RF Linear Transconductor Feed-Forward Linearization for Low Noise
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Solution Overview
Problem
RF mixers suffer from intermodulation distortion due to nonlinearity, which degrades receiver performance and requires linearization that compromises gain and noise figure.
Innovation Solution
A linear transconductor with feed-forward linearization using a differential pair of NMOS transistors and cascode configuration to sense and cancel nonlinearity, minimizing intermodulation products without affecting gain or noise figure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If source degeneration is used to linearize the transconductor, then intermodulation distortion is reduced, but noise figure deteriorates and gain is reduced
Solution Approach 1:
The transconductor is divided into two separate stages: a first transconductor stage that performs the primary voltage-to-current conversion, and a second transconductor stage that provides linearization by canceling intermodulation products. This segmentation allows each stage to be optimized for its specific function without compromising the other, thereby improving linearity without significantly degrading noise figure or gain.
Solution Approach 2:
A current mirror circuit is introduced as an intermediary element between the two transconductor stages. The current mirror copies and transfers the linearized current from the first stage to the second stage, enabling the linearization function to be achieved without directly affecting the noise performance of the input stage. This intermediary mechanism facilitates the separation of linearity enhancement from noise degradation.
2Manufacturing precision
If source degeneration is used to linearize the transconductor, then intermodulation distortion is reduced, but gain is reduced
Solution Approach 1:
The transconductor is divided into two separate stages: a first transconductor stage that performs the primary voltage-to-current conversion, and a second transconductor stage that provides linearization by canceling intermodulation products. This segmentation allows each stage to be optimized for its specific function without compromising the other, thereby improving linearity without significantly degrading gain.
Solution Approach 2:
A current mirror circuit is introduced as an intermediary element between the two transconductor stages. The current mirror copies and transfers the linearized current from the first stage to the second stage, enabling the linearization function to be achieved without directly affecting the gain of the input stage. This intermediary mechanism facilitates the separation of linearity enhancement from gain reduction.
Data Source
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AI summary
The present patent application comprises a linear transconductor having at least one input and at least one output, comprising a differential amplifier having a plurality of transistors and a plurality of inputs, wherein a difference of input signals is amplified, a cascode circuit having a plurality of transistors, wherein the transistors are operably connected to the differential amplifier, wherein reverse isolation between an input and an output of the linear transconductor is improved by decoupling the input and the output of the linear transconductor by mounting at least one transistor of the plurality of transistors of the cascode circuit as a common-gate stacked on the at least one transistor of the differential amplifier, an active load having a plurality of transistors operably connected between the cascode circuit and supply voltage, and an auxiliary device operably connected to the connection between the active load, the cascode device and ground.