Analog Devices ADRV9002 User Manual

UG-1828 Preliminary Technical Data
Rev. PrC | Page 132 of 338
Figure 127 describes the simplified transmit and receive signal path between the antenna and the ADRV9001 device. The components
between the antenna and the ADRV9001 device are external components. In the transmit path, typically, the output signal from the
device goes through a variable gain amplifier (VGA), a low-pass filter (LPF) and a power amplifier before transmitting through antenna.
In the receive path, typically, the RF signal receiving from antenna goes through a low noise amplifier (LNA) and a band-pass filter (BPF)
before sending to the device. The duplexer is for supporting both FDD and TDD modes, which could stand for a frequency duplexer in
FDD mode and a RF switch in TDD mode.
As shown in Figure 136, for each receiver, besides acting as a primary data channel for receiving RF signals, it could also serve as an
observation channel, which receives loopback signals from transmitter. There are 3 loopback paths, which are internal loopback (ILB),
external loopback type 1 (ELB1) and external loopback type 2 (ELB2) as shown in Figure 136. When users are in full control of the
loopback channel for running their own algorithms, we rename the receiver as observation receiver (ORx). In such a case, user can use
either ELB1 or ELB2 depending on the algorithm requirements. For example, if running an external DPD, user should use the ELB2 path.
Figure 136. ADRV9001 Rx/ORx/Loopback Diagram
The 3 loopback paths could also be used internally by ADRV9001 for two major purposes: transmitter init calibrations and transmitter
tracking calibrations, including the integrated digital pre-distortion (DPD) operation. Transmitter init calibrations is to configure the
device properly based on system configurations during the initialization time. It can be done through either ILB, ELB1 or ELB2. The
major advantage of using ELB1 comparing with ILB is to observe common mode voltage. In addition, during transmitter init calibrations
procedure, test tones are generated and present at transmitter output. Therefore, users must ensure an appropriate level of isolation from
ADRV9001 transmitter output to the antenna to ensure that test tones are not transmitted by the system. This isolation could be achieved
by disabling power amplifier during transmitter init calibration in ELB1. For ELB2, the calibration signal might be transmitted out
through the antenna. Although the power level of calibration signal is set as low as possible, the user should make sure that this will not
cause any problem when using this option. See the Transmitter/Receiver/Observation Receiver Signal Chain Calibrations section for
more information.
Transmitter tracking calibrations is to tweak the system on the fly during its normal operations for optimal performance. Similarly, it
could use ILB, ELB1 or ELB2. ILB and ELB1 are used when DPD is not required, while ELB2 is used when DPD is required, in which the
transmit signal is looped back to the receiver after power amplifier. Note ELB1 and ELB2 shares the same receiver input, so they can’t be
used simultaneously.
No matter used by the user or internally by the device, the observation channel shares the same datapath as the regular receiver, therefore
the observation can only be performed when no regular reception is required at the same time. This is the case for transmitter init
calibrations and the user should aware that receiver might not be idle since it works as observation channel during the time period of
initialization internally by the device. Different from transmitter init calibrations, transmitter tracking calibrations are performed on the
fly, so they have to time share with the regular receiver operations. For example, in a TDD system, when transmitter is transmitting
receiver should not be receiving, therefore, it could be used for observation for transmitter tracking calibrations. For a system where
receiver is fully occupied all the time for receiving RF signals, such as a 2Tx2Rx FDD system, it is not possible to perform transmitter
PA
ELB2
ELB1
VGA
LNA
DUPLEXER
(TDD,FDD)
LPF TX1TX1
ILB
RX1/ ORX1
Rx1A
ILB INPUT
Rx1B
BPF
ANTENNA A
ADRV9001
PA
ELB2
ELB1
VGA
LNA
DUPLEXER
(TDD,FDD)
LPF
TX2TX2
ILB
RX2/ ORX2
Rx2A
ILB INPUT
Rx2B
BPF
ANTENNA B
24159-096

Analog Devices ADRV9002 Specifications

General

Brand	Analog Devices
Model	ADRV9002
Category	Transceiver
Language	English