TIDA029A july   2019  – june 2023 CC2640R2F-Q1 , CC2642R , CC2642R-Q1

 

  1.   1
  2.   Bluetooth Angle of Arrival (AoA) Antenna Design
  3.   Trademarks
  4. 1Introduction
  5. 2Angle of Arrival Antenna Design Considerations
    1. 2.1 Antenna Spacing
    2. 2.2 RF Switch Considerations
  6. 3Dipole Antenna Array
    1. 3.1 Dipole Antenna Strengths and Weaknesses
    2. 3.2 Angle Measurement Plane
    3. 3.3 PCB Implementation
    4. 3.4 Two Dipole Array Test Results
      1. 3.4.1 Total Radiated Power (TRP)
      2. 3.4.2 Measuring Antenna 1 and 2 Phase Difference
        1. 3.4.2.1 Bare PCB
        2. 3.4.2.2 PCB + RF Absorbing Material
        3. 3.4.2.3 PCB + RF Absorbing Material + Tin-Plated Copper Foil
        4. 3.4.2.4 PCB + RF Absorbing Material + Tin-Plated Copper Foil + Metal
      3. 3.4.3 Phase Difference vs Distance
  7. 4Calculating AoA From IQ Measurements
    1. 4.1 Dipole Antenna Array Uncompensated Angle of Arrival Results
      1. 4.1.1 Bare PCB Uncompensated AoA
      2. 4.1.2 PCB + RF Absorbing Material Uncompensated AoA
      3. 4.1.3 PCB + RF Absorbing Material + Tin-Plated Copper Foil Uncompensated AoA
      4. 4.1.4 PCB + RF Absorbing Material + Tin-Plated Copper Foil + Metal Uncompensated AoA
    2. 4.2 Dipole Antenna Array Compensated AoA Results
      1. 4.2.1 Bare PCB AoA With Compensation
      2. 4.2.2 PCB + RF Absorbing Material + Tin-Plated Copper Foil Compensated AoA
      3. 4.2.3 PCB + RF Absorbing Material + Tin-Plated Copper Foil + Metal Compensated AoA
      4. 4.2.4 Hardware Setup Compensated Results Comparison
  8. 5References
  9. 6Revision History

Bare PCB AoA With Compensation

The bare PCB required the least amount of compensation as the results were fairly close to Phi. However, Table 4-1 shows the gain and offset values used for each frequency.

Table 4-1 Bare PCB AoA Compensation Values
Frequency (MHz) Channel Gain Offset
2402 37 1.12 –4.69
2404 0 1.12 –4.69
2406 1 1.12 –5.04
2408 2 1.14 –4.82
2410 3 1.14 –4.82
2412 4 1.14 –5.1
2414 5 1.15 –4.81
2416 6 1.15 –4.73
2418 7 1.15 –4.45
2420 8 1.15 –4.73
2422 9 1.15 –4.16
2424 10 1.15 –4.37
2426 38 1.15 –4.22
2428 11 1.15 –4.36
2430 12 1.15 –3.86
2432 13 1.14 –3.65
2434 14 1.14 –3.72
2436 15 1.15 –3.57
2438 16 1.14 –3.43
2440 17 1.14 –3.29
2442 18 1.14 –2.93
2444 19 1.12 –3
2446 20 1.12 –2.09
2448 21 1.12 –2.79
2450 22 1.12 –2.65
2452 23 1.12 –2.57
2454 24 1.12 –2.64
2456 25 1.12 –2.36
2458 26 1.12 –2.64
2460 27 1.12 –2.36
2462 28 1.12 –2.08
2464 29 1.11 –2.49
2466 30 1.11 –2.35
2468 31 1.11 –2.63
2470 32 1.11 –2.14
2472 33 1.11 –2.55
2474 34 1.11 –2.41
2476 35 1.11 –2.07
2478 36 1.11 –1.86
2480 39 1.09 –1.99

Figure 4-14 shows the uncompensated AoA error vs Phi (the actual angle) and Figure 4-15 the compensated AoA error vs Phi.

GUID-AACB37DC-75D9-4A6E-B208-950AD9E83F5D-low.pngFigure 4-14 Bare PCB Uncompensated AoA Error Results
GUID-99D029AB-6E55-4C0F-86B1-C67B8647E6CF-low.pngFigure 4-15 Bare PCB Compensated AoA Error Results

It is clear that the error is greatly reduced over the most linear range (–65° to 65°). Figure 4-16 and Figure 4-17 show how the results have been adjusted to follow the ideal AoA vs Phi plot. There is less than 10° of error across the majority of frequencies from –70° to 65°.

GUID-1FAE9072-BF48-4FF8-B444-A169074CA257-low.pngFigure 4-16 Bare PCB Uncompensated AoA Results Over all Bluetooth Low Energy Channels
GUID-FAB60C2A-1A56-4CA0-8F92-B8976A371723-low.pngFigure 4-17 Bare PCB Compensated AoA Results Over all Bluetooth Low Energy Channels