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Summary of Contents for Acconeer A111
- Page 1 Hardware and physical integration guideline PCR Sensors A111 & A121 User Guide...
- Page 2 Hardware and physical integration guideline A1 PCR sensors Hardware and physical integration guideline PCR sensors A111 & A121 User Guide Author: Acconeer Version 1.7: 2024-02-07 Acconeer AB Page 2 of 30 © 2024 by Acconeer – All rights reserved 2024-02-07...
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Page 3: Table Of Contents
Introduction ............................. 5 Electrical integration ........................6 A111 Power ........................... 6 A121 Power ........................... 6 Choosing a 1.8 V power regulator for A111/A121 ..............7 SPI Interface ........................... 7 Hardware schematics design checklist ................... 7 Electromagnetic Integration ......................8 Radar loop equation ....................... 8 Radar loop gain pattern ...................... - Page 4 Hardware and physical integration guideline A1 PCR sensors Appendix A: Materials ........................28 Revision ............................29 Disclaimer ............................. 30 Page 4 of 30 © 2024 by Acconeer – All rights reserved 2024-02-07...
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Page 5: Introduction
This document aims to provide general guidelines for making a hardware design with the Acconeer A121 and A111 radar sensors. We will provide the essential guidelines to ensure good electrical integration as well as electromagnetic integration. Including PCB design, use of lenses and integration into a radome. -
Page 6: Electrical Integration
SPI interface are pulled low during this time, otherwise reverse leakage will occur via the ESD diodes in the A111. If it is not possible to set the SPI interface in such a state (either via SW or by configuring any level-shifters that might be used in the design), the problem can be solved by adding a power switch only to VIO1 and VIO2. -
Page 7: Choosing A 1.8 V Power Regulator For A111/A121
~3 mA to ~75 mA on the 1.8 V power domain. It must be ensured that the power regulator used to supply the A111/A121 has a load transient response that handles this change in current without the output voltage dropping below the minimum operating supply voltage of A111/A121. -
Page 8: Electromagnetic Integration
Hardware and physical integration guideline A1 PCR sensors 3 Electromagnetic Integration The A111 and A121 pulsed coherent radar sensors are fully integrated 60 GHz radar sensors with integrated transmitter and receiver antennas. The Tx and Rx antennas are of folded-dipole type and the E-plane and H-planes are indicated in Figure 3. -
Page 9: Pcb Layout
The service “Sparse IQ” (A121) or the “Envelope detector” (A111) can be used to collect the reflected signal at the fixed distance from the radar target for different rotation angles. The figure of merit for amplitude variation stated in the document is the radar loop gain (RLG). -
Page 10: Impact Of Pcb Routing And Nearby Components
In terms of regulatory compliance, any openings in the ground plane inside the A111/A121 BGA footprint must be significantly smaller than the wavelength of the radiation that is being blocked, to effectively approximate an unbroken conducting surface. - Page 11 PCB traces close to the sensor, see Figure 7. Figure 6. A111 routing examples with vias placed close to sensor for maximizing ground plane size. (a) Without GND thermal reliefs, (b) with decoupling capacitors and without GND thermal reliefs, (c) with GND thermal reliefs. Trace to copper clearance is 0.127 mm.
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Page 12: Impact Of Conformal Coating
Hardware and physical integration guideline A1 PCR sensors Example PCB designs can be found on the Acconeer developer page [1]. For designs requiring larger components close to the sensor, a tapered shielding wall can be designed as shown in Figure 8. -
Page 13: Sensor Underfill
Dielectric constant determines the reflectivity of the medium and loss tangent indicates the dissipation effect of the material and both are frequency dependent. Page 13 of 30 2024-02-07 © 2024 by Acconeer – All rights reserved... -
Page 14: Electromagnetic Propagation
Conductors have a high dielectric constant (�� → ∞) and will therefore give a strong reflection. Most polymers have a dielectric constant in the range of 2 – 4 and will therefore give a weaker reflection. Page 14 of 30 © 2024 by Acconeer – All rights reserved 2024-02-07... -
Page 15: Radomes
Figure 11. Transmitted and reflected signals from a half wavelength radome. Secondary reflections have been omitted for simplicity. As an example, if the material relative permittivity is �� = 2.6, the optimal radome thickness becomes Page 15 of 30 2024-02-07 © 2024 by Acconeer – All rights reserved... -
Page 16: Radome Distance
Amplitude is normalized by the free space amplitude for each profile. Amplitude variation is stated in one direction (Tx or Rx side). For Radar loop Gain (RLG) the values will be doubled. Page 16 of 30 © 2024 by Acconeer – All rights reserved 2024-02-07... - Page 17 For multi-layer radome optimization, readers can find more information in [5]. Page 17 of 30 2024-02-07 © 2024 by Acconeer – All rights reserved...
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Page 18: Impact Of Radome On The Rlg Pattern
E- and H-plane when the cover (ABS plastic sheet) is located on top of the sensor. In comparison with free space, there is around 6 dB loss on both max. power and total radiated power for this case. Page 18 of 30 © 2024 by Acconeer – All rights reserved 2024-02-07... - Page 19 Figure 16: RLG pattern of E-plane and H-plane, cover placed directly on the sensor vs free space. The radial axis is the amplitude, stated in two directions (Tx and Rx side), i.e. Radar Loop Gain (RLG) and normalized to free space radiation. Page 19 of 30 2024-02-07 © 2024 by Acconeer – All rights reserved...
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Page 20: Dielectric Lenses
Dielectric lenses are also more compact and cheaper to fabricate than corresponding horn antennas and reflectors. To quickly get started using a lens, Acconeer provides two example lenses, one plano-convex and one FZP type lens, see Figure 17. Both lenses can be used with all module evaluation kits. The FZP lens is similar to the example lens in Ch. -
Page 21: Convex-Planar Lens (Hyperboloidal Lens)
Eq. (7) by solving for �� = �� (�� ), �� ∈ [��, �� + ��]. A parametrization �� (��), �� (��) may be required for generating the lens profile in CAD software. One such parametrization is Page 21 of 30 2024-02-07 © 2024 by Acconeer – All rights reserved... -
Page 22: Plano-Convex Lens
Contrary to the hyperboloidal lens, we now have refraction at both the inner and the outer surfaces. The lens profile given in Eq. (9) do not resemble any known function and we therefore simply call this lens a plano-convex lens. Page 22 of 30 © 2024 by Acconeer – All rights reserved 2024-02-07... -
Page 23: Lens Gain
PCB size. Figure 20. Simulated RLG patterns for different size hyperbolic lenses assuming lossless dielectrics. Figure 21. Simulated RLG patterns for different size plano-convex lenses assuming lossless dielectrics. Page 23 of 30 2024-02-07 © 2024 by Acconeer – All rights reserved... -
Page 24: Fresnel Zone Plate (Fzp) Lenses
Eq. (11) gives us the step thickness of s= 2.02 mm. Total thickness of the lens is then 4*2.02 = 8.1 For further details regarding FZP lens design, see [7]. Page 24 of 30 © 2024 by Acconeer – All rights reserved 2024-02-07... -
Page 25: Lens Thickness Comparison
For maximum gain and low side lobe level, it is important to also follow the PCB ground plane guidelines in Chapter 3.3. Page 25 of 30 2024-02-07 © 2024 by Acconeer – All rights reserved... -
Page 26: Focal Distance Tuning
Acconeer can construct optimized lenses for maximizing the gain, minimizing side lobes or customizing radiation patterns. The impact of lens housings, nearby mechanics and the PCB can also be simulated. Acconeer provides a design service for this, visit the Acconeer Developer page for details [1]. -
Page 27: References
Press, 2013. [10] "Acconeer Expolration Tool," [Online]. Available: https://acconeer-python- exploration.readthedocs.io/en/latest/sensor_introduction.html. [11] "Acconeer PCR sensor A111 EVK hardware userguide," [Online]. Available: https://developer.acconeer.com/download/xc112_xr112-user-guide-pdf. [12] T. Milligan, Modern Antenna Design, 2nd Edition, Wiley & Sons, 2005. [13] E. Hecht, Optics, 5th Edition, Pearson Education, 2017. - Page 28 Hardware and physical integration guideline A1 PCR sensors 6 Appendix A: Materials Table 1. Measured dielectric constant and loss tangent of different materials at 60 GHz [8]. Page 28 of 30 © 2024 by Acconeer – All rights reserved 2024-02-07...
- Page 29 2023-03-30 Updates for A121 sensor. Added chapter on dielectric lens design. 2024-02-07 Fixed typo in Eq. (9). Updated Figure 11. Corrected Equation (11) has therefore been corrected. Page 29 of 30 2024-02-07 © 2024 by Acconeer – All rights reserved...
- Page 30 Hardware and physical integration guideline A1 PCR sensors Disclaimer The information herein is believed to be correct as of the date issued. Acconeer AB (“Acconeer”) will not be responsible for damages of any nature resulting from the use or reliance upon the information contained herein.
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