Hardware and physical integration guideline PCR Sensor A111
Page 27 of 32
2022-03-08
© 2022 by Acconeer
– All rights reserved
Figure 30. Detailed geometry of an FZP lens with quarter wavelength phase correction step.
𝑟
𝑖
= √ (𝑖
𝜆
𝑝
)
2
+ 2𝐹𝑖
𝜆
𝑝
𝑖 = 1,2,3,4
𝑠 =
𝜆
𝑝(√𝜀
𝑟
− 1)
where
𝑟
𝑖
is the radius of each step,
s
is the thickness of each step,
F
is the focal point,
p
is the
number of steps,
𝜆
is the wavelength in free-space (5 mm at 60 GHz), and
𝜀
𝑟
is the dielectric
constant of the chosen material at 60 GHz.
By using the equations mentioned above, one concludes that a four-step FZP lens in ABS-M30 plastic
(ε
r
= 2.48), with the focal point at 10mm, needs the following dimensions:
r
1
= 5.1mm
r
2
= 7.46mm
r
3
= 9.39mm
r
4
= 11.12mm
s= 2.17 mm
Total thickness of the lens: 4*2.17 = 8.7 mm
