Receiver Gain Control - Analog Devices ADRV9001 User Manual

Reference Manual

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 ensures that the
receiver digital output data is representative of the root mean square (RMS) power of the receiver input signal so that any internal front-end gain
changes to avoid overloading are transparent to the baseband processor.
The two gain control modes in the ADRV9001 are called automatic gain control (AGC) and manual gain control (MGC). The AGC allows
receivers to autonomously adjust the receiver gain depending on the variations of the input signal. It controls the gain of the device based
on the information from signal detectors called peak detector and power detector. The receivers can also operate in the 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, the baseband processor can optionally use the information from the signal detectors through the DGPIO pins to properly
control the gain.
The gain control is highly flexible and is configured differently in various scenarios. For example: for BTS receivers, the received signal is a
multicarrier signal in most cases. Perform a gain change only under large overrange or underrange conditions, and gain changes should not
occur very often for typical 3G/4G operations. Use peak detectors in such cases. Nevertheless, if an asynchronous blocker does appear, there
is a "fast attack" mode, which reduces the gain at a fast rate. As another example, to support GSM blockers and radar pulses, which have fast
rise and rapid fall times, there is a "fast attack and fast recovery" mode. This mode is capable of fast recovery in addition to the fast attack.
Section Topics
The following is the list of topics reviewed in detail.
Receiver Datapath: This section outlines the gain control and signal observation elements of the receiver chain, followed by a description of
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the receiver gain table concept.
Gain Control Modes: Advises on how to select between the AGC and MGC modes, followed by a detailed description of how to operate in
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each mode. The AGC mode section further discusses and compares peak and peak/power detect modes.
Gain Control Detectors: Outlines the operation and configuration of various gain control detectors in the device.
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AGC Clock and Gain Block
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Analog Gain Control API Programming: Outlines how to configure the analog gain control using API commands, explaining each parameter
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of the API structures. It also provides a summary of all supported API functions.
Digital Gain Control and Interface Gain
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Digital Gain Control and Interface Gain API
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commands, explaining each parameter of the API structures. It also provides a summary of all supported API functions.
Usage Recommendations: Provides a list of recommended gain control configurations to achieve optimal performance.
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TES Configuration and Debug Information
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debugging when encountering some gain control performance problems.
Important Terminology
The following is a summary of the important terms used in the following sections.
Manual Gain Control (MGC)
A use case when the user is in control of the currently applied gain settings in the receiver chain.
Automatic Gain Control (AGC)
The device's own internal AGC, where the device is in control of the receiver gain settings. If the internal AGC is not used, an AGC is expected
to run in the baseband processor. However, in this document, such a case is referred to as MGC because the gain of the receive path is under
the user's control.
Gain Attack
Indicates the reduction of the receiver gain due to an overloaded signal path.
Gain Recovery
Indicates the increase of the receiver gain due to a reduction in the power of the signal received.
Gain Compensation
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Timing: Describes the speed of the AGC clock and the various gain event and delay timers.
(Slicer): Outlines the various forms of digital gain control in the ADRV9001.
Programming: Outlines how to configure the digital gain control and interface gain using API
: Advises on how to configure receiver gain control functionality through TES and perform simple
ADRV9001
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