Single-Layer LC Oscillator Calibration Without Crystal Resonators
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Solution Overview
Problem
Existing oscillators for IoT devices, such as those used in BLE transmitters, face challenges including high power consumption, large size, cost, and calibration difficulties, especially when implemented on low-cost inlay substrates, and require a stable frequency reference which is often provided by expensive crystal or MEMS resonators.
Innovation Solution
An inductor-capacitor (LC) oscillator with a single-layer inductor configured in a spiral pattern within an inlay substrate, integrated with a capacitor and an oscillator calibration circuit that uses an over-the-air signal to calibrate its frequency, reducing the need for additional resonators and allowing temperature-dependent frequency adjustments through a look-up table.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a crystal or MEMS resonator is used to provide frequency reference, then frequency stability is improved, but device cost and complexity increase
Solution Approach 1:
The patent extracts the frequency reference function from external crystal or MEMS resonators and implements it using an on-chip RC oscillator with temperature compensation. The frequency reference is now generated within the oscillator circuit itself using resistors, capacitors, and transistors that can be integrated on the same chip, eliminating the need for separate resonator components.
Solution Approach 2:
The patent combines multiple functions into a single integrated circuit: the RC oscillator, temperature sensing, look-up table storage, and frequency compensation are all merged into one chip. This integration eliminates the need for separate crystal resonators and temperature compensation circuits, reducing device complexity while maintaining frequency stability.
2Device complexity
If an RC oscillator is used instead of crystal resonator, then device complexity is reduced, but frequency accuracy and stability deteriorate
Solution Approach 1:
The patent implements a feedback mechanism where the oscillator's output frequency is monitored, compared against expected values from a look-up table, and corrected by adjusting the RC time constant. The microcontroller reads the oscillator frequency, determines the temperature based on frequency characteristics, and adjusts the oscillator components to maintain accurate frequency despite temperature variations.
Solution Approach 2:
The patent changes the operating parameters of the RC oscillator dynamically based on temperature. By storing pre-calibrated frequency-temperature data in a look-up table and adjusting the RC time constant accordingly, the system maintains frequency accuracy across different temperatures. The oscillator frequency is deliberately allowed to vary with temperature, then corrected through parameter adjustment.
3Reliability
If temperature compensation is implemented, then frequency stability is improved, but power consumption increases
Solution Approach 1:
The patent implements temperature compensation through periodic rather than continuous operation. The microcontroller measures the oscillator frequency, determines temperature, and adjusts compensation parameters only when needed (e.g., at power-up or when temperature changes are detected). This periodic measurement and adjustment approach maintains frequency stability while minimizing power consumption compared to continuous temperature sensing and compensation.
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 a low-power, compact, and cost-effective oscillator with high temperature stability, enabling accurate frequency calibration and operation as a temperature sensor without additional hardware, reducing power consumption and manufacturing dependencies.
Implementation Method 1
a single layer inductor disposed within a single layer inlay, wherein the single layer inductor is configured in a spiral pattern within the layer of the inlay
Implementation Method 2
a capacitor included in the integrated circuit, wherein the capacitor is connected to the single layer inductor
Implementation Method 3
an inductor-capacitor (LC) oscillator with an inductor implemented within an inlay substrate
Data Source
AI summary
A temperature sensor is provided. The temperature sensor comprises: an inductor-capacitor (LC) oscillator configured; and a look-up table stored in a memory, wherein the look-up table contains a set of frequencies as a function of ambient temperature values, wherein when the LC oscillator is calibrated to a frequency from amongst the set of frequencies, the respective ambient temperature as stored in the look-up table is retrieved.