Preliminary Technical Data
UG-1828
Rev. PrC | Page 147 of 338
When ELB2 feedback path is used, it requires that the power amplifier be enabled such that a full external loop is made between the
transmitter outputs and the observation channel inputs. The advantage of this calibration is to obtain a good estimate (gain/phase) of the
external loop channel conditions prior to operation. The device configuration is shown in Figure 133. Note in this case, the calibration
signal might be transmitted out through the antenna. Although the power level of calibration signal is set as low as possible, user should
make sure that this will not cause any problem when using this option.
It is important that a suitable attenuator be chosen between the power amplifier output and the observation channel input. This is to
prevent transmit data from saturating the observation channel input. The following paragraph summarizes the external system
requirement.
External system requirement: a suitable attenuator must be chosen between the power amplifier output and the observation channel input
to prevent transmit data from saturating the observation channel input. The LNA (or RF switch if no LNA presented externally) for the
loopback path should be switched off to avoid receiving signals from RF port.
System Considerations for Receiver Initial Calibrations
In this section, similarly, high level block diagrams are used to show the device configurations and external system requirements for
receiver initial calibrations. In all the diagrams, grayed-out lines and blocks are not active in the calibration. Blue blocks are related
calibrations. It should be noted that the ADRV9001 ARM performs each of the calibrations. It is tasked with configuring the ADRV9001
device as per the diagrams below, with respect to enabling/disabling paths, and so on. No user input is required in this regard. However, it
is important that the user ensures that external system conditions are met, such as having the receiver input properly terminated for Rx
initialization calibrations.
Among 13 different receiver initial calibrations, RX_HPADC_RC, RX_HPADC_FLASH, RX_HPADC_DAC (not enabled) and
RX_LPADC calibration are performed in the analog domain and the corrections are applied to HP ADC or LP ADC (based on which one
is used), while all other receiver initial calibrations are performed in the digital domain. For RX_QEC_FIC, RX_QEC_TCAL,
RX_GAIN_PATH_DELAY and RX_DMA_PATH_DELAY, the calibration results are applied in 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. Figure 134 shows the high level block diagram of system configurations for receiver initial
calibrations. Note different calibration performs at different locations in the receiver datapath which is simplified in Figure 143.
HP ADC
LP ADC
LP ADC
HP ADC
Data port
CMOS-SSI
or
LVDS-SSI
LPF
LPF
90°
0°
LO1
LO2
To BBP
RX_QEC_FIC
RX_QEC_TCAL
RX_RF_DC_OFFSET
RX_TIA_CUTOFF
RX_GROUP_DELAY
RX_DCC
RX_QEC_ILB_LO_
DELAY
RX_DMR_PATH_DEL
AY
RX_GAIN_PATH_DEL
AY
CAL
PLL
LNA
HPADC_RC
HPADC_FLASH
LPADC
ADRV9001 Rx
LNA Switch Off
Figure 143. Receiver Initial Calibration System Configuration
During receive initial calibration, as shown in Figure 143, the data port is disabled to avoid sending data to baseband processor. This is
controlled by ADRV9001 ARM which requires no user interaction. Except for RX_RF_DC_OFFSET calibration, all other digital domain
calibration algorithms require injecting calibration tones generated by calibration PLL and 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 receive calibration, it is required to
not receive any incoming signals from RF port which could interfere with the calibration tones. To ensure that, it is important to isolate
the device receiver input port from incoming signals by disabling LNA (or by switching off the external RF switch if no LNA is presented
externally). This also prevents the calibrations tones from reaching antenna through RF coupling. 50Ω termination is needed to prevent
tone signals bouncing back from external LNA output and reaching receiver input confusing internal calibrations. The following
paragraph summarizes the external system requirement.
External system requirement: for optimal performance, and lower calibration duration, during receiver initial calibrations, the device
receiver input port should be isolated from incoming signals. For many receiver calibrations, the calibration tones will appear on the
receiver pins, therefore, must be prevented from reaching the antenna through the receiver port being properly terminated. This also