Automatic Gain Control Circuit With PVT-Compensated Linear Gain
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Solution Overview
Problem
CMOS gain circuits in wireless communication devices exhibit non-linear relationships between gain and input control voltage, which are exacerbated by supply voltage, temperature, and process variations, leading to suboptimal performance and potential non-compliance with standards.
Innovation Solution
A voltage generating circuit with a monitor circuit and digital compensator is used to sense and convert measurable parameters like supply voltage, temperature, and process variations into offset addresses, which are combined with input voltage to generate a compensated gain control voltage, maintaining a linear relationship between gain and input control voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If CMOS technology is used for gain circuit fabrication, then manufacturing cost is reduced, but gain-linearity deteriorates
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the gain control voltage based on measured process, temperature, and supply voltage parameters. The system stores multiple calibration values in a lookup table and selects the appropriate compensation value based on the current operating conditions, thereby maintaining linear gain characteristics across varying parameters while using cost-effective CMOS technology.
2Adaptability or versatility
If process, temperature, and supply voltage variations occur, then device adaptability is improved, but gain-linearity deteriorates
Solution Approach 1:
The patent implements feedback by continuously measuring process parameters, temperature, and supply voltage using dedicated sensing circuits. These measured values are fed into a compensation mechanism that adjusts the gain control voltage accordingly, creating a closed-loop system that maintains linear gain characteristics despite variations in operating conditions.
Solution Approach 2:
The patent applies preliminary action by pre-calculating and storing compensation values in a lookup table during the manufacturing process. The calibration data, which accounts for various process corners and operating conditions, is stored in non-volatile memory, allowing the system to quickly retrieve and apply the appropriate compensation without real-time computation, thereby maintaining linearity across different operating conditions.
3Device complexity
If no compensation is applied, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent introduces an intermediary compensation circuit that acts as a mediator between the input control voltage and the gain circuit. This intermediary block includes a lookup table storage, measurement circuits for process/temperature/supply voltage, and a compensation mechanism that adjusts the control voltage before it reaches the gain circuit, thereby improving measurement precision without significantly increasing overall device complexity.
Data Source
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AI summary
A system for generating a supply voltage, temperature and process compensated gain control voltage from a digital data word. In particular, the compensated gain voltage control voltage maintains a linear relationship between a change in gain in response to an input gain control voltage for a gain circuit of a transmitter circuit. A monitor circuit senses at least one of the supply voltage, temperature and process parameters, and generates a first set of digital signals corresponding to the sensed parameter. A digital compensator circuit converts the input gain control voltage into a second set of digital signals, and decodes the combined first and second set of digital signals to provide a data word. The data word is converted into an analog voltage representing the compensated gain voltage control voltage. The digital compensator circuit includes a table of compensation values, each accessible by a distinct combination of the first and second set of digital signals.