Analog Devices ADRV9001 User Manual page 154

Reference Manual ADRV9001
TRANSMITTER/RECEIVER/OBSERVATION RECEIVER SIGNAL CHAIN CALIBRATIONS
Figure 142. Tx Initial Calibration System Configuration with Signal Generation and Internal Loop Back
Figure 142 shows how TX_LB_PD, TX_QEC, TX_LO_LEAKAGE, TX_DCC, and TX_ATTEN_DELAY use the ILB for calibrations.
TX_LO_LEAKAGE and TX_QEC calculate the initial correction parameters. TX_LB_PD provides a measurement of the loop back path
delay for the TX_LO_LEAKAGE and TX_QEC algorithms. Both TX_LO_LEAKAGE and TX_QEC calibrations sweep through a series of
attenuation values and create a table of initial calibration values. Then, during operation and upon application of a new transmitter attenuation
setting, the corresponding QEC and LO_LEAKAGE correction values are applied to the transmitter channel by the ADRV9001 ARM. TX_DCC
estimates the duty cycle error in the digital domain, but applies the correction in the analog domain. TX_ATTEN_DELAY measures the delay
between the transmitter digital attenuation block and the transmitter analog attenuation block, and it uses the ILB to observe and estimate the
delay.
Similarly, during all these calibrations, the power amplifier connected to the device output is switched off, and 50 Ω termination is needed. In
addition, it is important to switch off the LNA (or RF switch if no LNA is present externally) external to the receiver datapath to avoid interference
from the RF port into the receiver input used for data traffic. The following paragraph summarizes the external system requirement.
External system requirement: For transmitter initial calibrations using the ILB, power off the power amplifier in the transmitter path during these
calibrations. When the power amplifier is disabled, the load at the transmitter output should be 50 Ω. Also switch off the LNA (or RF switch if no
LNA is present externally) for the loopback path to avoid receiving signals from the RF port.
Initial Transmitter Calibration Utilizing Internal Signal Generation and ELB
It is also possible to perform some transmitter initial calibrations using external loop back (ELB). The Receiver/Observation Receiver Signal
Chain section shows how using the ELB1 for initial calibrations provides the advantage of observing common-mode voltage. The use of ELB1
has the same external system requirements as when using ILB. Figure 143 shows the high level block diagram of initial transmit calibrations
using internal signal generation and ELB1. Note that the ELB1 Initial calibration is a reserved function and the ADRV9001 does not support it.
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