Gain Control Modes - Analog Devices ADRV9001 User Manual

Preliminary Technical Data
The 2 fields which are used in the gain table are the Front-end Attenuator and the Digital Gain/Attenuator. The Front-end Attenuator is
an 8-bit control word. The amount of attenuation applied depends on the value set in this column of the selected gain table index. The
following equation provides an approximate relationship between the internal attenuator and the front-end attenuation value
programmed in the gain table, N:
The Digital Gain/Attenuator column is used to apply gain or attenuation digitally. The 11-bit signed word defines the digital gain
applied, which equals to the control word times 0.05 in dB. As shown in Table 47, for gain index 253, the digital gain can be calculated as
-2*0.05 = -0.1dB.
2 Types of Rx gain tables are provided. One is for gain correction in which the digital gain is for correcting the small step size inaccuracy
in the Front-end Attenuator. The other is for gain compensation which compensates the entire front-end attenuation. The example
shown in Table 47 stands for a Rx gain correction table. In the Receiver/Observation Receiver Signal Chain Section of this User Guide, it
mentions that Rx can also be used as ORx for signal observation. Note another gain table exists for ORx gain control. However, for ORx
gain control, there is no AGC mechanism but only MGC. In addition, the digital gain is only for gain correction.

GAIN CONTROL MODES

The gain control mode is selected through the API function adi_adrv9001_Rx_GainControl_Mode_Set() for a specified channel. Please
refer to API doxygen document for more details.
adi_adrv9001_RxGainControlMode_e is an enum for selecting the gain mode. The possible options are shown in Table 49.
Table 49. Definition of adi_adrv9001_RxGainControlMode_e
ENUM
ADI_ADRV9001_RX_GAIN_CONTROL_MODE_SPI
ADI_ADRV9001_RX_GAIN_CONTROL_MODE_PIN
ADI_ADRV9001_RX_GAIN_CONTROL_MODE_AUTO
adi_common_ChannelNumber_e is an enum which indicates which Rx channel is used:
Table 50. Definition of adi_common_ChannelNumber_e
ENUM
ADI_CHANNEL_1
ADI_CHANNEL_2
Automatic Gain Control (AGC)
In Automatic Gain Control (AGC) mode, a built-in state machine automatically controls the gain based on user defined configuration.
The AGC can be configured to one of two modes:
Peak Detect mode, where only the peak detectors are used to make gain changes.
•
• Peak/Power Detect mode, where information from both the power detector and the peak detectors are used jointly to make gain
changes.
Peak Detect Mode
In this mode, the peak detectors alone are used to inform the AGC to make gain changes. This section explains the basic premise of the
operation, while more explicit details of configuring the peak detectors is covered in subsequent sections.
EXTERNAL
ATTENUATOR
Figure 106. AGPIO Control of an External Gain Element to Rx1
Rev. PrA | Page 123 of 253
Rx1
AGPIO[0]
AGPIO[1]
Gain Mode
Manual Gain Control SPI Mode
Manual Gain Control PIN Mode
Automatic Gain Control Mode
Rx channel
Rx1
Rx2
UG-1828