SPRACF4C June   2018  – January 2023 AWR1243 , AWR1443 , AWR1642 , AWR1843 , AWR1843AOP , AWR2243 , AWR2944 , AWR6843 , AWR6843AOP , IWR1843 , IWR6443 , IWR6843 , IWR6843AOP

 

  1.   Trademarks
  2. 1Introduction
    1. 1.1 Purpose of Calibrations
    2. 1.2 Purpose of Monitoring Mechanisms
  3. 2Hardware Infrastructure to Support Calibration and Monitoring
  4. 3List of Calibrations
    1. 3.1  APLL Calibration
    2. 3.2  Synthesizer VCO Calibration
    3. 3.3  LO Distribution Calibration
    4. 3.4  ADC DC Offset Calibration
    5. 3.5  HPF Cutoff Calibration
    6. 3.6  LPF Cutoff Calibration
    7. 3.7  Peak Detector Calibration
    8. 3.8  TX Power Calibration
    9. 3.9  RX Gain Calibration
    10. 3.10 IQ Mismatch Calibration
    11. 3.11 TX Phase Shifter Calibration
  5. 4Impact of Calibration on Gain and Phase
  6. 5Impact of Interference on the Calibrations and Emissions Caused Due to Calibrations
  7. 6Scheduling of Runtime Calibration and Monitoring
    1. 6.1 Selection of CALIB_MON_TIME_UNIT
    2. 6.2 Selection of CALIBRATION_PERIODICITY
    3. 6.3 Application-Controlled One Time Calibration
  8. 7Software Controllability of Calibration
    1. 7.1  Calibration and Monitoring Frequency Limits
    2. 7.2  Calibration and Monitoring TX Frequency and Power Limit
    3. 7.3  Calibration Status Reports
      1. 7.3.1 RF Initialization Calibration Completion
      2. 7.3.2 Runtime Calibration Status Report
      3. 7.3.3 Calibration/Monitoring Timing Failure Status Report
    4. 7.4  Programming CAL_MON_TIME_UNIT
    5. 7.5  Calibration Periodicity
    6. 7.6  RF Initialization Calibration
    7. 7.7  Runtime Calibration
    8. 7.8  Overriding the TX Power Calibration LUT
    9. 7.9  Overriding the RX Gain Calibration LUT
    10. 7.10 Retrieving and Restoring Calibration Data
  9. 8References
  10.   A Calibration and Monitoring Durations
    1.     A.1 Duration of Boot Time Calibrations
  11.   Revision History

4 Impact of Calibration on Gain and Phase

As the temperature of the device changes, the gains of the RX and TX blocks also change. If the gain settings are not corrected over temperature, the Rx and Tx gains continue to reduce as the temperature increases. For example, on the AWR2243 device, Rx gain variation for a fixed gain setting is roughly 0.4 dB per 10deg change in temperature. The Tx gain variation for a fixed bias setting and 0-dB backoff scenario is 0.2 dB per 10deg change in temperature. To reduce the impact of this gain change with temperature, run time calibrations can be used in either periodic mode or one shot mode issued by the user application based on temperature change.

When a calibration adjustment is done, there is a possibility of a step change in the Rx or Tx gain or phase. The step change in the gain depends on the change in gain codes caused due to calibration. One gain code change in RX gain causes a 2dB change in gain. Because the same calibration codes are applied to all the receiver or transmit chains within a single MMIC, there is typically minimal gain/phase mismatch change between the channels. However, the absolute gain/phase before and after the calibrations can be different.

Some processing algorithms (such as Historical static clutter estimate) which rely on coherence or amplitude/phase consistency across frames can be sensitive to this abrupt change in absolute gain/phase resulting from calibrations. They should account for this by resetting their estimates just after calibration. In a single chip configuration, if gain/phase coherence is needed between frames, then the periodic run time calibrations can be avoided. Application can use the Run time calibrations in One Time Calibration mode, as explained in Section 6.3. The application can monitor the internal temperature and in case of significant change in temperature (for example 30°C change), it can issue a one time calibration. At this point, the gain and phase would change for the subsequent frames, hence the application must reset the algorithm if it is using any phase estimates from previous frames.

In a cascade use case, where the gain/phase mismatch across multiple MMICs becomes critical, the absolute gain/phase change in one MMIC can cause a mismatch across multiple MMICs. To handle this change, refer to the Cascade Coherency and Phase Shifter Calibration application note (https://www.ti.com/lit/pdf/https://www.ti.com/lit/pdf/spracv2).