Preliminary Technical Data
UG-1828
Rev. PrC | Page 13 of 338
Dual-Band 2T2R FDD Overview
With a minimum number of external components, the ADRV9001 transceiver can be used to build complete dual and RF-to-bits signal
chain that can serve as RF front end in small cell type applications. Note that in proposed solution, only one band can be used at the time.
ADRV9001 dual Rx and Tx signal chains enables user to implement MIMO or diversity in their system. ADRV9001 internal AGC can be
used to autonomously monitor and set appropriate gain level for Rx signal chains. For none time critical FDD type applications control of
the ADRV9001 TRx can be done thru API commands that use SPI interface.
Table 2. Constrains and Limitations in Dual-Band 2T2R FDD Type Small-Cell Application
Functionality
Constrains and Limitations
Rx Signal Path
The user must ensure that appropriate level of isolation between Rx1 and Rx2 as well as Rx to Tx is provided at the
system level. In the previously described example, RxB inputs are used to work with Rx Band B signals as well as
during initialization calibrations. In this scenario, RF Balun selected for RxB inputs must work with both Band B and Tx
Bands. The user must ensure that appropriate attenuation is present in line to prevent Rx being overloaded by Tx
signal.
Tx Signal Path
The user must ensure that appropriate level of isolation between Tx1 and Tx2 as well as Rx to Tx is provided at the system
level.
LO Generation
In FDD type small cell applications, ADRV9001 can use its internal LO to generate RF LO1 for uplink (Rx1 and Rx2) and
RF LO2 for downlink (Tx1 and Tx2). It is also possible to use external LO inputs in this mode of operation. External LO1
operating at 2× RF LO can be used for uplink and External LO2 operating at 2× RF LO can be used for downlink. It
should be noted that only one set of Rx inputs can be used at the time. This system can operate with two different
FDD bands but only one of those bands can be active at particular moment in time.
RF Front End
For LO generation, the ADRV9001 uses internal VCO that generates square wave type signal. A square wave LO would
produce harmonics. For example: depending of RF matching used on the RF ports user 2
nd
LO harmonic can be as
high as −50 dBc and 3
rd
harmonic can be as high as −9 dBc. Therefore, the RF filtering on the Rx and Tx path must
ensure that signals at the LO harmonic frequencies (up to 9
th
in some cases) are not affecting overall system performance.
DPD
The DPD functionality is not available when ADRV9001 operates in 2R2T FDD mode.
Calibrations
During Rx initialization sequence user needs to ensure that there are no signals at the Rx input (external LNA should
be disabled) and appropriate termination should be present at LNA output to avoid reflections of Rx calibration tones.
The maximum input signal amplitude must not exceed −82 dBm/MHz for wideband modes, TBD dBm/MHz for
narrowband modes. During the transmitter initialization sequence, the user needs to ensure that the power amplifier
is powered down to avoid unwanted emission of transmitter calibration tones at the antenna. No transmitter tracking
calibrations are available when ADRV9001 operates in 2R2T FDD mode.
AGPIOs
Analog GPIOs (operating at 1.8 V level) can be used as read or write digital levels of in the end user system. AGPIOs
can be used to control states of external components or read back digital logic levels from external components.
DGPIOs
Digital GPIOs can be used to perform real-time monitoring of states of internal ADRV9001 blocks. Digital GPIOs
operating as inputs can allow user to control Rx gain, Tx attenuation, AGC operation and other elements of ADRV9001
TRx. Depending on the ADRV9001 operation up to 4 GPIOs may be used by data port interface.
AuxADC
AuxADC can be used to monitor analog voltage (for example, temperature sensor). Maximum AuxADC input voltage
must not exceed 0.9 V.
AuxDAC
AuxDAC can be used to control the VCXO responsible for generating the ADRV9001 device clock, control any circuitry
that requires analog control voltage up to 1.8 V.
DEV_CLK_OUT
ADRV9001 provides divided down version of DEV_CLK reference clock input signal on the DEV_CLK_OUT output. This
output is intended to provide a reference clock signal to the digital components in the overall system. This output can
be configured to be active after power up and before the ADRV9001 configuration stage.
Multichip Sync
If there is no need for multichip synchronization, the ADRV9001 can be initialized using API functions only.