Radio Communication Device Frequency Error Compensation
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Solution Overview
Problem
Utility meters face challenges with accurate time stamping due to the susceptibility of low-power quartz crystal resonators to temperature fluctuations and aging, leading to significant frequency drift over their 10-20 year service cycle, which affects the precision of timestamping in utility metering applications, especially in battery-operated devices where energy conservation is crucial.
Innovation Solution
A radio communication device with a microcontroller that compensates for frequency errors in a lower precision time frequency reference using a higher precision radio frequency reference, minimizing energy consumption by performing measurements during active radio signal generation periods, thereby maintaining high precision time stamping without increasing energy usage or component costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a low-power quartz crystal resonator is used for time reference in battery-operated utility meters, then energy consumption is reduced, but frequency stability deteriorates due to temperature fluctuations and aging
Solution Approach 1:
The patent introduces a high-precision radio frequency reference as an intermediary to propagate timing information to the low-power quartz crystal resonator. The radio frequency reference, which is active only during transmission periods, serves as a mediator that synchronizes the timekeeping function, allowing the quartz crystal to maintain accuracy without continuous high-power operation.
Solution Approach 2:
The system employs periodic action by activating the high-precision radio frequency reference only during radio signal transmission periods rather than continuously. This periodic activation allows the reference to provide timing corrections at intervals, enabling the low-power quartz crystal to maintain frequency stability without requiring continuous high energy consumption.
2Measurement precision
If a high-precision radio frequency reference is used continuously to maintain accurate time stamping, then measurement precision is improved, but energy consumption increases
Solution Approach 1:
The patent implements periodic action by activating the high-precision radio frequency reference only during radio signal transmission periods. The microcontroller measures transmission duration and calculates frequency errors of the quartz crystal reference during these active periods, then uses these corrections to maintain accurate time stamping without requiring continuous operation of the high-precision reference.
Solution Approach 2:
The system employs self-service by having the low-power quartz crystal resonator perform the continuous timekeeping function while the high-precision radio frequency reference periodically corrects its frequency drift. The quartz crystal essentially serves itself by maintaining continuous operation at low power, receiving periodic synchronization corrections from the radio frequency reference without requiring continuous high-power operation.
3Measurement precision
If frequent adjustments of the RTC are performed to compensate for drift, then time measurement accuracy is improved, but energy consumption increases
Solution Approach 1:
The patent applies preliminary action by measuring and calculating frequency error corrections during radio signal transmission periods before they are needed for time stamping. The microcontroller proactively determines the frequency drift of the quartz crystal reference during transmission and pre-calculates correction values, which are then applied to maintain accurate time measurements without requiring frequent high-energy adjustments.
Data Source
Figure 1
AI summary
A radio communication device comprising a radio frequency circuit and a microcontroller arranged to control the radio frequency circuit. The radio communication device further comprises: a radio frequency reference connected to the radio frequency circuit and arranged to be the frequency reference of at least the symbol frequency; a MCU and a time frequency reference connected to the microcontroller. The microcontroller is arranged to determine a frequency error of the time frequency reference relative to the radio frequency reference by performing the steps of: transmitting a radio signal, and signal a timing signal on a control interface, comprising information on start of transmission and end of transmission of the radio signal; receive the timing signal from the radio frequency circuit and measure a transmission duration of the radio signal with reference to the MCU frequency reference and calculate a frequency error of the MCU frequency reference relative to the radio frequency reference based on the measured transmission duration of the radio signal and the number of symbols and the symbol frequency. Further, the microcontroller measures a time period of the time frequency reference with reference to the MCU frequency reference; and calculate the frequency error of the time frequency reference relative to the radio frequency reference.