B bends to the negative side in the Y-axis direction. In other words, the bending directions of the relay lines 24A of adjacent antenna units 1A and 1B are opposite. The slot 24B is formed along the X-axis direction from the edge of the fourth conductor layer M4 (the spaced apart portion of the radiation portion 23).

If the bending directions of the relay line 24A are not reversed between adjacent antenna units 1A and 1B, the conversion from single-ended to differential signals will not be complete, resulting in a slight bias in the current flowing through the left and right arms of the second antenna element 22, which has a dipole structure. Furthermore, the biased power supply direction will result in poor symmetry and tilted beams of the array antenna. Therefore, in this embodiment, the bending directions of the relay line 24A are reversed between adjacent antenna units 1A and 1B.

The relay line 24A and slot 24B are arranged perpendicular to each other in a plan view from the Z-axis direction, and are electromagnetically coupled without contact. The signal conversion unit 24 is a microstrip-to-slot converter, and the power supply directions of the signal conversion units 24 of adjacent antenna units 1A and 1B are opposite.

The electromagnetic field formed around the relay line 24A induces an electromagnetic field in the slot 24B of the ground pattern of the fourth conductor layer M4. As a result, the single-ended signal from the second transmission line 21 is converted into a differential signal and transmitted to the radiation portion 23. The signal is then radiated from the radiation portion 23 as a horizontally polarized wave.

In antenna device A, when the input signals have the same phase, the horizontally polarized waves radiated from adjacent antenna units 1A-1H (for example, first antenna unit 1A and second antenna unit 1B) have opposite phases. On the other hand, when the input signals have the same phase, the vertically polarized waves radiated from adjacent antenna units 1A-1H have the same phase. That is, in antenna units 1A and 1B, each first antenna element 12 radiates a vertically polarized wave with a phase delayed by a predetermined phase (first phase) from the phase of the input signal. One of the second antenna elements 22 radiates a horizontally polarized wave with a phase delayed by a predetermined phase (second phase) from the phase of the input signal, and the other second antenna element 22 radiates a horizontally polarized wave with a phase that is the opposite of the phase of the input signal, delayed by a predetermined phase (second phase).

For example, when the antenna gain peak is set in the X direction (front), the horizontally polarized input signals (second input signals) of adjacent antenna units 1A-1H are alternately inverted and controlled to have opposite phases (see Figure 8). Furthermore, the vertically polarized input signals (first input signals) of adjacent antenna units 1A-1H are controlled to have the same phase. As a result, the horizontally polarized and vertically polarized waves radiated from adjacent antenna units 1A-1H are all in phase in the radiation direction, and the outputs of adjacent antennas reinforce each other, improving the antenna gain.

Below, we will specifically explain the antenna output when the control unit 61 controls transmission to the first to fourth antenna units 1A to 1D, using the example of setting the antenna gain peak in the +X direction. In each of the antenna units 1A to 1D, the first transmission line 11 for vertical polarization and the second transmission line 21 for horizontal polarization are formed from microstrip lines and are arranged close to each other. Because the first transmission line 11 and the second transmission line 21 have the same transmission mode, isolation is lower than when the transmission modes between the lines are different.

Figures 9 to 11 show the phases of the vertically polarized waves V1 to V4 and horizontally polarized waves H1 to H4 of the first to fourth antenna units 1A to 1D, as well as the phases of the BFIC output (input signal) output from the control unit 61, the transmission signal in the transmission path, and the antenna output (output signal) from the antenna element.

Figure 9 shows the antenna output when there is no coupling between the lines.

As shown in Figure 9, for vertically polarized waves V1 to V4, the BFIC output (first input signal), transmission signal, and antenna output are all in phase. By having the antenna outputs in phase, high antenna gain is obtained in the radiation direction.

On the other hand, horizontally polarized waves H1 to H4 are controlled so that the BFIC outputs (second input signals) are opposite in phase in adjacent antenna units 1A to 1H (for example, first antenna unit 1A and second antenna unit 1B). Because they are transmitted as is through the transmission line, the opposite phases are maintained. Ultimately, in adjacent antenna units 1A to 1H, one remains in phase and the other is inverted and converted to opposite phase by the second antenna element 22, resulting in the antenna outputs being in phase. Having the antenna outputs in phase results in high antenna gain in the radiation direction.

Figure 10 shows the horizontally polarized component at the antenna output when a horizontally polarized component is coupled to a vertically polarized input signal.

As shown in Figure 10, in antenna units 1A-1D, horizontally polarized signals can leak between the first transmission line 11 for vertical polarization and the second transmission line 21 for horizontal polarization, potentially coupling horizontally polarized components to the vertically polarized signals. Because the BFIC outputs of horizontally polarized waves H1-H4 are out of phase, the coupled horizontally polarized components are out of phase on the first transmission line 11. Because the phase of the transmission signal is maintained in the first antenna element 12 for vertical polarization, the antenna outputs of adjacent antenna units 1A-1H are out of phase. Therefore, the horizontally polarized components included in the antenna outputs are canceled out between adjacent antenna units 1A-1H in the radiation direction, reducing the gain of the cross-polarized components in the radiation direction and resulting in improved cross-polarization discrimination.

Figure 11 shows the vertically polarized component at the antenna output when a vertically polarized component is coupled to a horizontally polarized input signal.

As shown in Figure 11, in antenna units 1A-1D, vertically polarized signals can leak between the first transmission line 11 for vertical polarization and the second transmission line 21 for horizontal polarization, potentially coupling the vertically polarized components to the horizontally polarized signals. Because the BFIC outputs of vertically polarized waves V1-V4 are in phase, the coupled vertically polarized components are in phase on the second transmission line 21. In adjacent antenna units 1A-1H, the second antenna element 22 for horizontal polarization maintains one component in phase while inverting the other component to an opposite phase, resulting in opposite-phase antenna outputs. Therefore, the vertically polarized components included in the antenna outputs are canceled out between adjacent antenna units 1A-1H, reducing the gain of the cross-polarized components in the radiation direction and improving cross-polarization discrimination.

Figures 12A and 12B show the intensity of cross-polarized components in the radiation direction. Figure 12A shows the measurement results for antenna device A according to the embodiment, and Figure 12B shows the measurement results for a conventional antenna device.

As shown in Figure 12A, in antenna device A, the intensity of the cross-polarized component is reduced in the main radiation direction (0 [deg]). In conventional antenna devices, the cross-polarized component is also output in phase, so like the polarized component, its intensity is high in the main radiation direction.

As such, antenna device A according to one aspect of the present invention has the following features, either alone or in any suitable combination:

In other words, antenna device A (polarized dual-band antenna) has multiple antenna units 1A-1H arranged in a row, and is a polarized dual-band antenna capable of transmitting and receiving vertically polarized waves (first polarization) that oscillate in the vertical direction (first direction) and horizontally polarized waves (second polarization) that oscillate in the horizontal direction (second direction) orthogonal to the vertical direction. Each of the multiple antenna units 1A-1H has a first antenna element 12 for vertically polarized waves and a second antenna element 22 for horizontally polarized waves. In adjacent antenna units 1A-1H, each first antenna element 12 radiates vertically polarized waves with a predetermined first phase delay relative to the phase of a first input signal, one of the second antenna elements 22 radiates horizontally polarized waves with a predetermined second phase delay relative to the phase of the second input signal, and the other second antenna element 22 radiates horizontally polarized waves in the opposite phase relative to the second input signal with a second phase delay.

With antenna device A, by controlling the horizontally polarized input signal to be in opposite phase, even if cross-polarized components couple between transmission lines, the effect of the cross-polarized components on the radiation characteristics can be reduced, improving cross-identification accuracy. Furthermore, the transmission lines to the first antenna element 12 and the second antenna element 22 can be formed using microstrip lines, simplifying the transmission lines and reducing the mounting area. Furthermore, the end-fire design allows for easy miniaturization and a low profile, making it particularly useful when installed close to metal components such as vehicle roofs.

In addition, in the antenna device A, the second antenna element 22 has a signal conversion unit 24 that converts a single-ended signal into an differential signal, and the signal conversion units 24 of adjacent antenna units 1A to 1H have opposite feeding directions of the single-ended signal.
Specifically, the signal conversion section 24 has a relay line 24A and a slot 24B that are electromagnetically coupled without contact, and the signal conversion sections 24 of adjacent antenna units 1A to 1H have relay lines 24A extending in opposite directions relative to the slots 24B.
This makes it easy to realize a configuration in which, in adjacent antenna units 1A to 1H, one of the second antenna elements 22 radiates a horizontally polarized wave in the same phase as the input signal, and the other of the second antenna elements 22 radiates a horizontally polarized wave in the opposite phase to the input signal.

Antenna device A also includes a first transmission line 11 that transmits a first input signal to a first antenna element 12, and a second transmission line 21 that transmits a second input signal to a second antenna element 22. The first transmission line 11 and the second transmission line 12 are microstrip lines. This allows the dual-polarized antenna to be made smaller. While inter-line isolation decreases, high cross-polarization discrimination is maintained.

Antenna device A also includes control units 61 and 62 that adjust the phase of each transmission line. The control units 61 and 62 output opposite-phase second input signals to the second antenna elements 22 of adjacent antenna units 1A to 1H. The control units 61 and 62 set the phase of each input signal to each of the antenna units 1A to 1H, for example, so that the antenna gain peaks at a desired angle. At this time, adjacent antenna units 1A to 1H output input signals to their second antenna elements 22 that are opposite in phase to the set phase calculated from the angle at which the peak occurs. As a result, the horizontally polarized and vertically polarized waves radiated from adjacent antenna units 1A to 1H are all in phase at the set angle, and the adjacent antenna outputs reinforce each other, improving the antenna gain.

The invention made by the inventor has been specifically described above based on the embodiments, but the present invention is not limited to the above embodiments and can be modified within the scope of its gist.

For example, in the embodiment, the first transmission line 11 and the second transmission line 21 are formed as microstrip lines, but the first transmission line 11 and the second transmission line 21 may also be other strip lines or coplanar lines.

In addition, in the embodiment, a dipole antenna is applied to the second antenna element 22 for horizontal polarization, but another antenna structure, such as a Yagi antenna, may be applied to the second antenna element 22. Furthermore, in addition to the substrate integrated waveguide shown in the embodiment, another antenna structure, such as a dipole antenna formed vertically using vias, may be applied to the first antenna element 12 for vertical polarization.

Furthermore, while the embodiments have been described using a transmitting antenna that radiates horizontally polarized and vertically polarized waves as an example, the dual-polarized antenna of the present invention can be applied to any antenna that can transmit or receive horizontally polarized and vertically polarized waves, or that has both functions.

Furthermore, the dual-polarized antenna of the present invention may be equipped with multiple antenna units, and there is no particular limit to the number of antenna units.

The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims, not the above description, and is intended to include all modifications that are equivalent in meaning to and within the scope of the claims.

1 Antenna main body 1A to 1H Antenna unit 11 First transmission line 12 First antenna element 21 Second transmission line 22 Second antenna element A Antenna device (polarized dual antenna)

Claims (5)

A dual-polarized antenna having a plurality of antenna units arranged in a row, capable of transmitting and receiving a first polarized wave oscillating in a first direction and a second polarized wave oscillating in a second direction orthogonal to the first direction,
Each of the plurality of antenna units comprises:
a first antenna element for the first polarization;
a second antenna element for the second polarization;
a transmission line that transmits an input signal to the first antenna element and the second antenna element ,
In the adjacent antenna units,
each of the first antenna elements radiates the first polarized wave with a phase delayed by a predetermined first phase with respect to the phase of a first input signal;
one of the second antenna elements radiates the second polarized wave at a phase delayed by a predetermined second phase with respect to the phase of a second input signal, and the other of the second antenna elements radiates the second polarized wave at a phase opposite to the second phase delayed by the predetermined second phase with respect to the phase of the second input signal;
Dual polarized antenna. the second antenna element has a signal conversion unit that converts a single-ended signal into a differential signal;
The signal conversion units of the adjacent antenna units have opposite feeding directions of the single-ended signals.
The dual-polarized antenna according to claim 1 . the signal conversion unit has a relay line and a slot that are electromagnetically coupled in a non-contact manner;
The signal conversion units of the adjacent antenna units have the relay lines extending in opposite directions relative to the slot.
The dual-polarized antenna according to claim 2 . the transmission line includes a first transmission line that transmits a first input signal to the first antenna element and a second transmission line that transmits a second input signal to the second antenna element;
the first transmission line and the second transmission line are microstrip lines.
The polarized antenna according to claim 1 . a control unit that adjusts the phase of each of the transmission lines;
The control unit transmits an input signal of an opposite phase to the second antenna element of the adjacent antenna unit.
The polarized antenna according to claim 1 .