JP2009225159A - Reflecting surface of electromagnetic wave - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a reflecting surface of an electromagnetic wave which can form a magnetic wall in which a reflection phase becomes 0° in a plurality of frequency bands, with a simple single-layer structure in which an inductance element and a capacitance element are alternately loaded between conductor patches. <P>SOLUTION: There are provided: a substrate 2; a ground plate 1 formed on a first face of the substrate 2; a plurality of conductor patches 3 which are formed on a second face of the substrate 2 and arranged at a given interval, and each of which has a dimension of at least one wavelength or less at an operating frequency; an inductance element 4 which is loaded between the adjacent conductor patches, and indicates inductiveness in a specific frequency range; and a capacitance element 5 which is loaded between the adjacent conductor patches, and indicates a capacitance property in a specific frequency range. The inductance element 4 and the capacitance element 5 are alternately loaded. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electromagnetic wave reflection surface that forms a magnetic wall having a reflection phase of 0 ° in a plurality of frequency bands.

  A textured surface having a large electromagnetic impedance in a multi-frequency band is known as an electromagnetic wave reflecting surface forming a magnetic wall having a reflection phase of 0 ° in a plurality of frequency bands (see, for example, Patent Document 1). This textured surface forms a high-impedance surface with a reflection phase of 0 ° in multiple frequency bands, and is placed in a ground plane and a first array placed at a distance from the ground plane. A plurality of conductive plates, wherein the distance between the ground plane and the first array is shorter than the wavelength of the radio frequency beam, and the first array has a first lattice constant; A plurality of conductive elements associated with the plurality of conductive plates form a second array having a lattice constant greater than that of the one array.

JP-T-2004-514364

  However, the conventional electromagnetic wave reflecting surface uses a multilayer structure in order to obtain a magnetic wall having a reflection phase of 0 ° in a plurality of frequency bands, so that the structure becomes complicated and the manufacturing cost increases. there were.

  The present invention has been made to solve the above-described problems, and its object is to provide a simple single-layer structure in which an inductance element and a capacitance element are alternately loaded between conductor patches, and to reflect in a plurality of frequency bands. An electromagnetic wave reflecting surface capable of forming a magnetic wall having a phase of 0 ° is obtained.

  The electromagnetic wave reflecting surface according to the present invention is formed on a substrate, a conductor formed on the first surface of the substrate, and a second surface of the substrate, arranged at a predetermined interval, each at least at an operating frequency A plurality of conductor patches having a dimension of one wavelength or less, an inductance element loaded between adjacent conductor patches and exhibiting inductivity in a specific frequency range, and loaded between adjacent conductor patches and having a capacitance in a specific frequency range And a capacitance element that exhibits the characteristics, and the inductance element and the capacitance element are alternately loaded.

  The electromagnetic wave reflecting surface according to the present invention has a simple single layer structure in which an inductance element and a capacitance element are alternately loaded between conductor patches, and can form a magnetic wall having a reflection phase of 0 ° in a plurality of frequency bands. There is an effect.

Embodiment 1 FIG.
The electromagnetic wave reflecting surface according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a configuration of an electromagnetic wave reflecting surface according to Embodiment 1 of the present invention. FIG. 4A is a plan view, and FIG. 4B is a cross-sectional view taken along line AA ′ in FIG. In the following, in each figure, the same reference numerals indicate the same or corresponding parts.

  In FIG. 1, an electromagnetic wave reflecting surface according to Embodiment 1 of the present invention includes a ground plane (conductor) 1, a substrate 2, a conductor patch 3, an inductance element 4 exhibiting inductivity in a specific frequency range, and a specific A capacitance element 5 that exhibits capacitance in the frequency range is provided.

  The substrate 2 is made of a dielectric or the like, and a ground plane 1 is formed on the first surface of the substrate 2. On the second surface of the substrate 2 facing the ground plane 1 across the substrate 2, a plurality of conductor patches 3 having a dimension of one wavelength or less at least at the operating frequency are one-dimensionally at a predetermined interval. Or they are arranged two-dimensionally. Further, the inductance elements 4 and the capacitance elements 5 are alternately loaded between adjacent conductor patches of the plurality of conductor patches 3.

  Next, the operation of the electromagnetic wave reflecting surface according to the first embodiment will be described with reference to the drawings.

  When an electromagnetic wave is incident on the electromagnetic wave reflecting surface according to the first embodiment, a capacitance component is generated between the adjacent conductor patches 3. Further, an inductance component is generated by the current flowing on the conductor patch 3. A plurality of LC resonance circuits are formed by combining the capacitance component and the inductance component formed by the structure of the electromagnetic wave reflecting surface with the inductance element 4 or the capacitance element 5 alternately loaded between the adjacent conductor patches 3. Therefore, a plurality of resonances can be obtained. Since each LC resonance circuit exhibits high impedance characteristics at each resonance frequency, the surface on which the plurality of conductor patches 3 are arranged becomes a high impedance surface. When an electromagnetic wave is incident on this high impedance surface, it operates as a magnetic wall whose reflection phase is 0 °. Therefore, it operates as a magnetic wall at a plurality of frequencies.

  In the electromagnetic wave reflecting surface according to the first embodiment, the inductance elements 4 or the capacitance elements 5 are alternately loaded between the adjacent conductor patches 3, and a magnetic wall operation can be obtained in a plurality of frequency bands with a single layer structure. . On the other hand, since the conventional electromagnetic wave reflecting surface has a multilayer structure in order to obtain a magnetic wall operation in a plurality of frequency bands, the electromagnetic wave reflecting surface according to Embodiment 1 has a simpler structure and is easier to manufacture. It becomes. Further, in the conventional electromagnetic wave reflecting surface, the magnetic wall operating band is determined only from the structure, but in the first embodiment, not only from the structure such as the size of the conductor patch 3 and the distance between the adjacent conductor patches 3, Since the magnetic wall operation band can be changed by changing the element value of the inductance element 4 or the capacitance element 5, it is possible to easily obtain the magnetic wall operation in a desired frequency band.

  Here, the electromagnetic wave reflection surface according to the first embodiment will be described using a calculation example. 2A and 2B are diagrams showing a unit cell structure of the electromagnetic wave reflection surface used for the calculation. FIG. 2A is a plan view and FIG. 2B is a side view.

  In the calculation, in the unit cell structure of the electromagnetic wave reflecting surface shown in FIG. 2, the conductor patch 3 is 2.9 mm × 2.9 mm, the distance between adjacent conductor patches is 0.2 mm, and the thickness of the substrate 2 is 0.8 mm. The dielectric constant of the substrate 2 was 4.2. The element values of the inductance element 4 and the capacitance element 5 loaded between adjacent conductor patches 3 were 0.5 nH and 4 pF, respectively.

  FIG. 3 is a diagram showing a result of calculating the reflection phase characteristics when the unit cell structure shown in FIG. 2 is arranged in an infinite period and a plane wave having an electric field component is perpendicularly incident in the x direction in FIG. As shown in FIG. 3, the reflection phase is 0 ° at two frequencies of about 2 GHz and about 15 GHz, and the magnetic wall operation is shown in two frequency bands.

  In the first embodiment, a ground plane 1 is formed on a first surface of a substrate 2 such as a dielectric, and at least an operating frequency is disposed on a second surface of the substrate 2 that faces the ground plane 1 across the substrate 2. Are arranged in a one-dimensional or two-dimensional manner at a predetermined interval, and between the adjacent conductor patches of the plurality of conductor patches 3, an inductance element 4 or The configuration in which the capacitance elements 5 are alternately loaded has been described. However, the configuration is not limited thereto. In the above configuration, the same configuration may be adopted in which a plurality of conductor patches 3 are connected to the ground plane 1 through conductors such as via holes. An effect can be obtained.

Embodiment 2. FIG.
An electromagnetic wave reflecting surface according to Embodiment 2 of the present invention will be described with reference to FIGS. FIG. 4 is a diagram showing the configuration of the electromagnetic wave reflecting surface according to the second embodiment of the present invention. FIG. 4A is a plan view, and FIG. 4B is a cross-sectional view taken along line AA ′ in FIG.

  In FIG. 4, the electromagnetic wave reflecting surface according to the second embodiment of the present invention includes a ground plane 1, a substrate 2, a conductor patch 3, and an inductance element 4 (4 a and 4 b) that exhibits inductivity in a specific frequency range, Capacitance elements 5 (5a, 5b) exhibiting capacitance in a specific frequency range are provided.

  The substrate 2 is made of a dielectric or the like, and a ground plane 1 is formed on the first surface of the substrate 2. On the second surface of the substrate 2 facing the ground plane 1 across the substrate 2, a plurality of conductor patches 3 having a dimension of one wavelength or less at least at the operating frequency are one-dimensionally at a predetermined interval. Or they are arranged two-dimensionally. Further, the inductance elements 4 and the capacitance elements 5 are alternately loaded between adjacent conductor patches of the plurality of conductor patches 3.

  The element values of the inductance element 4 and the capacitance element 5 loaded between adjacent conductor patches of the plurality of conductor patches 3 are the horizontal direction (x direction in the figure) and the vertical direction (y direction in the figure), that is, the inductance element. 4a and 4b and capacitance elements 5a and 5b are set differently.

  Next, the operation of the electromagnetic wave reflecting surface according to the second embodiment will be described with reference to the drawings.

  When an electromagnetic wave is incident on the electromagnetic wave reflecting surface according to the second embodiment, a capacitance component is generated between the adjacent conductor patches 3. Further, an inductance component is generated by the current flowing on the conductor patch 3. Since the capacitance component and the inductance component formed by the structure of the electromagnetic wave reflecting surface are combined with the inductance element 4 or the capacitance element 5 alternately loaded between the adjacent conductor patches 3, an LC resonance circuit is formed. , You will get multiple resonances. Each LC resonance circuit exhibits high impedance characteristics at the resonance frequency, and thus operates as a magnetic wall having a reflection phase of 0 °.

  In the electromagnetic wave reflecting surface according to the second embodiment, the inductance element 4 or the capacitance element 5 is alternately loaded between the adjacent conductor patches of the plurality of conductor patches 3, and further, the inductance element 4 or the element of the capacitance element 5. The value is set to be different between the x direction and the y direction. Therefore, since the contribution method of the inductance element 4 and the capacitance element 5 loaded between the conductor patches 3 differs depending on the direction of the electric field component of the incident electromagnetic wave, the resonance frequency becomes different.

  For example, if an electromagnetic wave is incident on the surface shown in FIG. 4 and the electromagnetic wave has an electric field component in the x direction in FIG. 4, it is the inductance element 4a and the capacitance element 5a that contribute to the magnetic wall operation. It becomes.

  On the other hand, when the electromagnetic wave incident on the surface in which the unit cell structure shown in FIG. 4 is arranged in an infinite period has an electric field component in the y direction in FIG. 4b and capacitance element 5b.

  Therefore, as in the second embodiment, by setting the element values of the inductance element 4 and the capacitance element 5 loaded in the x direction and the y direction to be different from each other, the magnetic wall operation depends on the direction of the electric field component of the incident wave. The bandwidth can be different.

  Here, the electromagnetic wave reflecting surface according to the second embodiment will be described using a calculation example. 5A and 5B are diagrams showing the unit cell structure of the electromagnetic wave reflection surface used in the calculation, where FIG. 5A is a plan view and FIG. 5B is a side view.

  In the calculation, in the unit cell structure of the electromagnetic wave reflecting surface shown in FIG. 5, the conductor patch 3 is 2.9 mm × 2.9 mm, the distance between adjacent conductor patches 3 is 0.2 mm, and the thickness of the substrate 2 is 0.2 mm. The dielectric constant of 8 mm and the substrate 2 was 4.2. Also, the element values of the inductance element 4 and the capacitance element 5 loaded between the adjacent conductor patches 3 are 0.5 nH and 2 pF for the x-direction inductance element 4a and the capacitance element 5a in the figure, respectively, and the y-direction inductance The element 4b and the capacitance element 5b were 1 nH and 4 pF, respectively.

  6 and 7 show the results of calculating the reflection characteristics when electromagnetic waves are vertically incident on a surface in which the unit cell structure shown in FIG. 5 is arranged in an infinite period. FIG. 6 shows the incident wave having an electric field component in the x direction. FIG. 7 shows the result when the incident wave has an electric field component in the y direction. As shown in FIG. 6, the reflection phase is 0 ° at about 3 GHz and about 15 GHz, and the magnetic wall operation is shown in two frequency bands, whereas, as shown in FIG. 7, the reflection phase is about 2 GHz. At about 13 GHz, the reflection phase is 0 °, indicating magnetic wall operation in two frequency bands. Thus, in the electromagnetic wave reflecting surface according to the second embodiment, the magnetic wall operating band can be changed depending on the direction of the electric field component of the incident wave.

  In the second embodiment, the ground plane 1 is formed on the first surface of the substrate 2 such as a dielectric, and at least the operating frequency is disposed on the second surface of the substrate 2 that faces the ground plane 1 across the substrate 2. Are arranged in a one-dimensional or two-dimensional manner at a predetermined interval, and between the adjacent conductor patches of the plurality of conductor patches 3, an inductance element 4 or Regarding the configuration in which the capacitance elements 5 are alternately loaded, and the element values of the inductance elements 4 or the capacitance elements 5 loaded between the adjacent conductor patches of the plurality of conductor patches 3 are set to be different in the x direction and the y direction. Although described above, the present invention is not limited to this. In the above configuration, the same effect can be obtained even when the plurality of conductor patches 3 are connected to the ground plane 1 through conductors such as via holes. It is possible.

Embodiment 3 FIG.
An electromagnetic wave reflecting surface according to Embodiment 3 of the present invention will be described with reference to FIGS. FIG. 8 is a diagram showing a configuration of an electromagnetic wave reflecting surface according to Embodiment 3 of the present invention. FIG. 4A is a plan view, and FIG. 4B is a cross-sectional view taken along line AA ′ in FIG.

  In FIG. 8, the electromagnetic wave reflecting surface according to the third embodiment of the present invention includes a ground plane 1, a substrate 2, a conductor patch 3, an inductance element 4 exhibiting inductivity in a specific frequency range, and a specific frequency range. A capacitance element 5 having a capacitive property is provided.

  The substrate 2 is made of a dielectric or the like, and a ground plane 1 is formed on the first surface of the substrate 2. On the second surface of the substrate 2 facing the ground plane 1 across the substrate 2, a plurality of conductor patches 3 having a dimension of one wavelength or less at least at the operating frequency are one-dimensionally at a predetermined interval. Or they are arranged two-dimensionally. Further, at least two or more inductance elements 4 or capacitance elements 5 are alternately loaded between adjacent conductor patches of the plurality of conductor patches 3.

  Since the basic operation of the electromagnetic wave reflecting surface according to the third embodiment is the same as that of the first embodiment and the second embodiment, the description thereof will be omitted here, and different parts will be described below. In the electromagnetic wave reflecting surface according to the third embodiment, since at least two or more inductance elements 4 or capacitance elements 5 are alternately loaded between adjacent conductor patches 3, a current flowing on the conductor patch 3 easily flows. Thus, the effect of widening the magnetic wall operating band can be obtained.

  The widening of the magnetic wall operating band of the electromagnetic wave reflecting surface according to the third embodiment will be described using a calculation example. 9 and 10 are diagrams showing a unit cell structure of the electromagnetic wave reflection surface for obtaining the relationship between the number of the inductance elements 4 loaded between the conductor patches 3 and the magnetic wall operating band. FIG. 9 shows a unit cell structure in the case where one inductance element is loaded between the conductor patches 3. FIG. 9 (a) is a plan view and FIG. 9 (b) is a side view. FIG. 10 shows a unit cell structure when two inductance elements are loaded between the conductor patches 3. FIG. 10 (a) is a plan view and FIG. 10 (b) is a side view.

  FIG. 11 shows the unit cell structure of FIG. 9 in which the conductor patch 3 is 6 mm × 3 mm, the distance between adjacent conductor patches 3 is 0.2 mm, the thickness of the substrate 2 is 0.8 mm, and the dielectric constant of the substrate 2 is 4. .2, when a plane wave having an electric field component in the x direction in the figure is incident on the surface in which the element value of the inductance element 4 is 0.1 nH and the element value of the capacitance element 5 is 5.4 pF arranged in an infinite period Is the reflection phase characteristic. As shown in FIG. 11, the reflection phase is 0 ° at 2.19 GHz, and it operates as a magnetic wall in the vicinity of this frequency. Assuming that the frequency band in which the reflection phase is ± 90 ° is the magnetic wall operating band, the magnetic wall operating bandwidth is 0.051 GHz, and the magnetic wall operating band ratio bandwidth defined by the following equation 1 is 2.33%. It becomes.

(Magnetic wall motion ratio bandwidth) = (Magnetic wall motion bandwidth) / (Frequency at which reflection phase is 0 °)
(Formula 1)

  FIG. 12 shows the unit cell structure of FIG. 10 where the conductor patch 3 is 6 mm × 3 mm, the distance between the adjacent conductor patches 3 is 0.2 mm, the thickness of the substrate 2 is 0.8 mm, and the dielectric constant of the substrate 2 is 4. .2, a plane wave having an electric field component in the x direction in the figure on the surface in which the element values of the two inductance elements 4 are 0.2 nH and the element value of the capacitance element 5 is 5.4 pF are arranged infinitely. This is a reflection phase characteristic when incident. As shown in FIG. 12, the reflection phase becomes 0 ° at 2.37 GHz, and the magnetic wall operates near this frequency. Assuming that the frequency band where the reflection phase is ± 90 ° is the magnetic wall operating band, the magnetic wall operating bandwidth is 0.066 GHz, and the magnetic wall operating band ratio bandwidth defined by the above equation 1 is 2.79%. It becomes.

  As described above, by increasing the number of inductance elements 4 loaded between the conductor patches 3, the effect of widening the magnetic wall operating band can be obtained.

  FIGS. 13 and 14 show unit cell structures of the electromagnetic wave reflecting surface for obtaining the relationship between the number of capacitance elements 5 loaded between the conductor patches 3 and the magnetic wall operating band. FIGS. 13A and 13B show a unit cell structure when one capacitance element 5 is loaded between the conductor patches 3. FIG. 13A is a plan view and FIG. 13B is a side view. FIG. 14 shows a unit cell structure when two capacitance elements 5 are loaded between the conductor patches 3. FIG. 14A is a plan view and FIG. 14B is a side view.

  FIG. 15 shows the unit cell structure of FIG. 13 in which the conductor patch 3 is 6 mm × 6 mm, the distance between adjacent conductor patches 3 is 0.2 mm, the thickness of the substrate 2 is 0.8 mm, and the dielectric constant of the substrate 2 is 4. .2. Reflection phase characteristics when a plane wave having an electric field component in the x direction in the figure is incident on a surface in which the element value of the capacitance element 5 is 8 pF and arranged in an infinite period. As shown in FIG. 15, the reflection phase is 0 ° at 2.14 GHz, and it operates as a magnetic wall in the vicinity of this frequency. Assuming that the frequency band where the reflection phase is ± 90 ° is the magnetic wall operating band, the magnetic wall operating bandwidth is 0.057 GHz, and the magnetic wall operating band ratio bandwidth defined by Equation 1 is 2.66%. .

  FIG. 16 shows the unit cell structure of FIG. 14 in which the conductor patch 3 is 6 mm × 6 mm, the distance between adjacent conductor patches 3 is 0.2 mm, the thickness of the substrate 2 is 0.8 mm, and the dielectric constant of the substrate 2 is 4. .2 is a reflection phase characteristic when a plane wave having an electric field component in the x direction is incident on a surface in which the element values of the two capacitance elements 5 are 4 pF and arranged infinitely. As shown in FIG. 16, the reflection phase becomes 0 ° at 2.31 GHz, and the magnetic wall operates near this frequency. Assuming that the frequency band in which the reflection phase is ± 90 ° is the magnetic wall operating band, the magnetic wall operating bandwidth is 0.086 GHz, and the magnetic wall operating band ratio bandwidth defined by Equation 1 is 3.73%. .

  As described above, by increasing the number of capacitance elements 5 loaded between the conductor patches 3, the effect of widening the magnetic wall operating band can be obtained.

  As described above, in the electromagnetic wave reflecting surface according to the third embodiment, by alternately loading at least two inductance elements 4 or capacitance elements 5 between adjacent conductor patches of the plurality of conductor patches 3, A plurality of magnetic wall operation bands can be widened.

  In the third embodiment, the ground plane 1 is formed on the first surface of the substrate 2 such as a dielectric, and at least the operating frequency is disposed on the second surface of the substrate 2 that faces the ground plane 1 across the substrate 2. A plurality of conductor patches 3 having a dimension of one wavelength or less are arranged one-dimensionally or two-dimensionally at a predetermined interval, and at least two or more conductor patches 3 are adjacent to each other. Although the configuration in which the inductance elements 4 or the capacitance elements 5 are alternately loaded has been described, the present invention is not limited to this, and in the configuration described above, a plurality of conductor patches 3 are connected to the ground plane 1 via conductors such as via holes. However, the same effect can be obtained.

  In the above embodiment, the case where the shape of the conductor patch constituting the electromagnetic wave reflecting surface is rectangular has been described as an example. However, the shape of the conductor patch is not limited to a rectangle, but a regular hexagon, a regular octagon, an ellipse, or the like. May be.

  In the above embodiment, the magnetic wall operation in the two frequency bands has been described as an example. However, the distance between the plurality of conductor patches 3 constituting the electromagnetic wave reflecting surface and the adjacent conductor patches 3, the substrate 2 It is possible to operate the magnetic wall in a plurality of frequency bands by setting the thickness, the structure such as the dielectric constant of the substrate 2, the element value of the inductance element 4, and the element value of the capacitance element 5.

It is a figure which shows the structure of the electromagnetic wave reflective surface which concerns on Embodiment 1 of this invention. It is a figure which shows the unit cell structure used for calculation of the electromagnetic wave reflective surface which concerns on Embodiment 1 of this invention. It is a figure which shows the reflection phase characteristic calculated of the electromagnetic wave reflective surface which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of the electromagnetic wave reflective surface which concerns on Embodiment 2 of this invention. It is a figure which shows the unit cell structure used for calculation of the electromagnetic wave reflective surface which concerns on Embodiment 2 of this invention. It is a figure which shows the reflective phase characteristic (when an incident wave has an electric field component in x direction) calculated by the electromagnetic wave reflective surface which concerns on Embodiment 2 of this invention. It is a figure which shows the reflective phase characteristic (when an incident wave has an electric field component in ay direction) of the electromagnetic wave reflective surface which concerns on Embodiment 2 of this invention. It is a figure which shows the structure of the electromagnetic wave reflective surface which concerns on Embodiment 3 of this invention. It is a figure which shows the unit cell structure at the time of loading one inductance element between conductor patches. It is a figure which shows the unit cell structure at the time of loading two inductance elements between conductor patches. It is a figure which shows the reflection phase characteristic in the unit cell structure of FIG. It is a figure which shows the reflection phase characteristic in the unit cell structure of FIG. It is a figure which shows the unit cell structure at the time of loading one capacitance element between conductor patches. It is a figure which shows the unit cell structure at the time of loading two capacitance elements between conductor patches. It is a figure which shows the reflection phase characteristic in the unit cell structure of FIG. It is a figure which shows the reflection phase characteristic in the unit cell structure of FIG.

Explanation of symbols

  1 ground plane, 2 substrate, 3 conductor patch, 4 inductance element, 4a inductance element, 4b inductance element, 5 capacitance element, 5a capacitance element, 5b capacitance element.

Claims (3)

A substrate,
A conductor formed on the first surface of the substrate;
A plurality of conductor patches formed on the second surface of the substrate, arranged at predetermined intervals, each having a dimension of one wavelength or less at least at an operating frequency;
An inductance element loaded between adjacent conductor patches and exhibiting inductivity in a specific frequency range;
A capacitance element loaded between adjacent conductor patches and exhibiting capacitance in a specific frequency range;
The electromagnetic wave reflecting surface, wherein the inductance element and the capacitance element are alternately loaded. The element value of the inductance element loaded in the horizontal direction with respect to the conductor patch is different from the element value of the inductance element loaded in the vertical direction with respect to the conductor patch, and loaded in the horizontal direction with respect to the conductor patch. 2. The electromagnetic wave reflecting surface according to claim 1, wherein an element value of the capacitance element and an element value of the capacitance element loaded in a direction perpendicular to the conductor patch are different. The electromagnetic wave according to claim 1 or 2, wherein at least two or more inductance elements are loaded between adjacent conductor patches, and at least two or more capacitance elements are loaded between adjacent conductor patches. Reflective surface.

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