Process variation: To account for manufacturing process variation, the devices
must perform RF INIT self-calibrations, but only once, at the customer factory.
The ambient temperature (called factory calibration temperature) may be 25°C or
the middle of the expected in-field temperature range.
Save restore: Let the RF INIT calibration results be saved in a nonvolatile
memory and restored later into the devices before each RF INIT during in-field
operation.
Offsets measurement at customer factory: the customer factory calibration
procedures must measure the offsets (such as inter-channel imbalances and phase
shift nonlinearity). These offsets must be stored in a nonvolatile memory and
used during in-field operation by the DSP.
Multiple front end settings: the customer factory calibration procedure must be
performed with the AWR device in multiple (3) calibration settings, optimized
for various operating temperatures. The ambient temperature is still kept the
same while only varying the devices’ analog configurations, according to other
temperature settings.
Temperature compensation in-field: the host must use its real-time knowledge of
temperature trends (such as increasing or decreasing, expected operating range)
and based on it, simultaneously communicate its chosen temperature index to all
the AWR devices in the cascade. To minimize jump magnitudes, this transition is
recommended to be near the factory calibration temperature.
DSP compensation: in tandem with the calibration settings change, the DSP layer
processing must also use the corresponding offsets data from factory
calibration.