Analog Devices ADRV9001 User Manual page 156

Reference Manual ADRV9001
TRANSMITTER/RECEIVER/OBSERVATION RECEIVER SIGNAL CHAIN CALIBRATIONS
used), while all other receiver initial calibrations are performed in the digital domain. For RX_QEC_FIC, RX_QEC_TCAL, RX_GAIN_PATH_DE-
LAY, and RX_DMA_PATH_DELAY, the calibration results are applied in the digital domain for correction. For RX_DCC, RX_RF_DC_OFFSET,
RX_TIA_CUTOFF, RX_GROUP_DELAY, and RX_QEC_ILB_LO_DELAY, the calibration results are applied in the analog domain for correction.
The Figure 145 shows the high level block diagram of system configurations for receiver initial calibrations. Note that different calibrations
perform at different locations in the receiver datapath, which is simplified in Figure 145.
Figure 145. Receiver Initial Calibration System Configuration
During the receive initial calibration, as shown in Figure 145, the data port is disabled to avoid sending data to the baseband processor.
The ADRV9001 ARM controls this without user interaction. Except for the RX_RF_DC_OFFSET calibration, all other digital domain calibration
algorithms must be injected with calibration tones generated by the calibration PLL and these must be injected internally at the receiver input.
For example, the RX_QEC_TCAL calibration routine sweeps a number of internally generated test tones across the desired frequency band,
and then measures quadrature performance and calculates correction coefficients. Therefore, during the receive calibration, any incoming
signals from the RF port must not be received, as these can interfere with the calibration tones. To ensure this, it is important to isolate the
device receiver input port from the incoming signals by disabling the LNA (or by switching off the external RF switch if no LNA is present
externally). This also prevents the calibration tones from reaching the antenna through the RF coupling. A 50 Ω termination is needed to
prevent the tone signals bouncing back from an external LNA output and reaching the receiver input, confusing the internal calibrations. The
following paragraph summarizes the external system requirements.
External system requirements: For optimal performance, lower calibration duration during receiver initial calibrations, and the device receiver
input port requirements are isolated from incoming signals. For many receiver calibrations, the calibration tones appear on the receiver pins.
Therefore, prevent it from reaching the antenna through the receiver port by terminating it properly. This also prevents the calibration tones
from reaching the antenna through the RF coupling. A 50 Ω termination is needed to prevent tone signals bouncing back from an external LNA
output and reaching the receiver input, confusing the internal calibrations.
Configure the Initial Calibrations Through TES
To achieve optimal performance, enable all initial calibrations. However, the TES allows to disable some initial calibrations, mainly for
debugging purposes. Table 65 briefly compares all initial calibrations in terms of "User Override Capability", "Run at Boot", "Signal Used by
Calibration", "External Termination Needed", and "Dependency". A minimum set of initial calibrations must be rerun after "LO changes equal to
or more than a certain range (for example, 100 MHz) ". This set of initial calibrations is defined by the bit mask "ADI_ADRV9001_INIT_LO_RE-
TUNE = 0x000B902B" in "adi_ADRV9001_InitCalibrations_e" enumerator type, as suggested by the Table 65. Note that the full suite of initial
calibrations can also be rerun to achieve optimal performance. Figure 146 and Figure 147 demonstrate the transmitter LO leakage performance
and transmitter image rejection performance under different initial calibrations. In this experiment, the LO is swept from 100 MHz to 2.9 GHz at
the 100 MHz step size. The blue line stands for the performance if the full suite of initial calibrations are rerun at each LO change. The red line
stands for the performance of running the full suite of initial calibrations and then the minimum set of initial calibrations, alternatively (full initial
calibrations for LO = 100 MHz, 300 MHz, 500 MHz,... and minimum initial calibrations for LO = 200 MHz, 400 MHz, 600 MHz,... ). The gray line
stands for the performance of running the full suite of initial calibrations and then no initial calibrations, alternatively (full initial calibrations for LO
= 100 MHz, 300 MHz, 500 MHz,... and no initial calibrations for LO = 200 MHz, 400 MHz, 600 MHz,... ). It is clear that not rerunning any initial
calibrations after LO change = 100 MHz causes a significant performance penalty. However, the optimal performance (achieved by rerunning
the full suite of initial calibrations) is mostly retained if rerunning the minimum set of initial calibrations.
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