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Acconeer A111 User Manual

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Hardware and physical integration
guideline PCR Sensor A111
User Guide

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  • Page 1 Hardware and physical integration guideline PCR Sensor A111 User Guide...
  • Page 2 Hardware and physical integration guideline PCR Sensor A111 Hardware and physical integration guideline PCR Sensor A111 User Guide Author: Acconeer Version 1.0: 2019-11-13 Acconeer AB Page 2 of 32 深圳市佰誉达科技有限公司 Tel: 0755-2328 2845 2019-12-04...

  • Page 3: Table Of Contents

    Hardware and physical integration guideline PCR Sensor A111 Table of Contents Introduction ............................. 4 Radar loop equation ......................... 4 Radar radiation pattern ......................5 HW Integration - Schematics ......................6 Power ............................6 SPI Interface ..........................7 HW Integration - PCB ........................8 Sensor ground plane ........................

  • Page 4: Introduction

    This document aims to provide general guidelines for the hardware and physical integration of the Acconeer A111 radar sensor. The A111 sensor is a fully integrated 60 GHz radar including the transmitter and receiver antenna. The Tx/Rx antenna is a folded-dipole type and the E-plane and H- plane of the antennas are indicated in Figure 1.

  • Page 5: Radar Radiation Pattern

    Hardware and physical integration guideline PCR Sensor A111 1.2 Radar radiation pattern When characterizing the gain, we refer to the radar loop gain defined in the radar equation section. Figure 2 shows the radar setup configuration for the radar radiation pattern measurement. The reflector which in this case is circular trihedral corner (radius of 5 cm) is located at the far-field distance from the sensor (1 m).

  • Page 6: Hw Integration - Schematics

    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: Spi Interface

    Hardware and physical integration guideline PCR Sensor A111 Figure 4 An example of how to connect a power switch to reduce the leakage current when A111 is powered off. 2.2 SPI Interface To optimize the performance and speed of the SPI interface, the A111 and the MCU should be placed on the same PCB.

  • Page 8: Hw Integration - Pcb

    For manufacturing reasons, it is recommended to not flood the ground area in between the A111 ground balls. It is recommended to connect the ground balls of A111 with individual traces. It is very important to connect the ground below A111 to the Main ground plane surrounding the A111. An example of how to properly connect the sensor ground plane is shown in Figure 7.

  • Page 9: Sensor Underfill

    Hardware and physical integration guideline PCR Sensor A111 Figure 7 An example of a properly connected ground plane below the A111 radar sensor. 3.2 Sensor underfill Underfills are usually made of materials which are characterized by their dielectric properties. The sensor underfill material should be chosen to have as low dielectric constant and loss tangent as possible.

  • Page 10: A111 Decoupling Capacitors

    A111 VIO ball and the decoupling capacitor should be minimized. In practice, that means that the via should be placed as close as possible to the VIO balls on A111 and the trace between the A111 balls and the via, as well as the trace between the via and the decoupling capacitor, should be as short as possible.

  • Page 11: A111 Crystal

    Figure 10 An example how to place the Layer 1:4 via and decoupling capacitor C (Layer 4) that decouples ball D10 on A111 (Layer 1). All components with orange component outlines are placed on Layer 4 while the A111 is placed on Layer 1.
  • Page 12 Hardware and physical integration guideline PCR Sensor A111 Figure 11 An example how to place the A111 crystal (Layer 4), its tuning capacitors (C1, C2, Layer 4) and vias (Layer 1:4). The crystal is connected to balls J10 and H10 on A111 (Layer 1). All components with light blue component outline are placed on Layer 4 while the A111 is placed on Layer 1.

  • Page 13: Physical Integration

    This chapter provides the integration guidelines for simplified sensor cover scenarios. In any case, it is important to carefully design and characterize the integration to ensure that the desired performance is obtained. The radiation pattern presented in the A111 datasheet (www.developer.acconeer.com), shows the sensor performance when integrated in free space.
  • Page 14 Hardware and physical integration guideline PCR Sensor A111 Figure 12 Placement of the radome in relation to the sensor. Figure 13 Measured reflected power from the target versus the radome to sensor distance for two different service profiles (ACC_SERVICE_ENVELOPE_PROFILE_MAXIMIZE_SNR and ACC_SERVICE_ENVELOPE_PROFILE_MAXIMIZE_DEPTH_RESOLUTION).

  • Page 15: Radome Thickness

    Hardware and physical integration guideline PCR Sensor A111 4.2 Radome thickness When an EM wave travels in a dielectric material, its effective propagation speed and the wavelength will change depending on the dielectric material: �� �� �� , �� ������...

  • Page 16: Radome Distance

    Hardware and physical integration guideline PCR Sensor A111 �� ������ ℎ = = 1.55 ���� Figure 16 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.
  • Page 17 Hardware and physical integration guideline PCR Sensor A111 The optimum distance is valid if the thickness of the radome is optimum as well. Otherwise, to have a minimum insertion loss on the received signal, the distance to the sensor should follow the marginal criteria below: ��...

  • Page 18: Impact On The Radiation Pattern

    Hardware and physical integration guideline PCR Sensor A111 4.4 Impact on the radiation pattern The radiation pattern of the integrated antennas will be affected by the dome that is put on top of the sensor. Figure 17 shows the measured radar loop pattern for three different materials, ABS plastic, gorilla glass and free space.
  • Page 19 Hardware and physical integration guideline PCR Sensor A111 Figure 18 Impact of the radome-to-sensor distance on the radiation pattern (H-plane). It is not recommended to place the cover directly on the sensor. Figure 19 shows the radiation pattern on the H-plane when the cover (ABS plastic sheet) is located on top of the sensor. In comparison with Free Space, there is around 3 dB loss on both max.

  • Page 20: Multi-Layer Radome Integration

    Hardware and physical integration guideline PCR Sensor A111 4.5 Multi-layer radome integration Radomes can also be constructed from a multi-layer dielectric. Particularly, where the thickness of a single layer dielectric is fixed, thus additional layer can be added to the radome which can act as an anti-reflection layer.
  • Page 21 Hardware and physical integration guideline PCR Sensor A111 Figure 21 Simulation scenario: Sensor, air-gap, the matching layer and the screen. Figure 22 Normalized antenna gain where the matching layer dielectric constant is set to 1.1 and 3. Page 21 of 32 Tel: 0755-2328 2845 深圳市佰誉达科技有限公司...

  • Page 22: Physical Integration - Lens

    Acconeer have designed two type of lens to narrow the beamwidth and improve the gain. First is the hyperbolic lens and the second is based on the phase correcting plate which is called Fresnel Zone Plate (FZP) lens.

  • Page 23: Focal Distance

    Hardware and physical integration guideline PCR Sensor A111 Figure 24 3D-printed examples of the hyperbolic and FZP lenses. The material used for printing is ABS plastic. 5.1 Focal distance Radar loop measurement was done to characterize the focal point of the lens. The reflected power from a fixed radar target was captured for different sensor-to-lens distance.
  • Page 24 Hardware and physical integration guideline PCR Sensor A111 Figure 25 Gain variation of the lens versus the distance to the XM112 radome. The amplitude is normalized to Free Space (FS). Figure 26 Gain variation of the HPL and FZP lens versus the distance to the XR112 radome. The amplitude is normalized to Free Space (FS).

  • Page 25: Radiation Pattern

    Hardware and physical integration guideline PCR Sensor A111 5.2 Radiation pattern Two focal distances, D = 2 and 8 mm, are chosen for characterizing the radar loop radiation sensor-lens pattern of the lenses. Figure 27 and Figure 28 show the measured radar loop pattern for free-space, HPL and FZP lenses for the selected focal distances.

  • Page 26: Fzp Lens Design

    Hardware and physical integration guideline PCR Sensor A111 Figure 29 Half-power beam width for the FZP and hyperbolic lenses placed at a distance from the sensor of 8mm and 2mm respectively. In Figure 30 the maximum gain of the lenses in the E-plane is shown for the two different focal distances.
  • Page 27 Hardware and physical integration guideline PCR Sensor A111 FZP lens is shown, as well as the equations needed to design one. For further details regarding FZP and hyperbolic lens design, refer to [5]. Figure 31 Detailed description of an FZP lens and the equations needed to calculate its dimensions.
  • Page 28 Hardware and physical integration guideline PCR Sensor A111 = 5.1mm = 7.46mm = 9.39mm = 11.12mm s= 2.17 mm Total thickness of the lens: 4*2.17 = 8.7 mm Page 28 of 32 Tel: 0755-2328 2845 深圳市佰誉达科技有限公司 2019-12-04...

  • Page 29: Appendix A: Materials

    Hardware and physical integration guideline PCR Sensor A111 6 Appendix A: Materials Table 1 Measured dielectric constant and loss tangent of different materials at 60 GHz [6]. Page 29 of 32 Tel: 0755-2328 2845 深圳市佰誉达科技有限公司 2019-12-04...

  • Page 30: References

    Hardware and physical integration guideline PCR Sensor A111 7 References https://developer.acconeer.com/download/a111-datasheet-pdf/ https://acconeer-python-exploration.readthedocs.io/en/latest/sensor_introduction.html https://developer.acconeer.com/download/xm112-datasheet-pdf/ https://developer.acconeer.com/download/xc112_xr112-user-guide-pdf/ Thornton, John, and Kao-Cheng Huang. “Modern lens antennas for communications engineering.” Vol. 39. John Wiley & Sons, 2013. Boriskin, Artem, and Ronan Sauleau, eds. “Aperture Antennas for Millimeter and Sub-Millimeter Wave Applications”.

  • Page 31: Revision

    Hardware and physical integration guideline PCR Sensor A111 8 Revision Date Version Changes 2019-11-13 Original version Page 31 of 32 深圳市佰誉达科技有限公司 2019-12-04 Tel: 0755-2328 2845...

  • Page 32: Disclaimer

    Hardware and physical integration guideline PCR Sensor A111 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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