User's Manual

Nova Electronics (Shanghai) Co., LTD File No：R-JS-AS-13 Version：V1.0
6
Table 3 Relationship between optimal thickness, loss and dielectric constant of materials
Material
Dielectric
constant
Best
thickness 1
(mm)
Best
thickness 2
(mm)
Best
thickness 3
(mm)
Loss (dB); 77GHz,
optimal thickness 2
Polypropylene
2.35
1.28
2.55
3.83
0.10
Polyamide
2.75
1.18
2.36
3.54
0.30
Polycarbonate
2.8
1.16
2.33
3.49
0.17
ABS
3.12
1.10
2.21
3.31
0.30
3.2.3 Bumper Thickness Requirements
In order to ensure that the radar achieves high conductivity, the thickness of the bumper needs to be
selected carefully. Among the above mentioned materials,the thickness of the bumper should be an
integer multiple of half the wavelength of the 77GHz millimeter-wave radar. Such as ABS material
bumper thick the degree should be n*1.2mm (in the 77GHz range, n=1, 2, ...). Attenuation increases
with bumper thickness increase and increase.
In order to prevent the radar beam from being distorted, the bumper should be kept as flat as possible,
and the thickness should be uniform,any slight bend can have a big impact on the radar beam.
3.2.4 Bumper shape requirements
The surface of the bumper or shield must be smooth (roughness should be less than one-tenth of a
wavelength, about 400 microns), uniform in thickness, and its radius of curvature should be as large
as possible (small curvature) to reduce distortion and attenuation of the radar beam . Figure 8
shows the influence of the shape of the bumper on the radar performance, from left to right are
bumper digging (completely unobstructed), parallel, small curvature, thickness gradient, and sharp edge.