Fractional N-PLL Radio Transmitter With Digital Temperature Compensation

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Solution Overview

Problem

Radio transmission apparatuses that require frequency precision, such as those conforming to ARIB STD-T67, face challenges in achieving precise frequency stability without using expensive temperature compensated crystal oscillators (TCXO), particularly in cost-sensitive applications like miniature devices.

Innovation Solution

A radio transmission apparatus utilizing a vibration element, a fractional N-PLL circuit, and a temperature detection element to digitally control the frequency of the radio transmission signal, allowing for temperature compensation without the need for a TCXO, by incorporating the frequency temperature characteristics of the vibration element and using a thermistor or AT vibration element for precise temperature detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a temperature compensated crystal oscillator (TCXO) is used to achieve frequency precision, then frequency stability is improved, but device cost increases

Engineering Contradiction:

Improvefrequency precisionVSAvoiddevice cost

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent replaces the expensive TCXO with a combination of a standard crystal oscillator and a temperature detection element. The system uses temperature information from the detection element to control the crystal oscillator frequency, achieving the same frequency precision as TCXO but with significantly lower cost components.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent introduces a temperature detection element as an intermediary between the crystal oscillator and the frequency control system. This intermediary provides temperature information that enables dynamic frequency adjustment, allowing the system to compensate for temperature effects without requiring an expensive TCXO.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If a temperature compensated crystal oscillator (TCXO) is used to achieve frequency precision, then frequency stability is improved, but device size increases

Engineering Contradiction:

Improvefrequency precisionVSAvoiddevice size

Core Design Contradiction:

Manufacturing precisionVSVolume of moving object

Solution Approach 1:

The patent divides the frequency control function into separate components: a standard crystal oscillator for frequency generation and a temperature detection element for temperature monitoring. This segmentation allows each component to be optimized independently, resulting in a more compact overall design compared to integrating temperature compensation directly into the oscillator as in TCXO.

Inventive Principle:

Principle #1Segmentation

3Temperature

If analog temperature compensation is used in TCXO, then temperature compensation is achieved, but manufacturing variation increases

Engineering Contradiction:

Improvetemperature compensationVSAvoidmanufacturing variation

Core Design Contradiction:

TemperatureVSManufacturing precision

Solution Approach 1:

The patent replaces the analog mechanical temperature compensation mechanism in TCXO with a digital control system. The temperature detection element provides digital temperature information that is used to control the crystal oscillator frequency digitally, eliminating the manufacturing variations inherent in analog compensation circuits.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enables the achievement of the same frequency precision as TCXO-based systems at a lower cost, with improved temperature compensation accuracy and reduced manufacturing variation, while minimizing the size of the apparatus.

Implementation Method 1

the temperature detection element may be a thermistor that detects temperature of the vibration element

Methodology Applied

Scientific EffectThermistor temperature detection: Thermistor

Implementation Method 2

a vibration element; a radio transmission semiconductor device that includes a fractional N-PLL circuit generating a radio transmission clock signal based on an output signal of the vibration element

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 3

The control device controls the fractional N-PLL circuit based on temperature information obtained from the temperature detection element such that a frequency of the radio transmission signal is temperature-compensated

Methodology Applied

Scientific EffectTemperature-compensated frequency control:

Data Source

PatentUS9628087B2Radio transmission apparatus

Publication Date: 2017.04.18 SEIKO EPSON CORP

AI summary

A radio transmission apparatus includes a radio transmission IC including a vibration element and a fractional N-PLL circuit and a power amplifier generating a radio transmission signal and a control device that controls the radio transmission IC, and a temperature detection element. The control device controls the fractional N-PLL circuit based on temperature information obtained from the temperature detection element such that a frequency of the radio transmission signal is temperature-compensated.