RF DC Offset Cancellation via Adaptive Gain-Dependent Filtering
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Solution Overview
Problem
Conventional methods for removing Radio Frequency (RF) Direct Current (DC) offset in signals are ineffective due to difficulties in measuring and stabilizing the offset, particularly with transient changes in receiving channel gain, leading to performance degradation in communication systems.
Innovation Solution
A method and system that involve detecting gain combinations of RF and analog Base Band amplifiers, setting corresponding canceling DC values, and using high-pass filters tailored to each gain combination to remove RF DC offsets, with an adjustable canceling DC to account for residual offsets and improve signal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fine gain digital cancellation loop acts as a high-pass filter to remove RF DC offsets, then the RF DC offset is filtered out, but the digital transient response time becomes long and the system cannot respond quickly to transient changes in receiving channel gain
Solution Approach 1:
The patent applies dynamics by making the filter characteristics adaptive rather than fixed. The system dynamically adjusts the filter order and coefficients based on the current receiving channel gain state, allowing the high-pass filter to respond quickly to transient changes while maintaining effective RF DC offset removal. This resolves the contradiction by making the filtering behavior flexible and responsive to changing conditions.
Solution Approach 2:
The patent changes the parameters of the digital cancellation loop based on the receiving channel gain state. When a transient is detected, the system modifies the filter order and coefficients to achieve faster response. This parameter adaptation allows the system to maintain both effective offset removal and quick response to gain changes, resolving the contradiction between filtering effectiveness and response speed.
2Reliability
If the receiving channel gain changes constantly, then the RF DC offset changes continuously, but conventional offset adjustment methods cannot effectively remove the offset due to difficulty in measuring all affecting factors
Solution Approach 1:
The patent implements feedback by continuously monitoring the RF DC offset level and automatically adjusting the digital cancellation loop parameters accordingly. The system measures the actual offset in real-time and feeds this information back to adjust the filter characteristics, eliminating the need for complex pre-measurement of all affecting factors. This feedback mechanism resolves the contradiction by providing adaptive offset removal without increasing measurement complexity.
Solution Approach 2:
The system performs self-adjustment by automatically detecting transients in the receiving channel gain and modifying its own filter parameters in response. Rather than requiring external calibration or complex measurement systems, the digital cancellation loop serves itself by adapting to changing conditions, thereby resolving the contradiction between effectiveness and complexity.
3Reliability
If a high-pass filter with narrow stop-band is used to minimize harm to system performance, then the filtering harm is reduced, but the transient response time becomes longer
Solution Approach 1:
The patent makes the filter characteristics dynamic by adjusting the stop-band width and filter order based on the signal conditions. When transients are present, the system temporarily modifies the filter parameters to achieve faster response, then returns to the optimized configuration for minimal performance harm. This dynamic adaptation resolves the contradiction between performance preservation and response speed.
Solution Approach 2:
The system periodically monitors for transient conditions and adjusts the filter parameters accordingly. During normal operation, the filter maintains narrow stop-band for performance preservation. When a transient is detected, the filter parameters are periodically adjusted to widen the stop-band temporarily, enabling faster response. This periodic adaptation resolves the time-performance contradiction.
Data Source
AI summary
Embodiments of the present invention provide a method and a system for removing a Radio Frequency (RF) Direct Current (DC) offset in a signal. The method includes: subtracting a canceling DC from a signal carrying an RF DC offset and generating an RF DC offset residual; outputting the signal when the RF DC offset residual in the signal is zero; adjusting the canceling DC according to the RF DC offset residual in the signal if the RF DC offset residual is not zero. The system includes a receiver, an RF DC offset canceling unit, a determining unit, a canceling DC adjusting unit, and an output unit. With embodiments of the present invention, the RF DC offset in the signal may be effectively removed.