Serial AGC Filter Stages for Fast Gain Adaptation
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Solution Overview
Problem
Wireless receivers face challenges with slow gain response times in adjustable gain circuits, which hinder the effective filtering of unwanted signals and optimization of wanted signals due to limitations in filter bandwidth and AGC settling time.
Innovation Solution
The implementation of adjustable gain circuits within serial filter stages that are initialized to maximum gain, with digital sampling and control logic-driven gain adjustments, and the use of fast-adapting cells with switched capacitances to reduce direct current gain through charge sharing, allowing for quick gain adaptation across multiple cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an adjustable gain circuit (AGC) is integrated with the filter, then the power level of the wanted signal can be raised as early as possible, but the response time becomes slow due to filter bandwidth and AGC settling time limitations
Solution Approach 1:
The filter is divided into multiple serial filter stages, each with its own independent AGC circuit. This segmentation allows individual stages to be adjusted independently, enabling faster overall gain adaptation without being constrained by a single slow-settling filter stage.
Solution Approach 2:
The AGC circuits are initialized to maximum gain before operation begins. This preliminary setting allows the system to quickly establish the highest possible signal level immediately, with subsequent adjustments made in discrete steps rather than requiring continuous slow settling.
2Power
If capacitances are switched into the input path and feedback loop of an amplifier, then the direct current gain is reduced through charge sharing, but the circuit complexity increases
Solution Approach 1:
The amplifier's gain parameter is dynamically changed by switching capacitances into the input path and feedback loop. By altering the capacitive parameters through switching, the DC gain is reduced through charge sharing without requiring complex additional circuitry, as the same capacitors serve dual purposes in different switching states.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables rapid and efficient gain adaptation, enhancing performance by allowing the gain to be adjusted quickly, independent of filter bandwidth, thereby improving the filtering of unwanted signals and optimizing the power level of wanted signals in wireless receivers.
Implementation Method 1
capacitances are switched into the input path and feedback loop of an amplifier to reduce direct current gain within the transfer function through charge sharing dividing down the output voltage
Data Source
AI summary
Adjustable gain circuits (AGCs) within serial filter stages are initialized to maximum gain. The output of each AGC is then sampled and converted to digital representation for use by control logic in setting the gain for the respective AGC. The gain adjustment decision for each AGC is performed in one shot, sequentially backwards from the last AGC, such that gain may be adapted simply and quickly within a number of cycles equal to the number of AGCs. Performance is enhanced by a fast-adapting cell in which capacitances are switched into the input path and feedback loop of an amplifier to reduce direct current gain within the transfer function through charge sharing dividing down the output voltage.