Motion-Adaptive AGC Bandwidth for Lower BER in WCDMA Terminals
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Solution Overview
Problem
Conventional automatic gain control (AGC) systems in WCDMA terminals have a fixed bandwidth, which degrades bit error rate (BER) performance when the terminal speed does not match the preset speed, leading to suboptimal signal tracking and increased gain noise.
Innovation Solution
An AGC circuit with adjustable bandwidth based on the motion of the terminal, using a bandwidth control signal indicative of the terminal's speed to optimize the AGC loop's response and reduce gain noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the AGC bandwidth is set to be constant (fixed), then the device complexity is reduced, but the BER performance degrades when terminal speed does not match the preset speed
Solution Approach 1:
The patent applies the dynamics principle by making the AGC bandwidth adjustable rather than fixed. The AGC circuit now dynamically adapts its bandwidth based on detected terminal motion, transitioning from a static configuration to a dynamic one that responds to changing conditions. This resolves the contradiction by allowing the system to maintain low complexity when motion is minimal while achieving high reliability when motion varies.
Solution Approach 2:
The patent implements parameter changes by varying the AGC bandwidth parameter according to terminal motion characteristics. The system detects motion parameters and adjusts the AGC bandwidth accordingly, changing the operational parameters of the AGC circuit to match the terminal's motion state. This enables optimal BER performance across different motion scenarios without significantly increasing overall system complexity.
2Speed
If the AGC bandwidth is increased to track power changes faster, then the signal tracking capability is improved, but the gain noise increases
Solution Approach 1:
The patent applies dynamics by making the AGC bandwidth variable rather than fixed. The system dynamically adjusts bandwidth based on terminal motion - using wider bandwidth when rapid tracking is needed and narrower bandwidth when noise reduction is prioritized. This dynamic adaptation resolves the contradiction between tracking speed and noise generation.
Solution Approach 2:
The patent implements local quality by applying different bandwidth settings in different operational contexts. Instead of using a uniformly wide or narrow bandwidth, the system selects appropriate bandwidth characteristics locally matched to the current terminal motion state, achieving optimal performance for each specific operating condition.
3Object-generated harmful factors
If the AGC bandwidth is decreased to reduce gain noise, then the gain noise is reduced, but the ability to track power changes is insufficient
Solution Approach 1:
The patent resolves this contradiction through dynamic bandwidth adjustment. The AGC circuit adapts its bandwidth in real-time based on terminal motion detection, switching between narrow bandwidth (for noise reduction) and wide bandwidth (for fast tracking) depending on the operational requirements. This dynamic behavior eliminates the need to choose between noise reduction and tracking speed.
Solution Approach 2:
The system changes the AGC bandwidth parameter based on detected terminal motion characteristics. When terminal motion indicates need for fast tracking, the bandwidth parameter is increased; when noise reduction is prioritized, the bandwidth parameter is decreased. This parameter adaptation resolves the contradiction between noise and tracking capability.
Data Source
AI summary
An apparatus including automatic gain control (AGC) includes at least one variable gain amplifier (VGA) operative to receive an input signal and to generate an amplified signal. A gain of the VGA is controlled as a function of at least a first control signal. The apparatus further includes an AGC circuit coupled to the VGA and being operative to generate the first control signal. The AGC circuit has a bandwidth that is controlled as a function of at least the amplified signal and a second control signal, the second control signal being indicative of a motion of the apparatus.