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UG-1828
Preliminary Technical Data
Rev. PrC | Page 154 of 338
RECEIVER GAIN CONTROL
The ADRV9001 receivers feature automatic and manual gain control modes for flexible gain control in a wide array of applications. It
controls the gain at various stages of the receiver datapath to avoid overloading during the onset of a strong interferer. In addition, it could
ensure that the receiver digital output data is representative of the RMS power of the receiver input signal so that any internal front-end
gain changes to avoid overloading are transparent to the baseband processor.
In ADRV9001, the two gain control modes are named Automatic Gain Control (AGC) and Manual Gain Control (MGC). AGC allows for
receivers to autonomously adjust the receiver gain depending on variations of the input signal. It controls the gain of the device based on
the information from a number of signal detectors named peak detector and power detector. The receivers are also capable of operating in
MGC mode where changes in gain are initiated by the baseband processor through API commands or Digital GPIO (DGPIO) pins. In the
MGC mode, by enabling the signal detectors, baseband processor could optionally use the information provided from signal detectors
through Digital GPIO (DGPIO) pins to properly control the gain.
The gain control is highly flexible and can be configured differently in various scenarios. For example: for BTS receivers the received
signal is a multi-carrier signal in most cases. A gain change should be performed only under large over range or under range conditions
and gain changes should not occur very often for typical 3G/4G operations. In such a case, it might be sufficient to use peak detectors.
Nevertheless, if an asynchronous blocker does appear, a “fast attack” mode exists which could reduce the gain at a fast rate. As another
example, to support GSM blockers and radar pulses which have fast rise and rapid fall times, a “fast attack and fast recovery” mode can be
employed. This mode is capable of fast recovery in addition to the fast attack as mentioned earlier.
Section Topics
The list of topics reviewed in detail are found in the following sections:
•
Receiver Data Path: This section outlines the gain control and signal observation elements of the receiver chain, followed by a
description of the receiver gain table concept.
•
Gain Control Modes: This section advises how to select between AGC and MGC mode, followed by a detailed description of how to
operate in each mode. In AGC mode, peak detect mode and peak/power detect mode will be further discussed and compared.
•
Gain Control Detectors: This section outlines the operation and configuration of various gain control detectors in the device.
•
AGC Clock and Gain Block Timing: This section describes the speed of the AGC clock and the various gain event and delay timers.
•
Analog Gain Control API Programming: This section outlines how to configure the analog gain control using API commands,
explaining each parameter of the API structures. It also provides a summary of all API functions currently supported.
•
Digital Gain Control and Interface Gain (Slicer): This section outlines the various forms of digital gain control available in the
ADRV9001.
•
Digital Gain Control and Interface Gain API Programming: This section outlines how to configure the digital gain control and
interface gain using API commands, explaining each parameter of the API structures. It also provides a summary of all API
functions currently supported.
•
Usage Recommendations: This section provides a list of recommended gain control configurations to achieve optimal performance.
•
TES Configuration and Debug Information: This section advises user how to configure receiver gain control functionality through
TES and perform simple debugging when some gain control performance problems are encountered.
Important Terminology
A list of important terms used in following sections are summarized below:
Manual Gain Control (MGC)
This term is used to refer to a use case when the user is in control of the currently applied gain settings in the receiver chain.
Automatic Gain Control (AGC)
This term is used to refer to the device’s own internal AGC, where the device is in control of the receiver gain settings. If the user does not
use the internal AGC, then it is expected that an AGC would run in the baseband processor. However, in this document such a case
would be referred to as MGC because the gain of the receive path is under user’s control.
Gain Attack
This term is used to indicate the reduction of the receiver gain due to an overloaded signal path.
Gain Recovery
This term is used the indicate the increase of the receiver gain due to a reduction in the power of the signal being received.