Analog Devices ADRV9002 User Manual

Preliminary Technical Data UG-1828
Rev. PrC | Page 125 of 338
Transmit Attenuation Control
Transmit Gain Table
The transmitter attenuation block controls the transmitter output power. A transmitter gain table with 960 entries is loaded into the
ADRV9001’s memory during initialization. (Currently, only the first 840 entries are used and the remaining 120 entries are reserved for
future use.) Each entry equals a 0.05 dB gain step. Therefore, there is a total gain range of 42 dB. The total Tx attenuation is distributed
into two portions, an analog attenuation portion and a digital attenuation portion. In the analog attenuation, there is a digitally controlled
step attenuator (DSA) with 64 unit steps on a linear scale. The gaps between the analog gain steps are interpolated by a 12-bit digital
multiplier to 0.05dB steps. The maximum analog attenuation is 36 dB and the maximum digital attenuation is 6 dB. Note in direct
FM/FSK mode, the maximum transmitter attenuation is 12 dB with 0.5 dB step size.
Table 46 shows the first 5 rows of the transmitter gain table.
Table 46. Sample Rows from the Tx Gain Table
Tx
Attenuation
Index
Total Tx
Attenuation
(dB)
Analog
Attenuation
Control Word[5:0]
Analog
Attenuation
(dB)
Digital
Attenuation
(dB)
Digital
Attenuation
(Linear)
Digital
Attenuation
Control
Word[11:0]
0 0 0 0.00 0.00 1.00 4095
1 0.05 0 0.00 0.05 0.9943 4072
2 0.10 0 0.00 0.10 0.9886 4049
3 0.15 1 0.14 0.01 1.00 4090
4 0.20 1 0.14 0.06 0.9928 4066
… … … … … … …
As shown in Table 46, the 1st column is the transmitter attenuation index. The 2nd column shows the total transmitter attenuation in dB
for the corresponding index. Note the attenuation step size for adjacent index is 0.05dB. The 3rd column is the control word used to
calculate the analog gain shown in the 4th column. The equation used for this calculation is:
Analog Gain (dB) = 20 × log
10(1 − Analog Attenuation Control Word/64)
The 5th and 6th column show the required digital attenuation in dB and linear domain respectively to achieve the total attenuation in the
2nd column. The last column stands for the digital attenuation control word, which is used to calculate the linear digital gain in the 6th
column based on the following algorithm:
If Digital Attenuation Control Word = 4095
Digital Attenuation = 4096/2^12
else
Digital Attenuation = Digital Attenuation Control Word/2
12
Note only the 3rd column and the 7th column are actually stored in memory. Other columns shown in Table 46 are only for explanation
purpose.
The user is allowed to read and write the table through the following API command, “adi_adrv9001_Tx_AttenuationTable_Read()” and
“adi_adrv9001_Tx_AttenuationTable_Write()”. Please refer to the doxygen document for more details about API functions.
Note the table content is defined by the data structure “adi_adrv9001_TxAttenTableRow_t” as the following:
typedef struct adi_adrv9001_TxAttenTableRow
{
uint16_t txAttenMult;
uint8_t txAttenHp;
uint8_t Reserve;
} adi_adrv9001_TxAttenTableRow_t
where “txAttenMult” denotes the “Digital Attenuation Control Word” (in the range of 0 to 4095) and the “txAttenHp” denotes the “Analog
Attenuation Control Word” (in the range of 0 to 63) as shown in Table 46.
Transmitter Attenuation Mode
There are 3 modes to control the transmitter attenuation block, which are bypass mode, SPI mode, and GPIO mode. The API command
“adi_adrv9001_Tx_AttenuationMode_Set()” is provided to the user to set the transmitter attenuation mode.

Analog Devices ADRV9002 Specifications

General

Brand	Analog Devices
Model	ADRV9002
Category	Transceiver
Language	English