Multi-Point Injection-Locked Ring Oscillator for Harmonic Rejection
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Solution Overview
Problem
Existing frequency multipliers face challenges in achieving high harmonic rejection over process, voltage, and temperature variations, as well as across a wide input frequency range, due to limitations in filter quality and locking range.
Innovation Solution
A frequency multiplier comprising a phase generator that produces phase-shifted versions of an oscillation signal, an injection-locked ring oscillator with multi-point injection, and a combiner to combine output signals, ensuring high harmonic rejection by cleaning up phase errors and maintaining signal quality over a wide frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a band-pass filter with high quality factor is used to achieve high harmonic rejection, then harmonic rejection is improved, but filter complexity and difficulty in centering pass band over PVT variations worsen
Solution Approach 1:
The harmful harmonics are extracted and removed from the output signal using a band-pass filter centered at the desired frequency N·fLO. The filter selectively passes only the fundamental harmonic while rejecting higher-order harmonics, thereby separating the desired signal from unwanted frequency components.
Solution Approach 2:
An intermediate frequency stage is introduced between the frequency multiplier and the output. The band-pass filter acts as an intermediary element that mediates between the harmonic-rich output of the multiplier and the final clean output signal, enabling harmonic rejection without directly modifying the multiplier structure.
2Object-generated harmful factors
If a band-pass filter with high quality factor is used to achieve high harmonic rejection, then harmonic rejection is improved, but ease of operation worsens due to difficulty in centering pass band over PVT variations
Solution Approach 1:
A feedback mechanism is implemented where the output of the band-pass filter is fed back to the input of the frequency multiplier. This feedback loop automatically adjusts and stabilizes the operating point, compensating for PVT variations and maintaining the pass band centered at the desired frequency N·fLO without requiring manual recalibration.
3Object-generated harmful factors
If an injection locking stage with narrow locking range is used, then harmonic rejection is improved within the locking range, but adaptability worsens due to limited frequency range
Solution Approach 1:
The injection locking stage is designed with dynamic characteristics that allow the locking range to adapt to frequency variations. By optimizing the Q-factor and bandwidth of the tank circuit, the system maintains effective injection locking over a broader frequency range while preserving harmonic rejection performance within the operational bandwidth.
Solution Approach 2:
The injection locking stage is designed to perform multiple functions: it provides harmonic rejection, frequency stabilization, and broad frequency coverage. By carefully selecting the tank circuit parameters and injection strength, the stage achieves universal applicability across different operating frequencies while maintaining high harmonic rejection ratios.
4Reliability
If LC-VCO free running frequency is adjusted to match fout, then locking performance is improved, but manufacturing precision worsens due to process variations
Solution Approach 1:
A frequency feedback loop is implemented that continuously monitors the output frequency and adjusts the VCO control voltage to maintain accurate frequency matching. This feedback mechanism compensates for manufacturing variations and ensures that the free running frequency of the LC-VCO remains synchronized with the desired output frequency fout despite process, voltage, and temperature variations.
Solution Approach 2:
The control voltage parameter of the VCO is dynamically adjusted to compensate for manufacturing variations. By changing the control voltage in response to detected frequency deviations, the system maintains accurate frequency matching between the VCO free running frequency and the desired output frequency, thereby overcoming limitations imposed by manufacturing precision constraints.
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
The solution achieves high harmonic rejection by ensuring phase errors are cleaned up over process, voltage, and temperature variations, and across a wide frequency range, resulting in an output signal with a specific multiple of the input frequency with improved harmonic suppression.
Implementation Method 1
an injection-locked ring oscillator comprising a plurality of stages, wherein each of the phase generator outputs is coupled to a different stage of the plurality of stages for multi-point-injection
Data Source
AI summary
A frequency multiplier comprises a phase generator configured to receive an oscillation signal and to provide at phase generator outputs versions of the oscillation signal, which are phase-shifted with respect to each other. An injection-locked ring oscillator comprises a plurality of stages, wherein each of the phase generator outputs is coupled to a different stage of the plurality of stages for multi-point injection. A combiner combines output signals of the plurality of stages of the injection-locked ring oscillator into a signal having a frequency which is a multiple of a frequency of the oscillation signal.