Crystal-Less RF Transmitter With Temperature-Corrected VCO

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Solution Overview

Problem

Crystal oscillators used in RF transmitters face issues with frequency stability and accuracy, especially with low-quality crystals, and are costly and space-consuming, making them unsuitable for compact IoT devices.

Innovation Solution

A crystal-less RF transmitter is developed, incorporating a digitally controlled oscillator (DCO), frequency control and locking circuit (FCLC), digital-to-analog converter (DAC), and memory with a look-up table (LUT) to correct frequency based on temperature, eliminating the need for a crystal oscillator.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a crystal oscillator is used to generate stable frequency, then frequency stability is improved, but device cost and size increase

Engineering Contradiction:

Improvefrequency stabilityVSAvoiddevice cost and size

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent removes the crystal oscillator from the system and replaces it with a digitally controlled oscillator (DCO) that achieves frequency stability through digital control mechanisms and temperature compensation algorithms, thereby eliminating the need for expensive and large crystal components

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent uses temperature sensors to detect temperature changes and adjusts the DCO frequency parameters dynamically through lookup tables and calibration data, compensating for temperature-induced frequency drift without requiring a crystal oscillator

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If low-quality crystals are used to reduce cost, then device cost is reduced, but frequency stability deteriorates

Engineering Contradiction:

Improvedevice costVSAvoidfrequency stability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent replaces the mechanical crystal resonance system with a digitally controlled electronic oscillator system that uses software algorithms and temperature compensation to achieve frequency stability, eliminating the need for physical crystals of any quality

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent implements a feedback mechanism where temperature sensors continuously monitor environmental conditions and the system adjusts DCO control parameters accordingly, maintaining frequency stability through active compensation rather than relying on passive crystal quality

Inventive Principle:

Principle #23Feedback

3Measurement precision

If crystal oscillator layout requirements are followed to maintain frequency accuracy, then frequency accuracy is improved, but device layout complexity increases

Engineering Contradiction:

Improvefrequency accuracyVSAvoidlayout complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent removes the crystal oscillator and its associated strict layout requirements, replacing it with a DCO that is inherently more tolerant to layout variations and does not require specialized placement for frequency accuracy

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent uses digital parameter adjustment and temperature compensation algorithms to maintain frequency accuracy without being constrained by physical layout considerations, allowing greater design flexibility

Inventive Principle:

Principle #35Parameter changes

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

This solution provides stable frequency correction across temperature changes, reduces device size and cost, and minimizes electromagnetic interference, enabling the miniaturization and cost-effectiveness of IoT devices.

Implementation Method 1

a temperature sensor that measures ambient temperature

Methodology Applied

Scientific EffectTemperature sensing: Thermistor

Implementation Method 2

a digitally controlled oscillator (DCO) that digitally controls an output frequency for the RF signal

Methodology Applied

Scientific EffectElectromagnetic signal generation: Electromagnetic Induction

Implementation Method 3

a digital-to-analog converter (DAC) that transmits a control voltage to the DCO based on a digital code received from the FCLC

Methodology Applied

Scientific EffectDigital-to-analog conversion:

Implementation Method 4

a frequency control and locking circuit (FCLC) that performs frequency locking related to correction of the output frequency

Methodology Applied

Scientific EffectFrequency comparison and locking: Resonance

Data Source

PatentUS20250096824A1RF transmiter integrated circuit including crystal-less VCO and electronic tag including the same

Publication Date: 2025.03.20 3A LOGICS CO LTD

AI summary

The present specification provides a crystal-less radio frequency (RF) transmitter for correcting frequency depending on temperature. The RF transmitter may include: an antenna that transmits an RF signal; a temperature sensor that measures ambient temperature; a digitally controlled oscillator (DCO) that digitally controls an output frequency for the RF signal; a frequency control and locking circuit (FCLC) that performs frequency locking related to correction of the output frequency; a digital-to-analog converter (DAC) that transmits a control voltage to the DCO based on a digital code received from the FCLC; and a memory in which a look up table (LUT) that corrects the output frequency based on the temperature is stored.