RF Amplifier Cell Switching for PVT-Stable Gain and Linearity
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Solution Overview
Problem
RF amplifiers face a tradeoff between linearity and gain controllability, leading to sub-optimal performance due to temperature and power supply voltage variations, which results in reduced range coverage and increased complexity in meeting spectral mask requirements.
Innovation Solution
The RF amplifier is divided into multiple cells, with a shared bias block and a digital signal processor that enables or disables cells to adjust gain, maintaining linearity while compensating for variations in temperature and power supply voltage, using a feedback loop or lookup table for precise gain control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If transconductance is changed to adjust amplifier gain, then gain controllability is improved, but linearity deteriorates due to moving the zero-crossing point away from the optimal region
Solution Approach 1:
The amplifier is divided into multiple amplifier cells (first, second, third cells) that can be independently controlled. Each cell contributes a portion of the total gain, allowing gain adjustment by selectively enabling or disabling cells rather than changing the bias point of individual transistors. This segmentation maintains optimal operating points for linearity while achieving gain controllability through cellular activation patterns.
2Adaptability or versatility
If bias is changed to adjust gain, then gain controllability is improved, but distortion increases and spectral performance deteriorates
Solution Approach 1:
The amplifier employs dynamic control of individual amplifier cells based on the instantaneous signal envelope. The controller selectively activates or deactivates cells in response to changing signal conditions, enabling gain adjustment without static bias changes. This dynamic cellular activation maintains optimal bias points throughout operation, preventing distortion while achieving adaptive gain control.
3Adaptability or versatility
If load impedance is changed to adjust gain, then gain controllability is improved, but matching requirements and system complexity increase
Solution Approach 1:
The amplifier is segmented into multiple cells with individual control capabilities. By activating or deactivating specific cells, the total gain is adjusted through additive combination of cell gains rather than changing load impedance. This approach maintains fixed load impedance matching while achieving gain controllability through cellular configuration, reducing matching complexity.
Data Source
AI summary
Methods and apparatus control the gain of an RF amplifier. In an example, the RF amplifier is biased for low distortion. The bias is not changed to adjust gain. Rather, the amplifier's gain is controlled by selectively activating or deactivating RF amplifier cells of the RF amplifier. This individual RF amplifier cells to be biased for good linearity and relatively good spectral performance, while permitting gain control.