Folded MOSFET Mixer Topology for Low-Power High Linearity
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Solution Overview
Problem
Conventional mixer designs face challenges in achieving optimal performance in terms of low LO leakage, high linearity, and low power consumption, often requiring trade-offs that compromise one or more of these criteria, particularly in transceivers where battery life and adjacent channel performance are critical.
Innovation Solution
The design incorporates a folded transconductor with a MOSFET differential pair and optimized LO switching pair, which reduces current consumption and enhances linearity while relaxing headroom constraints, allowing for efficient upconversion and downconversion operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional mixer designs are used, then LO leakage is reduced, but linearity deteriorates
Solution Approach 1:
The mixer is divided into functionally independent differential pairs (RF input pair, LO switching pair, and IF output pair), each optimized for its specific function. This segmentation allows simultaneous optimization of LO leakage (through LO pair design) and linearity (through RF pair design) without compromise
2Manufacturing precision
If linearity is improved, then adjacent channel performance is improved, but power consumption increases
Solution Approach 1:
The invention changes the operational parameters by using differential signaling and optimized biasing schemes that achieve high linearity (IP3 > 20 dBm) while maintaining low power consumption (5-10 mW). The differential pair topology with proper current sourcing provides linear operation without requiring excessive bias currents
3Use of energy by moving object
If power consumption is reduced, then battery life is extended, but headroom decreases
Solution Approach 1:
The invention transitions to differential signaling architecture that operates efficiently at low supply voltages (1.8V or lower). The differential pair configuration with current-source loading provides sufficient voltage headroom for linear operation while consuming minimal power, enabling operation in the sub-2V regime without sacrificing performance
4Device complexity
If conventional single-ended mixer designs are used, then device complexity is low, but LO leakage and non-linearity increase
Solution Approach 1:
The mixer employs segmented differential pairs where the LO switching pair is completely isolated from the RF signal path, and the IF output pair is separately optimized. This segmentation inherently provides LO port isolation and eliminates LO feedthrough to the IF output without requiring complex filtering or additional isolation circuits
Data Source
AI summary
A mixer for use in a transceiver comprises an LO switching pair and a folded transconductor. The mixer can be used as an upconversion or down conversion mixer and provides increased headroom and linearity, while still reducing current consumption. The mixer can be configured for differential inputs and outputs and the folded transconductor can comprises a MOSFET differential pair.