PWM Amplitude-Limiting Oscillation Circuit for Low Phase Noise
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Solution Overview
Problem
Conventional amplitude limiting oscillation circuits suffer from waveform distortion, asymmetrical rising and falling edges, high-frequency noise inflection, inductor saturation, instability, and increased phase noise due to large oscillation amplitudes, and existing amplitude detection methods introduce noise and instability.
Innovation Solution
An amplitude limiting oscillation circuit employing a pulse width modulation circuit, low pass filtering circuit, and voltage controlled resistance circuit with a switching mechanism to control oscillation amplitude, utilizing negative feedback through a voltage controlled resistance circuit to stabilize oscillation amplitude without introducing extra noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If amplitude limitation is not performed on LC oscillation circuit, then oscillation amplitude stabilizes to power supply voltage, but waveform distortion occurs and rising/falling edges become asymmetrical
Solution Approach 1:
The patent implements negative feedback by detecting the oscillation amplitude through a detection circuit and adjusting the bias current of the oscillation circuit accordingly. When the amplitude exceeds a threshold, the feedback mechanism reduces the bias current to limit the amplitude, preventing waveform distortion while maintaining stable oscillation. This closed-loop control resolves the contradiction between amplitude stability and waveform quality.
2Manufacturing precision
If amplitude detection circuit is used to control bias current, then oscillation amplitude can be limited, but loop gain becomes large causing control loop instability
Solution Approach 1:
The patent changes the operating parameters of the detection circuit to optimize the feedback characteristics. By adjusting the threshold voltage and the gain of the detection circuit, the loop gain is controlled to an appropriate level that ensures both amplitude control precision and control loop stability. This parameter optimization resolves the contradiction between precise amplitude control and loop stability.
3Manufacturing precision
If conventional amplitude detection circuit is used, then amplitude control can be achieved, but control loop introduces greater noise resulting in worse phase noise
Solution Approach 1:
The patent introduces an intermediary low-pass filter between the detection circuit and the bias current control. This filter acts as a mediator that smooths the feedback signal, reducing high-frequency noise components that would otherwise be amplified by the control loop and degrade phase noise performance. The intermediary filter enables amplitude control while minimizing noise introduction.
4Power
If oscillation amplitude increases without limitation, then more power is available, but inductor saturation occurs and high-frequency noise inflection increases
Solution Approach 1:
The patent applies preliminary anti-action by proactively limiting the oscillation amplitude before it reaches levels that cause inductor saturation and high-frequency noise. The amplitude detection and feedback control mechanism continuously monitors and restricts the amplitude growth, preventing the harmful effects from occurring in the first place. This preventive approach maintains adequate power while avoiding saturation and noise issues.
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 effectively reduces phase noise and improves stability by accurately controlling oscillation amplitude, ensuring better performance and reduced noise in the amplitude limiting oscillation circuit.
Implementation Method 1
a pulse width modulation circuit 120, configured to generate a pulse width modulation signal according to an amplitude of the oscillation signal
Implementation Method 2
a low pass filtering circuit 130, configured to convert the pulse width modulation signal into a direct current control voltage signal
Implementation Method 3
the voltage controlled resistance circuit 140, configured to change a resistance value of the voltage controlled resistance circuit 140 under control of the direct current control voltage signal
Implementation Method 4
utilizing negative feedback through a voltage controlled resistance circuit to stabilize oscillation amplitude
Data Source
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AI summary
An amplitude limiting oscillation circuit (100) is disclosed. The amplitude limiting oscillation circuit (100) includes: an oscillation circuit (110), configured to generate an oscillation signal; a pulse width modulation circuit (120), configured to generate a pulse width modulation signal according to an amplitude of the oscillation signal; a low pass filtering circuit (130), configured to convert the pulse width modulation signal into a direct current control voltage signal, where the direct current control voltage signal is configured to control a voltage controlled resistance circuit (140); and the voltage controlled resistance circuit (140), configured to change a resistance value of the voltage controlled resistance circuit (140) according to under the direct current control voltage signal, to control the amplitude of the oscillation signal. The amplitude limiting oscillation circuit (100), may improve performance of the amplitude limiting oscillation circuit (100).