Antenna device

Abstract

To reduce influence on antenna characteristics due to mounting of a circuit element, and to prevent short circuit of the circuit element.SOLUTION: The antenna device 1 includes a film 101, an antenna element 11, a detection resistor 20, a resistance wiring section 30, and a coaxial cable 40. The antenna element 11 has a radiation element 12 and a GND element 13 formed on a film 101. The detection resistor 20 is mounted on the film 101 and connected to the GND element 13. The resistance wiring section 30 is connected to the detection resistor 20 and the radiation element 12. One end of the coaxial cable 40 is connected to the communication module, a core wire 41 at the other end is connected to the radiation element 12, and an external conductor 43 at the other end is connected to the GND element 13.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an antenna device. [Background technology]

[0002] Conventionally, antenna devices equipped with film antennas have been known, and are built into vehicle door mirror devices, etc. Film antennas are antennas in which a metal foil antenna element is formed on an insulating film. The antenna element of the film antenna is electrically connected to an on-board communication module via a coaxial cable.

[0003] Also, an antenna device is known that includes an antenna element and a detection resistor for detecting whether the antenna element is connected to an in-vehicle electronic device (see Patent Document 1). The antenna element is housed in an antenna case. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7002340 Summary of the Invention [Problem to be solved by the invention]

[0005] There is a demand for mounting a sensing resistor on a film antenna. However, if the sensing resistor is close to the power feed point of the core wire of the coaxial cable, the core wire and the sensing resistor may come into contact and cause a short circuit. Conversely, if the sensing resistor is placed too far from the power feed point, the antenna characteristics of the film antenna may change significantly, and in some cases, the antenna characteristics may deteriorate.

[0006] An object of the present invention is to reduce the influence of the mounting of circuit elements such as a sensing resistor on antenna characteristics and to prevent short circuits of the circuit elements. [Means for solving the problem]

[0007] In order to solve the above problems, the antenna device of the present invention comprises: Film and an antenna element having a radiating element and a ground element formed on the film; a circuit element mounted on the film and connected to the ground element; a circuit element wiring portion connected to the circuit element and the radiating element; a coaxial cable having one end connected to the communication module, a core wire at the other end connected to the radiating element, and an outer conductor at the other end connected to the ground element.

[0008] Moreover, the antenna device of the present invention comprises: Film and an antenna element having a radiating element and a ground element formed on the film; a circuit element mounted on the film and connected to the radiating element and the ground element; a coaxial cable having one end connected to a communication module, a core wire at the other end connected to the radiating element, and an outer conductor at the other end connected to the ground element; The circuit element is disposed at a position offset in a direction perpendicular to the axial direction of the core wire. [Effects of the Invention]

[0009] According to the present invention, it is possible to reduce the influence of the mounted circuit element on the antenna characteristics and to prevent short circuits of the circuit element. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a plan view showing an antenna device according to an embodiment of the present invention; [Figure 2] FIG. 1 is a perspective view showing an antenna device having a waterproof structure. [Figure 3] FIG. 2 is a plan view showing the surrounding area of ​​a sensing resistor of the antenna device. [Figure 4]2 is a plan view showing the peripheral area of ​​the tip of the coaxial cable of the antenna device. FIG. [Figure 5] 10 is a diagram showing the VSWR frequency characteristics of an antenna device in which the length of the resistive wiring portion is changed. FIG. [Figure 6] 2 is a plan view showing the peripheral area of ​​the tip of the coaxial cable of the antenna device. FIG. [Figure 7] 10 is a diagram showing the VSWR frequency characteristics of an antenna device in which the length of the resistive wiring portion is changed. FIG. [Figure 8] 2 is a plan view showing the peripheral area of ​​the tip of the coaxial cable of the antenna device. FIG. [Figure 9] 10 is a diagram showing the VSWR frequency characteristics of an antenna device without a sensing resistor, an antenna device without a resistive wiring portion, and an antenna device with an L-shaped resistive wiring portion. FIG. [Figure 10] FIG. 10 is a perspective view showing the overall configuration of an antenna device according to a first modified example. [Figure 11] FIG. 10 is a perspective view showing the peripheral area of ​​the tip end of a coaxial cable of an antenna device according to a first modified example. [Figure 12] 10 is a plan view showing the peripheral area of ​​the tip end of the coaxial cable of the antenna device of the second modified example. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment and first and second modifications of the present invention will be described in detail with reference to the accompanying drawings, however, the scope of the invention is not limited to the illustrated examples.

[0012] (Embodiment) An embodiment of the present invention will be described with reference to Figs. 1 to 9. First, the overall device configuration of this embodiment will be described with reference to Figs. 1 and 2. Fig. 1 is a plan view showing an antenna device 1 of this embodiment. Fig. 2 is a perspective view showing the antenna device 1 having a waterproof structure 50.

[0013] As shown in FIG. 1, the antenna device 1 is an in-vehicle film antenna device that can be stored in a small space. The antenna device 1 is disposed, for example, on a bracket (not shown) inside a door mirror device (not shown) of a vehicle such as an automobile. The bracket is a molded integral part made of a resin such as ABS (Acrylonitrile Butadiene Styrene) resin as a dielectric. The wireless communication method of the antenna device 1 is cellular communication. The cellular communication is assumed to be communication in the frequency bands of 3G (Generation), 4G, and 5G (including Sub6). The frequency band for cellular communication is approximately 617 MHz to 6 GHz.

[0014] The placement (storage) of the antenna device 1 is not limited to the door mirror device, but may be in a space inside or outside the vehicle, such as the dashboard of the vehicle. The wireless communication method of the antenna device 1 is not limited to cellular communication.

[0015] The antenna device 1 includes a film antenna 10, a detection resistor 20, a resistive wiring section 30, a coaxial cable 40, and a waterproof structure section 50 (FIG. 2). As shown in FIG. 1, the x-axis, y-axis, and z-axis are defined. The plane of the film antenna 10 is defined as the xy plane. The axial direction on the surface side perpendicular to the plane of the film antenna 10 is defined as the +z direction. These three axes are the same in other figures.

[0016] The film antenna 10 includes a film section 100 and an antenna element 11. The film section 100 includes a film 101 and a resist 102. The film 101 is a single film made of an insulating (dielectric) resin such as polyimide, and is laminated on the back surface of the antenna element 11 to cover the antenna element 11 from below. The film 101 supports and protects the antenna element 11. The film antenna 10 is bendable. The antenna element 11 and the film 101 have a resist 102 formed on the upper layer (surface) thereof. However, in an area AR1 surrounded by a dotted line in FIG. 1 and where a waterproof structure 50 (described later) is attached, the resist 102 is not formed only at the lands where the core wire 41 and outer conductor 43 of the coaxial cable 40 are soldered and at the soldered portion of the sensing resistor 20. In the area AR1 where the resist 102 is not formed, the antenna element 11 is exposed on the surface.

[0017] Antenna element 11 has a radiating element 12 and a GND element (ground element) 13. Radiating element 12 is an antenna element of a dipole antenna that receives radio waves and passes an antenna current. Radiating element 12 has an antenna wiring portion 121. Antenna wiring portion 121 is a wiring portion that extends toward GND element 13 (in the -y direction) for connection to coaxial cable 40. GND element 13 is an antenna element that is grounded.

[0018] The detection resistor 20 is a chip resistor. The detection resistor 20 is a resistor for detecting that the antenna device 1 is connected to an in-vehicle communication module (not shown) such as a TCU (Telematics Control Unit). The detection resistor 20 is electrically connected between the antenna wiring section 121 and the GND element 13. The resistive wiring section 30 is a wiring section disposed between the detection resistor 20 and the antenna wiring section 121. The resistive wiring section 30 is formed integrally with the antenna wiring section 121, for example. FIG. 1 shows an L-shaped resistive wiring section 30 as an example.

[0019] The coaxial cable 40 has a core 41, an insulator 42, an outer conductor 43, and a covering layer 44. The core 41 is a metal wire such as a single copper wire, and carries the antenna current. The insulator 42 is an insulating layer such as polyethylene that concentrically covers the core 41 in an axial cross section. The outer conductor 43 is a metal wire such as a braided copper wire that concentrically covers the axial cross section of the insulator 42. The outer conductor 43 is at ground potential, blocking external electromagnetic waves and preventing noise from being carried over the signals flowing through the core 41. The covering layer 44 is an insulator such as vinyl that concentrically covers the axial cross section of the outer conductor 43, and protects the inside of the coaxial cable 40.

[0020] The core wire 41 at one end of the coaxial cable 40 is electrically connected to the antenna wiring section 121 by solder or the like. The point where the core wire 41 is connected to the antenna wiring section 121 is defined as a feed point A. Similarly, the outer conductor 43 at one end is electrically connected to the GND element 13 by solder or the like. The area AR1 includes the tip of the coaxial cable 40 including the connected core wire 41 and outer conductor 43, the detection resistor 20, and the resistive wiring section 30.

[0021] The other end of the coaxial cable 40 is connected to a communication module. The communication module detects the value of a current flowing through the detection resistor 20 when, for example, a DC voltage is applied to the antenna device 1 via the coaxial cable 40. The communication module detects whether the antenna device 1 is connected or not based on the detection result of the current value.

[0022] 2, the waterproof structure 50 has an upper case 51, a lower case 52, an upper gasket 54, and a lower gasket 55. The upper case 51 has a waterproof rib 53. Note that the antenna pattern of the film antenna 10 is not shown in FIG.

[0023] The upper case 51 is a resin case that covers the film antenna 10 including the area AR1, the tip of the coaxial cable 40, etc. from the +z direction. The lower case 52 is a resin case that covers the film antenna 10 including the area AR1, the tip of the coaxial cable 40, etc. from the -z direction. A screw S1 that passes through a hole 14 drilled in the film antenna 10 from the lower case 52 is screwed into a female screw (not shown) in the upper case 51. As a result, the upper case 51 and the lower case 52 function as an integrated, approximately rectangular parallelepiped case. At this time, the upper case 51 is positioned with respect to the film antenna 10 by inserting a protrusion (not shown) into a hole 15 drilled in the film antenna 10.

[0024] The waterproof rib 53 is a rib that surrounds and waterproofs the components and wiring patterns in an area AR1 on the front side (+z direction side) of the film antenna 10. Note that the lower case 52 has a waterproof rib (not shown) that surrounds and waterproofs the components in a predetermined area on the back side (-z direction side) of the film antenna 10, similar to the waterproof rib 53. The upper gasket 54 is a gasket made of an elastic material such as silicone that is disposed within the upper case 51 and covers the base portion of the tip of the coaxial cable 40 from the +z direction. The lower gasket 55 is a gasket made of an elastic material such as silicone that is disposed within the lower case 52 and covers the base portion of the tip of the coaxial cable 40 from the -z direction. The upper gasket 54 and the lower gasket 55 waterproof the components and wiring patterns in the area AR1 against water and the like from the -x direction.

[0025] Next, an antenna device 1a will be described as a configuration in which the resistive wiring portion 30 is not included in the antenna device 1 with reference to Fig. 3. Fig. 3 is a plan view showing the peripheral area of ​​the sensing resistor 20 of the antenna device 1a.

[0026] The antenna device 1a includes a film antenna 10a, which is a film antenna 10 without a resistive wiring section 30. Consider the appropriate placement of the sensing resistor 20 in the antenna device 1a. The film antenna 10a includes an antenna wiring section 121 and a GND element 13a. The connection between the core wire 41 and the antenna wiring section 121 is a feed point A. As viewed from the feed point A, the +x-side end of the antenna wiring section 121 is defined as point B on an extension of the axial direction of the core wire 41 (dotted line in FIG. 3 ) in the +x direction. The −x-side end of the GND element 13a is defined as point C on an extension of the axial direction from the feed point A in the +x direction. From the perspective of antenna characteristics, it is appropriate to mount the sensing resistor 20 between points B and C. The reason for aligning the axial direction of the coaxial cable 40 with the sensing resistor 20 on the y-axis is that the waterproof structure 50 becomes smaller in size compared to when the axial direction is shifted, and to prevent the waterproof structure 50 from becoming complicated. Furthermore, since the sensing resistor 20 on the axial direction is closer to the feeding point A, the change in the antenna characteristics is smaller compared to a configuration in which the sensing resistor 20 is not provided.

[0027] Furthermore, if the sensing resistor is placed too far away from the power feed point A, the antenna characteristics will change significantly, and in some cases, the antenna characteristics will deteriorate. For this reason, the sensing resistor 20 is placed between points B and C, which are relatively close to the power feed point A. However, if the sensing resistor 20 is mounted between points B and C, there is a risk that the core wire 41 and the sensing resistor 20 will come into contact with each other during soldering, etc., and a short circuit will occur.

[0028] Next, referring to Figures 4 and 5, an antenna device 1b having a configuration in which the antenna device 1 has a linear resistive wiring portion 30 will be described. Figure 4 is a plan view showing the peripheral area of ​​the tip of the coaxial cable 40 of the antenna device 1b. Figure 5 is a diagram showing the frequency characteristics of the VSWR (Voltage Standing Wave Ratio) of the antenna device 1b when the length L of the resistive wiring portion 30b is changed.

[0029] 4, the antenna device 1b includes a film antenna 10b, a detection resistor 20, a resistive wiring portion 30b, and a coaxial cable 40. The film antenna 10b includes a film portion 100, and an antenna element 11 including a radiating element 12 and a GND element 13b. The GND element 13b has the same configuration as the GND element 13, and is shaped such that the area corresponding to the resistive wiring portion 30b is missing.

[0030] The resistive wiring portion 30b is a linear wiring and is formed integrally with the antenna wiring portion 121. The resistive wiring portion 30b is electrically connected to the end of the antenna wiring portion 121 on the +x direction side and to the detection resistor 20. The connection position between the resistive wiring portion 30b and the antenna wiring portion 121 is defined as point B. The connection position between the resistive wiring portion 30b and the detection resistor 20 is defined as point B1. The length L of the resistive wiring portion 30b is the distance BB1 ​​in the x-axis direction between point B and point B1.

[0031] Here, consider an antenna device 1b in which the length L of the resistive wiring portion 30b is changed to 1, 3, 5, 7, 9, 10, 15, and 20 mm. As shown in Figure 5, the VSWR versus frequency was simulated as the antenna characteristics of the antenna device 1b for each length L. In this case, the resistance value of the detection resistor 20 was set to 10 kΩ.

[0032] In the 3 to 4.5 GHz frequency band required for cellular communications, a significant change was observed when L = 9 mm. The longer the resistive wiring section 30b is, the further away it is from the feed point A, the greater the change in antenna characteristics. When implementing a 10 kΩ sensing resistor 20, good antenna characteristics can be obtained by setting 3 mm ≦ L < 9 mm. The lower limit of the length L range, 3 mm, is based on the required safety distance of approximately 3 mm to prevent contact between the core wire 41 and the sensing resistor 20 when soldering the coaxial cable 40.

[0033] Next, referring to Fig. 6 and Fig. 7, an antenna device 1c having an L-shaped resistive wiring portion 30 in the antenna device 1 will be described. Fig. 6 is a plan view showing the peripheral area of ​​the tip of the coaxial cable 40 of the antenna device 1c. Fig. 7 is a diagram showing the VSWR frequency characteristics of the antenna device 1c when the length L of the resistive wiring portion 30c is changed.

[0034] 6, the antenna device 1c includes a film antenna 10c, a detection resistor 20, a resistive wiring portion 30c, and a coaxial cable 40. The film antenna 10c has a film portion 100, and an antenna element 11 including a radiating element 12 and a GND element 13c. The GND element 13c has the same configuration as the GND element 13, and further has a shape lacking an area corresponding to the resistive wiring portion 30c.

[0035] The resistive wiring portion 30c is an L-shaped wiring and is formed integrally with the antenna wiring portion 121. The resistive wiring portion 30c is electrically connected to the end of the antenna wiring portion 121 on the +x direction side and the detection resistor 20. The connection position between the resistive wiring portion 30c and the antenna wiring portion 121 is defined as point B. The resistive wiring portion 30c extends in the +x direction from point B and the position where the extension direction changes to the -y direction is defined as point B1. The connection position between the resistive wiring portion 30c and the detection resistor 20 is defined as point B2. The length L of the resistive wiring portion 30c is the sum of the distance BB1 ​​of the straight portion 31c in the x-axis direction between point B and point B1 and the distance B1B2 (length L1) of the straight portion 32c in the y-axis direction between point B1 and point B2.

[0036] For example, if the sensing resistor 20 cannot be moved or rotated due to the constraints of the waterproof structure 50, the linear resistive wiring portion 30b may be replaced with an L-shaped resistive wiring portion 30c.

[0037] Consider an antenna device 1c in which the length L of the resistive wiring portion 30c is varied to 4, 6, 8, 10, and 13 mm. As shown in Figure 7, we simulated the VSWR versus frequency as the antenna characteristics of the antenna device 1c with each length L. Here, the resistance value of the sensing resistor 20 was set to 10 kΩ. Furthermore, due to the constraints of the waterproof structure 50, the distance BB1 ​​was fixed at 3 mm. The fixed value of the distance BB1 ​​is based on the waterproof constraints of the waterproof structure 50 and the process condition of approximately 3 mm to prevent contact between the core wire 41 and the sensing resistor 20 during soldering. The distance BB1 ​​was fixed at 3 mm, and the length L1 was varied to 1, 3, 5, 7, and 10 mm. The configuration with length L1 = 13 was excluded because the resistive wiring portion 30c would be electrically connected to the radiating element 12 and would not be within the impedance-adjustable area.

[0038] In the 3 to 4.5 GHz frequency band that must be guaranteed for cellular communications, large changes were observed when L1 was 10 mm or greater. The longer the resistive wiring section 30c was, and the farther it was from the feed point A, the greater the change in antenna characteristics. When implementing a 10 kΩ sensing resistor 20, good antenna characteristics can be obtained by setting 3 mm ≦ L < 13 mm (within the impedance adjustment area).

[0039] Next, a comparison will be made between an antenna device 1d having a configuration without a sensing resistor 20, an antenna device 1a, and an antenna device 1c with reference to Figures 8 and 9. Figure 8 is a plan view showing the area surrounding the tip of the coaxial cable 40 of the antenna device 1d. Figure 9 is a diagram showing the VSWR frequency characteristics of the antenna device 1d without a sensing resistor, the antenna device 1a without a resistive wiring portion, and the antenna device 1c having an L-shaped resistive wiring portion.

[0040] 8, the antenna device 1d includes a film antenna 10d and a coaxial cable 40. The film antenna 10d includes a film portion 100, and an antenna element 11 including a radiating element 12 and a GND element 13d. The GND element 13d has the same configuration as the GND element 13, and further has a shape that does not include the cutout regions (FIG. 1) corresponding to the detection resistor 20 and the resistive wiring portion 30.

[0041] Here, we consider antenna device 1d, antenna device 1a without a resistive wiring portion, and antenna device 1c with an L-shaped resistive wiring portion 30c. The length L1 of resistive wiring portion 30c was set to 3 [mm]. As shown in Figure 9, we simulated the VSWR versus frequency as the antenna characteristics of antenna devices 1d, 1a, and 1c. In this case, the resistance value of sensing resistor 20 was set to 10 [kΩ].

[0042] In the frequency band of 3 to 4.5 [GHz] that should be guaranteed for cellular communications, the antenna devices 1d, 1a, and 1c exhibited antenna characteristics with approximately the same VSWR.

[0043] 5 and 9, when a 10 kΩ sensing resistor 20 is implemented in the antenna device 1b, good antenna characteristics equivalent to those of the ideal antenna device 1a can be obtained by setting 3 mm ≦ L < 9 mm. As can be seen from FIGS. 7 and 9, when a 10 kΩ sensing resistor 20 is implemented in the antenna device 1c, good antenna characteristics equivalent to those of the ideal antenna device 1a can be obtained by setting 3 mm ≦ L < 13 mm.

[0044] As described above, according to this embodiment, the antenna device 1 includes the film 101, the antenna element 11, the sensing resistor 20, the resistive wiring section 30, and the coaxial cable 40. The antenna element 11 has the radiating element 12 and the GND element 13 formed on the film 101. The sensing resistor 20 is mounted on the film 101 and connected to the GND element 13. The resistive wiring section 30 is connected to the sensing resistor 20 and the radiating element 12. One end of the coaxial cable 40 is connected to the communication module, and the core wire 41 at the other end is connected to the radiating element 12, and the outer conductor 43 at the other end is connected to the GND element 13. Therefore, the resistive wiring section 30 can reduce the effect of the mounting of the sensing resistor 20 on the antenna characteristics and can prevent a short circuit between the coaxial cable 40 and the sensing resistor 20.

[0045] The antenna device 1 includes a waterproof structure 50 that surrounds and waterproofs an area AR1 that includes the tip of the coaxial cable 40 and the sensing resistor 20. This makes it possible to waterproof and protect the tip of the coaxial cable 40, the sensing resistor 20, and their wiring.

[0046] The circuit element of the antenna device 1 is a sensing resistor 20. Therefore, by detecting a current through the coaxial cable 40, it is possible to detect that the communication module and the antenna device 1 are connected.

[0047] The resistive wiring section 30 is a linear resistive wiring section 30b. This allows the resistive wiring section to be easily configured. The length L of the resistive wiring section 30b is equal to or greater than 3 mm and less than 9 mm. This ensures that the influence of the sensing resistor 20 on the antenna characteristics is reduced.

[0048] The resistive wiring section 30 is an L-shaped resistive wiring section 30c. This allows the resistive wiring section to be easily configured within, for example, the area AR1. The length L of the resistive wiring section 30c is equal to or greater than 3 mm and less than 13 mm. This ensures that the influence of the sensing resistor 20 on the antenna characteristics is reduced.

[0049] (First Modification) A first modified example of the above embodiment will be described with reference to Figures 10 and 11. Figure 10 is a perspective view showing the overall configuration of an antenna device 1e of this modified example. Figure 11 is a perspective view showing the area surrounding the tip of a coaxial cable 40 of the antenna device 1e.

[0050] An antenna device 1e of this modified example will be described with reference to Figures 10 and 11. The antenna device 1e includes a film antenna 10e, a sensing resistor 20, a coaxial cable 40, and a waterproof structure 50 (not shown). The film antenna 10e includes a film portion 100 and an antenna element 11e. The antenna element 11e includes a radiating element 12e and a GND element 13e. The antenna pattern of the radiating element 12e is different from that of the radiating element 12 of the above embodiment. The radiating element 12e includes an antenna wiring portion 121e.

[0051] The antenna wiring portion 121e extends from the +y direction to the -y direction and then extends in the -x direction halfway. The GND element 13e has the same configuration as the GND element 13 of the above embodiment, and has a shape that lacks a region corresponding to the antenna wiring portion 121e. The antenna device 1e does not have a resistive wiring portion, and is therefore a modified example of the antenna device 1a of the above embodiment.

[0052] The sensing resistor 20 is electrically connected to the end of the GND element 13e on the -y direction side and the end of the portion of the antenna wiring unit 121e extending in the -x direction on the +y direction side. In this way, the sensing resistor 20 is disposed at a position shifted in a direction perpendicular to the +x direction of the core 41 of the coaxial cable 40 (the y axis direction). This provides a greater distance between the core 41 and the sensing resistor 20 than in the antenna device 1a, preventing the occurrence of a short circuit.

[0053] Furthermore, the antenna wiring portion 121e has an extending portion that extends in the −x direction toward the feed point A of the core wire 41. The sensing resistor 20 is disposed so as to be electrically connected to the extending portion. This makes it easy to adjust the distance between the feed point A and the sensing resistor 20, and the sensing resistor 20 is disposed at a position where good antenna characteristics are achieved.

[0054] As described above, according to the first modification, the antenna device 1e includes the film 101, the antenna element 11e, the sensing resistor 20 as a circuit element, and the coaxial cable 40. The antenna element 11e has a radiating element 12e and a GND element 13e formed on the film 101. The sensing resistor 20 is mounted on the film 101 and connected to the radiating element 12e and the GND element 13e. The coaxial cable 40 has one end connected to the communication module, a core 41 at the other end connected to the radiating element 12e, and an outer conductor 43 at the other end connected to the GND element 13e. The sensing resistor 20 is positioned offset in the y-axis direction, which is orthogonal to the axial direction of the core 41. Therefore, the positioning of the sensing resistor 20 can reduce the effect of the mounting of the sensing resistor 20 on the antenna characteristics and can prevent a short circuit between the coaxial cable 40 and the sensing resistor 20.

[0055] The radiating element 12e also has an antenna wiring portion 121e extending in the axial direction of the core wire 41. The sensing resistor 20 is connected to the antenna wiring portion 121e (portion extending in the -x direction) and the GND element 13e. This makes it easy to adjust the distance between the feeding point A and the sensing resistor 20, and the sensing resistor 20 can be easily disposed in a favorable position that reduces the impact of the mounting on the antenna characteristics.

[0056] (Second Modification) A second modification of the above embodiment will be described with reference to Fig. 12. Fig. 12 is a plan view showing the area around the tip of the coaxial cable 40 of an antenna device 1f of this modification.

[0057] An antenna device 1f of this modified example will be described with reference to Fig. 12. The antenna device 1f includes a film antenna 10f, a sensing resistor 20, a coaxial cable 40, and a waterproof structure 50 (not shown). The film antenna 10f includes a film part 100 and, as antenna elements, a radiating element 12f and a GND element 13f. The antenna pattern of the radiating element 12f differs from that of the radiating element 12 of the above embodiment. The radiating element 12f includes an antenna wiring part 121f.

[0058] The antenna wiring portion 121f extends from the +y direction side to approximately the -y direction and then extends in the +x direction midway. The GND element 13f has the same configuration as the GND element 13 of the above embodiment, and has a shape that lacks a region corresponding to the antenna wiring portion 121f. The antenna device 1f does not have a resistive wiring portion, and is therefore a modified example of the antenna device 1a of the above embodiment.

[0059] In the xy plane within the area AR1 for the waterproof structure 50, the resist 102 is not formed only at the lands where the core wire 41 and outer conductor 43 of the coaxial cable 40 are soldered and at the soldered portion of the sensing resistor 20. In the parts of the area AR1 where the resist 102 is not formed, the antenna wiring part 121f or the GND element 13f is exposed on the surface. In the xy plane outside the area AR1, the resist 102 of the film part 100 is formed on the radiating element 12f, the GND element 13f, and the film 101.

[0060] The sensing resistor 20 is electrically connected to the end of the GND element 13f on the -y direction side and the end of the antenna wiring portion 121f on the +y direction side of the portion extending in the +x direction. Furthermore, a thermal cutoff portion 60 is formed around the sensing resistor 20. The thermal cutoff portion 60 is a portion where there is no conductor (copper foil) formed near each of the four vertices of the rectangular sensing resistor 20. The thermal cutoff portion 60 ensures that the heat generated from the sensing resistor 20 is transmitted equally in all four directions. Therefore, the thermal cutoff portion 60 can prevent defects such as floating of the sensing resistor 20 due to heat generated by the sensing resistor 20.

[0061] As described above, according to the second modification, in the antenna device 1f, the heat-cutting portion 60 is formed around the sensing resistor 20. This makes it possible to prevent problems such as the sensing resistor 20 floating.

[0062] The above-described embodiment and modifications are merely examples of the antenna device according to the present invention, and the present invention is not limited to these. For example, the present invention may be configured by appropriately combining at least two of the above-described embodiment and the first and second modifications.

[0063] In addition, in the antenna devices of the above-described embodiment and modified example, the sensing resistor 20 is mounted on the film antenna as a circuit element, but this is not limited to this. The antenna device may also be configured so that other circuit elements, such as a capacitor or inductor, are mounted on the film antenna. The capacitor or inductor is provided, for example, to adjust the impedance of the antenna device.

[0064] Furthermore, the detailed configurations and operations of the antenna devices 1 (1b to 1f) in the above-described embodiments and modifications can also be modified as appropriate without departing from the spirit of the present invention. [Explanation of symbols]

[0065] 1, 1a, 1b, 1c, 1d, 1e, 1f Antenna device 10, 10a, 10b, 10c, 10d, 10e, 10f Film Antenna 100 film units 101 Film 102 Resist 11,11e antenna element 12, 12e, 12f Radiating elements 121, 121e, 121f Antenna wiring section 13, 13a, 13b, 13c, 13d, 13e, 13f GND elements 14,15 holes 20 Sense resistor 30,30b,30c Resistor wiring section 31c,32c Straight section 40 Coaxial Cable 41 Core Wire 42 Insulators 43 Outer conductor 44 Covering layer 50 Waterproof structure 51 Upper case 52 Lower case 53 Waterproof Rib 54 Upper gasket 55 Lower gasket S1 screw 60 Heat cutting section AR1 area A Power supply point

Claims

1. Film and an antenna element having a radiating element and a ground element formed on the film; a circuit element mounted on the film and connected to the ground element; a circuit element wiring portion connected to the circuit element and the radiating element; an antenna device comprising: a coaxial cable having one end connected to a communication module, a core wire at the other end connected to the radiating element, and an outer conductor at the other end connected to the ground element;

2. The antenna device according to claim 1 , wherein the circuit element wiring portion is linear.

3. 3. The antenna device according to claim 2, wherein the length of the circuit element wiring portion is equal to or greater than 3 mm and less than 9 mm.

4. The antenna device according to claim 1 , wherein the circuit element wiring portion is L-shaped.

5. 5. The antenna device according to claim 4, wherein the length of the circuit element wiring portion is equal to or greater than 3 mm and less than 13 mm.

6. Film and an antenna element having a radiating element and a ground element formed on the film; a circuit element mounted on the film and connected to the radiating element and the ground element; a coaxial cable having one end connected to a communication module, a core wire at the other end connected to the radiating element, and an outer conductor at the other end connected to the ground element; The antenna device wherein the circuit element is disposed at a position offset in a direction perpendicular to the axial direction of the core wire.

7. the radiating element has an antenna wiring portion extending in the axial direction of the core wire, The antenna device according to claim 6 , wherein the circuit element is connected to the antenna wiring portion and the ground element.

8. The antenna device according to claim 1 , wherein the circuit element is a resistor.

9. The antenna device according to claim 1 , further comprising a waterproof structure that surrounds and waterproofs an area including the tip end of the coaxial cable and the circuit element.

10. The antenna device according to claim 1 , wherein a heat cut portion is formed around the circuit element.

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