Receiver Gain Control Using Blocker Detection for RF Linearity
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Solution Overview
Problem
Radio frequency communication devices face performance degradation due to in-band and out-of-band blocker signals, which compress the receiver and increase noise floor, making it difficult to detect and mitigate blockers, especially when supply voltages are reduced, leading to suboptimal linearity and increased noise figures.
Innovation Solution
Implementing a receiver linearity enhancement system that uses a combination of RF, IF, and RSSI detectors to provide feedback for gain and filtering adjustments, allowing the receiver to accurately determine blocker frequency and power, and thereby optimize gain settings to reduce compression and noise, using a digital baseband processor to control gains and filtering characteristics across various operating regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If receiver linearity is enhanced to accommodate blockers, then receiver performance in presence of blockers is improved, but device complexity increases due to multiple detectors and control mechanisms
Solution Approach 1:
The receiver is segmented into multiple functional paths: an RF detector path for detecting blockers across wide bandwidth, an IF detector path for detecting in-band interferers, and a normal signal processing path. Each path handles specific detection tasks, allowing the system to manage complexity through functional segmentation while maintaining reliable performance in various blocker conditions.
Solution Approach 2:
The RF detector serves multiple functions: it detects out-of-band blockers, in-band blockers, and provides information for AGC control. The system integrates multiple detection capabilities (RF detector, IF detector, baseband detector) into a unified blocker mitigation framework that handles various blocker scenarios (out-of-band, in-band, modulated interferers) using a common gain control mechanism.
2Use of energy by moving object
If supply voltage is reduced in successive process nodes, then power consumption is reduced, but linearity performance deteriorates making it difficult to meet communication standards
Solution Approach 1:
The RF detector is positioned at the front of the RF chain where there is less filtering and the detection bandwidth is largest, enabling early detection of blockers before they propagate through the receiver chain. This preliminary detection allows the AGC to adjust gains in advance, preventing compression issues that would otherwise require higher supply voltages to maintain linearity.
Solution Approach 2:
The system implements feedback mechanisms where RF detector output feeds into AGC control, and IF detector output provides additional blocker information. This feedback loop allows the receiver to dynamically adjust gain settings based on detected blocker conditions, maintaining linearity performance with reduced supply voltage by actively compensating for compression effects.
3Adaptability or versatility
If RF detector is used to detect far out blockers, then detection bandwidth is increased, but frequency location information is lost making gain selection difficult
Solution Approach 1:
The system merges information from multiple detectors: the RF detector provides wideband blocker detection capability and power level information, while the IF detector provides frequency location information for in-band blockers. By combining the outputs of these detectors, the AGC system gains both the wide detection bandwidth from the RF detector and the frequency discrimination capability from the IF detector, enabling informed gain selection without losing frequency location information.
Data Source
AI summary
Methods and apparatus to implement receiver linearity enhancement are described. One example method includes controlling receiver gain by determining a level of a received signal that is to be provided to a radio frequency component; determining if the level of the received signal would cause the radio frequency components internally generated noise to increase; and when the level of the received signal would cause the radio frequency components internally generated noise to increase, reducing the level of the received signal prior to providing the received signal to the radio frequency component.