Digitally Controlled Oscillator Shielding for Lower DNL
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In digitally controlled oscillator (DCO) circuits for wireless communication systems, the variation in parasitic capacitance between oscillation nodes leads to increased differential non-linearity (DNL), affecting the quality of transmission and reception signals by causing phase errors and spectrum degradation.
Innovation Solution
A digitally controlled oscillator device is designed with shield layers between the control lines and oscillation output nodes to stabilize impedance, reducing variations in parasitic capacitance and thereby minimizing DNL, and incorporating a control circuit to manage the coupling of capacitive elements for precise frequency control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dynamic element matching is applied to select capacitors coupled to oscillation nodes, then DNL is improved on average, but calibration is required at start-up to optimize capacitor selection
Solution Approach 1:
The patent makes the DCO circuit self-calibrating by using the oscillation output signals themselves to drive the capacitor selection process. The control circuit automatically selects capacitors based on the oscillation state without requiring external calibration operations, allowing the circuit to optimize its own capacitor selection dynamically during operation.
Solution Approach 2:
The patent implements feedback by using the oscillation output nodes to drive the capacitor selection process. The control circuit monitors the oscillation state and adjusts capacitor selection accordingly, creating a closed-loop system that continuously optimizes DNL performance based on actual oscillation conditions.
2Measurement precision
If parasitic capacitance variation between oscillation nodes occurs, then DNL increases, but adding shield layers increases device complexity
Solution Approach 1:
The patent introduces shield layers as intermediary structures between the oscillation nodes and surrounding circuit elements. These shield layers act as mediators that block parasitic capacitance coupling paths, reducing DNL without requiring fundamental changes to the oscillator core structure.
Solution Approach 2:
The patent extracts and isolates the parasitic capacitance sources by separating the oscillation nodes from nearby conductive elements using shield layers. This extraction approach removes the harmful parasitic effects while maintaining the functional integrity of the oscillator circuit.
3Productivity
If capacitors are sequentially controlled according to digital code, then oscillation frequency is controlled, but linearity between digital code and capacitance value degrades causing phase error
Solution Approach 1:
The patent makes the capacitor selection dynamic by using the oscillation output signals to control which capacitors are coupled to the oscillation nodes. Instead of static digital code control, the system dynamically adjusts capacitor selection based on real-time oscillation state, improving linearity between digital code and effective capacitance.
Solution Approach 2:
The patent changes the control parameter from simple digital code to oscillation-based feedback signals. By using the actual oscillation state as the control parameter, the system achieves better linearity in the relationship between digital code and capacitance value, reducing phase errors in the output signal.
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 reduces DNL, enhancing the quality of transmission and reception signals by stabilizing parasitic capacitance and improving frequency control, without the need for calibration operations typically required in dynamic element matching systems.
Implementation Method 1
the variation in parasitic capacitance between oscillation nodes leads to increased differential non-linearity (DNL)
Data Source
AI summary
The present invention provides a digitally controlled oscillator device capable of realizing a reduction in DNL. The digitally controlled oscillator device includes, for example, an amplifier circuit block, coil elements and a plurality of unitary capacitor units coupled in parallel between oscillation output nodes. Each of the unitary capacitor units is provided with capacitive elements, and a switch which selects whether the capacitive elements should be allowed to contribute as set parameters for an oscillation frequency. The switch is driven by an on/off control line extending from a decoder circuit. The on/off control line is shielded between the oscillation output nodes by a shield section.