Current-Reuse VCO Coupling for Lower Phase Noise
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Solution Overview
Problem
Voltage controlled oscillator (VCO) circuits in high-linearity radio receivers face issues with phase noise, which degrades the signal-to-noise ratio (SNR) and limits receiver sensitivity due to reciprocal mixing, and existing methods to reduce phase noise, such as increasing power consumption, are inefficient.
Innovation Solution
A VCO circuit design that employs a current re-use technique by coupling two VCOs in series with passive elements, reducing power consumption and phase noise without increasing power dissipation, and incorporates a regulating module to maintain constant output voltage amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DC power is doubled to reduce phase noise, then phase noise decreases and SNR improves, but power dissipation increases
Solution Approach 1:
The patent combines two VCO circuits in parallel configuration where both VCOs share a common current source. This merging allows the system to achieve phase noise reduction equivalent to doubling power while maintaining the same total power dissipation, as the current is shared between both oscillators rather than requiring double the power for a single oscillator
Solution Approach 2:
The current source serves multiple functions simultaneously: it provides bias current for both VCOs, enables phase noise reduction through current sharing, and maintains power efficiency. This multi-functionality allows the system to achieve phase noise improvement without the penalty of increased power dissipation
2Reliability
If load resistance is lowered to reduce phase noise, then phase noise decreases, but power dissipation increases
Solution Approach 1:
By merging two VCOs in parallel with shared current source, the system achieves the phase noise benefits of lower effective load resistance without actually lowering the physical load resistance, thereby avoiding the associated power dissipation increase
Data Source
AI summary
Embodiments of the present invention include a low phase noise oscillator circuit using a current-reuse technique to reduce power consumption and improve phase noise, where the oscillator circuit comprises a first VCO coupled to a second VCO, and the outputs of the first and second VCOs are coupled with passive elements, such as capacitors. The overall power consumption of both the first and second VCOs is about the same as a single VCO. Furthermore, the phase noise is lowered by around 3 dB. Thus, the phase noise performance is improved without increasing the power consumption of the oscillator circuit.