Tx Power Monitor; Overview; Tx Power Monitor Description - Analog Devices AD9361 Reference Manual

UG-570

Tx POWER MONITOR

OVERVIEW

This section describes the Tx power monitor (TPM) circuit
operation and features. TPM is available in TDD mode only
because it uses the inactive receiver to perform power
measurements during transmit. This feature is very useful as a
transmit power detector with over 66 dB of linear dynamic
range (the linear range can be extended to more than 80 dB as
shown later in this section). The
TX_MON1 (Pin M5) and TX_MON2 (Pin A5). The maximum
input signal level is +4 dBm CW referenced to 50 Ω. If the
inputs are not being used, tie them to ground.
This section explains in detail how to set up transmit control
registers and how to use transmit power control (TPC) in
normal operation.

Tx POWER MONITOR DESCRIPTION

One of the many features that the
to accurately measure the level of a received signal resulting in
an receiver signal strength indicator (RSSI) reading available to
the system. Recognizing that in TDD systems the receiver and
TX DATA
ENABLE PIN
(STATE MACHINE
CONTROL)
SPI BUS
MODE/REGISTER
CONFIG
AD9361 has two TPM inputs,
AD9361 contains is the ability
AD9361
MODULATOR
DAC
CONTROL
RMS
RX DATA
Figure 28. TPM Circuit Block Diagram
Rev. A
transmitter are not operating simultaneously, the
provides the ability to reuse the receiver circuitry by
multiplexing the power detector into the receive path. The
receiver RSSI circuitry is then turned on during the transmit
burst and results in accurate Tx RSSI measurements. Refer to
Figure 28 for a TPM circuit block diagram in a typical TDD
system diagram.
Since the Tx signal is high level (with respect to a Rx signal), it
is multiplexed into the receiver chain after the LNA. The
receiver circuitry reuses results in an accurate, wide dynamic
range measurement utilizing the existing otherwise idle
circuitry. The measurement is an RMS level that has a
configurable time measurement window and returns results in
TxRSSI units with 0.25 dB/LSB resolution in –dBFS units over a
more than 66 dB of detector dynamic range. The measurement
starts as the device is moved into Tx mode by the enable state
machine. The measurement can be performed once after the
enable state machine (ENSM) enters the Tx state or the
measurement can be done continuously until ENSM exits the
Tx state.
TX
PA
DECODE
TxRSSI
ADC
TIA
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AD9361 Reference Manual
EXTERNAL ANTENNA
INTERFACE
30dB
(TYP)
TX_MON BALUN
RX
LNA
AD9361