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Texas Instruments Self-Calibration of mmWave Radar Devices Application notes
Application Report
SPRACF4 – June 2018
Self-Calibration in TI’s mmWave Radar Devices
Anand Gadiyar, Karthik Subburaj, Sumeer Bhatara
ABSTRACT
TI’s mmWave radar sensors include an internal processor and hardware architecture to enable selfcalibration and monitoring. Calibration ensures that the performance of the radar front end is maintained
across temperature and process variation. Monitoring enables the periodic measurement of RF/analog
performance parameters and the detection of potential failures.
This application note briefly describes the calibration and monitoring mechanisms and focuses mainly on
the software configurability of the calibration routines run by the internal processor.
Table 1. Abbreviations
Abbreviation
Description
BIST
Built-in Self Test
CLPC
Closed Loop Power Control
LNA
Low Noise Amplifier
LUT
Lookup Table
OLPC
Open Loop Power Control
VCO
Voltage Controlled Oscillator
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Contents
1
Introduction ................................................................................................................... 3
2
Hardware Infrastructure to Support Calibration and Monitoring ....................................................... 4
3
List of Calibrations ........................................................................................................... 5
4
Scheduling of Periodic Runtime Calibration and Monitoring ........................................................... 7
5
Software Controllability of Calibration ................................................................................... 11
6
References .................................................................................................................. 13
Appendix A
Calibration and Monitoring Durations ........................................................................... 14
List of Figures
1
Radar Front-End Architecture in a TI mmWave Device ................................................................ 3
2
RX Gain and TX Power With and Without Calibration .................................................................. 4
3
On-Chip TX-RX Test Signal Loopback Architecture: TX Monitoring, RX Monitoring, RX Baseband
Monitoring ..................................................................................................................... 5
4
Calibration and Monitoring Activity During Inter-Frame Idle Times ................................................... 8
5
Example 1
6
7
8
.................................................................................................................... 9
Example 2 ................................................................................................................... 10
Example 3 ................................................................................................................... 10
Example 4 ................................................................................................................... 11
List of Tables
1
Abbreviations ................................................................................................................. 1
2
Duration of Boot Time Calibrations ...................................................................................... 14
3
Duration of Run Time Calibrations ....................................................................................... 14
4
Duration of Analog Monitors .............................................................................................. 14
5
Duration of Digital Monitors ............................................................................................... 15
6
Duration of Software Overheads ......................................................................................... 15
Trademarks
All trademarks are the property of their respective owners.
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Self-Calibration of mmWave Radar Devices
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Introduction
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1
Introduction
TI’s mmWave radar sensors include an internal processor to stabilize the radar front end performance
across temperature and process by running calibration routines. The processor also enables the sensor’s
functional safety by periodically determining RF/analog performance parameters and detecting functional
failures by running monitoring routines. The processor is programmed by TI and is dedicated for RF
calibration and functional safety monitoring.
This document describes the various calibration mechanisms available in TI’s mmWave radar sensors and
their configurability.
1.1
Purpose of Calibrations
Figure 1 illustrates the radar front-end architecture in a TI mmWave radar device. The performance
parameters of the RX LNA, IF amplifiers, TX PA, X4 (frequency multiplier), LO distribution buffers, and the
clock sources shown all vary with process and temperature.
Figure 1. Radar Front-End Architecture in a TI mmWave Device
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Introduction
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The purpose of calibrations is illustrated in Figure 2 using RX gain and TX power as examples. The gain
of the RX LNA and the TX PA vary from device to device due to manufacturing process variations and
also across temperature. The purpose of calibration is to ensure the RX gain and output power are
maintained as configured by the user despite variations in process and temperature. To achieve this, the
internal processor adjusts the mmWave circuit configurations at initialization (to mitigate effects of process
variation) and periodically at runtime (to mitigate effects of temperature drifts). Figure 2 illustrates how
calibration can be used to maintain the RX Gain and TX Power close to the configured settings across
temperature drifts. These charts are illustrative and may not reflect actual device performance.
Figure 2. RX Gain and TX Power With and Without Calibration
Some of the calibrations (for example, the gain and power calibrations) are implemented as adjustments
of circuit configurations based on measurement of RF/analog parameters. Other calibrations are
implemented as adjustments based on process/temperature look up tables.
1.2
Purpose of Monitoring Mechanisms
To enable functional safety, such as in automotive applications, the monitoring mechanisms in the device
can be configured to periodically provide the host processor with RF/analog health and diagnostic
information. These mechanisms enable determination of RF/analog performance parameters and
detection of failures arising from transistor and interconnect faults in the field. The diagnostic information
they provide can also be helpful during development and optimization of designs integrating TI mmWave
radar devices.
2
Hardware Infrastructure to Support Calibration and Monitoring
The calibration and monitoring mechanisms in TI’s mmWave devices are implemented using a
combination of hardware and firmware. Some of the hardware infrastructure blocks enabling these are
illustrated here.
Several TX, RX RF and IFA parameter measurements are enabled by the mmWave power detectors
coupled to the TX PA outputs and RX LNA inputs, and the TX-RX RF and RX IF loopback structures in
the device, illustrated in Figure 3.
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Figure 3. On-Chip TX-RX Test Signal Loopback Architecture: TX Monitoring, RX Monitoring, RX Baseband
Monitoring
For example, the RX RF gain and inter-RX imbalance measurement is enabled by the RX RF loopback
architecture. For this, an RF loopack signal with a slight frequency offset from the RX mixer LO frequency
is created using a frequency shifter in the TX and coupled symmetrically to the RXs. The firmware
measures the loopback signal power at the RX LNA input (using the mmWave power detectors) and at the
RX ADC output (by digital signal processing of the RX ADC output). From these, the RX gains and interRX gain and phase imbalances are determined.
Similarly, to enable TX monitoring, power detectors are instantiated at the TX PA outputs. Also, inter-TX
imbalance and TX phase modulation measurements are enabled by the TX RF loopback architecture. For
this, all TX PA outputs are symmetrically coupled to the RX input through a square wave on-off-keying
modulator, which provides a frequency offset between the signal at the RX LNA input and the RX mixer
LO. The firmware measures the loopback signal amplitude and phase (by digital signal processing of the
RX ADC output). From these, the inter-TX imbalance and TX phase modulation parameters are
determined.
To enable RX baseband monitoring (for example, filter responses), an IF loopback test signal is generated
and fed to the RX IF amplifiers. The firmware uses digital signal processing of the loopback signal at the
RX ADC output to calibrate and monitor the RX IF filter frequency response.
The device also includes a shared general purpose ADC (GPADC) to measure various internal voltage
levels for monitoring. For example, various supply voltages, circuit bias voltages, PLL VCO control
voltages, temperature sensor output voltages, and mmWave power detector output voltages are all
multiplexed and forwarded to the GPADC. The firmware uses this multiplexor and GPADC to detect
transistor and interconnect faults through internal voltage monitoring. It also uses them for calibration
adjustments: for example, the firmware observes the PLL and synthesizer VCO control voltages to tune
their VCOs and enable them to always remain in lock across process and temperature.
3
List of Calibrations
TI’s mmWave radar devices support the calibrations described in the following sections. All calibrations
can be performed at the RF initialization phase (typically after every power cycle), and some can also be
carried out at runtime. Two of these calibrations (APLL and Synthesizer VCO calibrations) are always
enabled at boot time and at runtime, and cannot be disabled. The time required for these two calibrations,
and for all enabled periodic runtime calibrations, must be budgeted for when defining the frame
configuration.
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List of Calibrations
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Except for APLL and Synthesizer VCO calibrations, all the other calibrations can be individually disabled
at the RF initialization phase. If a calibration is disabled at the RF initialization phase, it cannot be enabled
at run time. In this case, the corresponding blocks always use fixed settings and will not compensate for
changes in temperature.
NOTE: The term "boot time" in this document refers to the RF initialization phase.
3.1
APLL Calibration
The APLL supplies the clock to the processor, digital logic as well as the ADCs, DACs and FMCW
synthesizer. APLL calibration is done to keep the system clock always locked at a constant frequency
irrespective of process and temperature. It is done at the RF initialization phase by measuring the VCO’s
control voltage and adjusting the VCO tuning.
This is periodically and incrementally repeated at run time to account for the temperature drift. Runtime
APLL calibration is triggered when the age of the last calibration result exceeds 1 second. Due to the
importance of the system clock, APLL calibration cannot be disabled by the user and the calibration
periodicity is not user controllable. The user should account for this calibration time while programming the
frame timing.
3.2
Synthesizer VCO Calibration
Synthesizer VCO calibration is done for both VCOs at boot time, and is also triggered when the age of the
last calibration result exceeds 1 second. The calibration algorithm measures the synthesizer control
voltage for both VCOs, and acts to maintain these voltages within a fixed range at all times.
Again, due to the importance of the synthesizer VCO frequency, this calibration cannot be disabled by the
user and the calibration periodicity is not user controllable. The user should account for this calibration
time while programming the frame timing.
3.3
LO Distribution Calibration
The LO Distribution chain registers are updated using an internal lookup table based on temperature. This
calibration is carried out at boot time, and can also be carried out at runtime.
3.4
ADC DC Offset Calibration
The ADC DC offset is only calibrated once, at boot time. This calibration is carried out without any signal
at the RF LNA input. The LNA input is terminated to block reception of any RF signal during the
calibration, and the DC power is measured using the DFE statistics collection. The measured DC offsets
are programmed into the digital DC correction block for cancellation.
3.5
HPF Cutoff Calibration
The HPF1 and HPF2 high pass filters are only calibrated once, at boot time. The RX IFA square wave
loopback is used to feed a known tone at the IFA input, and the ADC output’s FFT component at the
same frequency is measured. The filter is tuned to achieve the desired attenuation at the desired cutoff
frequency.
3.6
LPF Cutoff Calibration
The LPF1 and LPF2 low pass filters are only calibrated once, at boot time. The IFA square wave loopback
is used to feed a known tone at the IFA input, and the filter is tuned to achieve the desired attenuation at
the desired cutoff frequency.
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3.7
Peak Detector Calibration
The peak detectors aim at providing an absolute voltage and power reference throughout the radar chip.
They allow monitoring of voltage stress on the RF nodes, and quantify the output power at both the TX
output and RF inputs. This allows for accurate RF BIST and impedance detector measurements. To make
these measurements accurate, the peak detectors must be calibrated for variation in temperature. This
calibration is carried out for all critical peak detectors, especially the ones used for TX power calibration.
The peak detectors are calibrated at boot time, and can also be recalibrated at runtime.
3.8
TX Power Calibration
TX power calibration is carried out to ensure that the device is transmitting at exactly the specified transmit
power for a given profile.
TX power calibration can be done in Open Loop Power Control (OLPC) or Closed Loop Power Control
(CLPC) modes. In OLPC mode, the TX stage codes are set based on a coarse measurement and a LUT
is generated for every temperature range. The final stage codes are picked from the LUT and applied to
the device based on the temperature at the time of calibration.
In CLPC mode, the TX stage codes are picked from the coarse LUT as in the OLPC step. Then, the
actual TX power is measured using the peak detectors and the TX stage codes are refined to achieve the
desired TX power accuracy.
The LUT used for TX power calibration can be read back from the device using an API. The LUT can also
be replaced with a user-programmed LUT (for example, with an LUT that was previously read back from
the device). The APIs to read and write the TX power calibration LUT are covered in Section 5.7.
NOTE: In CLPC mode, the LUT used for TX power calibration may be updated by the device after
run time calibration events. The updated LUT can be read back from the device if needed.
TX power calibration is carried out at boot time for all enabled TXs, and can be carried out again at
runtime. When recalibrating at runtime, the TX power calibration is done per-profile, per-TX.
3.9
RX Gain Calibration
The RX RF gain is calibrated to ensure that the overall RX gain is retained across changes in
temperature. The RF gain is measured once, at boot time, before any profiles are configured. The boot
time temperature at which the gain is measured is also stored for use during run time recalibration.
The current RF gain for a profile is computed using the device temperature at the time of calibration, the
temperature at boot time, and the measured RX RF gain at boot time. Variation in the RX gain is
compensated in the RX IFA and DFE, to achieve the desired overall gain for the profile.
The LUT used for RX gain calibration can be read back from the device using an API. The LUT can also
be replaced with a user-programmed LUT (for example, with an LUT that was previously read back from
the device). The APIs to read and write the RX gain calibration LUT are covered in Section 5.8.
4
Scheduling of Periodic Runtime Calibration and Monitoring
The device receives the desired chirp and frame configuration from the corresponding API messages, and
schedules transmission of chirps accordingly. Chirps are transmitted in bursts or frames, as per the
configuration programmed.
All periodic calibrations and monitoring are scheduled by the device in the large inter-frame (or inter-burst,
for advanced frames) idle time periods in every frame. Individual monitors and calibrations can be enabled
or disabled as needed in the application. The periodicity of calibration and monitoring is configurable by
two programmable parameters: CALIB_MON_TIME_UNIT and CALIBRATION_PERIODICITY.
One cycle of monitoring covering all enabled monitors is carried out every CALIB_MON_TIME_UNIT
frames, (as programmed by the user). Therefore:
MonitoringPeriod (in µs) = FramePeriod (in µs) × CALIB_MON_TIME_UNIT
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Periodic calibrations (except APLL and Synthesizer VCO calibrations) are carried out at a configurable
multiple of CALIB_MON_TIME_UNIT. This multiple is configured using the CALIBRATION_PERIODICITY
parameter.
CalibrationPeriodicity (in µs) = MonitoringPeriod (in µs) × CALIBRATION_PERIODICITY
(2)
NOTE: APLL and Synthesizer VCO calibrations are always carried out in the next available idle
period after every 1 second; this is not controllable by the host. APLL and Synthesizer VCO
calibrations are always enabled.
The value of CALIB_MON_TIME_UNIT must be large enough to accommodate all enabled monitors, all
enabled periodic runtime calibrations and some software overheads. Even though calibration may not
necessarily be carried out in every monitoring period, it must still be budgeted for when selecting
CALIB_MON_TIME_UNIT.
Every CALIBRATION_PERIODICITY, the processor reads the temperature and performs a calibration
update if needed. This update is done only if the temperature deviates by ±10 degrees compared to the
temperature when the last calibration was done. LO Distribution calibration updates are done only if the
temperature deviates by ±20 degrees from the temperature at last update.
This temperature measurement and calibration happens during the idle time between frames (or bursts). If
any calibration results in an update to the device registers, the host is notified about the calibration update
through an asynchronous event message.
The device determines the available idle time before the start of each frame (or burst) to ensure that there
is enough idle time to complete each calibration. The minimum idle time needed to schedule any
calibration is 200 µs.
Figure 4 shows an example where CALIB_MON_TIME_UNIT is 2 and CALIBRATION_PERIODICITY is 3.
Note that monitoring activity can be spread across several inter-frame idle times.
Figure 4. Calibration and Monitoring Activity During Inter-Frame Idle Times
4.1
Selection of CALIB_MON_TIME_UNIT
The first step is to compute the total available idle time per frame. For advanced frames, this includes all
inter-burst idle times, inter-subframe idle times, and the inter-frame idle time. From this number, 100 µs
should be reserved to allow for the preparation time for the next frame.
The next step is to compute the duration of all enabled periodic calibrations, all enabled monitors, and the
software overheads. The duration of each of the monitors and calibrations are listed in Appendix A.
Then, the smallest allowed value of CALIB_MON_TIME_UNIT is the number of frames needed to
accommodate the above duration in the available idle time per frame. The software overhead for the
windowed watchdog depends on the CALIB_MON_TIME_UNIT, and thus this calculation must be
iterative.
CALIB_MON_TIME_UNIT can be chosen to be any number higher than this, as required by the
application.
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4.2
Selection of CALIBRATION_PERIODICITY
The calibration periodicity must be at least 1 second or higher. The smallest allowed value for
CALIBRATION_PERIODICITY is:
CALIBRATION_PERIODICITY > = CEIL(1/(FramePeriod (in s) × CALIB_MON_TIME_UNIT))
4.3
(3)
Examples to Select CAL_MON_TIME_UNIT and CALIBRATION_PERIODICITY
The following examples illustrate the process of selecting CAL_MON_TIME_UNIT and
CALIBRATION_PERIODICITY. In each case, the minimum allowed value of these two parameters is
shown. CAL_MON_TIME_UNIT will usually be chosen based on the desired monitoring interval for the
application, subject to the minimum allowed value. CALIBRATION_PERIODICITY will then be chosen
such that calibrations are attempted once in slightly more than 1 second.
4.3.1
Example 1
A use case has 2 TX enabled, uses only 1 profile, frame configuration consists of 64 chirps, each chirp is
of duration is 66 µs (56-µs ramp time and 10-µs chirp idle time), and frame periodicity is 10 ms. All run
time calibrations are enabled. None of the analog monitorings are enabled.
Idle time per frame is 10000 - (56 + 10) × 64 = 5776 µs
Idle time available for calibration and monitoring per frame is 5676 µs (100 µs is for frame preparation).
Time needed for all run-time calibrations is 150 + 300 + 30 + 500 + (800 × 2) + 30 + 150 = 2760 µs
The minimum time needed for software overheads is 20 + 1000 + 500 + 10000 × 1/8 = 2770 µs, if
CALIB_MON_TIME_UNIT=1
Total time needed per frame for calibration is 2760 + 2770 = 5530 µs, which is less than the frame idle
time available (5676 µs); thus, setting CALIB_MON_TIME_UNIT to 1 is honored by the AWR1XXX device.
Set CALIB_MON_TIME_UNIT to 1 and CALIBRATION_PERIODICITY to 100. With this setting, monitoring
is carried out every 10 ms, and calibrations are triggered once every 100 frames (in other words, every 1
s).
Figure 5. Example 1
4.3.2
Example 2
Consider another example where the frame configuration remains the same as in example 1, but frame
periodicity is reduced to 8 ms.
Idle time per frame is 8000 - (56 + 10) × 64 = 3776 µs
Idle time available for calibration and monitoring per frame is 3676 µs (100 µs is for frame preparation).
Time needed for all run time calibrations is 150 + 300 + 30 + 500 + (800 × 2) + 30 + 150 = 2760 µs
The minimum time needed for software overheads is 20 + 1000 + 500 + 8000 × 1/8 = 2520 µs, if
CALIB_MON_TIME_UNIT=1
Total time needed per frame for calibration is 2760 + 2520 = 5280 µs. which is more than the available
frame idle time (3676 µs), and thus setting CALIB_MON_TIME_UNIT to 1 is not honored by the
AWR1XXX device. If CALIB_MON_TIME_UNIT is set to 1 and framing is started, the device issues the
AWR_CAL_MON_TIMING_FAIL_REPORT_AE_SB report indicating insufficient available idle time.
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Set CALIB_MON_TIME_UNIT to 2 and CALIBRATION_PERIODICITY to 63. With this setting, monitoring
is carried out every 16 ms, and calibrations are triggered every 126 frames (in other words, every 1.008
s).
Figure 6. Example 2
4.3.3
Example 3
Consider a use case which has 2 TX enabled, uses 2 profiles, frame configuration consists of 32 chirps,
each chirp is of duration is 90 µs (80-µs ramp time and 10-µs chirp idle time), and frame periodicity is 6
ms. All run time calibrations are enabled. None of the analog monitorings are enabled.
Idle time per frame is 6000 - (80 + 10) × 32 = 3120 µs
Idle time available for calibration and monitoring per frame is 3020 µs (100 µs is for frame preparation).
Time needed for all run time calibrations is 150 + 300 + 30 + 500 + (800 × 2 × 2) + 30 + 150 = 4360 µs
The minimum time needed for software overheads is 20 + 1000 + 500 + (6000 × 1/8) = 2270 µs, if
CALIB_MON_TIME_UNIT=1
Total time needed per frame for calibration is 4360 + 2270 = 6630 µs, which is more than the available
frame idle time (3020 µs), and thus setting CALIB_MON_TIME_UNIT to 1 is not honored by the
AWR1XXX device. If CALIB_MON_TIME_UNIT is set to 1 and framing is started, the device issues the
AWR_CAL_MON_TIMING_FAIL_REPORT_AE_SB report indicating insufficient available idle time.
Set CALIB_MON_TIME_UNIT to 3 and CALIBRATION_PERIODICITY to 56. With this setting, the
minimum required idle time is 8130 µs, and the available time across 3 frames is 9160 µs. Calibrations are
triggered every 168 frames (in other words, every 1.008 s).
Figure 7. Example 3
4.3.4
Example 4
Consider another example where the frame configuration remains the same as in Example 3. All run time
calibrations are enabled. The following analog monitorings are enabled: (a) TX output power monitor for
TX0 and TX1 (b) TX BPM monitor for TX0 and TX1 (c) RX gain phase monitor and (d) RX noise figure
monitor. Each of the monitors are configured to be run for 1 profile and 3 RF frequencies (low, mid and
high) as defined by the profile.
Idle time per frame is 6000 - (80 + 10) × 32 = 3120 µs
Idle time available for calibration and monitoring per frame is 3020 µs (100 µs is for frame preparation).
Time needed for all run time calibrations is 150 + 300 + 30 + 500 + (800 × 2 × 2) + 30 + 150 = 4360 µs
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Time needed for all monitoring is (1250 × 3) + (250 × 3) + (200 × 3 × 2) + (575 × 2) = 6850 µs
The minimum time needed for software overheads is 20 + 1000 + 500 + (6000 × 1/8) = 2270 µs, if
CALIB_MON_TIME_UNIT=1
Total time needed per frame for calibration and monitoring is 4360 + 6850 + 2270 = 13480 µs, which is
more than the available frame idle time (3020 µs), and thus setting CALIB_MON_TIME_UNIT to 1 is not
honored by the AWR1XXX device. If CALIB_MON_TIME_UNIT is set to 1 and framing is started, the
device issues the AWR_CAL_MON_TIMING_FAIL_REPORT_AE_SB report indicating insufficient
available idle time.
Set CALIB_MON_TIME_UNIT to 6 and CALIBRATION_PERIODICITY to 28. With this setting, the
minimum required time for calibration and monitoring is 17230 µs, and the available idle time across 6
frames is 18120 µs. Monitoring is triggered once in 6 frames, and calibrations are triggered once in 168
frames (in other words, every 1.008 s).
Figure 8. Example 4
5
Software Controllability of Calibration
This section lists the calibration-related software APIs available in mmWaveLink. The most up to date
information on these APIs is available in the AWR1xx Radar Interface Control Document.
5.1
Calibration and Monitoring Frequency Limits
The rlRfSetCalMonFreqLimitConfig function can be used to program the lower and higher RF frequency
limits for calibration and monitoring. These limits are applied to all TXs. TI recommends using the
rlRfTxFreqPwrLimitConfig function instead, as it allows for greater flexibility.
NOTE: If both rlRfSetCalMonFreqLimitConfig and rlRfTxFreqPwrLimitConfig functions are called,
then the function that is called later decides the limits used during calibration and monitoring.
5.2
Calibration and Monitoring TX Power Limits
There might be a need to restrict the frequency bands and power levels at which the device transmits.
During normal framing, this is enforced by limits in the configured profile. However, profiles are configured
only after boot time.
In order to restrict the frequency bands and power levels during boot time calibration, the
rlRfTxFreqPwrLimitConfig function can be used to program the lower and higher RF frequency limits and
the TX power backoff for each TX individually. The frequency limits and TX power backoff settings
configured using this function are used during boot time calibrations. These limits should be programmed
explicitly before calling rlRfInit as profiles are not defined until after rlRfInit is called.
If this API is not explicitly called, then the frequency range used for boot time calibrations is 76 to 81 GHz,
and the TX power backoff is 0.
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Software Controllability of Calibration
5.3
5.3.1
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Calibration Status Reports
RF Initialization Calibration Completion
When rlRfInit is called, the boot time calibrations are run and the application should wait for the RF
initialization/calibration completion asynchronous event AWR_AE_RF_INITCALIB_STATUS_SB.
This report indicates the pass/fail status for all enabled boot time calibrations, and whether any calibration
data were updated in the hardware as a result of the calibration. The report also contains the timestamp at
which calibration was carried out, and the measured temperature at the time of calibration (this is the
average of the temperature sensor readings from the temperature sensors located near the TX and RX
channels).
5.3.2
Runtime Calibration Status Report
If calibration reports are enabled using the rlRfRunTimeCalibConfig API, the
AWR_RUN_TIME_CALIB_SUMMARY_REPORT_AE_SB asynchronous event message is sent by the
mmWave device upon completion of any run-time calibrations (both one-time and periodic).
This report indicates the status of each enabled runtime calibration, and whether any calibration data were
updated in the hardware as a result of the calibration. The report also contains the timestamp at which
calibration was carried out, and the measured temperature at the time of calibration (this is the average of
the temperature sensor readings from the temperature sensors located near the TX and RX channels).
5.3.3
Calibration/Monitoring Timing Failure Status Report
The AWR_CAL_MON_TIMING_FAIL_REPORT_AE_SB asynchronous event message is sent by the
mmWave device if the total monitoring and calibration times do not fit in one CALIB_MON_TIME_UNIT.
This report is also sent when there is a run-time violation wherein the monitoring and calibrations could not
be carried out in one CAL_MON_TIME_UNIT.
5.4
Programming CAL_MON_TIME_UNIT
The rlRfSetCalMonTimeUnitConfig function is used to set the CALIB_MON_TIME_UNIT.
CALIB_MON_TIME_UNIT is the basic time unit for calibration and monitoring, and determines the period
over which the various monitors are cyclically executed.
5.5
RF Initialization Calibration
The rlRfInitCalibConfig function can be used to control the set of calibrations carried out when rlRfInit is
called. By default, all calibrations are carried out at RF initialization. This function must be called before
rlRfInit is called.
5.6
Runtime Calibration
The rlRfRunTimeCalibConfig function can be used to:
• Trigger one-time calibrations instantaneously
• Schedule periodic run time calibrations
• Configure the calibration periodicity
• Enable the calibration summary reports
• Configure the TX power calibration mode (OLPC+CLPC or OLPC only)
This function should be issued only when the device is not framing.
If enabled in the API call, the one-time calibration will run as soon as the function is called. If reporting is
also enabled at the same time as one-time calibration, a run-time calibration summary report will also be
immediately issued.
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5.7
Overriding the TX Power Calibration LUT
The LUT used for TX power calibration can be read back using the rlTxGainTempLutGet function. This
returns the lookup table that is applied for TX power calibration for a given profile. The function should
only be called after the profile has been configured in the device.
The LUT structure is described in the AWR1xx Radar Interface Control document. The LUT for a given
profile consists of a set of 19 TX gain codes for each TX, with each code corresponding to a particular 10
degree temperature bin. Each TX gain code is a 6-bit number with higher values corresponding to higher
gain.
If the CLPC mode is enabled, then the entries in the LUT may be updated automatically by the device as
a consequence of run time calibration.
The rlTxGainTempLutSet function can be used to replace the LUT used by the device for TX power
calibration with a different set of gain codes. This function should be called once for each profile for which
the LUT needs to be replaced. This function should only be called after the profile has been configured in
the device.
5.8
Overriding the RX Gain Calibration LUT
The LUT used for RX gain calibration can be read back using the rlRxGainTempLutGet function. This
returns the lookup table that is applied for RX gain calibration for a given profile. The function should only
be called after the profile has been configured in the device.
The LUT structure is described in the AWR1xx Radar Interface Control document. The LUT for a given
profile consists of a set of 19 RX gain codes, each corresponding to a particular 10 degree temperature
bin. Each RX gain code is further divided into an IF gain code and a RF gain code.
The rlRxGainTempLutSet function can be used to replace the LUT used by the device for TX power
calibration with a different set of gain codes. This function should be called once for each profile for which
the LUT needs to be replaced. This function should only be called after the profile has been configured in
the device.
5.9
Retrieving and Restoring Calibration Data
The rlRfCalibDataStore and rlRfCalibDataRestore functions allow the retrieval and reprogramming of all
calibration data from the device. These APIs can be used to store all calibration data to non-volatile
memory at the factory and restore them at each power up.
The calibration data consist of 3 chunks of 228 bytes each. The rlRfCalibDataStore function reads one
chunk of calibration data from the device at a time, and the rlRfCalibDataRestore function restores one
chunk of calibration data to the device at a time.
The rlRfCalibDataRestore API must be called before rlRfInit is called.
Once the calibration data are restored properly and validated, the device will issue the
AWR_AE_RF_INITCALIB_STATUS_SB report indicating the result of the calibrations based on the
restored calibration data.
6
References
•
AWR1xx Radar Interface Control Document, Rev 0.96, Texas Instruments, April 2018
SPRACF4 – June 2018
Submit Documentation Feedback
Self-Calibration of mmWave Radar Devices
Copyright © 2018, Texas Instruments Incorporated
13
Appendix A
SPRACF4 – June 2018
Calibration and Monitoring Durations
A.1
Duration of Boot Time Calibrations
Table 2. Duration of Boot Time Calibrations
Sl. No
Calibration
Duration (µs)
1
APLL
330
2
Synth VCO
1300
3
LO DIST
12
4
ADC DC
600
5
HPF cutoff
3500
6
LPF cut off
3200
7
Peak detector
4200
8
TX power
(per TX, per profile)
6000
9
RX gain
2300
A.2
Duration of Run Time Calibrations
Table 3. Duration of Run Time Calibrations
A.3
Sl. No
Calibration
Duration (µs)
1
APLL
150
2
Synth VCO
300
3
LO DIST
30
4
Peak detector
500
5
TX power
(per TX, per profile)
800
6
RX gain
30
7
Application of calibration to hardware
(This must always be included)
150
Monitoring Durations
Table 4. Duration of Analog Monitors
14
Sl. No
Monitors
Duration (µs)
1
RX gain phase
(per RF frequency)
1250
2
RX noise figure
(per RF frequency)
250
3
RX IF stage
(per RF frequency)
1000
4
TX power
(per TX, per RF frequency)
200
Self-Calibration of mmWave Radar Devices
Copyright © 2018, Texas Instruments Incorporated
SPRACF4 – June 2018
Submit Documentation Feedback
Duration of Software Overheads
www.ti.com
Table 4. Duration of Analog Monitors (continued)
Sl. No
Monitors
Duration (µs)
5
TX ballbreak
(per TX)
250
6
TX gain phase mismatch
(per TX, per RF frequency)
400
7
TX BPM
(per TX)
575
8
Synthesizer frequency
0
9
External analog signals
(all 6 GPADC channels enabled)
150
10
TX Internal analog signals
(per TX)
200
11
RX internal analog signals
1700
12
PM, CLK, LO internal analog signals
400
13
GPADC internal signals
50
14
PLL control voltage
210
15
Dual clock comparator
(all 6 clock comparators)
110
16
RX saturation detector
0
17
RX signal and image band monitor
0
18
RX mixer input power
350
Table 5. Duration of Digital Monitors
A.4
Sl. No
Monitors
Duration (µs)
1
Periodic configuration register read back
100
2
ESM monitoring
50
3
DFE LBIST monitoring
1000
4
Frame timing monitoring
10
Duration of Software Overheads
Table 6. Duration of Software Overheads
Sl. No
Software Overhead
Duration (µs)
1
Periodic monitoring of stack usage
20
2
Minimum monitoring duration
(report formation, digital energy monitor read, temperature
read)
1000
3
Minimum calibration duration
(report formation, temperature read)
500
4
Idle time needed for windowed watchdog
Frame period *
CALIB_MON_TIME_UNIT/8
SPRACF4 – June 2018
Submit Documentation Feedback
Self-Calibration of mmWave Radar Devices
Copyright © 2018, Texas Instruments Incorporated
15
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