Oscillator Temperature Compensation With Slot-Based Drift Tables
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Solution Overview
Problem
Existing oscillator technologies face challenges in compensating for temperature-related frequency drift, particularly in Global Navigation Satellite System (GNSS) receivers, where memory requirements for storing compensation data are high due to the need for wide temperature range coverage and resolution, especially in mobile devices.
Innovation Solution
A method that uses an external reference frequency signal to derive and store oscillator compensation data in a table, subdividing the temperature range into slots and bins, allowing for dynamic data collection and updating, thereby reducing memory requirements by retaining only data relevant to the current and adjacent temperature slots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a look-up table stores compensation data for the entire temperature range with fine resolution, then temperature compensation accuracy is improved, but memory requirements increase significantly
Solution Approach 1:
The temperature range is divided into multiple temperature slots, each covering a specific temperature interval. For each slot, compensation parameters (such as frequency offset and temperature coefficient) are stored and calculated separately. This segmentation allows the system to maintain high compensation accuracy within each slot while significantly reducing the total memory requirements compared to storing data for every temperature point across the entire range.
Solution Approach 2:
The patent implements dynamic updating of compensation parameters based on the current temperature slot. When the temperature changes and enters a new slot, the system dynamically selects and updates the corresponding compensation parameters for that slot. This dynamic approach ensures that the most relevant compensation data is always used, maintaining accuracy while avoiding the need to store and manage the entire temperature range data simultaneously in memory.
2Reliability
If the oscillator is disciplined continuously using external reference, then frequency stability is improved, but the system cannot operate when external reference is unavailable
Solution Approach 1:
The system performs preliminary characterization of the oscillator's temperature-dependent frequency drift during periods when the external reference is available. Compensation parameters for each temperature slot are pre-calculated and stored in memory based on measurements taken during normal operation. This preliminary action ensures that when the external reference becomes unavailable, the system already has the necessary compensation data ready to maintain frequency stability during holdover operation.
Solution Approach 2:
The system continuously monitors the oscillator frequency and temperature, and uses this feedback to update the compensation parameters in each temperature slot. During holdover mode, the feedback mechanism allows the system to detect frequency deviations and apply appropriate compensation from the stored parameters, maintaining frequency stability without continuous external reference. The feedback loop ensures the system adapts to aging and drift while operating autonomously.
Data Source
AI summary
A method of compensating for the temperature related frequency drift of an oscillator. The method comprises using an external reference frequency signal to derive oscillator compensation data over a range of operating temperatures, storing the oscillator compensation data in a first table, and, for a given operating temperature, using the first table to obtain corresponding oscillator compensation data and applying that data to provide compensation for the temperature related frequency drift. The method further comprises defining, for the range of operating temperatures, a series of temperature slots each sub-divided into a series of temperature bins. The step of using an external reference frequency signal to derive oscillator compensation data over the range of operating temperatures comprisesa) measuring an operating temperature and using the external reference frequency signal to determine oscillator compensation values for respective temperatures as the operating temperature varies;b) accumulating the determined oscillator compensation values in corresponding temperature bins of a second table;c) at spaced intervals in time, using the data accumulated in the temperature bins of the second table to determine or update the oscillator compensation data stored for one or more slots in the first table.