Circular polarization antenna device

Abstract

This circularly polarized antenna device is provided with: element antennas (10) that emit circularly polarized waves; and a space matching layer (200) that is disposed in firm contact with the surface of the element antennas (10) on the side that emits radio waves, and that has a thickness such that the phase shift amount of the radio waves that are incident by being radiated from the element antennas (10) at a specific scanning angle is in the range from 75 degrees to 105 degrees.

Description

[Technical Field]

[0001] This disclosure relates to a circularly polarized antenna device equipped with an element antenna. [Background technology]

[0002] In a phased array antenna in which multiple element antennas are arranged and the main beam can be directed in any direction by electronically changing the excitation phase of each element antenna, Patent Document 1 proposes an antenna that prevents a decrease in operating gain due to the deterioration of the active reflection coefficient, which is the reflection coefficient of the element antennas in their operating state at a wide angle when scanned at a wide angle.

[0003] The antenna described in Patent Document 1 comprises an aperture having multiple element antennas capable of radiating radio frequency (RF) energy, and a single-layer wide-angle impedance matching (WAIM) structure coupled to the aperture to provide impedance matching between the aperture and free space, wherein the WAIM structure is an antenna that is a capacitive patch isolated from the aperture by a dielectric spacer or foam. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Special Publication No. 2023-526456 [Overview of the project] [Problems that the invention aims to solve]

[0005] Since the antenna device shown in Patent Document 1 is configured as described above, the wider the incident angle of the radio waves radiated from the element antenna to the capacitive patch constituting the WAIM structure, the greater the difference in the pass phase between TE (Transverse Electric) waves and TM (Transverse Magnetic) waves. In the antenna device disclosed in Patent Document 1, if the element antenna is configured to radiate circularly polarized waves, the transmission phase difference between TE waves and TM waves increases as the radiation direction of radio waves is scanned over a wider angle, which gives rise to the problem that axial ratio characteristics deteriorate.

[0006] The present disclosure has been made in view of the above points, and an object of the present disclosure is to obtain a circularly polarized antenna device capable of preventing a decrease in operating gain due to deterioration of an active reflection coefficient in wide-angle scanning and obtaining good axial ratio characteristics for circularly polarized radio waves. [Means for Solving the Problem]

[0007] A circularly polarized antenna device according to the present disclosure comprises: an element antenna that radiates circularly polarized waves; and a spatial matching layer that is arranged in close contact with the surface of the element antenna on a radio wave radiation side, and has a thickness such that a phase shift amount of radio waves radiated from the element antenna at a specific scanning angle and incident thereon falls within a range of 75 degrees to 105 degrees The specific scanning angle is the maximum scanning angle of the antenna device's coverage area. . [Effect of the Invention]

[0008] According to the present disclosure, the spatial matching layer prevents a decrease in operating gain due to deterioration of the active reflection coefficient in wide-angle scanning, and since no transmission phase difference between TE waves and TM waves is caused by the spatial matching layer, good axial ratio characteristics for circularly polarized radio waves can be obtained. [Brief Description of the Drawings]

[0009] [Figure 1] FIG. 1 is a perspective view showing the antenna device according to the first embodiment, as seen through the spatial matching layer and a second dielectric substrate. [Figure 2] FIG. 2 is a top view showing the element antenna in the antenna device according to the first embodiment, as seen through the spatial matching layer and the second dielectric substrate. [Figure 3] FIG. 3 is a cross-sectional view taken along line A-A in FIG. 2 [Figure 4] FIG. 4 is an equivalent circuit diagram of the spatial matching layer in the antenna device according to the first embodiment. [Figure 5]This figure shows the relationship between relative permittivity and transmission amplitude in the antenna device according to Embodiment 1. [Figure 6] This figure shows the relationship between the phase shift amount and the pass-through amplitude in the antenna device according to Embodiment 1. [Figure 7] This figure shows the relationship between the phase shift amount and the pass phase difference between TE waves and TM waves in the antenna device according to Embodiment 1. [Figure 8] This is a top view showing the spatial matching layer in the antenna device according to Embodiment 2. [Figure 9] This is a side view showing the spatial matching layer in the antenna device according to Embodiment 3. [Modes for carrying out the invention]

[0010] Embodiment 1. A circularly polarized antenna device according to Embodiment 1 will be described with reference to Figures 1 to 7. The circular polarization antenna device according to Embodiment 1 is a circular polarization antenna device comprising an antenna substrate 100 which is a phased array antenna that emits circular polarization with a plurality of element antennas 10 arranged in a row, and a spatial matching layer 200.

[0011] As shown in Figure 1, the antenna substrate 100 constitutes an array antenna having multiple element antennas 10 arranged two-dimensionally in the X and Y directions, and comprises a first dielectric substrate 1, a second dielectric substrate 2, cavities 3 having hollow structures 3a at the positions where each of the multiple element antennas 10 is formed, and a ground plate (ground layer) 4. The antenna substrate 100 is a non-excited patch antenna with a hollow structure 3a.

[0012] In other words, the array antenna comprises a cavity 3 sandwiched between a first dielectric substrate 1 and a second dielectric substrate 2 that are arranged opposite each other, and having a plurality of hollow structures 3a, and the plurality of element antennas 10 are unexcited patch element antennas formed in the hollow structures 3a in the cavity 3.

[0013] The first dielectric substrate 1 is mounted on the lower surface of the cavity 3, and the second dielectric substrate 2 is mounted on the upper surface of the cavity 3. In the hollow structure 3a of cavity 3, the first dielectric substrate 1, the second dielectric substrate 2, and cavity 3 form a hollow portion. Cavity 3 is a dielectric substrate with metal plating covering its entire surface. The base plate 4 is a metal layer attached to the lower surface of the first dielectric substrate 1.

[0014] Each element antenna 10 located in the hollow structure 3a of cavity 3 is composed of a first dielectric substrate 1, a second dielectric substrate 2, the hollow structure 3a in cavity 3, a ground plate 4, an excited patch element (antenna element) 11, and an unexcited patch (unexcited element) 12, as shown in Figures 2 and 3. The element antenna 10 is a non-excited patch element antenna. The element antenna 10 is a patch element antenna having a hollow structure 3a.

[0015] The excitation patch element 11 has a patch portion 11a, a first feed point 11b, and a second feed point 11c. The patch portion 11a is formed on the upper surface of the first dielectric substrate 1 by a conductive pattern. The first power supply point 11b and the second power supply point 11c are formed on the lower surface of the first dielectric substrate 1, separated from the ground plate 4 and electrically insulated from the ground plate 4. The first power supply point 11b and the second power supply point 11c are electrically connected to the patch section 11a via through-holes.

[0016] A radio frequency (RF) signal with electronically controlled excitation phase is input to the first feed point 11b and the second feed point 11c, respectively, and a circularly polarized radio wave consisting of plane waves, namely TE waves and TM waves, is emitted from the patch section 11a. RF signals are supplied to the first feed point 11b and the second feed point 11c with equal amplitude and a 90° phase difference, and radio waves based on the RF signals having circular polarization characteristics are generated from the patch section 11a.

[0017] The non-excited patch 12 is formed on the lower surface of the second dielectric substrate 2 by a conductive pattern facing the patch portion 11a of the excited patch element 11. When power is supplied to the excitation patch element 11, a current is also excited in the unexcited patch 12, which is electromagnetically coupled to the patch portion 11a of the excitation patch element 11.

[0018] The spatial matching layer 200 is positioned in close contact with the surface of the element antenna 10 that emits radio waves. In other words, the spatial matching layer 200 is an array antenna in which multiple element antennas 10 are arranged in close contact with the surface on which the radio waves are emitted on the antenna substrate 100. In Embodiment 1, the antenna substrate 100 is bonded to the upper surface of the second dielectric substrate 2 by prepreg. The spatial matching layer 200 may also be attached to the antenna substrate 100 by screw fastening while in close contact with the upper surface of the second dielectric substrate 2.

[0019] The spatial matching layer 200 has a thickness such that, at a specific scanning angle, the phase shift of the radio waves passing through the spatial matching layer 200 is in the range of 75 to 105 degrees. In Embodiment 1, the thickness is such that the phase shift of the radio waves is 90 degrees. A specific scanning angle refers to the maximum scanning angle of the antenna device's coverage area, for example. In the following explanation, the specific scanning angle from which radio waves are emitted from the element antenna 10 is referred to as the specific direction.

[0020] The spatial matching layer 200 is composed of a medium with a relative permittivity such that the transmission amplitudes of two orthogonal linear polarization components of radio waves incident from a specific direction on the element antenna 10, namely the TE wave and the TM wave, are equal. The spatial matching layer 200 is a dielectric material with a relative permittivity of 1.7 or less. By using a dielectric material with a low dielectric constant of 1.7 or less as the spatial matching layer 200, the occurrence of scan blindness, which is a degradation of the active coefficient due to surface waves on the spatial matching layer 200 caused by radio waves from the element antenna 10, can be eliminated.

[0021] Preferably, the spatial matching layer 200 is made of a dielectric having a relative dielectric constant of 1.05 to 1.35, more preferably 1.05 to 1.15. In Embodiment 1, the spatial matching layer 200 is a rigid foam that is a dielectric with a relative dielectric constant of 1.1. The thickness of the spatial matching layer 200 is larger than one quarter of the guide wavelength at the operating frequency.

[0022] The spatial matching layer 200 will be described in further detail below. Let the relative dielectric constant of the dielectric constituting the spatial matching layer 200 be ε r , and let the incident angle (specific scanning angle) of radio waves from the element antenna 10 to the spatial matching layer 200 be θ. Then, the propagation constant β of the electromagnetic wave component propagating in the z-direction shown in FIGS. 1 to 3 in the dielectric, that is, in the forward direction with respect to the element antenna 10 i is represented by the following formula (1).

[0023] TIFF0007915924000001.tif14166In the above formula (1), β i TE is the propagation constant of TE waves, β i TM is the propagation constant of TM waves, and the propagation constant β of TE waves i TE and the propagation constant β of TM waves i TM have equal values.

[0024] The thickness t of the dielectric constituting the spatial matching layer 200 gives a phase shift amount β of the radio wave propagating through the spatial matching layer 200 i t [rad.], so the thickness t of the dielectric at which the phase shift amount is 90 degrees is represented by the following formula (2).

[0025] TIFF0007915924000002.tif14166In the above formula (2), λ is the guide wavelength at the operating frequency, which is the wavelength of the radio wave emitted from the element antenna 10.

[0026] As can be understood from equation (2) above, this can be applied when the scanning angle θ is widened by making the thickness t of the spatial matching layer 200 thicker than 1 / 4 of the in-tube wavelength λ of the operating frequency.

[0027] In a specific direction (specific scanning angle), the relative permittivity of the dielectric constituting the spatial matching layer 200 is set to a value such that the transmission amplitudes of TE waves and TM waves are equal. The wave impedance Z of the TE wave, an electromagnetic wave component, propagating in the z direction through the dielectric material constituting the spatial matching layer 200. i TE and the wave impedance Z of the TM wave i TM These are expressed by equations (3) and (4), respectively.

[0028] TIFF0007915924000003.tif14166 TIFF0007915924000004.tif15166

[0029] In equations (3) and (4) above, z0 is the characteristic impedance in free space, which is 120π. Since the spatial matching layer 200 is a dielectric layer, it can be represented as a transmission line as an equivalent circuit, as shown in Figure 4. Therefore, the F matrix F in the spatially consistent layer 200 i TE / TM This is expressed by equation (5).

[0030] TIFF0007915924000005.tif26166

[0031] In free space, the wave impedance of the TE / TM wave component of the electromagnetic wave propagating in the z direction is Z0. TE / TM The element antenna impedance in the TE / TM wave, with respect to the connection surface with the spatial matching layer 200, is Z. ant TE / TM Therefore, from equation (5) above, the transmission coefficient T of the spatially matching layer 200 is TE / TM This is expressed by equation (6).

[0032] TIFF0007915924000006.tif21166

[0033] In free space, the wave impedance Z0 of the TE wave at the incident angle (specific scanning angle) θ TE and the wave impedance Z0 of the TM wave TM These are expressed by equations (7) and (8), respectively.

[0034] TIFF0007915924000007.tif12166 TIFF0007915924000008.tif10166

[0035] Figure 5 shows the relationship between the relative permittivity and the transmission amplitude in the dielectric material constituting the spatial matching layer 200. In Figure 5, the horizontal axis represents the relative permittivity of the dielectric constituting the spatially matched layer 200, and the vertical axis represents the transmission amplitude in the dielectric. The solid line TE shows the relationship between relative permittivity and transmission amplitude in the TE wave, the dashed line TM shows the relationship between relative permittivity and transmission amplitude in the TM wave, and the dashed line TE+TM shows the relationship between relative permittivity and transmission amplitude in the TEM wave.

[0036] Figure 5 shows the element antenna impedance Z at a scanning angle θ of 70 degrees in the TE wave. ant TE The element antenna impedance Z is 300Ω in the TM wave. ant TM Let Ω be 100Ω, and the phase shift amount of the spatial matching layer 200 is the thickness condition β. i This is an example calculated using t = π / 4 [rad.]. As is clear from Figure 5, the relative permittivity of a dielectric material is 1.1 for which the transmission amplitudes of TE waves and TM waves are equal. Rigid foam is an example of a dielectric material with a relative permittivity of 1.1. Therefore, it is preferable to construct the spatially aligned layer 200 from a rigid foam.

[0037] As is clear from Figure 5, it is most preferable to use a dielectric with a relative permittivity of 1.1 for the spatial matching layer 200. However, if the relative permittivity is between 1.05 and 1.15, the transmission amplitudes of TE waves and TM waves are approximately the same. Therefore, even in wide-angle scanning, there is no particular problem in using a dielectric with a relative permittivity of 1.05 to 1.15 for the spatial matching layer 200.

[0038] Furthermore, the scanning angle θ is 70 degrees, and the element antenna impedance Z in the TE wave is also 70 degrees. ant TE The element antenna impedance Z is 200Ω in the TM wave. ant TM By changing the condition to 200Ω, the phase shift amount of the spatial matching layer 200 is determined by the thickness condition β. i Based on calculations using t = π / 4 [rad.], the relative permittivity of the dielectric material at which the transmission amplitudes of the TE wave and TM wave are equal is 1.35. In other words, a dielectric material with a relative permittivity of 1.35 or less can be used as the spatial matching layer 200.

[0039] Considering these factors, when we examined the appropriate relative permittivity of the dielectric material to be used as the spatial matching layer 200, we found that by using a dielectric material with a low relative permittivity of 1.7 or less as the spatial matching layer 200, when the spacing of the element antennas 10 is 0.47 wavelengths at the high-frequency end of the operating frequency and the scanning angle θ is 75 degrees, it is possible to eliminate the scan blindness phenomenon, in which the active coefficient deteriorates due to surface waves on the spatial matching layer 200 caused by radio waves from the element antennas 10. In other words, it is preferable to use a dielectric material with a low dielectric constant of 1.7 or less as the spatial matching layer 200.

[0040] Furthermore, the transmission phase ∠T when passing through the spatially matched layer 200 is TE / TM The transmission coefficient T of the spatially matching layer 200 is shown in equation (6) above. TE / TM It can be expressed by the following equation (9).

[0041] TIFF0007915924000009.tif26166

[0042] As can be understood from equation (9) above, the thickness of the spatial matching layer 200 is such that the phase shift is 90 degrees, and the wave impedance Z0 in free space at the scanning angle θ TE / TM and element antenna impedance Z in TE / TM waves ant TE / TM Regardless of the value, the pass-through phase in the spatially matched layer 200 is 90 degrees, and there is no pass-through phase difference between the TE wave and the TM wave. Therefore, no degradation of the axial ratio characteristics in circularly polarized waves occurs due to the phase difference between the TE wave and the TM wave, and good axial ratio characteristics can be obtained.

[0043] Next, we will explain the phase shift amount, that is, the thickness of the spatially matched layer 200. The radio waves emitted from the antenna substrate 100, that is, the radio waves emitted from the multiple element antennas 10, are radiated into space via the spatial matching layer 200. In this case, the spatial matching layer 200 has a thickness such that the phase shift of the passing radio waves is 90 degrees, so the spatial matching layer 200 operates as a matching circuit for a quarter-wavelength impedance line (transmission line), as shown in the equivalent circuit in Figure 4.

[0044] Therefore, the spatial matching layer 200 improves the transmission amplitude of the radio waves emitted from the element antenna 10 compared to the case where the radio waves emitted from the element antenna 10 are directly radiated into free space. In other words, the spatial matching layer 200 improves the matching between the element antenna 10 and free space, thereby mitigating the decrease in operating gain due to the deterioration of the active reflection coefficient.

[0045] The relationship between the pass-through amplitude and pass-through phase difference was investigated by changing the thickness of the spatial matching layer 200, i.e., the phase shift amount. Figure 6 shows the relationship between the phase shift amount and the transmission amplitude in the spatially matched layer 200. In Figure 6, the horizontal axis represents the phase shift amount in the spatially matched layer 200, and the vertical axis represents the transmission amplitude in the spatially matched layer 200. The solid line TE shows the relationship between the transmission amplitude and the phase shift amount in the TE wave, the dashed line TM shows the relationship between the transmission amplitude and the phase shift amount in the TM wave, and the dashed line TE+TM shows the relationship between the transmission amplitude and the phase shift amount in the TEM wave.

[0046] Figure 7 shows the relationship between the phase shift amount and the phase difference between TE waves and TM waves in the spatial matching layer 200. In Figure 7, the horizontal axis represents the phase shift amount in the spatially matched layer 200, and the vertical axis represents the phase difference between the TE wave and the TM wave.

[0047] Figures 6 and 7 show the element antenna impedance Z in the TE wave at a scanning angle θ of 70 degrees. ant TE The element antenna impedance Z is 300Ω in the TM wave. ant TM This is an example where the value is calculated as 100Ω.

[0048] As is clear from Figures 6 and 7, the most preferable thickness for the spatial matching layer 200 is one in which the phase shift of the passing radio waves is 90 degrees. If the phase shift of the passing radio waves is in the range of 75 to 105 degrees, the difference in transmission amplitude between TE waves and TM waves is small, and the transmission phase difference between TE waves and TM waves is small, so there is no risk of deterioration of the axial ratio characteristics even in wide-angle scanning.

[0049] Next, the operation of the circularly polarized antenna device according to Embodiment 1 will be described. Each of the multiple element antennas 10 on the antenna substrate 100 is excited with a phase difference so that the beam is directed at the scanning angle θ. In each element antenna 10, RF signals of equal amplitude and a 90-degree phase difference are input to the first feed point 11b and the second feed point 11c of the excitation patch element 11, and the patch portion 11a of the excitation patch element 11 is fed by the first feed point 11b and the second feed point 11c with equal amplitude and a 90-degree phase difference.

[0050] The patch portion 11a of the excitation patch element 11 is fed by a first feed point 11b and a second feed point 11c with equal amplitude and a 90-degree phase difference, thereby emitting radio waves with circular polarization characteristics. Furthermore, when the patch section 11a is powered, a current is also excited in the unexcited patch 12, which is electromagnetically coupled to the patch section 11a.

[0051] The circularly polarized radio waves emitted from patch section 11a are radiated into free space via the spatial matching layer 200.

[0052] The circularly polarized antenna device according to Embodiment 1 includes a spatial matching layer that is closely positioned on the surface of the element antenna 10 that radiates circularly polarized waves and has a thickness such that the phase shift amount of the incident radio waves radiated from the element antenna 10 at a specific scanning angle is in the range of 75 to 105 degrees. As a result, it is easy to manufacture, prevents gain reduction in wide-angle scanning, and provides good axial ratio characteristics.

[0053] The circularly polarized antenna device according to Embodiment 1 prevents deterioration of the axial ratio characteristics even during wide-angle scanning, because, during wide-angle scanning, no phase difference occurs between the TE wave and the TM wave, regardless of the wave impedance of the free space, the relative permittivity of the medium of the spatial matching layer 200, or the impedance of the element antenna 10. In the circularly polarized antenna device according to Embodiment 1, the spatial matching layer 200 operates like a quarter-wavelength impedance transmission line in circuit theory, thus improving the matching between free space and the element antenna 10 even in wide-angle scanning, and mitigating the decrease in operating gain due to the deterioration of the active reflection coefficient.

[0054] In the circular polarization antenna device according to Embodiment 1, the spatial matching layer 200 is composed of a medium with a relative permittivity such that the transmission amplitudes of two orthogonal linear polarization components of radio waves incident from a specific scanning angle of the element antenna 10 are equal, thereby obtaining good axial ratio characteristics even in wide-angle scanning. The circularly polarized antenna device according to Embodiment 1 is configured with a dielectric material having a low relative permittivity of 1.7 or less as the spatial matching layer 200, preferably a dielectric material with a relative permittivity of 1.05 to 1.35, more preferably a dielectric material with a relative permittivity of 1.05 to 1.15. Since the transmission amplitudes of TE waves and TM waves are approximately the same, deterioration of the axial ratio characteristics can be prevented even in wide-angle scanning.

[0055] The circularly polarized antenna device according to Embodiment 1 can relax the maximum element spacing condition that causes the scan blindness phenomenon, in which the active coefficient deteriorates significantly at a specific scanning angle due to surface waves emitted from the antenna substrate 100, to occur in the visible region, by selecting a dielectric with a low dielectric constant of 1.7 or less as the spatial matching layer 200, and in particular a medium with a low dielectric constant such as rigid foam as the spatial matching layer 200.

[0056] Although the antenna substrate 100 described is a non-excited patch antenna with a hollow structure 3a, a tightly coupled dipole, a tapered slot antenna, a bowtie antenna, or a patch antenna without a hollow structure may also be used.

[0057] Furthermore, while we mainly described a spatial matching layer 200 composed of a dielectric material with a relative permittivity of 1.05 to 1.15, we also described the element antenna impedance Z at the scanning angle θ and TE / TM waves. ant TE / TM Depending on the case, the dielectric material may have a relative permittivity outside the above range.

[0058] Furthermore, each element antenna 10 generates circular polarization characteristics using a two-point feeding method with a first feed point 11b and a second feed point 11c, but a notched patch antenna or polarizer may also be used. Furthermore, the circularly polarized waves excited (emitted) from the antenna substrate 100 do not have to be perfectly circularly polarized with an axial ratio of 0 dB; they may also be elliptically polarized.

[0059] Embodiment 2. A circularly polarized antenna device according to Embodiment 2 will be described with reference to Figure 8. The circular polarization antenna device according to Embodiment 2 differs from the circular polarization antenna device according to Embodiment 1 in that the spatial matching layer 201 is made of a dielectric material with multiple holes 201a, while all other aspects are the same. Therefore, the spatial matching layer 201, which is a difference from the circular polarization antenna device according to Embodiment 1, will be mainly described below.

[0060] The circularly polarized antenna device according to Embodiment 2 comprises an antenna substrate and a spatial matching layer 201. The antenna substrate in the circularly polarized antenna device according to Embodiment 2 is the same as the antenna substrate 100 in the circularly polarized antenna device according to Embodiment 1, and the spatial matching layer 201 is bonded in close contact with the upper surface of the second dielectric substrate 2 that constitutes the antenna substrate 100 shown in the circularly polarized antenna device according to Embodiment 1, using a prepreg. Therefore, the explanation of the antenna circuit board will be omitted.

[0061] The spatially matching layer 201 is a dielectric material in which multiple holes 201a are drilled in a two-dimensional manner. Hole 201a is a hole that penetrates from the upper surface to the lower surface (in the z direction as shown in Figure 8) of the spatially aligned layer 201. The shape of the hole is cylindrical.

[0062] Note that the hole 201a does not have to be cylindrical, and the shape of the hole 201a, the direction in which it is drilled, and whether or not it penetrates from the top surface to the bottom surface may be appropriately selected for each of the multiple holes 201a. The dielectric material constituting the spatial matching layer 201 is a rigid foam, a fluororesin, or a thermosetting resin.

[0063] The thickness of the spatial matching layer 201 is such that, at a specific scanning angle, the phase shift of the radio waves passing through the spatial matching layer 200 is in the range of 75 to 105 degrees. In Embodiment 2, the thickness is such that the phase shift of the radio waves is 90 degrees.

[0064] The equivalent relative permittivity of the spatial matching layer 201 is determined by the number of holes 201a drilled in the dielectric and the size (internal shape) of the holes 201a, and the transmission coefficient T of the spatial matching layer is shown in equation (6) above. TE / TM The spatial matching layer 201 is determined such that the transmission amplitude of the TE wave and the TM wave are approximately the same. In other words, the spatial matching layer 201 is a spatial matching layer 201 composed of a dielectric material having a plurality of holes 201a with an equivalent relative permittivity of 1.7 or less, preferably 1.05 to 1.35, more preferably 1.05 to 1.15, and particularly good is 1.1.

[0065] Next, the operation of the circularly polarized antenna device according to Embodiment 2 will be described. The operation of the circularly polarized antenna device according to Embodiment 2 is the same as that of the circularly polarized antenna device according to Embodiment 1, and each of the multiple element antennas on the antenna substrate is excited with a phase difference so that the beam is directed at the scanning angle θ. The circularly polarized radio waves emitted from each element antenna are radiated into free space via the spatial matching layer 201.

[0066] The circularly polarized antenna device according to Embodiment 2 has the same effects as the circularly polarized antenna device according to Embodiment 1. Furthermore, since the spatial matching layer 201 is made of a dielectric material with multiple holes 201a drilled in two dimensions, the equivalent relative permittivity of the spatial matching layer 201 can be adjusted by the material of the dielectric material constituting the spatial matching layer 201, the number and size of the holes 201a, and thus a highly flexible design is possible.

[0067] Embodiment 3. A circularly polarized antenna device according to Embodiment 3 will be explained with reference to Figure 9. The circularly polarized antenna device according to Embodiment 3 differs from the circularly polarized antenna device according to Embodiment 1 in that the spatial matching layer 202 is constructed of a dielectric material formed by stacking multiple dielectric layers 202a to 202e, but all other aspects are the same. Therefore, the spatial matching layer 202, which is a difference from the circular polarization antenna device according to Embodiment 1, will be mainly described below.

[0068] The circularly polarized antenna device according to Embodiment 3 comprises an antenna substrate and a spatial matching layer 202. The antenna substrate in the circularly polarized antenna device according to Embodiment 3 is the same as the antenna substrate 100 in the circularly polarized antenna device according to Embodiment 1, and the spatial matching layer 202 is bonded in close contact with the upper surface of the second dielectric substrate 2 that constitutes the antenna substrate 100 shown in the circularly polarized antenna device according to Embodiment 1, using a prepreg. Therefore, the explanation of the antenna circuit board will be omitted.

[0069] The spatial matching layer 202 is a dielectric material formed by stacking multiple dielectric layers 202a to 202e, and consists of at least two types of dielectric layers 202a to 202e with different relative permittivity. Each of the multiple dielectric layers 202a to 202e in the dielectric constituting the spatially matching layer 202 is selected from rigid foam, fluororesin, or thermosetting resin.

[0070] The thickness of the spatial matching layer 202 is such that, at a specific scanning angle, the phase shift of the radio waves passing through the spatial matching layer 200 is in the range of 75 to 105 degrees. In Embodiment 3, the thickness is such that the phase shift of the radio waves is 90 degrees.

[0071] The equivalent relative permittivity of the spatially matched layer 201 is determined by the ratio of the relative permittivity and thickness of each of the multiple dielectric layers 202a to 202e, and the transmission coefficient T of the spatially matched layer is shown in equation (6) above. TE / TM The spatial matching layer 202 is determined such that the transmission amplitude of the TE wave and the TM wave are approximately the same. In other words, the spatial matching layer 202 is a spatial matching layer 202 in which a plurality of dielectric layers 202a to 202e are stacked, each having an equivalent relative permittivity of 1.7 or less, preferably 1.05 to 1.35, more preferably 1.05 to 1.15, and particularly good is 1.1.

[0072] Next, the operation of the circularly polarized antenna device according to Embodiment 3 will be described. The operation of the circularly polarized antenna device according to Embodiment 3 is the same as that of the circularly polarized antenna device according to Embodiment 1, and each of the multiple element antennas on the antenna substrate is excited with a phase difference so that the beam is directed at the scanning angle θ. The circularly polarized radio waves emitted from each element antenna are radiated into free space via the spatial matching layer 202.

[0073] The circularly polarized antenna device according to Embodiment 3 has the same effects as the circularly polarized antenna device according to Embodiment 1. Furthermore, since the spatial matching layer 202 is composed of a dielectric in which multiple dielectric layers 202a to 202e are stacked, the equivalent relative permittivity of the spatial matching layer 202 can be adjusted by the ratio of the relative permittivity of each of the multiple dielectric layers 202a to 202e and their respective thicknesses in the dielectric constituting the spatial matching layer 201, allowing for a highly flexible design.

[0074] Furthermore, it is possible to freely combine the embodiments, modify any component of each embodiment, or omit any component of each embodiment. [Industrial applicability]

[0075] The circular polarization antenna device described herein is applicable to phased array antennas that radiate circular polarization, such as those used in satellite communication systems. [Explanation of Symbols]

[0076] 100 Antenna substrate, 10 Element antenna, 1 First dielectric substrate, 2 Second dielectric substrate, 3 Cavity, 4 Ground plate, 11 Excited patch element, 11a Patch section, 11b First feed point, 11c Second feed point, 12 De-excited patch, 200, 201, 202 Spatial matching layer, 201a Hole.

Claims

1. An element antenna that radiates circularly polarized waves, The device comprises a spatial matching layer, which is arranged in close proximity to the surface of the element antenna that emits radio waves, and has a thickness such that the phase shift of the incident radio waves emitted from the element antenna at a specific scanning angle is in the range of 75 to 105 degrees, The aforementioned specific scanning angle is the maximum scanning angle of the antenna device's coverage area for a circularly polarized antenna device.

2. An array antenna having a plurality of element antennas arranged in two dimensions, The array antenna comprises a spatial matching layer having a thickness such that the phase shift of the incident radio waves radiated from each of the multiple element antennas at a specific scanning angle is 75 to 105 degrees, and the multiple element antennas are arranged in close proximity to the surface on which the radio waves are radiated. The aforementioned specific scanning angle is the maximum scanning angle of the antenna device's coverage area for a circularly polarized antenna device.

3. An element antenna that radiates circularly polarized waves, The device comprises a spatial matching layer, which is arranged in close proximity to the surface of the element antenna that emits radio waves, and has a thickness such that the phase shift of the incident radio waves emitted from the element antenna at a specific scanning angle is in the range of 75 to 105 degrees, The spatial matching layer is composed of a medium with a relative permittivity such that the transmission amplitudes of two orthogonal linear polarization components of radio waves incident from a specific scanning angle of the element antenna are equal.

4. An array antenna having a plurality of element antennas arranged in two dimensions, The array antenna comprises a spatial matching layer having a thickness such that the phase shift of the incident radio waves radiated from each of the multiple element antennas at a specific scanning angle is 75 to 105 degrees, and the multiple element antennas are arranged in close proximity to the surface on which the radio waves are radiated. The spatial matching layer is composed of a medium with a relative permittivity such that the transmission amplitudes of two orthogonal linear polarization components of radio waves incident from a specific scanning angle of the element antenna are equal.

5. An element antenna that radiates circularly polarized waves, The device comprises a spatial matching layer, which is arranged in close proximity to the surface of the element antenna that emits radio waves, and has a thickness such that the phase shift of the incident radio waves emitted from the element antenna at a specific scanning angle is in the range of 75 to 105 degrees, A circularly polarized antenna device in which the thickness of the spatial matching layer is greater than 1 / 4 of the wavelength inside the tube at the operating frequency.

6. An array antenna having a plurality of element antennas arranged in two dimensions, The array antenna comprises a spatial matching layer having a thickness such that the phase shift of the incident radio waves radiated from each of the multiple element antennas at a specific scanning angle is 75 to 105 degrees, and the multiple element antennas are arranged in close proximity to the surface on which the radio waves are radiated. A circularly polarized antenna device in which the thickness of the spatial matching layer is greater than 1 / 4 of the wavelength inside the tube at the operating frequency.

7. An element antenna that radiates circularly polarized waves, The device comprises a spatial matching layer, which is arranged in close proximity to the surface of the element antenna that emits radio waves, and has a thickness such that the phase shift of the incident radio waves emitted from the element antenna at a specific scanning angle is in the range of 75 to 105 degrees, The spatial matching layer is a dielectric material in which multiple dielectric layers are stacked, forming a circularly polarized antenna device.

8. An array antenna having a plurality of element antennas arranged in two dimensions, The array antenna comprises a spatial matching layer having a thickness such that the phase shift of the incident radio waves radiated from each of the multiple element antennas at a specific scanning angle is 75 to 105 degrees, and the multiple element antennas are arranged in close proximity to the surface on which the radio waves are radiated. The spatial matching layer is a dielectric material in which multiple dielectric layers are stacked, forming a circularly polarized antenna device.

9. The array antenna comprises a first dielectric substrate and a second dielectric substrate arranged opposite each other, and a cavity having a plurality of hollow structures sandwiched between the first dielectric substrate and the second dielectric substrate, and the plurality of element antennas are unexcited patch element antennas formed in the hollow structures in the cavity. The spatial matching layer is arranged in close contact with the upper surface of the second dielectric substrate in the array antenna. A circularly polarized antenna device according to any one of claims 2, 4, 6, or 8.

10. The circular polarization antenna device according to any one of claims 1, 3, 5, or 7, wherein the element antenna is a non-excited patch element antenna.

11. The circular polarization antenna device according to any one of claims 1, 3, 5, or 7, wherein the element antenna is a patch element antenna having a hollow structure.

12. The circular polarization antenna device according to any one of claims 1, 3, 5, or 7, wherein the element antenna is a tightly coupled dipole.

13. The circular polarization antenna device according to any one of claims 1 to 8, wherein the spatial matching layer is a dielectric with a relative permittivity of 1.7 or less.

14. The circular polarization antenna device according to any one of claims 1 to 8, wherein the spatial matching layer is made of foam material.

15. The circular polarization antenna device according to any one of claims 1 to 6, wherein the spatial matching layer is a dielectric material with a plurality of holes drilled in two dimensions.

16. The circular polarization antenna device according to claim 15, wherein the hole drilled in the dielectric constituting the spatial matching layer is a hole drilled through from the upper surface to the lower surface of the spatial matching layer.

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