Analog Devices ADRV9002 User Manual

UG-1828 Preliminary Technical Data
Rev. PrC | Page 74 of 338
Tx Timing Parameters Provided By Bounds Comments
propagationDelay
(t
TxPD
)
Helper
Parameter
Min: N/A
Max: N/A
This parameter should be measured by user and it is profile
dependent and board layout dependent. It does not need to provide
to ADRV9001. It can be used to derive other parameters required by
the ADRV9001.
enableRiseToOnDelay
(t
TxEnaRise2On
)
User
Parameter
Min: 0
Typical: t
TxPD
Max: t
TxGT
+ t
TxPD
@ min bound: antenna switch occurs t
TxEnaSetup
+ some margin after Tx
enable rising edge
@ typical value: all symbols sent over interface (including guard
symbols) make it onto the air
@ max bound: no guard symbols are transmitted over the air
enableRiseToAnalogOnDelay
(t
TxEnaRise2AnaOn
)
User
parameter
Min: 0
Max: t
TxEnaRise2On
− t
TxEnaSetup
If Tx propagation delay is long, the analog power up can be delayed
for power saving or to keep Tx analog powered down during Rx
frame. If Tx propagation delay is small, this should be set to 0. If this
parameter is greater than its max bound, the antenna switch time
could be delayed.
enableGuardDelay
(t
TxGT
)
User
parameter
Min: TBD
Max: TBD
TBD
enableHoldDelay
(t
TxEnaHold
)
User
parameter
Min: 0
Max: None. Must be
optimized to be minimal.
Tx_enable falling edge should ideally come as last valid data is sent
over interface. This can be used to disable Tx algorithms whose
performance may be degraded if guard symbols are used. Interface
can be kept on even after Tx_enable falling edge to allow
transmission of user guard symbols.
enableFallToOffDelay
(t
TxEnaFall2Off
)
User
parameter
Min: t
TxEnaHold
Max: None. Must be
optimized to be minimal.
(Recommended Max:
t
TxEnaHold
+ t
TxPD
Note t
TxEnaHold
is forced to 0 currently.)
@ min bound: antenna switch occurs soon after Tx interface is
disabled. It should always occur prior to powering down of Tx analog.
Not all symbols in the path make it on air.
@ max bound: antenna is switched away from Tx channel just as last
user data has propagated to antenna.
Design Strategies for Transmit Timing Parameters
Use Case 1: t
TXPD
> t
TXENASETUP
In this case, because the propagation delay is larger than the transmit analog setup delay, user may choose to delay powering up analog
front end while the data is propagating through the digital datapath as shown in Figure 63. This could achieve better power savings. For
example, if the user measures the propagation delay as 2.5 ms, whereas the enableSetupDelay provided by ADRV9001 is 8 μs, analog front
end could be off to avoid burning power for the first 2.492 ms of the propagation time. Having the analog front end powered up early
could also be a liability. For example, if the transmit propagation path delay is longer than the guard time between receive and transmit
frames, the transmit enable rising edge may occur in the middle of an receive frame. In this case, the user may want to keep the analog
front end of the transmitter channel powered down until the end of the receive frame. In such a case, the enableRiseToAnalogOnDelay should be
set to some value less than or equal to
propagationDelay – enableSetupDelay
Set enableRiseToOnDelay equal to the propagationDelay or enableRiseToAnalogOnDelay + enableSetupDelay. The transmit enable rising
edge should occur enableRiseToOnDelay before on air transmit begins. The transmit interface could be set high at the same time as
transmit enable to start transmitting guard symbols.
When the frame ends, the transmit enable falling edge should ideally occur right as the last valid data that must be demodulated by a
receiver sent over interface. Interface can be held on for some time longer to allow guard data to be sent across by setting
enableHoldDelay to a value greater than zero (note currently enableHoldDelay is forced to 0 by ADRV9001). The parameter,
enableFallToOffDelay, determines how much after the transmit enable falling edge, the antenna is switched away from the transmit
channel. It must always be set to a value greater than or equal to enableHoldDelay. If both values are set equal, for example, both are set to
0, the interface turns off first, then analog powers down. To ensure that all the data that was sent over the interface makes it onto the air,
enableFallToOffDelay should be set greater than or equal to
enableHoldDelay + propagationDelay
If it is greater, then zeros are transmitted after all the data sent over the interface has been propagated.
Use Case 2: t
TxPD
< t
TxEnaSetup
In this case, as shown in Figure 64 the time taken for data to propagate from the digital interface to antenna is very small, that is, t
TxPD
is
smaller than the time to setup the analog front end t
TxEnaSetup
, in such a case, enableRiseToAnalogOnDelay can be set to 0, so that analog

Analog Devices ADRV9002 Specifications

General

Brand	Analog Devices
Model	ADRV9002
Category	Transceiver
Language	English