Reference Oscillator Low-Power Timekeeping for GNSS Receivers
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Solution Overview
Problem
Existing clock circuits in digital electronic equipment, particularly in GNSS receivers, face challenges in maintaining a reliable time reference during low-power modes due to high power consumption, additional board space, and limited precision of auxiliary real-time clocks, which hinder efficient reacquisition of satellite signals after idle periods.
Innovation Solution
A reference oscillator circuit with a crystal resonator, temperature compensation, and a counter that switches between normal and low-power states to conserve power while maintaining time accuracy, allowing the circuit to store and retrieve elapsed time during idle periods, thereby enabling quick reacquisition of satellite signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an auxiliary real-time clock (RTC) with a separate crystal resonator is used to keep time during low-power mode, then the receiver can maintain time reference during idle periods, but the board space is increased and the precision is limited
Solution Approach 1:
The patent combines the time-keeping function with the existing main oscillator circuit by adding a counter that accumulates clock cycles during low-power mode. This eliminates the need for a separate RTC crystal resonator and its associated circuitry, thereby reducing board space while maintaining time reference availability. The counter stores the elapsed time in low-power mode, which is then used to calculate the wake-up time and enable quick reacquisition of satellite signals.
2Reliability
If an auxiliary real-time clock (RTC) is used to keep time during low-power mode, then the receiver can maintain time reference, but the precision is limited and shock-sensitivity increases
Solution Approach 1:
The main oscillator circuit is designed to serve dual purposes: providing the primary time reference during normal operation and enabling time-keeping during low-power mode through the counter mechanism. By making the main oscillator multi-functional, the system eliminates the need for a separate, lower-precision RTC oscillator, thereby maintaining high time reference precision even during idle periods.
3Use of energy by moving object
If the receiver switches to low-power mode to conserve battery, then power consumption is reduced, but the time reference becomes less accurate and reacquisition is delayed
Solution Approach 1:
The counter continuously accumulates clock cycles even during low-power mode, preparing the elapsed time information in advance. When the receiver wakes up, this pre-calculated time information is immediately available, allowing the system to quickly determine the current time and resume satellite signal acquisition without delay. This preliminary accumulation of time data during low-power periods eliminates reacquisition delays.
4Measurement precision
If a high-precision quartz oscillator is used for the RTC, then time reference precision is improved, but the device cost increases appreciably
Solution Approach 1:
The system uses its own main high-precision oscillator to serve the time-keeping function during low-power mode, rather than requiring a separate RTC oscillator. The counter accumulates cycles from the existing main oscillator, allowing the system to self-service its time-keeping needs without additional precision components, thereby avoiding increased device cost while maintaining high time reference precision.
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 reduces power consumption and eliminates the need for an auxiliary real-time clock, providing a reliable and precise time reference for GNSS receivers, allowing for immediate reacquisition of satellite signals upon waking from low-power mode, thus optimizing power management and reducing system complexity.
Implementation Method 1
a crystal resonator, having a resonance frequency; an oscillator circuit arranged to maintain the resonator in oscillation at the resonance frequency
Implementation Method 2
a temperature compensation circuit, providing a temperature-compensated clock output signal
Data Source
Figure 1~2
AI summary
A reference clock circuit (170), has a low-power mode, in which the frequency consumption is reduced, and including an internal counter (100), accumulating time spent in low-power mode. The circuit includes a crystal resonator (60), an oscillator circuit (70), and a temperature compensation circuit (80), providing a stable clock output (85). During low-power mode temperature compensation can be switched off. The circuit further provides a wakeup signal (107) after a preset time in low-power mode. The reference clock circuit may be used in a GPS or GNSS receiver having an idle mode during which satellite tracking is not carried out and the reference circuit (170) is put into low-power mode. Time elapsed in the idle mode is retrieved from the internal counter (100) and used to resume acquisition and tracking of satellites.