Satellite Receiver Controller Using Non-TCXO and Adaptive Temperature Compensation

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Solution Overview

Problem

High accuracy GPS receivers require accurate clock frequencies, but temperature-compensated crystal oscillators (TCXOs) are costly and increase overall costs, necessitating a method to compensate frequency offsets without using TCXOs.

Innovation Solution

A satellite receiving controller with a temperature pin, frequency synthesizer, analog-to-digital converter (ADC), and control unit that generates oscillation frequency adjustments based on temperature and frequency offset data, using a non-temperature-compensated crystal oscillator (non-TCXO) to compensate for temperature-induced frequency variations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a temperature-compensated crystal oscillator (TCXO) is used to provide accurate clock frequency, then positioning accuracy is improved, but device cost increases significantly

Engineering Contradiction:

Improvepositioning accuracyVSAvoiddevice cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent replaces the expensive TCXO with a cheap non-TCXO crystal oscillator. Although the non-TCXO has temperature-dependent frequency drift, the system compensates for this using software algorithms and GPS timing data, achieving accurate positioning without the costly hardware component.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent changes the operating parameters of the crystal oscillator by applying frequency correction values derived from temperature compensation algorithms. The system adjusts the oscillator frequency dynamically based on temperature readings and GPS-derived timing information, effectively compensating for the non-TCXO's temperature drift characteristics.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If a non-temperature-compensated crystal oscillator (non-TCXO) is used to reduce cost, then device cost decreases, but frequency accuracy deteriorates under temperature variation

Engineering Contradiction:

Improvedevice costVSAvoidfrequency accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent implements a feedback mechanism where the system continuously monitors temperature via a temperature sensor and compares the oscillator's actual frequency (derived from GPS satellite timing) with the expected frequency. Based on this feedback, the system dynamically adjusts the oscillator frequency using correction algorithms stored in lookup tables or computed in real-time.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent introduces GPS satellite timing signals as an intermediary reference. The GPS signals provide an external, highly accurate time reference that the system uses to calibrate and compensate for the crystal oscillator's frequency drift, effectively using an external mediator to correct the oscillator's temperature-induced errors.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If frequency compensation algorithms are implemented to maintain accuracy, then positioning precision is improved, but computational complexity increases

Engineering Contradiction:

Improvepositioning precisionVSAvoidcomputational complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent performs preliminary action by pre-computing and storing temperature-compensation lookup tables in the device memory during manufacturing. These tables contain pre-calculated frequency correction values for various temperature conditions, allowing the runtime system to simply look up and apply the appropriate correction without performing complex real-time calculations.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces complex real-time computational mechanisms with simpler table-lookup and interpolation operations. Instead of implementing sophisticated frequency prediction algorithms that require extensive computation, the system uses pre-computed data structures and simple mathematical interpolation to achieve the same compensation effect with minimal processing overhead.

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 approach allows for high accuracy satellite positioning while reducing costs by eliminating the need for TCXOs, enabling mass production of reliable GPS receivers with adaptive frequency compensation.

Implementation Method 1

The temperature pin, coupled to an external thermistor, receives an analog temperature signal

Methodology Applied

Scientific EffectThermistor: Thermistor

Data Source

PatentUS8223070B2High accuracy satellite receiving controller and associated method

Publication Date: 2012.07.17 MEDIATEK INC

AI summary

A high accuracy satellite signal receiving controller and associated method is provided. The high accuracy satellite signal receiving controller includes a frequency synthesizer, and an analog-to-digital converter (ADC), a Global Positioning System (GPS) receiving module and a control unit. The frequency synthesizer, coupled to an external non-temperature-compensated crystal oscillator (non-TXCO), generates an oscillating frequency signal to the GPS receiving module. The ADC converts an analog temperature signal into a digital temperature signal. The control unit, coupled to the ADC, adaptively updates temperature/frequency offset data.