LC Oscillator Switching Network for Lower Phase Noise Tuning
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Solution Overview
Problem
Existing oscillators, particularly LC oscillators, face challenges in reducing phase noise, which affects the performance of electronic systems like transceivers and clock data recovery circuits, due to noise sources from active devices and capacitor switching networks.
Innovation Solution
The implementation of a passive impedance network that includes inductors to bias active devices in the sustaining amplifier and switch circuits, reducing thermal noise and switch noise contributions by optimizing the conduction angle and resonant frequency tuning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If LC resonator-based oscillator is used to generate high frequency output signal, then frequency performance is improved, but phase noise increases
Solution Approach 1:
The patent extracts and removes the noise-generating capacitor from the traditional LC oscillator circuit. By replacing the capacitor with an inductor and configuring the sustaining amplifier in a specific manner, the design eliminates the primary source of phase noise while maintaining the high frequency generation capability of the LC resonator.
Solution Approach 2:
The patent changes the circuit parameters by using an inductor instead of a capacitor in the resonant circuit and configuring the sustaining amplifier with specific impedance matching. This parameter change transforms the noise characteristics of the oscillator while preserving its frequency generation function.
2Stability of the object's composition
If sustaining amplifier is used to maintain oscillation, then oscillation stability is improved, but thermal noise from active devices increases
Solution Approach 1:
The patent substitutes the traditional capacitor-based feedback mechanism with an inductor-based impedance network. This substitution changes the noise generation mechanism while maintaining the oscillation stability provided by the sustaining amplifier, as the inductor introduces different loss characteristics with lower thermal noise.
3Adaptability or versatility
If capacitor switching network is used for frequency tuning, then frequency adaptability is improved, but switch noise increases
Solution Approach 1:
The patent removes the capacitor switching network entirely and replaces it with an inductor-based frequency tuning mechanism. This extraction eliminates the switch noise that was inherent in the capacitor switching approach while maintaining frequency tuning capability through alternative means.
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 approach significantly reduces phase noise in oscillators, improving noise performance and meeting stringent noise requirements for various applications, including wireless communications and CMOS/BiCMOS processes.
Implementation Method 1
blocking a DC bias to a first gate of a first transistor of a sustaining amplifier via a passive impedance network
Implementation Method 2
The passive impedance network is configured to resonate a capacitance associated with the sustaining amplifier
Implementation Method 3
reducing thermal noise and switch noise contributions by optimizing the conduction angle and resonant frequency tuning
Data Source
AI summary
Apparatus and methods are also disclosed related to an oscillator that includes a switching network configured to tune a resonant frequency of a resonant circuit. One such apparatus includes a switching network having a circuit element, such as a capacitor, that can be selectively coupled to the resonant circuit by a switch, such as a field effect transistor. For instance, the switch can electrically couple to circuit element to the resonant circuit when on and not electrically couple the circuit element to the resonant circuit when off. An active circuit can assert a high impedance on an intermediate node between the switch and the circuit element when the switch is off.