Switched-Capacitor Feedback Oscillator for Low Phase Noise
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Solution Overview
Problem
Feedback oscillators in signal generators face challenges with increased power consumption due to high loop gain, which is necessary to reduce phase noise and susceptibility to systematic errors, and this is compounded by the addition of components that increase size and cost.
Innovation Solution
A signal generator design using switched-capacitor circuits in voltage dividers to adjust resistances based on frequency deviations, allowing for increased loop gain without increasing current or operational amplifier gain, thereby stabilizing frequency and reducing phase noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If loop gain is increased to reduce phase noise and susceptibility to systematic errors, then signal quality is improved, but power consumption increases
Solution Approach 1:
The patent implements dynamic adjustment of the oscillation frequency based on detected signal characteristics. The frequency is varied within a range to optimize phase noise performance while maintaining stable operation, allowing the system to adapt to different operating conditions without increasing power consumption
Solution Approach 2:
The patent changes the oscillation frequency parameter dynamically to achieve optimal phase noise reduction. By varying the frequency within a specified range and detecting corresponding signal quality metrics, the system identifies and maintains the frequency that provides best phase noise performance without requiring increased loop gain or power consumption
2Stability of the object's composition
If components are added to compensate for feedback oscillator effects, then signal stability is improved, but device size and cost increase
Solution Approach 1:
The patent employs a feedback mechanism where the output signal is detected and used to adjust the oscillation frequency. This closed-loop feedback allows the system to automatically compensate for instabilities and maintain optimal performance without requiring additional compensation components
Solution Approach 2:
The system performs self-adjustment by detecting its own output signal characteristics and automatically modifying the oscillation frequency accordingly. This self-service capability eliminates the need for external compensation components while maintaining signal stability
Data Source
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AI summary
A signal generator (1) includes a first voltage generator (10), a second voltage generator (20), an operational amplifier (30), and an oscillator (50). The first voltage generator generates a first voltage (Vfb1), and the second voltage generator generates a second voltage (Vfb2). The operational amplifier generates an amplified error signal (35) based on the first voltage and the second voltage, and the oscillator generates a periodic signal (fclk) based on the amplified error signal. The first voltage generator and the second voltage generator are configured to generate their respective voltages based on the periodic signal. As a result, frequency deviation in the periodic signal may be corrected, for example, without increasing the source current of the oscillator or the gain of the operational amplifier. Also, improved phase noise performance may also be achieved through an increase in loop gain.