Ring Oscillator Resistor-Bank Tuning for Linear Frequency Control

Solution Overview

Problem

Digitally controlled oscillators face challenges in achieving a wide tuning range due to nonlinear frequency variation when using digital-to-analog converters and current-starved transistors, leading to degraded resolution.

Innovation Solution

Incorporating a parallel resistor bank and a serial resistor bank connected to a ring oscillator, where resistances vary according to digital codes, allowing for linear frequency variation and improved resolution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a DAC and current-starved transistor are used for frequency control in a ring oscillator, then the transistor size must be significantly larger, but the tuning range is limited and cannot achieve about 2 decades

Engineering Contradiction:

Improvetuning rangeVSAvoidtransistor size

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The resistor control is divided into two independent banks: a parallel resistor bank connected to the first terminal and a serial resistor bank connected to the second terminal of the ring oscillator. Each bank can be independently controlled by digital codes, allowing the system to achieve a wide tuning range without requiring oversized transistors. The segmentation enables flexible combination of resistance values to cover 2 decades of tuning range.

Inventive Principle:

Principle #1Segmentation

2Measurement precision

If a single resistor bank is used for frequency control, then the structure is simple, but the frequency variation becomes nonlinear following a 1/x curve, degrading resolution

Engineering Contradiction:

Improvefrequency resolutionVSAvoidresistor bank structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The resistor control is divided into two independent banks: a parallel resistor bank connected to the first terminal and a serial resistor bank connected to the second terminal of the ring oscillator. Each bank can be independently controlled by digital codes, allowing the system to achieve a wide tuning range without requiring oversized transistors. The segmentation enables flexible combination of resistance values to cover 2 decades of tuning range.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from single-dimension resistance control (one resistor bank) to two-dimension resistance control (parallel and serial resistor banks). By controlling both banks with independent digital codes, the system achieves linear frequency variation across a wide range, transforming the nonlinear 1/x relationship into a linear relationship between digital code and frequency output.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Adaptability or versatility

If frequency is controlled by switching resistors or capacitors according to digital code, then the tuning range can be extended, but the frequency varies nonlinearly along a 1/x curve, degrading resolution

Engineering Contradiction:

Improvetuning rangeVSAvoidfrequency resolution

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The resistor control is divided into two independent banks: a parallel resistor bank connected to the first terminal and a serial resistor bank connected to the second terminal of the ring oscillator. Each bank can be independently controlled by digital codes, allowing the system to achieve a wide tuning range without requiring oversized transistors. The segmentation enables flexible combination of resistance values to cover 2 decades of tuning range.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from single-dimension resistance control (one resistor bank) to two-dimension resistance control (parallel and serial resistor banks). By controlling both banks with independent digital codes, the system achieves linear frequency variation across a wide range, transforming the nonlinear 1/x relationship into a linear relationship between digital code and frequency output.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS8040196B2Digitally controlled oscillator

Publication Date: 2011.10.18 SAMSUNG ELECTRONICS CO LTD

AI summary

A digitally controlled oscillator includes a ring oscillator, a parallel resistor bank connected to a first terminal of the ring oscillator and having a resistance that varies according to a digital code, and a serial resistor bank connected to a second terminal of the ring oscillator and having a resistance that varies according to the digital code. A frequency of the ring oscillator linearly varies with a variation in the resistance of the parallel resistor bank and the resistance of the serial resistor bank according to the digital code.