Gilbert Cell Mixer Feedback Circuit for Flicker Noise Reduction
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Solution Overview
Problem
Conventional mixers, such as the Gilbert cell, suffer from flicker noise that degrades spectral purity and existing improvements like common-mode feedback circuits also generate noise, disturbing output signals.
Innovation Solution
A mixer design incorporating a switching circuit, amplifying stage, load circuit, and common-mode feedback path with PMOS transistors and resistors to reduce flicker noise and stabilize common-mode voltage, utilizing current bleeding and feedback mechanisms to adjust current through the switching circuit before mixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a Gilbert cell mixer is used, then signal gain at the output is improved, but flicker noise increases
Solution Approach 1:
The patent extracts and removes the flicker noise component from the mixer output by introducing a noise cancellation path that specifically targets and eliminates the 1/f noise generated by the Gilbert cell, while preserving the desired signal gain
Solution Approach 2:
The patent introduces an intermediary noise cancellation circuit that acts as a mediator between the Gilbert cell mixer and the output, using a replica of the mixer's noise characteristics to cancel out the flicker noise through destructive interference
2Stability of the object's composition
If a common-mode feedback circuit is added to fix DC voltage, then DC voltage stability is improved, but flicker noise increases
Solution Approach 1:
The patent segments the feedback function into two separate paths: one path handles DC voltage stabilization through common-mode feedback, while another path handles flicker noise cancellation through differential-mode feedback, allowing each function to operate independently without interfering with the other
Solution Approach 2:
The patent implements a dual feedback mechanism where common-mode feedback stabilizes DC voltage and differential-mode feedback cancels flicker noise, using separate feedback loops that target different aspects of the output signal to achieve both stability and low noise
3Object-generated harmful factors
If current-bleeding type mixer is used, then flicker noise is decreased, but device complexity increases
Solution Approach 1:
The patent merges the noise cancellation function with the existing mixer structure by integrating the differential-mode feedback path into the Gilbert cell architecture, sharing common components such as transistors and resistors to reduce overall device complexity while maintaining flicker noise reduction
Data Source
AI summary
Disclosed is a mixer comprising: a switching circuit, having a first pair of differential signal nodes and a second pair of differential signal nodes, for switching according to a local oscillation signal; an amplifying stage circuit, for receiving an input signal and amplifying the input signal; a load circuit, for serving as the loading of the mixer and generating an output signal of the mixer; a common-mode feedback circuit, for receiving the output signal and generating a feedback signal according to the output signal; a first current source, for receiving the feedback signal and generating a first current according to the feedback signal; and a second current source, for receiving the feedback signal and generating a second current according to the feedback signal.