PLL Sensing Circuit Using Frequency Pulling for Self-Trimming

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Solution Overview

Problem

Wireless sensing devices face challenges in reducing cost and footprint due to the frequency pulling effect caused by harmonics generated by power amplifiers, which requires complex and costly trimming processes and equipment.

Innovation Solution

A sensing device utilizing a phase locked loop circuit with a power amplifier that generates an interfering signal component at the oscillator frequency, allowing for measurement of frequency offset and trimming of the loop circuit and amplifier to minimize harmonics, thereby reducing the device's cost and footprint.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If a power amplifier is used to amplify the oscillator output signal, then the transmission capability is improved, but an interfering signal component at the oscillator frequency is generated due to the frequency pulling effect

Engineering Contradiction:

Improvetransmission capabilityVSAvoidinterfering signal component

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful frequency pulling effect into a useful sensing mechanism. The interfering signal component generated by the power amplifier is not filtered out but rather measured to detect environmental changes. The frequency offset caused by the interfering signal is used as the sensing parameter, transforming a previously harmful effect into the basis for environmental sensing capability.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Measurement precision

If complex trimming processes and equipment are used to compensate for the frequency pulling effect, then the frequency accuracy is improved, but the device complexity and cost increase

Engineering Contradiction:

Improvefrequency accuracyVSAvoidtrimming process complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system uses itself to measure and compensate for the frequency pulling effect. The same power amplifier that generates the interfering signal also provides the measurement signal for detecting the frequency offset. The sensing device self-diagnoses the frequency accuracy issue by measuring the offset caused by its own power amplifier, eliminating the need for external complex trimming equipment.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The power amplifier serves dual functions: it amplifies the oscillator signal for transmission and simultaneously generates a measurable interfering signal for frequency offset detection. This multi-functionality eliminates the need for separate trimming equipment, as the same component used for signal amplification also provides the reference signal for accuracy measurement and compensation.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If selective notch filters and power detectors are added to handle the interfering signal, then the signal quality is improved, but the production cost and time increase

Engineering Contradiction:

Improvesignal qualityVSAvoidproduction cost and time

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Instead of filtering out the interfering signal component using complex notch filters and power detectors, the patent measures and utilizes this interfering signal for environmental sensing. The frequency offset information extracted from the interfering signal replaces the need for traditional signal purification components, simplifying the device while adding sensing functionality.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 approach enables efficient trimming and sensing applications, reducing the need for selective notch filters and power detectors, lowering production costs and time, while allowing for cost-effective and compact wireless sensing devices.

Implementation Method 1

the frequency offset is due to a frequency pulling effect at the oscillator caused by the interfering signal component of the amplified output signal of the power amplifier

Methodology Applied

Scientific EffectFrequency pulling effect:

Data Source

PatentUS10998909B1Sensing device comprising a phase locked loop circuit

Publication Date: 2021.05.04 DIALOG SEMICONDUCTOR BV

AI summary

A sensing device with a phase locked loop circuit that has an oscillator to provide an oscillator output signal is presented. The sensing device has a power amplifier to provide at an output of the power amplifier an amplified output signal based on the oscillator output signal. The amplified output signal has an interfering signal component at the oscillator frequency. The sensing device has a measurement circuit to measure offset information regarding a frequency offset between the oscillator frequency and a target frequency of the oscillator. The frequency offset is due to a frequency pulling effect at the oscillator caused by the interfering signal component of the amplified output signal. The sensing device has a control circuit to use the offset information for trimming the phase locked loop circuit and/or the power amplifier, and/or for determining information regarding an environmental situation at the output of the power amplifier.