Digitally Controlled Oscillator Shield Layout 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 control lines and oscillation nodes leads to increased differential non-linearity (DNL), affecting the quality of transmission and reception signals.
Innovation Solution
A digitally controlled oscillator device is designed with shield layers between control lines and oscillation nodes to reduce impedance variations, using a configuration with coil elements, capacitor units, and a negative resistance generating circuit to control oscillation frequency, thereby minimizing DNL.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitor units are coupled to oscillation nodes in a DCO circuit, then oscillation frequency can be controlled, but parasitic capacitance variation increases DNL
Solution Approach 1:
A shield layer is introduced as an intermediary between the control lines and oscillation nodes. This shield layer acts as a mediator that blocks or reduces the parasitic capacitance coupling between control lines and oscillation nodes, thereby reducing DNL while preserving frequency control capability
Solution Approach 2:
The parasitic capacitance effect is extracted and isolated by introducing a dedicated shield layer structure. The shield layer captures and contains the parasitic capacitance effects, preventing them from directly affecting the oscillation nodes and DNL performance
2Area of stationary object
If control lines are placed near oscillation nodes for compact design, then area is reduced, but impedance variation increases
Solution Approach 1:
The shield layer serves as an intermediary barrier between control lines and oscillation nodes, allowing them to be placed in close proximity for compact design while the shield layer maintains impedance stability by blocking unwanted electromagnetic coupling
Solution Approach 2:
The solution moves from a two-dimensional planar arrangement to a three-dimensional layered structure. By stacking the shield layer between control lines and oscillation nodes in the vertical dimension, the design achieves both compact area and stable impedance
3Manufacturing precision
If dynamic element matching is applied to select capacitors, then DNL is improved, but calibration is required
Solution Approach 1:
The shield layer structure provides self-service by automatically reducing parasitic capacitance effects through its physical presence and configuration. The shield layer inherently compensates for parasitic effects without requiring external calibration or adjustment, achieving DNL improvement through passive structural design
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, improving the quality of transmission and reception signals by stabilizing parasitic capacitance variations, thus enhancing the precision and accuracy of frequency control in DCO circuits.
Implementation Method 1
the parasitic capacitance added to each oscillation node becomes a main factor as to the degeneration in DNL
Implementation Method 2
a DCO circuit for a wireless communication system is normally configured by an LC resonant type
Implementation Method 3
a negative resistance generating circuit that generates a negative resistance between the first oscillation output node and the second oscillation output node
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.