Filtered Feedback Mixer Linearization for Stable I/Q Modulation
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Solution Overview
Problem
There is a trade-off between linearity and signal-to-noise ratio (SNR) performance in I/Q modulators within transmitters, which is exacerbated by process, voltage, and temperature (PVT) variations, requiring robust solutions to ensure performance in mass production without introducing side effects.
Innovation Solution
A mixer with a filtering function and a method for linearization that includes an amplifier, a transconductance device, and a feedback network, where the transconductance device is part of a close-loop filter, improving linearity by reducing the impact of active device transconductance and maintaining cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If input voltage levels are limited to ensure linearity, then linearity performance is improved, but signal-to-noise ratio (SNR) performance deteriorates
Solution Approach 1:
The patent implements a dynamic linearization approach where the mixer operates in a nonlinear region but uses real-time feedback to compensate for distortions. The feedback network continuously adjusts the output based on the actual mixer performance, allowing the system to maintain linearity without limiting input voltage levels, thus resolving the contradiction between linearity and SNR performance
Solution Approach 2:
The patent introduces a feedback network that feeds the mixer output back to the input stage. This feedback mechanism detects nonlinear distortions and automatically compensates for them, enabling the system to achieve both high linearity and high SNR simultaneously by operating at optimal input voltage levels without the traditional trade-off
2Reliability
If large scale simulations are performed to ensure performance under PVT variation, then performance robustness is improved, but design time and complexity increase
Solution Approach 1:
The patent designs the mixer with inherent PVT compensation mechanisms built into the circuit architecture. The feedback network and biasing circuits are specifically designed to anticipate and counteract PVT variations, providing robustness without requiring extensive post-manufacturing simulations or adjustments
Solution Approach 2:
The patent employs parameter optimization techniques where key circuit parameters are carefully selected and tuned to be less sensitive to PVT variations. By changing specific design parameters such as transistor sizing, bias currents, and feedback network values, the system achieves robust performance across PVT conditions without requiring large-scale simulations
3Manufacturing precision
If additional filtering components are added to improve linearity, then linearity performance is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the feedback network serve multiple functions simultaneously: it provides linearization, acts as a filter to remove unwanted frequency components, and stabilizes the mixer operation. This multi-functionality achieves linearity improvement without adding separate filtering components, thus avoiding increased device complexity and cost
Solution Approach 2:
The patent merges the filtering function with the existing feedback network and mixer structure. Instead of adding separate filtering stages, the design integrates filtering capabilities into the feedback path and biasing circuits, combining multiple functions into existing components and avoiding additional complexity
Data Source
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AI summary
A mixer with a filtering function and a method for linearization of the mixer are provided. The mixer includes at least one amplifier, a transconductance device and a feedback network. The at least one amplifier is configured to output a filtered voltage signal according to an input voltage signal. The transconductance device is coupled to the at least one amplifier, and is configured to generate a filtered current signal according to the filtered voltage signal. The feedback network is coupled between any output terminal among at least one output terminal of the transconductance device and an input terminal of the at least one amplifier. More particularly, the mixer is configured to output a modulated signal according to the filtered current signal.