Analog Devices ADRV9001 User Manual page 168

UG-1828
amplifierType
Currently, the power amplifier type should always be set to ADI_ADRV9001_DPD_AMPLIFIER_DEFAULT if DPD is enabled. The
default power amplifier type is referring to "non GaN" type, such as MOS type. In the future, other power amplifier type might be
supported.
lutSize
Currently, the supported LUT sizes are 256 and 512. This size determines the number of entries in the DPD LUT. A larger number of
entries provides better LUT granularity.
model
Currently, the model should be set to ADI_ADRV9001_DPD_MODEL_4 only. The other models exist for backwards compatibility with
other transceivers and should not be used at this time. Model 4 consists of four taps (T=4) which can be described by the following
equation:
3
∑
ψ
= −
x n ( ) (| ( d n l ) |) (
t t
=
t 0
Delays for each tap are described in Table 72.
Table 72. Delays of DPD Model 4
Tap Delay of Data (k)
0 0
1 1
2 2
3 1
Based on Table 72, the equation could be rewritten as:
= ψ
x n ( ) (| ( ) |) ( ) d n d n
0
where ψ (|d(n)|), ψ (|d(n-1)|), ψ
0 1
DPD Model 4 tap configuration used to generate the final pre-distorted data x(t) is shown in Figure 148:
As shown in Figure 148, d(t) is the raw complex transmit (Tx) signal before predistortion. Its amplitude is the basis that the DPD
actuator uses to predistort the d(t) via its LUT. The LUT consists of four taps, which are calculated with precomputed DPD coefficients
(w), as the following:
TAP = a + a |d(t)| + a
0 0,0,0 0,0,1
TAP = a + a |d(t − 1)| + a
1 1,1,0 1,1,1
TAP = a + a |d(t − 2)| + a
2 2,2,0 2,2,1
TAP = a |d(t − 2)| + a
3 3,2,1
Note the TAPx equations represent the default power term setting for each tap in Model 4, from which,
following depending if a power term is included or excluded:
Tap 0: b = 1, b = 1, b
0,0,0 0,0,1
Tap 1: b = 1, b = 1, b
1,1,0 1,1,1
−
d n k )
t
+ ψ − − + ψ
(| ( d n 1) |) ( d n 1) (| (
1 2
(|d(n-2)|) and ψ (|d(n-2)|) represent four taps, generated by the LUT.
2 3
t
d( )
t
|d( )| 0
Z
1
1
LUT
Z
3
1
2
Z
1
Figure 148. ADRV9001 DPD Model 4 LUT Configuration
|d(t)| 2 + a |d(t)| 3 + a
0,0,2 0,0,3
|d(t − 1)| 2 + a |d(t − 1)|
1,1,2 1,1,3
|d(t − 2)| + a |d(t − 2)|
2
2,2,2 2,2,3
|d(t − 2)| 2 + a |d(t − 2)|
3,2,2 3,2,3
= 1, b = 1, b = 1, b
0,0,2 0,0,3 0,0,4
= 1, b = 1, b = 1, b
1,1,2 1,1,3 1,1,4
Delay of Magnitude (l)
0
1
2
2
− + ψ − −
d n 2) (| ( d n 2) |) ( d n
3
Z
1
(t)
d
TAP (t
d
0
x
TAP
1
x
+
TAP
3
Z
1
TAP
2
Z
1
|d(t)| 4
0,0,4
3 + a |d(t − 1)| 4 + a
1,1,4 1,1,5
+ a |d(t − 2)|
3 4
2,2,4
3 + a |d(t − 2)| 4
3,2,4
= 0, b = 0, b = 0
0,0,5 0,0,6 0,0,7
= 1, b = 1, b = 0
1,1,5 1,1,6 1,1,7
Rev. PrA | Page 168 of 253
Preliminary Technical Data
1)
Z
1
)
– 1
(t)
x
+
(t )
d – 2
x
|d(t – 1)| 5 + a |d(t – 1)| 6
1,1,6
can be easily derived as the