Binary Weighted Resistor Calibration for Direct Conversion Receiver Mismatches
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Solution Overview
Problem
Conventional direct conversion receivers face challenges in achieving high IIP2 characteristics due to component mismatches in mixers, which existing calibration methods struggle to accurately compensate for, leading to inefficiencies in mismatch compensation.
Innovation Solution
A binary weighted resistor architecture is introduced, where a fixed resistor and an adjustable resistor are cascaded in parallel, allowing for resistance adjustments linearly correlated with digital codes, enabling precise calibration by establishing a two-dimensional linear relationship between mismatches and DC offsets, and using interpolation to determine optimal digital codes for zero DC offset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional adjustable resistors are used for calibration, then IIP2 compensation is achieved, but the relationship between digital code and resistance is non-linear requiring wide range trial codes and sufficient accuracy cannot be permitted
Solution Approach 1:
The patent changes the resistance parameter to be linearly proportional to the digital code by using a binary weighted resistor architecture. This transforms the non-linear relationship into a linear one, where each digital code increment corresponds to a fixed resistance step, eliminating the need for wide range trial codes and ensuring sufficient calibration accuracy.
Solution Approach 2:
The adjustable resistor is segmented into multiple parallel resistor branches, each controlled by a digital code bit. This segmentation allows the total resistance to be precisely controlled by combining different resistor values based on the digital code, achieving linear relationship between code and resistance while maintaining high calibration accuracy.
2Manufacturing precision
If binary weighted resistor architecture is introduced, then linear resistance adjustment is achieved, but device complexity increases
Solution Approach 1:
The resistor architecture is segmented into multiple parallel branches with different resistor values, each controlled by a digital code bit. This segmentation enables precise resistance adjustment through binary weighting while keeping the implementation systematic and manageable.
Solution Approach 2:
The patent replaces mechanical or analog adjustment mechanisms with a digital code-controlled resistor network. The digital code directly controls the resistor configuration through binary weighting, eliminating the need for complex mechanical adjustments and achieving precise control with simpler implementation.
Data Source
AI summary
A mixer and calibration method thereof are provided. A direct conversion receiver comprises a differential loading pair utilizing at least one binary weighted resistor. The binary weighted resistor is adjustable to provide a resistance linear to a digital code, comprising a fixed resistor and an adjustable resistor cascaded to the fixed resistor in parallel. Every increment of the digital code induces an equal increment of the resistance. The magnitude of every incremental resistance is below a negligible ratio of the fixed resistor.