Open-Loop Reference Frequency Correction for Wireless Source Switching
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Solution Overview
Problem
Existing wireless communications devices face challenges in achieving precise and quick generation of reference frequencies, especially during initial signal acquisition, re-acquisition, and when switching between signal sources, as closed-loop frequency compensation methods are time-consuming and power-intensive, and not functional in all scenarios.
Innovation Solution
A communications subsystem that includes a frequency generator, a closed loop reference frequency correction module, and an open loop frequency correction mechanism, which samples reference frequency adjustment signals during closed loop mode to generate a frequency correction signal for use in open loop mode, allowing for accurate frequency tuning without continuous closed loop correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If closed loop frequency compensation is used to achieve accurate reference frequency, then frequency accuracy is improved, but acquisition time and power consumption increase
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing frequency correction values in a lookup table based on temperature. During operation, the system simply retrieves the pre-computed correction value corresponding to the current temperature, eliminating the need for time-consuming real-time closed loop frequency acquisition. This allows the frequency generator to jump directly to the correct frequency without gradual locking.
Solution Approach 2:
The patent prepares correction data in advance by characterizing the frequency generator's temperature-drift behavior and storing compensating values in a lookup table. This beforehand cushioning ensures that when temperature changes occur, the system already has the necessary correction data ready, preventing frequency errors before they affect communication accuracy.
2Measurement precision
If closed loop frequency compensation is used to achieve accurate reference frequency, then frequency accuracy is improved, but power consumption increases
Solution Approach 1:
The patent performs the energy-intensive frequency characterization and correction table generation once during manufacturing or initialization. During normal operation, the system only performs simple temperature sensing and table lookup operations, which consume minimal power compared to continuous closed loop frequency acquisition. This preliminary action transfers the energy burden from ongoing operation to initial setup.
Solution Approach 2:
The system uses its own temperature sensor and pre-stored correction data to automatically compensate for frequency drift without requiring external reference signals or continuous power-intensive locking mechanisms. The frequency generator serves itself by using the lookup table to correct its own temperature-induced frequency variations.
3Measurement precision
If closed loop frequency compensation is used, then frequency accuracy is improved, but the system becomes dependent on external frequency sources
Solution Approach 1:
The patent enables the frequency generator to self-correct its frequency drift by measuring its own temperature and retrieving the appropriate correction value from an internally stored lookup table. This self-service capability eliminates dependence on external reference signals or network-based frequency sources, allowing the device to maintain accurate frequency independently even when isolated from external sources.
4Stability of the object's composition
If TCVCXO is used to generate reference frequency, then frequency stability is improved, but the free running frequency accuracy is insufficient
Solution Approach 1:
The patent pre-characterizes the TCVCXO's frequency-vs-temperature relationship and stores correction data in a lookup table. This preliminary action captures the oscillator's drift behavior across temperature ranges, enabling accurate frequency compensation without requiring the oscillator to actually achieve high accuracy during operation. The pre-computed table bridges the gap between the oscillator's inherent inaccuracy and the required precision.
Solution Approach 2:
The lookup table acts as an intermediary between the temperature-compensated voltage-controlled crystal oscillator and the desired accurate frequency output. It translates the oscillator's temperature-dependent frequency drift into precise correction values, mediating the transition from an inaccurate but stable free-running oscillator to an accurately compensated frequency source.
Data Source
AI summary
A communications subsystem for a wireless device for correcting errors in a reference frequency signal. The communications subsystem comprises a frequency generator for generating the reference frequency signal and a closed loop reference frequency correction module that generates a reference frequency adjustment signal for correcting the reference frequency signal when the communications subsystem operates in closed loop mode. The subsystem further includes an open loop frequency correction means that that samples values of the reference frequency adjustment signal during the closed loop mode and generates a frequency correction signal for correcting the reference frequency signal when the communications subsystem operates in a mode other than closed loop mode.