Oscillator Frequency Lookup Table Using Capacitor Interpolation

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Solution Overview

Problem

The high cost of manufacturing transceivers that meet stringent mobile communication frequency error tolerances is a significant challenge, as existing methods for generating precise oscillator frequencies are time-consuming and costly due to the need for extensive measurement and data recording in oscillator frequency adjustment lookup tables.

Innovation Solution

A method is introduced to build an oscillator frequency adjustment lookup table using an adjustable capacitor set in a transceiver, where interpolation and Taylor expansion simplify the relationship between equivalent capacitance and frequency variations, allowing for the use of quadratic polynomials to approximate frequency changes, reducing the number of required measurements and data points.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If extensive measurement and data recording methods are used to build the oscillator frequency adjustment lookup table, then the frequency precision meets the 0.1 ppm error tolerance requirement, but the manufacturing cost and time increase significantly

Engineering Contradiction:

Improvefrequency precisionVSAvoidmanufacturing cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent divides the frequency adjustment range into multiple segments or intervals. Instead of measuring and recording data for the entire frequency range with fine granularity, the lookup table is constructed by segmenting the adjustment range and using interpolation between measured points. This reduces the number of required measurements while maintaining accuracy within each segment.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies partial measurement action by measuring only at key reference points within the frequency adjustment range rather than exhaustively measuring every possible frequency point. The interpolation method fills in the gaps between measured points, achieving acceptable precision with less measurement effort and lower manufacturing cost.

Inventive Principle:

Principle #16Partial or excessive action

2Measurement precision

Engineering Contradiction:

Improvefrequency precisionVSAvoidmanufacturing time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

By segmenting the frequency adjustment range and using interpolation between measured reference points, the patent reduces the total number of measurements required. This segmentation approach maintains frequency precision within each segment while significantly reducing the time needed to populate the lookup table during manufacturing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent performs partial measurements at strategically selected reference points rather than exhaustive measurements across the entire frequency range. This partial action approach, combined with interpolation, achieves the required 0.1 ppm precision while reducing manufacturing time by avoiding unnecessary measurements at every possible frequency point.

Inventive Principle:

Principle #16Partial or excessive action

3Ease of manufacture

If fewer measurement points are used to build the lookup table, then the manufacturing cost and time are reduced, but the frequency precision may not meet the 0.1 ppm error tolerance

Engineering Contradiction:

Improvemanufacturing costVSAvoidfrequency precision

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent performs preliminary measurements at key reference points that define the boundaries and critical regions of the frequency adjustment range. These preliminary measurements establish the foundation for the lookup table, and interpolation between these points achieves the required precision without needing extensive measurements at every frequency point, thus reducing manufacturing cost while maintaining accuracy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent incorporates feedback mechanisms where the measured frequency values at reference points are used to validate and refine the interpolation model. This feedback ensures that the reduced set of measurement points still produces frequency precision within the 0.1 ppm tolerance, allowing cost reduction without sacrificing measurement precision.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS11799423B2Method of building oscillator frequency adjustment lookup table and associated transceiver

Publication Date: 2023.10.24 REALTEK SEMICON CORP

AI summary

The application discloses a method, for building an oscillator frequency adjustment lookup table in a transceiver, wherein the transceiver generates a clock according to a crystal oscillator external to the transceiver for transceiving data. The transceiver includes adjustable capacitor arrays assembly connected to the crystal oscillator, wherein when an equivalent capacitance of the adjustable capacitor assembly is a reference value, the crystal oscillator has a reference frequency, and when the equivalent capacitance changes relative to the reference value, the crystal oscillator correspondingly has a frequency offset relative to the reference frequency. The method includes: performing an interpolation operation according to a first value, a second value, and a third value of the equivalent capacitance, and the corresponding frequency variations, so as to obtain the frequency variations corresponding to a first sub-value between the first value and the second values.