Electromagnetic wave transmissive cover
An electromagnetic wave transmissive cover includes: a base made of a dielectric material and having transmissiveness to electromagnetic waves; and a reflection hindering layer laminated on at least one of two surfaces of the base in a travel direction of the electromagnetic waves, made of a dielectric material, having transmissiveness to the electromagnetic waves, and hindering reflection of the electromagnetic waves. A wavelength of each electromagnetic wave in the reflection hindering layer is referred to as λ2 and 2π/λ2 is set as a phase constant β 2 . An amount of deviation between a phase of a reflected wave reflected on the front interface of the reflection hindering layer in the travel direction and a phase of a reflected wave reflected on the rear interface is referred to as a phase deviation amount β. Thickness L 2 of the reflection hindering layer is set to β/β 2 .
1. An electromagnetic wave transmissive cover, comprising:
a base configured to be arranged in a path of electromagnetic waves in a radar device that transmits and receives the electromagnetic waves, the base being made of a dielectric material and having transmissiveness to the electromagnetic waves, and
a reflection hindering layer laminated on at least one of two surfaces of the base in a travel direction of the electromagnetic waves, the reflection hindering layer being made of a dielectric material, the reflection hindering layer having transmissiveness to the electromagnetic waves and hindering reflection of the electromagnetic waves, wherein
a wavelength of each of the electromagnetic waves in the reflection hindering layer is referred to as λ2 and 2π/λ2 is set as a phase constant β 2 ,
an amount of deviation between a phase of a reflected wave reflected on an interface on a front side of the reflection hindering layer in the travel direction and a phase of a reflected wave reflected on an interface on a rear side of the reflection hindering layer in the travel direction is referred to as a phase deviation amount β, and
thickness L 2 of the reflection hindering layer is set to β/β 2 .
2. The electromagnetic wave transmissive cover according to claim 1 , wherein the reflection hindering layer is arranged on a rear surface of the two surfaces of the base in the travel direction, the reflection hindering layer being arranged at least in a region of the rear surface of the base irradiated with the electromagnetic waves.
3. The electromagnetic wave transmissive cover according to claim 1 , wherein
a wavelength of each of the electromagnetic waves in the base is referred to as λ1 and 2π/λ1 is set as a phase constant β 1 ,
an amount of deviation between a phase of a reflected wave reflected on an interface on a front side of the base in the travel direction and a phase of a reflected wave reflected on an interface on a rear side of the base in the travel direction is referred to as a phase deviation amount α,
a thickness of the base is referred to as L 1 ,
a relative permittivity of the base is referred to as ε α ,
a relative permittivity of the reflection hindering layer is referred to as ε β , and
the phase deviation amount β is set using the following Equations 1 to 5:
α
=
β
1
L
1
;
Equation
1
β
=
tan
-
1
-
A
±
A
2
-
4
BC
2
C
+
n
π
=
β
2
L
2
;
Equation
2
A
=
2
(
1
ε
β
-
ε
β
)
cos
α
;
Equation
3
B
=
(
1
ε
α
-
ε
α
)
sin
α
;
and
Equation
4
C
=
(
ε
β
ε
α
-
ε
α
ε
β
)
sin
α
.
Equation
5