RF AGC Gain Control Using VGA Compensation for Smooth Steps
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Solution Overview
Problem
Existing signal processors face challenges in providing a wide range of continuous front-end gain, particularly due to limitations in semiconductor processes like CMOS technology, which can only offer discrete gain steps, making it difficult to implement continuous gain variation effectively.
Innovation Solution
A signal processor design incorporating a combination of discrete step gain stages and a continuous variable gain amplifier (VGA) stage, along with an automatic gain control (AGC) system that compensates for gain steps by using a programmable gain amplifier (PGA) and VGA, allowing for continuous gain adjustment through calibration and control of LNA and VGA offsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If discrete step gain stages are used in CMOS technology, then the device complexity is reduced and manufacturing is simplified, but the gain variation becomes discontinuous and cannot provide smooth gain adjustment
Solution Approach 1:
The patent combines discrete step gain stages with a continuous variable gain amplifier (VGA) to merge the advantages of both approaches. The discrete stages provide wide gain range and easy manufacturing in CMOS, while the VGA provides continuous gain adjustment capability, resolving the contradiction between manufacturing simplicity and gain continuity.
Solution Approach 2:
The gain control function is segmented into two independent parts: discrete step gain stages for coarse adjustment and a VGA for fine continuous adjustment. This segmentation allows each part to optimize for its specific function while working together to provide both manufacturing simplicity and gain continuity.
2Stability of the object's composition
If continuous variable gain amplifier is used to provide smooth gain variation, then the gain continuity is improved, but the device complexity increases and special processes are required
Solution Approach 1:
The VGA is merged with discrete gain stages rather than used alone, allowing the system to achieve continuous gain adjustment without requiring the VGA to cover the entire gain range, thus reducing its complexity and avoiding special process requirements.
Solution Approach 2:
The VGA provides only the necessary continuous adjustment portion of the total gain range, while discrete stages handle the majority of gain variation. This partial action approach reduces VGA complexity and allows implementation in standard CMOS processes.
3Ease of manufacture
If discrete gain steps are used, then the manufacturing in CMOS is simplified, but the signal processing linearity deteriorates due to abrupt gain changes
Solution Approach 1:
The gain control is segmented into discrete stages for wide range adjustment and a VGA for fine continuous adjustment between steps. This segmentation smooths the overall gain transition, improving linearity while maintaining CMOS manufacturing simplicity.
Solution Approach 2:
The VGA acts as an intermediary element between discrete gain stages, smoothing out the abrupt transitions and providing continuous gain adjustment that improves signal processing linearity while the discrete stages maintain CMOS compatibility.
Data Source
AI summary
Embodiments of the present invention may provide a signal processor with a wide gain range. The signal processor may comprise at least a discrete step gain stage and a continuous variable gain amplifier (VGA) stage. The discrete step gain stage may comprise a programmable gain amplifier (PGA) (e.g., low noise amplifiers 1 and 2 (LNA1 and LNA2)). The VGA stage may provide a continuous range to compensate the LNAs gain steps. In one embodiment, the AGC controller enables an inherent hysteresis with the AGC step change if required.