Gm-Boosted Oscillator Circuit for Low Phase Noise Startup
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Solution Overview
Problem
Existing oscillators, such as cross-coupled negative resistance oscillators, face challenges in achieving low power consumption and low phase noise, with high phase noise performance due to the waveform characteristics and energy compensation mechanisms.
Innovation Solution
An oscillator design incorporating a resonance unit, a cross-coupled current source unit, and a positive feedback unit forms a transconductance boosted structure, allowing for adjustable bias current and reduced power consumption by amplifying the differential oscillation signal, thereby minimizing phase noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cross coupled negative resistance oscillator is used, then the oscillator can generate stable oscillation signals, but the phase noise is relatively high
Solution Approach 1:
The patent inverts the traditional negative feedback approach by using positive feedback through a feedback network. The feedback network feeds back a portion of the output signal to the input in phase, creating constructive interference that amplifies the oscillation signal while reducing phase noise through the inverted feedback mechanism
Solution Approach 2:
The patent implements a feedback network that takes the differential output signal from the active unit and feeds it back to the input nodes. This feedback mechanism allows the system to self-correct phase deviations and reduce phase noise while maintaining stable oscillation through continuous signal reinforcement
2Reliability
If bias current is increased to ensure normal startup, then the oscillator can start up reliably, but power consumption increases
Solution Approach 1:
The patent uses dynamic biasing where the bias current is automatically adjusted based on the oscillation state. During startup, higher current ensures reliable oscillation establishment, while during steady-state operation, the bias current reduces to minimize power consumption. This dynamic adjustment is achieved through the interaction of the active unit and feedback network
Solution Approach 2:
The patent changes the operating parameters of the active unit by using differential signaling and feedback-controlled gain adjustment. The bias current and signal amplitude are dynamically adjusted based on oscillation conditions, allowing the system to achieve reliable startup with lower average power consumption compared to traditional single-ended oscillators
Data Source
AI summary
An oscillator, including a resonance circuit, a cross coupled current source circuit, and a positive feedback circuit coupled between the current source circuit and the resonance circuit, where the resonance circuit is configured to generate a differential oscillation signal having a first oscillation frequency, the positive feedback circuit is configured to receive the differential oscillation signal, and amplify a gain of the differential oscillation signal to obtain a differential output oscillation signal, and the current source circuit is configured to provide an adjustable bias current for the resonance circuit and the positive feedback circuit. Since, the current source circuit provides the adjustable bias current for the positive feedback circuit and the resonance circuit, and forms a transconductance boosted (Gm-boosted) structure with the positive feedback circuit, the positive feedback circuit can amplify the gain of the received differential oscillation signal to obtain the differential output oscillation signal.