Differential line conversion structure and antenna device

Abstract

The present disclosure relates to a differential line conversion structure and an antenna device with which further size reduction can be achieved. This differential line conversion structure comprises: a single line in which one wire is disposed; a differential line in which two wires are disposed substantially parallel to each other; a propagation mode conversion region which converts the propagation mode of a signal to be inputted to the differential line at a connection point where one wire constituting the differential line is electrically connected to the wire constituting the single line; and a filter structure which is disposed adjacent to the propagation mode conversion region on the differential line side thereof and suppresses the propagation of a common mode through the differential line. The present technology can be applied to, for example, a differential line conversion structure used in a millimeter-wave radar.

Description

Differential Line Conversion Structure and Antenna Device

[0001] The present disclosure relates to a differential line conversion structure and an antenna device, and particularly to a differential line conversion structure and an antenna device that can be made more compact.

[0002] Conventionally, in a differential line conversion structure used in a millimeter-wave radar, a differential line that only handles a differential mode generally needs to incorporate a structure that shifts the phase and is connected to a single-ended line. For example, the differential line can be configured to propagate only the differential mode by forming one side of the line to have 2n times the phase (λg / 2) to obtain a phase difference.

[0003] Patent Document 1 discloses a balun circuit (differential-to-single-ended conversion circuit), which is a three-terminal circuit that combines two electrical signals (differential signals) with a 180-degree phase difference after compensating for the phase difference, in which a first substantially 1 / 4 wavelength line and a second substantially 1 / 4 wavelength line formed on a first metal wiring layer and a substantially 1 / 2 wavelength line formed on a second metal wiring layer are arranged to overlap in the thickness direction of a multilayer substrate.

[0004] Japanese Patent Application Laid-Open No. 2005-27148

[0005] However, the differential line conversion structure as described above has a large structure in terms of layer configuration and area. Therefore, it has been difficult to miniaturize a differential line conversion structure that can perform highly efficient differential conversion from a single-ended line and propagate only the differential mode without generating a common mode.

[0006] The present disclosure has been made in view of such a situation and aims to enable more miniaturization.

[0007] A differential line conversion structure according to one aspect of the present disclosure comprises a single line on which one wire is arranged, a differential line on which two wires are arranged substantially parallel to each other, a propagation mode conversion region that converts the propagation mode of a signal input to the differential line at a connection point where one of the wires constituting the differential line is electrically connected to the wire constituting the single line, and a filter structure arranged on the differential line side adjacent to the propagation mode conversion region to suppress the propagation of common mode to the differential line.

[0008] An antenna device according to one aspect of the present disclosure comprises a single line on which one wire is arranged, a differential line on which two wires are arranged substantially parallel to each other, a propagation mode conversion region that converts the propagation mode of a signal input to the differential line at a connection point where one of the wires constituting the differential line is electrically connected to the wire constituting the single line, a filter structure arranged on the differential line side adjacent to the propagation mode conversion region and suppressing the propagation of common mode to the differential line, and an antenna connected to the differential line.

[0009] In one aspect of this disclosure, the present invention provides a single line with one wire and a differential line with two wires arranged substantially parallel to each other, wherein the propagation mode of the signal input to the differential line is converted at the connection point where one of the wires constituting the differential line is electrically connected to the wire constituting the single line, and the propagation of common mode to the differential line is suppressed by a filter structure arranged on the differential line side adjacent to the propagation mode conversion region.

[0010] This figure shows an example configuration of the first embodiment of a differential transmission line conversion structure to which this technology is applied. This figure illustrates differential mode and common mode. This figure illustrates the characteristics of a common mode filter structure. This figure illustrates an example of the frequency characteristics of the reflection coefficient and transmission coefficient. This figure shows an example configuration of the second embodiment of a differential transmission line conversion structure to which this technology is applied. This figure shows an example configuration of the third embodiment of a differential transmission line conversion structure to which this technology is applied. This figure shows an example configuration of the fourth embodiment of a differential transmission line conversion structure to which this technology is applied. This figure shows a modified version of the differential transmission line conversion structure shown in Figure 7.

[0011] The following describes in detail a specific embodiment of this technology, with reference to the drawings.

[0012] <First Configuration Example of Differential Line Conversion Structure> Figure 1 is a diagram showing a configuration example of a first embodiment of a differential line conversion structure to which this technology is applied.

[0013] As shown in Figure 1, the dielectric substrate 21 on which the differential line conversion structure 11 is provided is configured such that a GND layer 22, which is grounded to GND potential, is provided on the lower surface of the dielectric layer 23, and a wiring layer 24, which constitutes wiring connecting the chip to a differential patch antenna or the like, is provided on the upper surface of the dielectric layer 23.

[0014] The wiring layer 24 is composed of a single line with one wire 24-1 and a differential line with two wires 24-2 and 24-3 arranged substantially parallel to each other. In the example shown in Figure 1, wires 24-1 and 24-2 are electrically connected. For example, a signal input to the differential line conversion structure 11 from a chip connected to wire 24-1 has its propagation mode converted at the connection point where wire 24-2 is electrically connected to wire 24-1, and is output via wires 24-2 and 24-3.

[0015] Hereinafter, the region where only wiring 24-1 is provided will be referred to as the single-line region 31, and the region on the wiring 24-2 and wiring 24-3 side near the connection point where wiring 24-2 is connected to wiring 24-1 will be referred to as the propagation mode conversion region 32. Furthermore, the differential line conversion structure 11 is configured such that a common-mode filter region 33 is provided on the wiring 24-2 and wiring 24-3 side adjacent to the propagation mode conversion region 32.

[0016] The common mode filter region 33 is provided with a common mode filter structure 41 that suppresses the propagation of common modes to the differential line. The common mode filter structure 41 is composed of multiple EBG (Electromagnetic Band Gap) structures 42 that have a band gap characteristic that controls the presence of electromagnetic waves in a specific frequency band, arranged periodically. In the example shown in Figure 1, the common mode filter structure 41 is composed of nine EBG structures 42 arranged in a 3x3 configuration.

[0017] In the single-line region 31, a single-ended line (for example, a microstrip line or a coplanar line) is provided, consisting of a single wire 24-1 arranged on the upper surface of the dielectric layer 23, as shown in the cross-sectional view on the right side of Figure 1.

[0018] In the propagation mode conversion region 32, as shown in the cross-sectional view on the right side of Figure 1, of the two wires 24-2 and 24-3 arranged on the upper surface of the dielectric layer 23, the wire 24-3 that is not connected to wire 24-1 is connected to the GND layer 22 via the connecting electrode 25. Then, at the interface where wires 24-2 and 24-3 are provided (upper surface of the dielectric layer 23), the wire 24-2 connected to wire 24-1 is placed close to the wire 24-3 which is grounded to GND potential, creating a structure in which a strong electric field is generated (electric field concentration) from wire 24-2 toward wire 24-3, thereby enabling mode conversion (electric field control) that facilitates the propagation of differential modes.

[0019] In the common-mode filter region 33, as shown in the cross-sectional view on the right side of Figure 1, an EBG structure 42 is provided inside the dielectric layer 23 below the wiring 24-2 and wiring 24-3 that constitute the differential line. This EBG structure 42 has a circular conductor (for example, copper foil) connected to the GND layer 22 via a connecting electrode 43 (a so-called mushroom structure). Above the EBG structure 42, an AMC (Artificial Magnetic Conductor) is formed on the surface, preventing the generation of a vertical electric field. Therefore, the common-mode filter structure 41, in which the EBG structures 42 are periodically arranged, can achieve a common-mode filtering effect. By providing the common-mode filter structure 41 in a region that includes directly above the interface where the differential line is provided (the upper surface of the dielectric layer 23), the differential line can transmit only differential modes.

[0020] For example, in a structure without a common-mode filter structure 41, both differential modes, as shown in Figure 2A, and common modes, as shown in Figure 2B, would exist. In contrast, by providing a common-mode filter structure 41, the common mode can be removed from the interface where the differential line is provided, so that only the differential mode is propagated to the differential line.

[0021] The differential line conversion structure 11 configured in this way converts the propagation mode of the signal input to the differential line in the propagation mode conversion region 32, which is the connection point where wiring 24-2 is electrically connected to wiring 24-1, and suppresses the propagation of common mode to the differential line in the common mode filter structure 41 located on the differential line side adjacent to the propagation mode conversion region 32. As a result, the differential line conversion structure 11 can be miniaturized to propagate only differential mode to the differential line without generating common mode.

[0022] In other words, the differential line conversion structure 11 connects a differential line (wiring 24-2 and wiring 24-3) having a propagation mode conversion region 32 and a common mode filter structure 41 to a single-ended line composed of wiring 24-1, thereby realizing a configuration that can efficiently convert to a differential line in which only differential modes are transmitted with a smaller structure. That is, because the differential line conversion structure 11 has a configuration that makes it difficult to generate common modes, the conversion efficiency can be improved, and thus the structure can be miniaturized (reduction in area, number of layers, etc.). Furthermore, by miniaturizing the structure in this way, the differential line conversion structure 11 can suppress the generation of unwanted radiation from structures such as transmission lines.

[0023] For example, the differential line conversion structure 11 can easily achieve waveguide conversion by connecting wiring 24-2 and wiring 24-3 to a differential patch antenna or the like. Furthermore, by employing the differential line conversion structure 11, the transmission line with high loss can be shortened, and antenna structures using differential lines such as waveguide antennas can be utilized in smaller millimeter-wave radar devices.

[0024] Furthermore, by employing the differential line conversion structure 11, it is not necessary to arrange a large structure in the width direction. Therefore, for example, antenna spacing can be set at λ / 2 intervals, which is often used as the optimal arrangement for millimeter-wave radar and communication array antennas.

[0025] Furthermore, in conventional differential transmission line conversion structures, for example, in structures where one transmission line has a phase difference of 2n, there is a concern that resonance will occur at the frequency used, resulting in unwanted radiation. However, the differential transmission line conversion structure 11 of this embodiment can suppress the generation of such unwanted radiation.

[0026] For example, the differential line conversion structure 11 can be applied to waveguide antennas and other antenna structures that require differential lines while arranging antennas at λ / 2 intervals in a small millimeter-wave radar device. Furthermore, the differential line conversion structure 11 can shorten the length in the direction along the differential line, thereby reducing the overall area of ​​the substrate. For example, the length of the common mode filter structure 41 and the differential line are not particularly limited and can be arranged to any length.

[0027] The characteristics of the common mode filter structure 41 will be described with reference to Figures 3 and 4.

[0028] Figure 3A shows a differential line conversion structure 11 equipped with a common mode filter structure 41 of a 3-cell model in which EBG structures 42 are arranged in a 3x3 array. Figure 3B shows a differential line conversion structure 11' equipped with a common mode filter structure 41' of a 1-cell model in which EBG structures 42 are arranged in a 3x1 array.

[0029] The reflection coefficient S11 shown in Figure 3 represents the ratio of the input power of the signal input from port 1 to wiring 24-1 to the reflected power of that signal reflected by the common mode filter structure 41 (including reflection in the propagation mode conversion region 32) and directed towards port 1. Similarly, the reflection coefficient S22 represents the ratio of the input power of the signal input from port 2 to wirings 24-2 and 24-3 to the reflected power of that signal reflected by the common mode filter structure 41 and directed towards port 2. For example, the closer the reflection coefficients S11 and S22 are to 0 dB, the more it indicates that almost no power can be supplied through the transmission line, and it is ideal if they are -20 dB or less.

[0030] Furthermore, the transmission coefficient S21 represents the ratio of the input power of the signal input from port Port1 to wiring 24-1 to the output power of the signal that has passed through the common mode filter structure 41 and is output from port Port2. For example, the closer the transmission coefficient S21 is to 0 dB, the more it is possible to transmit and convert the signal with virtually no loss through the transmission line.

[0031] Figure 4A shows an example of the frequency characteristics (vertical axis: S-parameters (dB), horizontal axis: frequency (GHz)) of the reflection coefficient S11, reflection coefficient S22, and transmission coefficient S21 in the common mode filter structure 41 shown in Figure 3A. Figure 4B shows an example of the frequency characteristics (vertical axis: S-parameters (dB), horizontal axis: frequency (GHz)) of the reflection coefficient S11, reflection coefficient S22, and transmission coefficient S21 in the common mode filter structure 41' shown in Figure 3B.

[0032] For example, as shown in Figure 4A, the differential line conversion structure 11 achieves a reflection coefficient S22 of -20 dB when propagating the differential mode, and has the characteristic that the propagation mode can exist within the bandwidth. Furthermore, the differential line conversion structure 11 also has a transmission coefficient S21 close to 0 dB when propagating the differential mode, and has the characteristic that the power input from port 1 is converted into a propagation mode as expected within the bandwidth and propagates as a differential mode at port 2.

[0033] On the other hand, as shown in Figure 4A, the differential transmission line conversion structure 11 has a reflection coefficient S22 close to 0 dB when common-mode propagation, and is characterized by reflection without the existence of propagation modes within the bandwidth. Furthermore, the transmission coefficient S21 of the differential transmission line conversion structure 11 is also -20 dB or less when common-mode propagation, and the common-mode filter structure 41 provided by the differential transmission line conversion structure 11 is operating as expected, and is characterized by being almost unable to convert the input signal of port 1 into common-mode.

[0034] Furthermore, as can be seen by comparing the characteristics shown in Figure 4A with those shown in Figure 4B, the effect of filtering common modes can be changed by changing the configuration of the common mode filter structure 41. In other words, the configuration of the common mode filter structure 41 (such as the number of EBG structures 42 installed) can be set according to the characteristics required of the common mode filter structure 41 and the size of the common mode filter region 33.

[0035] For example, the differential line conversion structure 11 can be made smaller by reducing the periodic structure of the EBG structure 42 that constitutes the common mode filter structure 41, thereby reducing the size of the differential line conversion structure 11 itself. Furthermore, the differential line conversion structure 11 can be formed with a minimum configuration of λg / 2 or less. In other words, it is possible to immediately connect the signal output from the chip to the differential line with a minimum size of approximately λg / 2.

[0036] <Second Configuration Example of Differential Line Conversion Structure> Figure 5 is a diagram showing a configuration example of a second embodiment of a differential line conversion structure to which this technology is applied. In the differential line conversion structure 11A shown in Figure 5, components common to the differential line conversion structure 11 shown in Figure 1 are denoted by the same reference numerals, and their detailed explanations are omitted.

[0037] As shown in Figure 5, the differential line conversion structure 11A has a configuration common to the differential line conversion structure 11 in Figure 1, in that it comprises a single-line region 31 where only wiring 24-1A is provided, a propagation mode conversion region 32 provided near the connection point where wiring 24A-2 is connected to wiring 24A-1, and a common mode filter region 33 where a common mode filter structure 41A is provided adjacent to the propagation mode conversion region 32.

[0038] Furthermore, the differential line conversion structure 11A differs from the differential line conversion structure 11 in that the dielectric substrate 21A has a GND layer 22A, which is grounded to GND potential, provided on the upper surface of the dielectric layer 23A, a wiring layer 24A, which constitutes wiring connecting the chip to a differential patch antenna, etc., provided inside the dielectric layer 23A, and a common mode filter structure 41A provided above the differential line.

[0039] In other words, the differential line conversion structure 11 in Figure 1 is configured such that a wiring layer 24 is provided on the upper surface of the dielectric layer 23, and a common mode filter structure 41 is provided below the differential line (wiring 24-2 and wiring 24-3), whereas the differential line conversion structure 11A is configured such that a wiring layer 24A is provided inside the dielectric layer 23A, and a common mode filter structure 41A is provided above the differential line (wiring 24A-2 and wiring 24A-3). That is, the common mode filter structure 41 can be placed either below or above the differential line as long as it can provide a filtering effect against common modes.

[0040] Similarly, the common-mode filter structure 41 may be positioned to the right or left of the differential line, as long as it can achieve a filtering effect against common modes. That is, the interface of the common-mode filter structure 41 may be in the same section as the propagation mode conversion region 32.

[0041] The differential line conversion structure 11A configured in this way, like the differential line conversion structure 11 in Figure 1, can achieve miniaturization of the structure that propagates only the differential mode to the differential line without generating the common mode.

[0042] <Third Configuration Example of Differential Line Conversion Structure>FIG. 6 is a diagram showing a configuration example of a third embodiment of a differential line conversion structure to which the present technology is applied. In the differential line conversion structure 11B shown in FIG. 6, the same reference numerals are given to the configurations common to the differential line conversion structure 11 shown in FIG. 1, and detailed descriptions thereof are omitted.

[0043] As shown in FIG. 6, in the differential line conversion structure 11B, a GND layer 22 grounded to the GND potential is provided on the lower surface of the dielectric layer 23 of the dielectric substrate 21, and a wiring layer 24 that forms wiring connected from a chip to a differential patch antenna or the like is provided on the upper surface of the dielectric layer 23. It has a single-wire region 31 where only the wiring 24-1 is provided, and is a configuration common to the differential line conversion structure 11 of FIG. 1.

[0044] And the differential line conversion structure 11B is provided with a common mode filter region 33B having a characteristic of filtering the common mode in an arbitrary band so that a part thereof overlaps with a propagation mode conversion region 32B near the connection point where the wiring 24-2 is connected to the wiring 24-1. This is a configuration different from the differential line conversion structure 11 of FIG. 1. That is, when the common mode filter region 33B can be arranged below the propagation mode conversion region 32B, there is no need to separately arrange the propagation mode conversion region 32B and the common mode filter region 33B.

[0045] The differential line conversion structure 11B configured as described above can further reduce the size of the structure that propagates only the differential mode to the differential line without generating the common mode by providing the common mode filter region 33B so as to partially overlap with the propagation mode conversion region 32B.

[0046] <Fourth Configuration Example of Differential Line Conversion Structure>FIG. 7 is a diagram showing a configuration example of a fourth embodiment of a differential line conversion structure to which the present technology is applied.

[0047] Referring to FIG. 7, an antenna device including a differential line conversion structure 11C will be described. In FIG. 7A, a plan view of a conductor layer 51 in which wirings 24C-1 to 24C-3 are formed in the differential line conversion structure 11C is shown, and in FIG. 7B, a plan view of a conductor layer 52 in which an EBG structure body 42C of a common mode filter structure 41C is provided in the differential line conversion structure 11C is shown.

[0048] As shown in FIG. 7A, in the differential line conversion structure 11C, in a single-wire region 31 where a wiring 24C-1 configured as a coplanar line is provided, conductor layers 51 adjacent to both sides of the wiring 24C-1 are connected to a GND layer 22 (not shown) via connection electrodes.

[0049] Further, in the differential line conversion structure 11C, in a propagation mode conversion region 32, the conductor layer 51 adjacent to the wiring 24C-1 (the conductor layer 51 adjacent on the opposite side to the side where the wiring 24C-3 is adjacent) is provided in a shape that gradually separates from the wiring 24C-2 so that the electric field on one side with respect to the wiring 24C-2 becomes weak. Thereby, the electric field can be maintained by the wiring 24C-3 adjacent to the wiring 24C-2 at a constant interval. Note that as long as there is no impedance mismatch, as long as the relative strength of the electric field can be adjusted, either one can be brought closer.

[0050] And in the differential line conversion structure 11C, the common mode can be filtered by the common mode filter structure 41C provided in the common mode filter region 33. For example, it is preferable to install the EBG structure body 42C constituting the common mode filter structure 41C so that the central axis of the mushroom structure coincides with the center of the differential line so that the characteristics are maximized.

[0051] In an antenna device equipped with a differential line conversion structure 11C, a differential patch antenna 61 is connected to wiring 24C-2 and wiring 24C-3 as a conversion structure capable of resonating and mode conversion at the frequency supplied from the differential line. Note that the conversion structure connected to the differential line in the conversion structure region 34 is not limited to the differential patch antenna 61 shown in the figure, as long as it is a structure that converts to another structure via a differential line.

[0052] In the differential line conversion structure 11C configured in this way, the propagation mode conversion region 32 can be simplified in a structure called a coplanar line, which is covered on the sides with GND, making it possible to realize a more compact conversion system structure and thus miniaturize the antenna device.

[0053] Figure 8 illustrates a modified example of the differential line conversion structure 11C shown in Figure 7. Figure 8A shows a plan view of the conductor layer 51 on which wiring 24C-1 to 24C-3 are formed, and Figure 8B shows a plan view of the conductor layer 53 which becomes the GND layer 22.

[0054] The differential line conversion structure 11C' shown in Figure 8 has a two-layer structure in which a conductor layer 51 on which a transmission line is provided and a conductor layer 53 that is grounded to GND potential are stacked, and the common mode filter structure 41C' is made of a Uniplanar EBG 62, which is a different configuration from the differential line conversion structure 11C in Figure 7.

[0055] The Uniplanar EBG 62 is composed of a conductive pattern formed on the conductive layer 53, and, similar to the EBG structure 42, has a bandgap characteristic that controls the absence of electromagnetic waves in a specific frequency band through the periodic structure of the conductive pattern as shown in the figure. Note that the periodic structure of the conductive pattern as shown in the figure is just one example of the Uniplanar EBG 62, and the common mode filter structure 41C' may be constructed with a periodic structure other than such a conductive pattern.

[0056] The differential line conversion structure 11C' configured in this way, by providing a Uniplanar EBG 62 on the conductor layer 53 grounded to GND potential, can filter out common modes and generate only differential modes in the transmission line, similar to the differential line conversion structure 11C in Figure 7. Furthermore, the differential line conversion structure 11C' can reduce the number of layers on the substrate without significantly increasing the mounting area compared to the configuration using the mushroom-shaped EBG structure 42C described above.

[0057] Figure 8 shows a differential line conversion structure 11C' in an example configuration where the transmission line is connected to a differential patch antenna 61. However, the conversion structure connected to the differential line in the conversion structure region 34 can be any structure that connects via a differential line and converts to another structure, and is not limited to the differential patch antenna 61 shown in the figure.

[0058] As described above, the differential line conversion structure 11 of each embodiment described above, as a conversion structure to a flat waveguide connected to a substrate having wiring from a chip (for example, a microstrip or coplanar line), is capable of converting to a compact size from the short axis direction of the waveguide while maintaining a wide bandwidth. This makes it possible to realize a differential line conversion structure for use in, for example, a compact millimeter-wave radar.

[0059] In the embodiment described above, a common-mode filter structure 41 composed of a so-called mushroom-shaped EBG structure 42 is employed. However, the common-mode filter structure 41 can be formed in any shape as long as a filtering effect against common modes can be obtained. Furthermore, the common-mode filter structure 41 can be positioned above, below, to the left, or to the right of the differential line. In addition, the single line and differential line do not need to be provided on the surface of the dielectric layer 23. As long as the effects described above can be obtained, a configuration in which the single line and differential line are provided inside the dielectric layer 23 may be adopted.

[0060] The technology described above can be applied to a configuration comprising an RF device using a single-wire / single-ended line (e.g., a chip), a single-wire / single-ended line (e.g., a single-wire region 31), a mode conversion structure using a GND structure (propagation mode conversion region 32), a differential line having a common mode filter (e.g., a common mode filter structure 41), and an RF device using a differential line (e.g., a differential patch antenna).

[0061] Furthermore, the technologies described in this specification can be implemented independently, as long as they do not create a contradiction. Of course, any multiple technologies can also be implemented in combination. For example, some or all of the technologies described in one embodiment can be combined with some or all of the technologies described in another embodiment. In addition, some or all of the above-mentioned technologies can be implemented in combination with other technologies not mentioned above.

[0062] <Examples of Configuration Combinations> The technology can also take the following configurations: (1) A differential line conversion structure comprising: a single line on which one wire is laid; a differential line on which two wires are laid substantially parallel to each other; a propagation mode conversion region that converts the propagation mode of a signal input to the differential line at a connection point where one of the wires constituting the differential line is electrically connected to the wire constituting the single line; and a filter structure arranged on the differential line side adjacent to the propagation mode conversion region to suppress the propagation of common mode to the differential line. (2) The differential line conversion structure according to (1) above, wherein at the interface where the single line and the differential line are provided, the other wire constituting the differential line is laid close to one of the wires constituting the differential line, and the other wire constituting the differential line is grounded to ground potential. (3) The differential line conversion structure according to (1) or (2) above, wherein the filter structure is provided in the interface on which the differential line is provided, or in a region including directly above the interface on which the single line and the differential line are provided. (4) A differential line conversion structure according to any one of (1) to (3) above, wherein the filter structure is provided such that a portion of it overlaps the propagation mode conversion region. (5) A differential line conversion structure according to any one of (1) to (4) above, wherein the filter structure and the differential line connected to the filter structure are arranged to be of any length. (6) A differential line conversion structure according to any one of (1) to (5) above, wherein the filter structure is configured by periodically arranging a plurality of EBG (Electromagnetic Band Gap) structures, which are structures having band gap characteristics. (7) A differential line conversion structure according to (6) above, wherein the number of EBG structures to be installed is set according to the characteristics required for the filter structure. (8) A differential line conversion structure according to any one of (1) to (7) above, wherein the single line and the differential line are provided on the upper surface of the dielectric layer, and the filter structure is located inside the dielectric layer and below the differential line. (9) The differential line conversion structure according to any one of (1) to (8) above, wherein the single line and the differential line are provided inside the dielectric layer.(10) The differential line conversion structure according to (9) above, wherein the filter structure is positioned above the differential line. (11) The differential line conversion structure according to any one of (1) to (10) above, wherein the filter structure can be formed in any shape and is positioned above, below, to the left, or to the right of the differential line. (12) An antenna device having a differential line conversion structure comprising: a single line on which one wire is laid; a differential line on which two wires are laid substantially parallel to each other; a propagation mode conversion region that converts the propagation mode of a signal input to the differential line at a connection point where one of the wires constituting the differential line is electrically connected to the wire constituting the single line; a filter structure positioned on the differential line side adjacent to the propagation mode conversion region and suppressing the propagation of common mode to the differential line; and an antenna connected to the differential line.

[0063] It should be noted that this embodiment is not limited to the embodiment described above, and various modifications are possible without departing from the spirit of this disclosure. Furthermore, the effects described herein are merely illustrative and not limiting, and other effects may also exist.

[0064] 11 Differential line conversion structure, 21 Dielectric substrate, 22 GND layer, 23 Dielectric layer, 24 Wiring layer, 25 Connecting electrode, 31 Single-line region, 32 Propagation mode conversion region, 33 Common mode filter region, 34 Conversion structure region, 41 Common mode filter structure, 42 EBG structure, 43 Connecting electrode, 51-53 Conductor layers, 61 Differential patch antenna, 62 Uniplanar EBG

Claims

1. A differential line conversion structure comprising: a single line on which one wire is laid; a differential line on which two wires are laid substantially parallel to each other; a propagation mode conversion region that converts the propagation mode of a signal input to the differential line at a connection point where one of the wires constituting the differential line is electrically connected to the wire constituting the single line; and a filter structure arranged on the differential line side adjacent to the propagation mode conversion region to suppress the propagation of common mode to the differential line.

2. The differential line conversion structure according to claim 1, wherein, at the interface where the single line and the differential line are provided, the other wiring constituting the differential line is arranged in close proximity to one of the wiring constituting the differential line, and the other wiring constituting the differential line is grounded to ground potential.

3. The differential line conversion structure according to claim 1, wherein the filter structure is provided in a region that includes the interface on which the differential line is provided, or the interface on which the single line and the differential line are provided.

4. The differential line conversion structure according to claim 1, wherein the filter structure is provided such that a portion of it superimposes on the propagation mode conversion region.

5. The differential line conversion structure according to claim 1, wherein the filter structure and the differential line connected to the filter structure are arranged to any length.

6. The differential line conversion structure according to claim 1, wherein the filter structure is configured by periodically arranging a plurality of EBG (Electromagnetic Band Gap) structures, which are structures having band gap characteristics.

7. The differential line conversion structure according to claim 6, wherein the number of EBG structures to be installed is set according to the characteristics required for the filter structure.

8. The differential line conversion structure according to claim 1, wherein the single line and the differential line are provided on the upper surface of the dielectric layer, and the filter structure is located inside the dielectric layer and below the differential line.

9. The differential line conversion structure according to claim 1, wherein the single line and the differential line are provided inside the dielectric layer.

10. The differential line conversion structure according to claim 9, wherein the filter structure is positioned above the differential line.

11. The differential line conversion structure according to claim 1, wherein the filter structure can be formed in any shape and is positioned above, below, to the left, or to the right of the differential line.

12. An antenna device comprising: a single line with one wire laid out; a differential line with two wires laid out substantially parallel to each other; a propagation mode conversion region that converts the propagation mode of a signal input to the differential line at a connection point where one of the wires constituting the differential line is electrically connected to the wire constituting the single line; a filter structure arranged on the differential line side adjacent to the propagation mode conversion region to suppress the propagation of common mode to the differential line; and an antenna connected to the differential line.

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