Injection-Locked Oscillator Sync Detection via Difference Tone
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Solution Overview
Problem
Existing methods for determining whether an output signal from an injection locked oscillator (ILO) is synchronized with an injection signal are either ambiguous, require expensive equipment, or are unsuitable for on-chip solutions due to environmental fluctuations and the need for additional components like IQ mixers or local oscillators.
Innovation Solution
An apparatus and method using a distorter to generate a difference tone in a predetermined frequency band when the output signal from the ILO is not synchronized, and a level detector to determine synchronization based on the level of this tone, which can be implemented on-chip, allowing for reliable synchronization detection without the need for complex equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the power/voltage level of the output signal from the ILO is captured to determine synchronization, then the measurement can be performed with simple equipment, but the measurement becomes ambiguous because the non-synchronized state generates a tone at the free-running resonant frequency that cannot be distinguished from the intended signal by conventional level detectors
Solution Approach 1:
The frequency spectrum is segmented into two distinct regions: the synchronization frequency (intended signal) and the free-running resonant frequency. By capturing both frequencies separately and comparing their levels, the method resolves the ambiguity of conventional single-frequency measurement. The synchronization state is determined by detecting whether the free-running frequency tone is present or absent, providing clear distinction without requiring complex equipment.
2Measurement precision
If an IQ mixer is used to measure the level at the synchronized frequency, then the measurement precision is improved by distinguishing the intended frequency from harmonics, but the device complexity and cost increase significantly
Solution Approach 1:
Instead of using a complex IQ mixer to extract the synchronized frequency component, the invention extracts the free-running resonant frequency component and uses its absence/presence as the synchronization indicator. This approach takes out the problematic harmonic interference issue by focusing on a different frequency region (the free-running frequency) that naturally separates from the intended signal, achieving frequency discrimination with simple level detection.
Solution Approach 2:
Conventional methods try to directly detect the presence of the intended signal frequency. This invention inverts the approach by detecting the absence of the free-running frequency signal. When the ILO is synchronized, the free-running frequency tone disappears; when desynchronized, it is present. This inverted detection strategy simplifies the measurement system while maintaining high precision.
3Measurement precision
If a fast Fourier transform (FFT) is carried out to analyze the frequency spectrum, then the measurement precision is improved by resolving multiple frequency components, but additional components like a local oscillator and increased bandwidth are required making it unsuitable for on-chip solutions
Solution Approach 1:
Instead of performing a full FFT analysis that requires additional oscillators and bandwidth, the invention extracts only the specific free-running resonant frequency component that indicates synchronization status. This selective extraction approach achieves the necessary frequency resolution with minimal additional components, making it suitable for on-chip implementation.
Solution Approach 2:
Rather than implementing the complete FFT algorithm with full spectral analysis, the invention applies partial action by focusing only on the critical frequency region (the free-running resonant frequency) that provides sufficient information for synchronization detection. This partial analysis achieves the required measurement precision without the overhead of complete spectral processing.
Data Source
AI summary
An apparatus for determining whether an output signal from an injection locked oscillator is synchronized with an injection signal coming from an input oscillator has a distorter and a level detector. The distorter uses the output signal from the injection locked oscillator to generate a distorter output signal which has a difference tone in a predetermined frequency band if the output signal from the injection locked oscillator is not synchronized with the injection signal. The level detector is designed to detect a level of the difference tone. The apparatus determines, on the basis of the level of the difference tone, whether the output signal from the injection locked oscillator is synchronized with the injection signal.