Packet-Boundary AGC Bandwidth Control for Fast Signal Tracking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional automatic gain control (AGC) systems in communication receivers are optimized for continuous signals and fail to effectively track step changes in signal strength during packet transmissions, leading to increased noise due to a fixed time-constant loop filter.
Innovation Solution
The AGC system dynamically adjusts its filter bandwidth or time constant based on data-packet boundaries, temporarily increasing bandwidth or decreasing time constant at packet boundaries to facilitate faster tracking of signal strength changes while maintaining noise suppression during most of the signal duration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the AGC loop bandwidth is kept narrow to reduce noise, then noise in signal strength estimates is suppressed, but the AGC loop cannot track step changes in received signal strength quickly
Solution Approach 1:
The patent applies dynamics by making the AGC loop filter bandwidth variable rather than fixed. The filter transitions between a narrow bandwidth mode (for noise suppression during continuous signals) and a wide bandwidth mode (for fast tracking during packet boundaries). This dynamic adjustment allows the system to optimize performance for different signal conditions without being constrained by a fixed bandwidth setting.
Solution Approach 2:
The patent changes the filter bandwidth parameter based on detected packet boundaries. When a packet boundary is detected, the filter bandwidth is increased to allow faster tracking of signal strength changes. Between packet boundaries, the filter bandwidth is reduced to suppress noise. This parameter change enables the system to adapt to the discontinuous nature of packet-based transmissions.
2Speed
If the AGC loop bandwidth is increased to track step changes quickly, then tracking speed improves, but noise in the AGC loop increases
Solution Approach 1:
The patent implements periodic action by alternating between narrow and wide bandwidth modes synchronized with the packet transmission rhythm. The filter operates in wide bandwidth mode periodically at packet boundaries to capture fast changes, then switches to narrow bandwidth mode for the majority of the time to suppress noise. This periodic switching aligns the high-noise-state with the brief packet boundary moments when fast tracking is needed.
Solution Approach 2:
The dynamic bandwidth adjustment allows the system to temporarily increase noise tolerance during packet boundaries when fast tracking is critical, then return to noise-sensitive mode during continuous signal periods. This dynamic behavior resolves the contradiction by making bandwidth increase temporary and context-dependent rather than permanent.
3Object-affected harmful factors
If a fixed time-constant filter is used to smooth instantaneous variations, then noise filtering is improved, but the AGC cannot respond quickly to packet boundary signal strength changes
Solution Approach 1:
The patent makes the filter time-constant dynamic by adjusting it based on packet boundary detection. During packet boundaries, the time-constant is reduced (equivalent to increasing bandwidth) to enable fast response. Between packet boundaries, the time-constant is increased (equivalent to decreasing bandwidth) to smooth noise. This dynamic time-constant adjustment resolves the contradiction between smoothing and fast response.
Solution Approach 2:
The filter parameter (time-constant) is changed based on the detected state of the signal. When a packet boundary is detected, the time-constant parameter is adjusted to a smaller value for fast tracking. During normal continuous signal periods, the time-constant is set to a larger value for noise smoothing. This parameter change enables adaptive filtering behavior.
Data Source
AI summary
Provided is automatic gain control (AGC) in which a feedback filter has a parameter that is changed based on information regarding data-packet boundaries. In one representative embodiment, the bandwidth of the filter temporarily is increased, or the time constant of the AGC filter temporarily is decreased, within a vicinity of each actual or potential packet boundary.