Offset-Mixer INSO Architecture for Lower Oscillator Phase Noise
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Solution Overview
Problem
Existing interferometric noise suppressed oscillators (INSOs) suffer from high phase noise contributions primarily from the variable attenuator and variable phase shifter, which degrade stability, lock time, and noise peaking due to finite phase misalignments and intrinsic noise levels.
Innovation Solution
An offset-mixer architecture is introduced, aligning the reference arm's variable phase shifter to the mixer's I-channel output and eliminating the variable attenuator, while using a mixer offset to reduce phase noise contributions by rotating the variable phase shifter and applying a control signal to the loop phase shifter to adjust the carrier frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a variable attenuator and variable phase shifter are used in the reference arm to balance the interferometric bridge, then the bridge balance and carrier suppression are improved, but the phase noise contribution increases due to intrinsic noise levels and finite phase misalignments
Solution Approach 1:
The patent removes the variable attenuator from the reference arm, extracting the noise-generating component while maintaining bridge balance functionality through the variable phase shifter alone. This eliminates the additive phase noise from the attenuator while preserving the carrier suppression capability.
Solution Approach 2:
The patent changes the operational parameters by rotating the variable phase shifter by 90 degrees and adjusting its control voltage to operate in a regime where phase noise is minimized. This parameter optimization reduces the intrinsic noise contribution while maintaining the necessary bridge balancing function.
2Device complexity
If the variable phase shifter is used for both amplitude and phase balancing, then the device complexity is reduced, but the phase noise contribution increases due to finite phase misalignments
Solution Approach 1:
The patent optimizes the control voltage and rotation angle of the variable phase shifter to minimize phase noise while maintaining effective bridge balance. By carefully selecting operational parameters, the single phase shifter achieves both amplitude and phase balancing with reduced noise contribution.
Solution Approach 2:
The patent employs feedback mechanisms to dynamically adjust the variable phase shifter control voltage, ensuring optimal balance while minimizing phase noise. The feedback loop compensates for finite phase misalignments in real-time, maintaining performance despite the simplified component structure.
3Object-generated harmful factors
If the variable attenuator is eliminated, then the phase noise contribution is reduced, but the ease of operation decreases due to loss of independent amplitude control
Solution Approach 1:
The variable phase shifter is designed to perform multiple functions: both amplitude balancing and phase balancing of the interferometric bridge. By operating the phase shifter in a optimized regime, it provides the full range of control previously requiring separate attenuator and phase shifter components.
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 dominant phase noise source is shifted to the mixer, reducing overall phase noise and improving stability and lock time by eliminating the variable attenuator and minimizing the impact of the variable phase shifter's noise contribution.
Implementation Method 1
An INSO may utilize a sapphire-loaded cavity as the resonator and incorporate a noise degeneration circuit to suppress phase noise
Implementation Method 2
A particular class of oscillator, often selected for use in high fidelity systems may be referred to as an Interferometric Noise Suppressed Oscillator (INSO). An INSO may utilize a sapphire-loaded cavity as the resonator
Data Source
AI summary
An offset-mixer INSO provides a fixed phase shift in the reference arm of the interferometric bridge to align the reference arms' variable phase shifter to the mixer's I-channel output and uses the variable phase shifter to amplitude balance the reference and reflection arms. A difference signal between the mixer's Q-channel output and an externally applied carrier frequency tuning voltage VPLL is applied to an amplification network to provide the control signal to the loop phase shifter to adjust the carrier frequency. Elimination of the variable attenuator and rotation of the variable phase shifter eliminates and reduces their respective phase noise contributions such that the dominant phase noise source is now the mixer.