Preliminary Technical Data
UG-1828
Rev. PrC | Page 77 of 338
immediately after receive enable rising edge (Note Figure 64 describes receive timing parameters in a general case with
enableRiseToAnalogOnDelay not equal to 0.). The parameter enableRiseToOnDelay could also be set to 0, in this case, the LNA is
powered up as soon as analog power up completes. For a more deterministic delay between RX_ENABLE rising edge and LNA power up
time, enableRiseToOnDelay can be set to a value greater than or equal to
enableRiseToAnalogOnDelay
+
enableSetupDelay
Once timing on air is established, the user may choose to raise RX_ENABLE, sometime before the start of the actual frame. As soon as
the Rx analog power up completes, the digital interface turns on, however, if the path has a long propagation delay, the initial data coming
off the interface are not the data received over the air.
When the frame ends, users may wish to continue receiving for a while, however, ADRV9001 may wish to stop all the tracking algorithms
to avoid any performance degradation. This can be achieved by bringing the RX_ENABLE signal low as soon as the frame ends, but
setting the enableFallToOffDelay equal to the time user wish to continue receiving data (Note enableFallToOffDelay is forced to 0
currently by ADRV9001.). This time should be no larger than the guard time before the next frame. The longer this value, the later the
next Rx_enable rising edge can occur. In cases where the receive path has a large propagation delay, users may wish to turn off the
receiver analog front end, so that users may commence a transmit frame, but still leave the digital datapath and interface on so that data
already received over the air may be sent over the interface. The enableHoldDelay parameter is used for this purpose. It must always be set
at least the enableFallToOffDelay. In order to receive all the data already received over the air, it should be set to
enableFallToOffDelay
+
propagationDelay
Guard/Hold Times Between Edges of TX_ENABLE and RX_ENABLE
By understanding the transmit and receive timing parameters discussed separately in the previous sections, the minimum guard/hold
time design between the rising and falling edges of TX_ENABLE and RX_ENABLE in a TDD system are further discussed in this section.
Six scenarios are considered, as follows:
•
Guard time between TX_ENABLE falling edge and RX_ENABLE rising edge
•
Guard time between RX_ENABLE falling edge and TX_ENABLE rising edge
•
Guard time between TX_ENABLE falling edge and TX_ENABLE rising edge
•
Guard time between RX_ENABLE falling edge and RX_ENABLE rising edge
•
Hold time between TX_ENABLE rising edge and TX_ENABLE falling edge
•
Hold time between RX_ENABLE rising edge and RX_ENABLE falling edge
The user should always set the guard/hold timer greater than the minimum requirement. Note no hardware or software restriction
prevents user from raising TX_ENABLE/RX_ENABLE at any time. Correct operation cannot be guaranteed if rules described in the
following sections are violated.
Guard Time Between TX_ENABLE Falling Edge and RX_ENABLE Rising Edge
The guard time between TX_ENABLE falling edge and RX_ENABLE rising edge is for making sure that the transmitter analog front end
and the receiver analog front end are not powered up simultaneously. As discussed in previous sections, after TX_ENABLE falling edge, it
takes t
TxEnaFall2Off
to power off the transmitter analog front end. Therefore, the earliest time the receiver analog front end can be powered up
is t
TxEnaFall2Off
after the TX_ENABLE falling edge. Because it takes t
RxEnaRise2On
to power up the receiver analog front end starting from the
RX_ENABLE rising edge, the minimum guard time is t
TxEnaFall2Off
− t
RxEnaRise2On
if t
TxEnaFall2Off
is greater than t
RxEnaRise2On
. In the case of t
TxEnaFall2Off
is less than t
RxEnaRise2On
(this could be possible when power saving modes are enabled as discussed in later sections), RX_ENABLE rising
edge could happen t
RxEnaRise2On
− t
TxEnaFall2Off
before TX_ENABLE falling edge. Figure 66 describes both cases.
Figure 66. Minimum Guard Time Between TX_ENABLE Falling Edge and RX_ENABLE Rising Edge
Guard Time Between RX_ENABLE Falling Edge and TX_ENABLE Rising Edge
Similarly, the guard time between RX_ENABLE falling edge and TX_ENABLE rising edge is for making sure that the Rx analog front end
and the Tx analog front end are not powered up simultaneously. As discussed in previous sections, after RX_ENABLE falling edge, it
takes t
RxEnaFall2Off
to power off the Rx analog front end. Therefore, the earliest time Tx analog front end can be powered up is t
RxEnaFall2Off
after
the RX_ENABLE falling edge. Because it takes t
TxEnaRise2On
to power up the transmitter analog front end starting from the TX_ENABLE
Tx_ENABLE
Rx_ENABLE
t
TxEnaFall2Off
– t
RxEnaRise2On
Tx_ENABLE
Rx_ENABLE
t
RxEnaRise2On
– t
TxEnaFall2Off
t
TxEnaFall2Off
> t
RxEnaRise2On
t
TxEnaFall2Off
< t
RxEnaRise2On
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058
