Clock Oscillator Calibration Using Coarse-Fine Frequency Search

Solution Overview

Problem

Conventional phase-locked loops in multi-standard communication systems require a long time to calibrate the oscillator for different communications standards, leading to inefficient frequency tuning.

Innovation Solution

A clock generating apparatus comprising a time-to-digital converter, a calibrating device, and a controllable oscillator, which uses a combination of coarse and fine successive approximation methods to rapidly calibrate the oscillating signal to a target frequency, reducing the need to search the entire frequency range.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the oscillator searches over the whole usable frequency range to calibrate for a specific communications standard, then the calibration can achieve the target frequency, but the calibration time becomes very long

Engineering Contradiction:

Improvefrequency calibration accuracyVSAvoidfrequency calibration time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The frequency calibration process is divided into two distinct stages: coarse calibration and fine calibration. The coarse calibration stage quickly brings the oscillator frequency close to the target frequency by searching a reduced frequency range, while the fine calibration stage precisely adjusts the frequency to match the target frequency exactly. This segmentation resolves the contradiction by separating the time-consuming precise search from the initial rapid approximation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The coarse calibration is performed as a preliminary action before fine calibration. By first bringing the oscillator close to the target frequency through coarse calibration, the system prepares the oscillator in a state that enables faster and more efficient fine calibration, thereby reducing the overall calibration time while maintaining accuracy.

Inventive Principle:

Principle #10Preliminary action

2Adaptability or versatility

If more communications standards are embedded into one wireless communication system, then the system becomes more versatile, but the time to search for the target frequency increases

Engineering Contradiction:

Improvemulti-standard capabilityVSAvoidfrequency searching time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The frequency calibration process is divided into two distinct stages: coarse calibration and fine calibration. The coarse calibration stage quickly brings the oscillator frequency close to the target frequency by searching a reduced frequency range, while the fine calibration stage precisely adjusts the frequency to match the target frequency exactly. This segmentation resolves the contradiction by separating the time-consuming precise search from the initial rapid approximation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The coarse calibration is performed as a preliminary action before fine calibration. By first bringing the oscillator close to the target frequency through coarse calibration, the system prepares the oscillator in a state that enables faster and more efficient fine calibration, thereby reducing the overall calibration time while maintaining accuracy.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS8570107B2Clock generating apparatus and frequency calibrating method of the clock generating apparatus

Publication Date: 2013.10.29 MEDIATEK SINGAPORE PTE LTD

AI summary

A clock generating apparatus includes: a time-to-digital converter (TDC) arranged to convert a timing difference between a reference clock and a variable clock to generate a digital value; a calibrating device arranged to generate a control signal according to the digital value and the reference clock; a controllable oscillator arranged to generate an oscillating signal according to the control signal and the digital value; and a feedback device arranged to generate the variable clock to the TDC according to the oscillating signal, and the calibrating device calibrates the controllable oscillator to make the oscillating signal have a target oscillating frequency.