SPRACV2 November   2020 AWR1843 , AWR2243

 

  1.   Trademarks
  2. 1Introduction
    1. 1.1 Background – Simple Single-Chip Applications
  3. 2Cascade Incoherence Sources and Mitigation Strategies
    1. 2.1 PCB Routing Imbalances and Device Processes
    2. 2.2 Temperature Drifts
    3. 2.3 Scheduling of Run Time Calibrations
  4. 3Enabling Cascade Coherence and Improved Phase Performance
    1. 3.1 High-Level Summary
      1. 3.1.1 Sequence of Proposed Steps and Introductory Flow Diagrams
    2. 3.2 Saving RF INIT Calibration Results at Customer Factory
      1. 3.2.1 Note on LODIST Calibration
      2. 3.2.2 TX Phase Shifter Calibration and Saving Results at Customer Factory
    3. 3.3 Corner Reflector-Based Offsets Measurement at Customer Factory
      1. 3.3.1 Corner Reflector-Based Inter-Channel Imbalances
      2. 3.3.2 Corner Reflector-Based TX Phase Shifter Errors
    4. 3.4 Restoring Customer Calibration Results In-Field
      1. 3.4.1 Restore RF INIT Calibrations Results In-Field
      2. 3.4.2 Restore TX Phase Shift Calibration Results In-Field
    5. 3.5 Host-Based Temperature Calibrations In-Field
      1. 3.5.1 Disabling AWR Devices’ Autonomous Run Time Calibrations
      2. 3.5.2 Enabling Host-Based Temperature Calibrations of Inter-Channel Imbalances
      3. 3.5.3 Switching of DSP Imbalance Data
      4. 3.5.4 Enabling TX Phase Shifter’s Host-Based Temperature Calibrations
        1. 3.5.4.1 Estimating TX Phase Shift Values at Any Temperature
        2. 3.5.4.2 Temperature Correction LUTs for AWR1843TX Phase Shifter
        3. 3.5.4.3 Temperature Correction LUTs for AWR2243 TX Phase Shifter
        4. 3.5.4.4 Restoring TX Phase Shift Values – Format Conversion
        5. 3.5.4.5 Restoring TX Phase Shift Values – Transition Timing and Constraints
        6. 3.5.4.6 Typical Post-Calibration TX Phase Shifter Accuracies
        7. 3.5.4.7 Correcting for Temperature Drift While Sweeping Across Phase Settings
        8. 3.5.4.8 Amplitude Stability Across Phase Shifter Settings
        9. 3.5.4.9 Impact of Customer PCB’s 20-GHz Sync Path Attenuation on TX Phase Shifters
      5. 3.5.5 Ambient and Device Temperatures
  5. 4Concept Illustrations
  6. 5Miscellaneous (Interference, Gain Variation, Sampling Jitter)
    1. 5.1 Handling Interference In-Field
    2. 5.2 Information on TX Power and RX Gain Drift with Temperature
    3. 5.3 Jitter Between Chirp Start and ADC Sampling Start
  7. 6Conclusion
  8.   A Appendix
    1.     A.1 Terminology
    2.     A.2 References
    3.     A.3 Flow Diagrams for Proposed Cascade Coherence Scheme
    4.     A.4 LUTs for TX Phase Shifter Temperature Drift Mitigation
    5.     A.5 Circular Shift of TX Phase Shifter Calibration Data Save and Restore APIs

4 Concept Illustrations

The below graphs illustrate solution concepts explained in this note. These are based on experiments on AWR1243 cascade sensor with two devices, with one RX and one TX from each considered for analysis.

The results with AWR2243 are expected to be similar in the context of this note. With this, there are 4 virtual channels or TX-RX combinations. The temperature in the experiments is varied and the absolute phase of the radar return signal for various TX-RX combinations is plotted. One of the graphs is with the AWR devices configured with their independent and autonomous periodic Run Time (temperature) Calibrations running (as would be typically recommended in single chip usages). The devices potentially can self-trigger calibration updates in 10°C resolution and create phase jumps of unknown magnitudes at different temperatures, as illustrated in this graph. The next graph illustrates the same but with externally triggered temperature calibrations with 3 bias settings (Low Bias, Mid Bias, and High Bias, as explained earlier). The last graph illustrates the same with additional post-compensation of the phase jumps across Low-Mid-High based on prior measurements of the jumps at 25°C ambient, and is devoid of phase jumps.

GUID-680CCE59-F3FD-4007-9257-FCA2913D2963-low.png Figure 4-1 Absolute Phase Variation with Independent, Autonomous Periodic Run Time Calibrations in the Devices
GUID-49D3EBC6-A2D3-437D-A02F-C538106EFE0A-low.png Figure 4-2 Absolute Phase Variation with External Triggering of Calibration Updates1
  1. Based on Low Bias, Mid Bias, and High Bias temperature ranges.
GUID-4B5A6349-6648-437E-B0BC-C68EE8620174-low.png Figure 4-3 Absolute Phase Variation with External Triggering of Calibration Updates1
  1. Based on Low Bias, Mid Bias, and High Bias temperature ranges with associated post-compensation using prior 25°C estimation of the jumps.