Hardware and physical integration guideline PCR Sensor A111
Page 15 of 32
2022-03-08
© 2022 by Acconeer
– All rights reserved
ℎ =
𝜆
𝑒𝑓𝑓
2
= 1.55 𝑚𝑚
Figure 15 shows the amplitude variation of the reflected wave from the radar target when the distance
between the sensor and the radome is varied for different radome thicknesses. A thickness of 1.6 mm,
which is very close to the thickness of half-a-wavelength, has the minimum impact on the amplitude
variation. It is worth to mention that when the thickness is set to quarter-of-a-wavelength, the amplitude
variation becomes maximum. When the radome thickness is set to quarter-of-a-wavelength, the round
trip of the wave inside the radome leads to a 180° phaseshift.
Figure 15. Impact of the thickness of the radome (made of ABS) on the reflected amplitude variation. The amplitude
is normalized to maximum value of the Free Space (FS). Profile set to Profile 2. Amplitude variation is stated in one
direction (Tx or Rx side). For Radar Loop Gain (RLG) the values will be doubled.
If absolute measurements are required for a certain use case, it is advised that an additional offset is
added to the distance measurement. The reason for this offset is that the propagation delay caused by
the radome must be compensated. This additional offset is obtained by making reference measurements,
and it will also allow you to place the reference plane at the desired location for your product.
4.3 Radome distance
The reflected waves from the radome wall should be in-phase with the transmit waves, which leads to
the optimum distance of
𝐷
𝑜𝑝𝑡𝑖𝑚𝑢𝑚
= 𝑛
𝜆
0
2
, 𝑛 = 1,2,3, …
