Protective plate-equipped reflective member
A protective plate-equipped reflective member includes a reflective member that reflects or re-radiates a radio wave incident thereon; and a protective plate that is installed on a radio wave-incident side of the reflective member, wherein d=α×λ 0 /(1.75×ε r 0.555 ) and α is greater than or equal to 1 and less than or equal to 1.25, where a wavelength specified with respect to an operating center frequency f 0 [Hz] is denoted by λ 0 [mm], a plate thickness of the protective plate is denoted by d [mm], a relative permittivity of the protective plate at the operating center frequency f 0 [Hz] is denoted by ε r , and a constant is denoted by α.
1. A protective plate-equipped reflective member comprising:
a reflective member that reflects or re-radiates a radio wave incident thereon; and
a protective plate that is installed on a radio wave-incident side of the reflective member,
wherein d=α×λ 0 /(1.75×ε r 0.555 ) and α is greater than or equal to 1 and less than or equal to 1.25, where a wavelength specified with respect to an operating center frequency f 0 [Hz] is denoted by λ 0 [mm], a plate thickness of the protective plate is denoted by d [mm], a relative permittivity of the protective plate at the operating center frequency f 0 [Hz] is denoted by ε r , and a constant is denoted by α.
2. The protective plate-equipped reflective member according to claim 1 , wherein the relative permittivity of the protective plate is 2 or more and 10 or less.
3. The protective plate-equipped reflective member according to claim 1 , wherein Δf/f 0 is 10% or more, where a frequency range, in which an angle of incidence of the radio wave at which normalized transmission loss of the protective plate is 1 dB is 60 degrees or more, around the operating center frequency f 0 [Hz], is denoted by Δf [Hz].
4. The protective plate-equipped reflective member according to claim 1 , wherein a material of the protective plate is a fluorine resin or glass.
5. The protective plate-equipped reflective member according to claim 1 , wherein a material of the protective plate is polytetrafluoroethylene.
6. The protective plate-equipped reflective member according to claim 1 , wherein normalized transmission loss of the protective plate decreases as an angle of incidence of the radio wave changes from 0 degrees to 50 degrees at the operating center frequency f 0 [Hz].
7. The protective plate-equipped reflective member according to claim 1 , wherein
the protective plate includes a first dielectric layer and a second dielectric layer that is provided between the first dielectric layer and the reflective member, and
ε ra ={(d 1 +d 2 )×ε r1 ×ε r2 }/(d 1 ×ε r2 +d 2 εε r1 ) da=d 1 +d 2 , da=α×λ 0 /(1.75×ε ra 0.555 ), and a is greater than or equal to 1 and less than or equal to 1.25, where a layer thickness of the first dielectric layer is denoted by d 1 [mm], a relative permittivity of the first dielectric layer is denoted by ε r1 , a layer thickness of the second dielectric layer is denoted by d 2 [mm], a relative permittivity of the second dielectric layer is denoted by ε r2 , an effective relative permittivity of the protective plate is denoted by ε ra , and a plate thickness of the protective plate is denoted by da.