Sampled-Feedback Crystal Oscillator for Low Phase Noise Control
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Solution Overview
Problem
Conventional crystal oscillator circuits face high power consumption, significant die area requirements, and excessive phase noise due to noise coupling from reference signals, making it challenging to control oscillation magnitude effectively.
Innovation Solution
An improved amplitude regulated resonant oscillator with sampled feedback is introduced, utilizing a sampling network that isolates the oscillator from transistor noise and allows for higher error amplifier gains, enabling peak-to-peak detection and reducing noise introduction, implemented using a switch and capacitor configuration with programmable control mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional continuous feedback amplitude control is used, then oscillation magnitude can be regulated, but phase noise increases due to noise coupling from reference signals
Solution Approach 1:
The patent implements periodic sampling of the oscillation signal at specific phases rather than continuous feedback. The amplitude detector samples the signal periodically at zero-crossing points or peak points, converting the continuous amplitude regulation problem into a periodic measurement and control process. This periodic action eliminates continuous noise coupling while maintaining amplitude regulation capability.
Solution Approach 2:
The patent extracts only the necessary amplitude information from the oscillation signal by sampling at specific phases, rather than using the entire continuous signal for feedback. The amplitude detector extracts peak-to-peak voltage information or zero-crossing timing information selectively, separating the useful amplitude data from the noisy continuous signal path.
2Measurement precision
If high error amplifier gain is used to improve amplitude control, then amplitude regulation precision improves, but die area and power consumption increase
Solution Approach 1:
By using periodic sampling with peak detect circuits or zero-crossing detectors, the system achieves high effective gain through timing-critical-path design rather than high-voltage-gain amplifiers. The periodic measurement at optimal signal points provides precise amplitude information without requiring large amplifier gains, thus reducing die area.
Solution Approach 2:
The patent replaces the traditional voltage-amplification-based amplitude control mechanism with a timing-based control mechanism. Instead of using high-gain voltage amplifiers to detect amplitude, the system uses zero-crossing timing detection or peak voltage sampling, substituting mechanical/electrical amplification with temporal measurement methods that require less area.
3Stability of the object's composition
If continuous amplitude detection and feedback is implemented, then oscillation stability is maintained, but power consumption increases
Solution Approach 1:
The patent replaces continuous amplitude detection and feedback with periodic sampling at critical phases of the oscillation cycle. The amplitude detector operates only at specific intervals (at zero-crossings or peaks), and the feedback is updated periodically rather than continuously. This maintains oscillation stability through regular correction while dramatically reducing power consumption by keeping the detection circuit inactive between samples.
Solution Approach 2:
The patent maintains the essential stability function through periodic action that is sufficient to control oscillation magnitude, rather than continuous action. The sampled feedback provides just enough continuous correction to maintain stability without the excess power consumption of continuous full-scale amplitude detection and regulation.
4Measurement precision
If reference voltage coupling is used for amplitude comparison, then amplitude detection accuracy is achieved, but noise is introduced to the oscillator
Solution Approach 1:
The patent extracts only the essential amplitude information through periodic sampling at zero-crossing points or peak points, rather than continuously comparing against a reference voltage. By taking out only the necessary timing or peak voltage information at specific phases, the system achieves sufficient detection accuracy without the continuous noise coupling inherent in traditional reference voltage comparison methods.
Solution Approach 2:
The patent introduces a sampling mechanism as an intermediary between the oscillation signal and the amplitude detection circuit. Instead of directly coupling the reference voltage to the oscillator through continuous comparison, the sampling circuit acts as an intermediary that captures amplitude information periodically and feeds it back, breaking the direct continuous noise coupling path while maintaining detection accuracy.
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 achieves reduced phase noise, lower power consumption, and smaller area usage, with a maximum theoretical noise reduction of 72 dB, effectively controlling oscillation magnitude and improving spectral purity.
Implementation Method 1
A crystal oscillator is an electronic circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a very precise frequency
Implementation Method 2
utilizing a sampling network that isolates the oscillator from transistor noise and allows for higher error amplifier gains, enabling peak-to-peak detection and reducing noise introduction, implemented using a switch and capacitor configuration
Data Source
AI summary
Disclosed is an oscillator circuit, comprising a crystal oscillator, an amplifier having an input and an output coupled across the crystal oscillator, a comparator having a reference input and an input coupled to the crystal oscillator and a pole network coupled between the comparator and the amplifier.