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Installation and Manual Documentation
CR5CPCCF
CC-DA/ESR1
18 Feb 2020
2.1.1.2.
Fascia design guidelines
Material
Material with low dielectric constant (
) and low dielectric loss factor tanδ at 77 GHz should be
r
used. Recommended are materials based on polypropylene (PP) and polymethyl methacrylate
(PMMA), while materials like polycarbonate (PC) and acrylonitrile butadiene styrene (ABS) are
still ok. The material shall be homogenous, compounds including glass fiber, carbon fiber or metal
particles are not recommended.
The fascia shall be designed for radar transparency. The thickness shall be a multiple of the half
wavelength (in the material) to minimize the influence of the fascia. The quality criteria of radar
transparency is the reflection coefficient of the radome/fascia. Tolerances of the overall thickness
and the dielectric constant of the used material influence the amount of reflection at the
radome/fascia. Additional influence occurs due to curvature of the fascia. Therefore the radius
has to be as large as possible. With sharp edges the negative influence will increase significantly.
Not allowed are ribs, structures and steps changing the thickness of the radome/fascia.
Painting
The layer structure of the painting, typically made of three painting layers consisting of primer,
base coating and clear coating, will increase the effective permittivity value
and dielectric loss
r,eff
factor tanδ of the painted plate used as fascia.
Fascia Classification (CR5CP)
The two-way radar loss caused by the fascia should be as low as possilbe. High losses decrease
the sensor performance regarding range and angle estimation. Therefore it is recommended to
achieve a two-way radar loss below 4 dB(t.b.c.). This corresponds to a loss of 20% of sensor
range.
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