Planar heat generation body

Abstract

Provided is a planar heat generation body that is capable of assuredly melting accreted snow which hinders radio waves and supports dual-polarization communication. The planar heat generation body is arranged along a transmissive plane through which radio waves from an antenna are transmitted, and comprises: a first layer grid-like body which has a plurality of first layer resistive parts and a plurality of first layer sub-electrodes, and in which the plurality of first layer resistive parts and the plurality of first layer sub-electrodes are arranged in a grid shape; and a second layer grid-like body which has a plurality of second layer resistive parts and a plurality of second layer sub-electrodes, and in which the plurality of second layer resistive parts and the plurality of second layer sub-electrodes are arranged in a grid shape. The plurality of first layer resistive parts and the plurality of second layer sub-electrodes are arranged in a manner overlapping each other in a transmissive plan view. The plurality of first layer sub-electrodes and the plurality of second layer resistive parts are arranged in a manner overlapping each other in the transmissive plan view.

Description

Planar heating element

[0001] The present invention relates to a sheet heating element.

[0002] When snow accumulates on millimeter-wave communication base station antennas, it causes radio wave attenuation, reducing radio wave penetration. To prevent this reduction in radio wave penetration, it is necessary to thoroughly melt the snow that blocks radio waves.

[0003] Furthermore, in urban areas, mountainous regions, and other places where radio waves are prone to diffuse reflection, the signal strength of the radio waves from communication base station antennas can vary greatly depending on the direction of polarization of the radio waves. Therefore, the transmitting antenna transmits signals using both vertical and horizontal polarization, and the receiving antenna selectively uses the stronger radio wave signal or combines the signals to communicate (polarization diversity).

[0004] As described above, communication base station antennas are required to reliably melt snow that blocks radio waves and to support dual polarized wave communication in order to prevent a decrease in radio wave transparency.

[0005] For example, Patent Document 1 discloses a planar heating element that includes a pair of electrodes arranged opposite each other and resistors (heat generating portions) arranged in a mesh pattern between the pair of electrodes.

[0006] Furthermore, for example, Patent Document 2 discloses a planar heating element that includes a resistor (heat generating portion) that applies or impregnates a conductive solution onto a mesh-like substrate formed by weaving vertical fiber material and horizontal transition material into a mesh-like structure at predetermined intervals, and a pair of electrodes arranged at the vertical ends of the mesh-like substrate.

[0007] Japanese Utility Model Registration No. 3149883 International Publication No. 2008 / 023447

[0008] Incidentally, the planar heating elements described in Patent Documents 1 and 2 each have heating wires arranged in a mesh pattern, so that the impedances seen from vertical waves and horizontal waves are the same.

[0009] However, the planar heating elements described in Patent Documents 1 and 2 each use hot wires to generate heat, and therefore are unable to control their own temperature, requiring an external temperature control circuit, which increases costs.

[0010] An object of the present invention is to provide a self-temperature-controlling planar heating element that can reliably melt snow that blocks radio waves and is compatible with dual-polarized wave communication.

[0011] In order to achieve the above object, the sheet heating element of the present invention is a sheet heating element arranged along a transmission plane through which radio waves from an antenna pass, and comprises: a first-layer grid having a plurality of first-layer resistance portions and a plurality of first-layer sub-electrodes, the plurality of first-layer resistance portions and the plurality of first-layer sub-electrodes being arranged in a grid pattern; and a second-layer grid having a plurality of second-layer resistance portions and a plurality of second-layer sub-electrodes, the plurality of second-layer resistance portions and the plurality of second-layer sub-electrodes being arranged in a grid pattern, wherein the plurality of first-layer resistance portions and the plurality of second-layer sub-electrodes are arranged so as to overlap each other in the transmission plane view, and the plurality of first-layer sub-electrodes and the plurality of second-layer resistance portions are arranged so as to overlap each other in the transmission plane view.

[0012] According to the present invention, snow that blocks radio waves can be reliably melted and dual polarized wave communication can be supported.

[0013] FIG. 1 is a diagram showing horizontally polarized waves. FIG. 2 is a diagram showing vertically polarized waves. FIG. 3 is an explanatory diagram of a sheet heating element in a comparative example. FIG. 4 is a diagram showing reflection and transmission characteristics when horizontally polarized waves are incident on a sheet heating element in a comparative example. FIG. 5 is a diagram showing reflection and transmission characteristics when vertically polarized waves are incident on a sheet heating element in a comparative example. FIG. 6 is an exploded perspective view showing a sheet heating element in an embodiment of the present invention. FIG. 7 is a front view showing a first layer unit in an embodiment of the present invention. FIG. 8 is a front view showing a first layer unit and an insulating layer in an embodiment of the present invention. FIG. 9 is a front view showing a first layer unit, a second layer unit, and an insulating layer in an embodiment of the present invention. FIG. 10 is a partially enlarged view of FIG. 9.

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a comparative sheet heating element will be described with reference to FIGS. 1 to 4 for comparison with the sheet heating element of the present invention.

[0015] Fig. 1 is a diagram showing horizontally polarized waves. In the horizontally polarized waves shown in Fig. 1, the electric field direction is parallel to the ground, and radio waves oscillate in the horizontal direction. Fig. 2 is a diagram showing vertically polarized waves. In the vertically polarized waves shown in Fig. 2, the electric field direction is perpendicular to the ground, and radio waves oscillate in the vertical direction.

[0016] Figure 3 is an explanatory diagram of a sheet heating element in a comparative example. The sheet heating element shown in Figure 3 is a heater for a radar cover with a snow-melting function. Since the polarization direction of the radio waves is fixed in the heater shown in Figure 3, the metal heating wire is arranged so that it is perpendicular to the polarization direction to minimize radio wave attenuation by the metal heating wire. The transmission plane through which the radio waves of the antenna pass is shown by a dashed line in Figure 3. As shown in Figure 3, the metal heating wire 1 is arranged so that it extends in the perpendicular direction (perpendicular to the polarization direction) in the region of the transmission plane 2a in the base film 2. Terminals 3 and 4 are electrically connected to both ends of the metal heating wire, respectively.

[0017] Figure 4 is a diagram showing the reflection and transmission characteristics when horizontally polarized waves are incident on a sheet heating element (see Figure 3) in a comparative example. The horizontal axis of Figure 4 represents frequency (GHz), and the vertical axis represents signal strength (dB). Also in Figure 4, the transmitted wave is shown by a solid line, and the reflected wave is shown by a dashed line. As shown in Figure 4, the signal strength of the transmitted wave is almost constant across the entire frequency band, while the signal strength of the reflected wave drops at one frequency and in the vicinity of that frequency.

[0018] Figure 5 is a diagram showing the reflection and transmission characteristics when a vertically polarized wave is incident on a sheet heating element (see Figure 3) in a comparative example. The horizontal axis of Figure 5 represents frequency (GHz), and the vertical axis represents signal strength (dB). Also, Figure 5 shows the transmitted wave with a solid line and the reflected wave with a dashed line. As shown in Figure 5, the signal strength of the transmitted wave is almost constant across the entire frequency band, while the signal strength of the reflected wave drops at two frequencies and in the vicinity of those frequencies.

[0019] For these reasons, the reflection and transmission characteristics when vertically polarized waves are incident on the planar heating element in the comparative example (see Figure 3) differ from those when horizontally polarized waves are incident. Base station heaters are used for both vertically and horizontally polarized waves (polarization diversity). From the technical standpoint of polarization diversity, it is required that the reflection and transmission characteristics be equal for both vertically polarized waves and horizontally polarized waves.

[0020] The sheet heating element 100 according to the embodiment of the present invention is configured to have equal reflection and transmission characteristics in both the vertically polarized and horizontally polarized directions. Fig. 6 is an exploded perspective view showing the sheet heating element according to the embodiment of the present invention. Fig. 7 is a front view showing the first layer unit according to the embodiment of the present invention.

[0021] 6 shows the radio wave propagation direction, the electric field direction in which the radio waves oscillate horizontally relative to the ground (horizontal direction), and the electric field direction in which the radio waves oscillate vertically relative to the ground (vertical direction). As shown in Fig. 6, the base film 2, the first layer unit 10U, the insulating layer 30, the second layer unit 20U, the adhesive layer 5 (double-sided tape), and the resin case 6 are arranged in the radio wave propagation direction of the antenna ANT.

[0022] 6 and 7 , the sheet heating element 100 according to the embodiment of the present invention comprises a first layer unit 10U, a second layer unit 20U, and an insulating layer 30. The sheet heating element 100 is disposed between a base film 2 and an adhesive layer 5, and is attached to a resin case 6 by the adhesive layer 5. The base film 2 is disposed along a transmission plane 2a through which radio waves from the antenna ANT pass. As a result, the sheet heating element 100 is also disposed along the transmission plane 2a.

[0023] (First layer unit 10U, second layer unit 20U) The first layer unit 10U includes a first layer grid 10, a first layer main anode 15, and a first layer main cathode 16. The second layer unit 20U includes a second layer grid 20, a second layer main anode 25, and a second layer main cathode 26. In the following description, the terms "vertical and horizontal grid," "vertical and horizontal grid shape," and "vertical and horizontal grid shape" will be simply referred to as "grid," "grid shape," and "grid shape."

[0024] (First Layer Grid 10) The first layer grid 10 includes a plurality of first-layer resistors 14 and a plurality of first-layer sub-electrodes 11. The plurality of first-layer resistors 14 and the plurality of first-layer sub-electrodes 11 are arranged in a grid pattern. Specifically, the first-layer resistors 14 are PTC (Positive Temperature Coefficient) heaters, which have linearly connected compounds containing semiconductor particles, carbon particles, and the like, and whose electrical conductivity changes with temperature. The first-layer resistors 14 extend vertically. The plurality of first-layer resistors 14 are arranged horizontally at predetermined intervals. The predetermined intervals at which the plurality of first-layer resistors 14 are arranged are determined, for example, based on the results of experiments or simulations. The predetermined intervals at which the plurality of first-layer resistors 14 are arranged are the same as the intervals at which the plurality of second-layer resistors 24 are arranged. Figure 10 shows the predetermined intervals W at which the plurality of second-layer resistors 24 are arranged.

[0025] The first-layer sub-electrodes 11 are, for example, conductive electrodes having a linear shape. The first-layer sub-electrodes 11 extend horizontally. The multiple first-layer sub-electrodes 11 are arranged vertically at predetermined intervals. The line width of the first-layer sub-electrodes 11 and the predetermined intervals at which the multiple first-layer sub-electrodes 11 are arranged are determined, for example, based on the results of experiments or simulations. The multiple first-layer sub-electrodes 11 include two or more first-layer sub-anodes 12 and two or more first-layer sub-cathodes 13. Specifically, the six first-layer sub-anodes 12 are arranged vertically at predetermined intervals and extend horizontally from the first-layer main anode 15 toward the transmitting plane 2a. The six first-layer sub-cathodes 13 are arranged vertically at predetermined intervals and extend horizontally from the first-layer main cathode 16 toward the transmitting plane 2a.

[0026] 6 and 7, twelve first-layer resistors 14, six first-layer secondary anodes 12, and six first-layer secondary cathodes 13 (a total of twelve first-layer secondary electrodes 11) are arranged in a grid pattern. Note that the respective numbers of first-layer resistors 14, first-layer secondary anodes 12, and first-layer secondary cathodes 13 are not limited to these numbers and can be determined, for example, based on the results of experiments or simulations.

[0027] (First-layer main anode 15, first-layer main cathode 16) The first-layer main anode 15 is formed in an elongated shape from a conductive material. The first-layer main anode 15 is disposed outside the transmitting plane 2a and extends in the vertical direction along the transmitting plane 2a. The base ends of each of the multiple (six in this embodiment) first-layer sub-anodes 12 are electrically connected to the first-layer main anode 15.

[0028] The first-layer main cathode 16 is made of a conductive material and has an elongated shape. The first-layer main cathode 16 is disposed outside the transmitting flat surface 2 a and extends in a vertical direction along the transmitting flat surface 2 a. The base ends of the plurality of first-layer sub-cathodes 13 (six in this embodiment) are electrically connected to the first-layer main cathode 16. The first-layer main anode 15 and the first-layer main cathode 16 are disposed to face each other with the transmitting flat surface 2 a between them.

[0029] (Second-layer grid 20) The second-layer grid 20 has a plurality of second-layer resistors 24 and a plurality of second-layer sub-electrodes 21. The second-layer resistors 24 and the second-layer sub-electrodes 21 are arranged in a grid pattern. Specifically, as shown in FIG. 6 , the second-layer resistors 24 are PTC element heaters having a linear shape, similar to the first-layer resistors 14. The second-layer resistors 24 extend horizontally. The second-layer resistors 24 are arranged vertically at a predetermined interval. The predetermined interval is set, for example, based on the results of experiments or simulations.

[0030] Like the first-layer sub-electrodes 11, the second-layer sub-electrodes 21 are conductive electrodes having a linear shape. The second-layer sub-electrodes 21 extend vertically. The multiple second-layer sub-electrodes 21 are arranged horizontally at predetermined intervals. The line width of the second-layer sub-electrodes 21 and the predetermined intervals at which the multiple second-layer sub-electrodes 21 are arranged are determined, for example, based on the results of experiments or simulations. FIG. 10 shows the predetermined intervals W at which the multiple second-layer sub-electrodes 21 are arranged. The multiple second-layer sub-electrodes 21 include two or more second-layer sub-anodes 22 and two or more second-layer sub-cathodes 23. Specifically, the six second-layer sub-anodes 22 are arranged horizontally at predetermined intervals and extend vertically from the second-layer main anode 25 toward the transmitting plane 2a. The six second-layer sub-cathodes 23 are arranged horizontally at predetermined intervals and extend vertically from the second-layer main cathode 26 toward the transmitting plane 2a.

[0031] 6, twelve second-layer resistors 24, six second-layer secondary anodes 22, and six second-layer secondary cathodes 23 (a total of twelve second-layer secondary electrodes 21) are arranged in a grid pattern. Note that the respective numbers of second-layer resistors 24, second-layer secondary anodes 22, and second-layer secondary cathodes 23 are not limited to these numbers and can be determined, for example, based on the results of experiments or simulations.

[0032] (Second-layer main anode 25, second-layer main cathode 26) The second-layer main anode 25 is formed in an elongated shape from a conductive material. The second-layer main anode 25 is disposed outside the transmitting flat surface 2a and extends horizontally along the transmitting flat surface 2a. The base ends of the plurality of second-layer sub-anodes 22 (six in this embodiment) are electrically connected to the second-layer main anode 25.

[0033] The second-layer main cathode 26 is made of a conductive material and has an elongated shape. The second-layer main cathode 26 is disposed outside the transmitting flat surface 2 a and extends horizontally along the transmitting flat surface 2 a. The base ends of the plurality of second-layer sub-cathodes 23 (six in this embodiment) are electrically connected to the second-layer main cathode 26. The second-layer main anode 25 and the second-layer main cathode 26 are disposed to face each other with the transmitting flat surface 2 a between them.

[0034] (Mutual Positional Relationship Between First Layer Unit 10U and Second Layer Unit 20U) Fig. 8 is a front view showing the first layer unit and insulating layer in an embodiment of the present invention. Fig. 9 is a front view showing the first layer unit, second layer unit, and insulating layer in an embodiment of the present invention. First, the mutual positional relationship between the first layer unit 10U and the second layer unit 20U will be described with reference to Figs. 8 and 9, and then the insulating layer 30 will be described.

[0035] As shown in Fig. 9, the twelve first-layer resistor portions 14 (see Fig. 7) and the twelve second-layer sub-electrodes 21 are arranged so as to overlap each other in a transmission plan view (as viewed in the direction of radio wave propagation). The twelve first-layer sub-electrodes 11 and the twelve second-layer resistor portions 24 are also arranged so as to overlap each other in a transmission plan view. This configuration makes it possible to equalize the impedances as viewed from both vertically and horizontally polarized waves.

[0036] Furthermore, in order to achieve the above configuration, in this embodiment, the first layer unit 10U and the second layer unit 20U are configured identically to each other and are arranged in a state where they are rotated by 90 degrees relative to each other around an axis (an axis extending in the radio wave traveling direction shown in FIG. 6) that is perpendicular to the transmission plane 2a. This allows the same unit to be used for the first layer unit 10U and the second layer unit 20U, thereby making it possible to reduce manufacturing costs accordingly.

[0037] As shown in Fig. 9 , by arranging the first layer unit 10U and the second layer unit 20U in a state rotated 90 degrees relative to each other, the end of the first layer main anode 15 and the end of the second layer main anode 25 overlap each other in a transparent plan view. In Fig. 9 , the region of the overlapping ends is indicated by region R1 surrounded by a dashed line. By electrically connecting the overlapping ends, the first layer main anode 15 and the second layer main anode 25 are electrically connected to each other. This results in a structure that makes it easy to electrically connect the first layer main anode 15 and the second layer main anode 25 to each other.

[0038] Furthermore, by arranging the first-layer unit 10U and the second-layer unit 20U in a state rotated 90 degrees relative to each other, the end of the first-layer main cathode 16 and the end of the second-layer main cathode 26 overlap each other in a transmitted plan view. In Fig. 9 , the region of the overlapping ends is indicated by region R2 surrounded by a dashed line. By electrically connecting the overlapping ends, the first-layer main cathode 16 and the second-layer main cathode 26 are electrically connected to each other. This results in a structure that makes it easy to electrically connect the first-layer main cathode 16 and the second-layer main cathode 26 to each other.

[0039] (Insulating Section 30) Next, the insulating section 30 will be described with reference to Figures 7, 8, 9, and 10. Figure 10 is a partial enlarged view of Figure 9. The insulating layer 30 is interposed between the first layer unit 10U and the second layer unit 20U. The insulating layer 30 has the same lattice shape as the first layer grid 10 (see Figure 7). However, the line widths of the vertical and horizontal lines constituting the lattice shape of the insulating layer 30 are wider than the line widths of the vertical and horizontal lines constituting the lattice shape of the first layer grid 10. The line width of the insulating layer 30 is determined based on the results of experiments and simulations in order to prevent a decrease in insulation performance and radio wave transmittance.

[0040] The lattice pattern of the insulating layer 30 is arranged so as to overlap the lattice pattern of the first layer grid 10 in a transparent plan view (see FIG. 8 ). Note that when assembling the insulating layer 30 and the first layer unit 10U, the lattice pattern of the insulating layer 30 can be simply overlapped with the lattice pattern of the first layer grid 10, which makes it easy to assemble the insulating layer 30 and the first layer unit 10U.

[0041] Next, the second layer unit 20U is assembled to a sub-assembly (see FIG. 8) that includes the insulating layer 30 and the first layer unit 10U. In the assembly process for assembling the sub-assembly and the second layer unit 20U, the second layer unit 20U is rotated 90 degrees relative to the first layer unit 10U around an axis perpendicular to the transmission plane 2a (the axis extending in the radio wave propagation direction shown in FIG. 6) (see FIG. 9). This allows the lattice pattern of the second layer grid 20 to be superimposed on the lattice pattern of the insulating layer 30. This facilitates the assembly of the sub-assembly and the second layer unit 20U.

[0042] As described above, the twelve first-layer resistor portions 14 and the twelve second-layer sub-electrodes 21 are arranged to overlap each other in a transmission plan view (as viewed in the direction of radio wave propagation). The twelve first-layer sub-electrodes 11 and the twelve second-layer resistor portions 24 are also arranged to overlap each other in a transmission plan view. Furthermore, as described above, the lattice shape of the insulating layer 30 and the lattice shape of the second-layer grid body 20 are arranged to overlap each other in a transmission plan view. This makes it possible to equalize the impedances as viewed from both vertically and horizontally polarized waves. Figure 10 shows the capacitance C between the second-layer sub-anode 22 and the second-layer sub-cathode 23 as an example of the impedance of a capacitor.

[0043] Next, the eyelet E21 and the eyelet E11 are arranged and crimped in the pilot holes for the eyelets of the first-layer main anode 15 so as to sandwich the base film 2. Next, the eyelet E22 and the eyelet E12 are arranged and crimped in the pilot holes for the eyelets of the first-layer main anode 15 so as to sandwich the base film 2. Lead wires (not shown) are connected to the eyelets E11 and the eyelet E21, and voltage is supplied from an external power source.

[0044] In a state in which the insulating layer 30 is interposed between the first layer unit 10U and the second layer unit 20U, the insulating layer 30 is arranged so as to overlap, in a transmitted plan view, each of the six first-layer secondary anodes 12, the six first-layer secondary cathodes 13, the twelve first-layer resistance portions 14, the six second-layer secondary anodes 22, the six second-layer secondary cathodes 23, and the twelve second-layer resistance portions 24.

[0045] The above assembly process assembles the base film 2, first layer unit 10U, second layer unit 20U, and insulating layer 30. Next, these assembled parts are inserted into the resin case 6 using the adhesive layer 5 (see FIG. 6 ). This completes the assembly of the sheet heating element 100 and the assembly of the sheet heating element 100 to the resin case 6.

[0046] The sheet heating element 100 of the above embodiment is a sheet heating element arranged along a transmission plane through which radio waves from the antenna pass, and comprises: a first-layer grid 10 having a plurality of first-layer resistance portions 14 and a plurality of first-layer sub-electrodes 11, with the plurality of first-layer resistance portions 14 and the plurality of first-layer sub-electrodes 11 arranged in a grid pattern; and a second-layer grid 20 having a plurality of second-layer resistance portions 24 and a plurality of second-layer sub-electrodes 21, with the plurality of second-layer resistance portions 24 and the plurality of second-layer sub-electrodes 21 arranged in a grid pattern, with the plurality of first-layer resistance portions 14 and the plurality of second-layer sub-electrodes 21 arranged so as to overlap each other in a transmission plane view, and the plurality of first-layer sub-electrodes 11 and the plurality of second-layer resistance portions 24 arranged so as to overlap each other in a transmission plane view.

[0047] With the above configuration, current flows from the first-layer sub-electrode to the first-layer resistor portion 14, and further current flows from the second-layer sub-electrode to the second-layer resistor portion 24, causing the first-layer resistor portion 14 and the second-layer resistor portion 24 to generate heat, thereby reliably melting snow that interferes with radio waves. Furthermore, by arranging the plurality of first-layer resistor portions 14 and the plurality of second-layer sub-electrodes 21 so as to overlap each other in a transmission plan view, and by arranging the plurality of first-layer sub-electrodes 11 and the plurality of second-layer resistor portions 24 so as to overlap each other in a transmission plan view, it is possible to make the impedances as seen from both vertically and horizontally polarized waves the same, thereby enabling support for dual-polarized wave communication.

[0048] The sheet heating element 100 according to the above embodiment further comprises a first-layer main anode 15, a first-layer main cathode 16, a second-layer main anode 25, and a second-layer main cathode 26 that are arranged outside the transmission plane, the plurality of first-layer sub-electrodes 11 having two or more first-layer sub-anodes 12 electrically connected to the first-layer main anode 15 and two or more first-layer sub-cathode 13 electrically connected to the first-layer main cathode 16, and the plurality of second-layer sub-electrodes 21 having two or more second-layer sub-anodes 22 electrically connected to the second-layer main anode 25 and two or more second-layer sub-cathode 23 electrically connected to the second-layer main cathode 26. As a result, current flows from the first-layer main anode 15 to the first-layer secondary anode 12, and then from the first-layer secondary anode 12 to the first-layer secondary cathode 13 via the first-layer resistance portion 14. Current also flows from the second-layer main anode 25 to the second-layer secondary anode 22, and then from the second-layer secondary anode 22 to the second-layer secondary cathode 23 via the second-layer resistance portion 24. Both the first-layer resistance portion 14 and the second-layer resistance portion 24 generate heat, which ensures that snow that obstructs radio waves can be melted.

[0049] The sheet heating element 100 according to the above embodiment includes a first layer unit 10U having a first layer grid 10, a first layer main anode 15, and a first layer main cathode 16, and a second layer unit 20U having a second layer grid 20, a second layer main anode 25, and a second layer main cathode 26. The first layer unit 10U and the second layer unit 20U are identical to each other and are rotated 90 degrees relative to each other around an axis perpendicular to the transmission plane. This allows the grid shape of the second layer grid 20 to be superimposed on the grid shape of the insulating layer 30, facilitating the assembly of the sub-assembly components and the second layer unit 20U. The first layer resistors 14 and the second layer sub-electrodes 21 are arranged to overlap each other in a transmission plane view (as viewed in the direction of radio wave propagation). The first layer sub-electrodes 11 and the second layer resistors 24 are arranged to overlap each other in a transmission plane view. This makes it possible to make the impedance seen from both vertically and horizontally polarized waves the same.

[0050] In the sheet heating element 100 according to the above embodiment, the first-layer main anode 15 and the first-layer main cathode 16 are disposed opposite each other with the transmitting flat surface 2a in between and extend vertically along the transmitting flat surface 2a, while the second-layer main anode 25 and the second-layer main cathode 26 are disposed opposite each other with the transmitting flat surface 2a in between and extend in a direction perpendicular to the vertical direction (horizontal direction) along the transmitting flat surface 2a, the first-layer main anode 15 and the second-layer main anode 25 are electrically connected to each other, and the first-layer main cathode 16 and the second-layer main cathode 26 are electrically connected to each other. This makes it possible to effectively use the space outside the transmitting flat surface 2a as arrangement space for the first-layer main anode 15, etc.

[0051] In the sheet heating element 100 according to the above embodiment, the two or more first-layer sub-anodes 12 are arranged at a predetermined interval in the vertical direction and extend horizontally from the first-layer main anode 15 toward the transmitting plane 2 a, the two or more first-layer sub-cathodes 13 are arranged at a predetermined interval in the vertical direction and extend horizontally from the first-layer main cathode 16 toward the transmitting plane 2 a, the two or more second-layer sub-anodes 22 are arranged at a predetermined interval in the horizontal direction and extend vertically from the second-layer main anode 25 toward the transmitting plane, and the two or more second-layer sub-cathodes 23 are arranged at a predetermined interval in the horizontal direction and extend vertically from the second-layer main cathode 26 toward the transmitting plane. This makes it possible to relatively easily configure a grid shape by using the first-layer sub-anodes 12, first-layer sub-cathodes 13, second-layer sub-anodes 22, and second-layer sub-cathode 23.

[0052] The sheet heating element 100 according to the above embodiment further includes an insulating layer 30 interposed between the first layer unit 10U and the second layer unit 20U. This makes it possible to provide an insulating region between, for example, the first-layer secondary anode 12 of the first layer unit 10U and the second-layer secondary cathode 23 of the second layer unit 20U, and also makes it possible to provide an insulating region between, for example, the first-layer secondary cathode 13 of the first layer unit 10U and the second-layer secondary anode 22 of the second layer unit 20U.

[0053] Furthermore, in the sheet heating element 100 according to the above embodiment, the insulating layer 30 is arranged so as to overlap, in a transmission plan view, the two or more first-layer sub-anodes 12, the two or more first-layer sub-cathodes 13, the plurality of first-layer resistors 14, the two or more second-layer sub-anodes 22, the two or more second-layer sub-cathodes 23, and the plurality of second-layer resistors 24. As a result, the lattice shape of the insulating layer 30, the lattice shape of the first-layer grid 10, and the lattice shape of the second-layer grid 20 are arranged so as to overlap one another in a transmission plan view. This makes it possible to make the impedances as viewed from both vertically and horizontally polarized waves the same.

[0054] In addition, in the planar heating element 100 of the above embodiment, if it is possible to make the impedance when viewed from both vertical and horizontal polarization the same, the first layer unit 10U and the second layer unit 20U do not have to be configured to be identical to each other and be arranged in a state rotated 90 degrees relative to each other around an axis perpendicular to the transmission plane.

[0055] Furthermore, the above-described embodiments are merely examples of specific embodiments for carrying out the present invention, and the technical scope of the present invention should not be construed as being limited by these embodiments. In other words, the present invention can be carried out in various forms without departing from the gist or main features thereof.

[0056] This application is based on a Japanese patent application (Patent Application No. 2024-097444) filed on June 17, 2024, the contents of which are incorporated herein by reference.

[0057] The present invention is suitably used for a communication base station antenna equipped with a planar heating element that is required to reliably melt snow that obstructs radio waves and to support dual polarized wave communication.

[0058] REFERENCE SIGNS LIST 1 Metal heating wire 2 Base film 2a Flat surface 3 Terminal 4 Terminal 5 Adhesive layer 6 Resin case 10 First layer grid 10U First layer unit 11 First layer sub-electrode 12 First layer sub-anode 13 First layer sub-cathode 14 First layer resistance portion 15 First layer main anode 16 First layer main cathode 20 Second layer grid 20U Second layer unit 21 Second layer sub-electrode 22 Second layer sub-anode 23 Second layer sub-cathode 24 Second layer resistance portion 25 Second layer main anode 26 Second layer main cathode 30 Insulating layer 100 Planar heating element

Claims

1. A sheet heating element arranged along a transmission plane through which radio waves from an antenna pass, comprising: a first-layer grid having a plurality of first-layer resistance portions and a plurality of first-layer sub-electrodes, the first-layer resistance portions and the first-layer sub-electrodes being arranged in a grid pattern; and a second-layer grid having a plurality of second-layer resistance portions and a plurality of second-layer sub-electrodes, the second-layer resistance portions and the second-layer sub-electrodes being arranged in a grid pattern, wherein the first-layer resistance portions and the second-layer sub-electrodes are arranged so as to overlap each other in a transmission plane view, and the first-layer sub-electrodes and the second-layer resistance portions are arranged so as to overlap each other in the transmission plane view.

2. The sheet heating element according to claim 1, further comprising a first-layer main anode, a first-layer main cathode, a second-layer main anode, and a second-layer main cathode arranged outside the transmission plane, wherein the plurality of first-layer sub-electrodes have two or more first-layer sub-anodes and two or more first-layer sub-cathodes electrically connected to the first-layer main cathode, and the plurality of second-layer sub-electrodes have two or more second-layer sub-anodes electrically connected to the second-layer main anode and two or more second-layer sub-cathodes electrically connected to the second-layer main cathode.

3. The sheet heating element according to claim 2, comprising a first layer unit having the first layer grid, the first layer main anode, and the first layer main cathode, and a second layer unit having the second layer grid, the second layer main anode, and the second layer main cathode, wherein the first layer unit and the second layer unit are configured identically to each other and are arranged rotated by 90 degrees relative to each other around an axis perpendicular to the transmission plane.

4. The sheet heating element according to claim 3, wherein the first-layer main anode and the first-layer main cathode are arranged to face each other with the transmitting plane between them and extend in a predetermined direction along the transmitting plane, the second-layer main anode and the second-layer main cathode are arranged to face each other with the transmitting plane between them and extend in a direction perpendicular to the predetermined direction along the transmitting plane, the first-layer main anode and the second-layer main anode are electrically connected to each other, and the first-layer main cathode and the second-layer main cathode are electrically connected to each other.

5. The sheet heating element according to claim 4, wherein the two or more first-layer auxiliary anodes are arranged at predetermined intervals in the predetermined direction and extend from the first-layer main anode into the transmission plane in the orthogonal direction, the two or more first-layer auxiliary cathodes are arranged at predetermined intervals in the predetermined direction and extend from the first-layer main cathode into the transmission plane in the orthogonal direction, the two or more second-layer auxiliary anodes are arranged at predetermined intervals in the orthogonal direction and extend from the second-layer main anode into the transmission plane in the predetermined direction, and the two or more second-layer auxiliary cathodes are arranged at predetermined intervals in the orthogonal direction and extend from the second-layer main cathode into the transmission plane in the predetermined direction.

6. The sheet heating element according to claim 3, further comprising an insulating layer interposed between the first layer unit and the second layer unit.

7. The sheet heating element according to claim 6, wherein the insulating layer is arranged so as to overlap each of the two or more first-layer secondary anodes, the two or more first-layer secondary cathodes, the plurality of first-layer resistance portions, the two or more second-layer secondary anodes, the two or more second-layer secondary anodes, and the plurality of second-layer resistance portions in the transmitted plan view.

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