AC-Coupled Inverter Stages for RF Duty-Cycle Correction
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Solution Overview
Problem
Existing RF duty-cycle correction circuits are electronically noisy, sensitive to process variations and environmental changes, and require additional circuits, leading to increased power consumption and silicon real estate, making them unsuitable for portable RF devices.
Innovation Solution
A duty-cycle correction circuit comprising AC-coupled, independently-biased inverter stages connected in series, where each stage has a resistive element in feedback and is AC-coupled to the next stage via a capacitor, allowing independent DC biasing and incremental correction of the duty-cycle without the need for calibration or feedback loops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If prior art duty-cycle correction circuits are used, then duty-cycle correction is achieved, but electronic noise increases and phase noise performance deteriorates
Solution Approach 1:
The correction circuit is divided into multiple independent inverter stages, each contributing to duty-cycle correction. This segmentation allows the circuit to achieve accurate duty-cycle correction through cumulative effect of individual stages without requiring complex feedback mechanisms that generate noise.
Solution Approach 2:
Each inverter stage is independently biased and self-regulating, automatically adjusting its operation to contribute to the overall duty-cycle correction. The circuit serves itself by using the inherent properties of the inverters and their biasing to achieve correction without external control signals or feedback loops.
2Measurement precision
If prior art duty-cycle correction circuits are used, then duty-cycle correction is achieved, but circuit complexity and silicon real estate increase
Solution Approach 1:
The circuit is segmented into simple, identical inverter stages that can be easily replicated. Each stage performs a basic function with independent biasing, making the overall circuit design simple and modular while achieving accurate duty-cycle correction through the combined effect of multiple stages.
Solution Approach 2:
The inverter stages serve multiple functions: signal inversion, duty-cycle correction contribution, and automatic biasing. This multi-functionality reduces the need for separate correction circuits or control mechanisms, simplifying the overall design and reducing silicon real estate requirements.
3Measurement precision
If prior art duty-cycle correction circuits are used, then duty-cycle correction is achieved, but power consumption increases
Solution Approach 1:
Each inverter stage is independently biased and self-regulating, automatically adjusting its operation to contribute to the overall duty-cycle correction. The circuit serves itself by using the inherent properties of the inverters and their biasing to achieve correction without external control signals or feedback loops.
4Measurement precision
If prior art duty-cycle correction circuits are used, then duty-cycle correction is achieved, but sensitivity to process variations and temperature changes increases
Solution Approach 1:
The correction circuit is divided into multiple independent inverter stages, each contributing to duty-cycle correction. This segmentation allows the circuit to achieve accurate duty-cycle correction through cumulative effect of individual stages without requiring complex feedback mechanisms that generate noise.
5Speed
If fractional dividers are used to generate periodic signals, then frequency division is achieved, but duty-cycle skew is introduced
Solution Approach 1:
The inverter stages act as intermediary elements between the fractional divider output and the final signal. Each inverter stage independently processes the signal and contributes to correcting the duty-cycle skew introduced by the fractional divider, effectively mediating the transition from skewed to corrected duty-cycle.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively corrects the duty-cycle of periodic signals to arbitrary values with reduced noise and power consumption, being insensitive to process variations and temperature changes, while maintaining balanced circuit architecture and phase noise performance.
Implementation Method 1
Each inverter stage is AC-coupled to a prior stage via a capacitor. The AC-coupling allows the signal to pass between inverter stages, but DC-isolates each inverter stage from adjacent stages
Implementation Method 2
Each inverter stage comprises an inverter with a resistive element connected in feedback between its input and output nodes. By virtue of the feedback resistive element, each stage defines a transition point between high and low signal states
Implementation Method 3
The independent DC bias of each stage is operative to incrementally shift the transition point of the periodic signal at each stage towards a desired duty-cycle
Data Source
AI summary
A duty-cycle correction circuit comprises a plurality of AC-coupled, independently-biased inverter stages connected in series. A periodic signal is applied to an input of the plurality of inverter stages. Each inverter stage comprises an inverter with a resistive element connected in feedback between its output and input nodes. Each inverter stage is AC-coupled to a prior stage via a capacitor. The AC-coupling allows the signal to pass between inverter stages, but DC-isolates each inverter stage from adjacent stages, allowing each stage to maintain an independent DC bias of the signal at that stage. By virtue of the feedback resistive element, each stage defines a transition point between high and low signal states. Due to non-zero rise and fall times of the periodic signal, the independent DC bias of each stage is operative to incrementally shift the transition point of the periodic signal at each stage towards a desired duty-cycle.