Parallel VCO Synthesizer Switching for Low-Phase-Noise MIMO
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Solution Overview
Problem
Current frequency synthesizer designs in wireless communication networks face challenges in achieving reduced phase noise and increased performance, particularly in multiple-input, multiple-output (MIMO) modes, due to the need for over-designing to cover diverse frequency requirements.
Innovation Solution
The use of multiple voltage-controlled oscillators (VCOs) in parallel, where a second VCO is connected in parallel with a first VCO if its phase-locked loop (PLL) is idle, utilizing connection circuitry with switches to manage the connection and disconnection of the VCOs, and ensuring the second VCO operates at the same frequency as the first VCO, to enhance signal-to-noise ratio and phase noise performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple VCOs are used in parallel to reduce phase noise and increase signal magnitude, then frequency synthesizer performance is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple VCOs (first VCO and second VCO) in parallel to generate oscillating signals, merging their outputs to achieve improved phase noise performance and increased signal magnitude (6 dB gain). This merging approach allows the system to benefit from multiple oscillators without requiring fully independent frequency synthesis paths.
Solution Approach 2:
The second VCO is designed with multi-functionality: it can operate independently when its PLL is active (for carrier aggregation modes) or be connected in parallel with the first VCO when its PLL is idle (for MIMO modes). This universal design allows a single VCO to serve multiple purposes, reducing the need for separate dedicated oscillators for different operational modes.
2Object-affected harmful factors
If the second VCO is connected in parallel with the first VCO to improve phase noise performance, then phase noise is reduced by 3 dB, but the device complexity increases due to additional connection circuitry
Solution Approach 1:
The connection between the first and second VCOs is made dynamic rather than static. The connection circuitry includes switches that can dynamically connect or disconnect the second VCO based on the operational mode (MIMO or carrier aggregation). This dynamic configuration allows the system to optimize phase noise performance only when needed (MIMO mode) while maintaining simplicity in other modes.
Solution Approach 2:
The connection circuitry with switches acts as an intermediary between the first and second VCOs. This intermediary component enables selective connection without requiring permanent integration, allowing the system to achieve phase noise reduction when needed while maintaining design flexibility and reducing overall complexity through conditional connectivity.
3Adaptability or versatility
If the second VCO is used in carrier aggregation mode with active PLL, then frequency coverage is expanded, but phase noise performance deteriorates compared to parallel connection mode
Solution Approach 1:
The system dynamically switches between two operational configurations: (1) second VCO connected in parallel with first VCO for MIMO mode to minimize phase noise, and (2) second VCO operating independently with active PLL for carrier aggregation mode to expand frequency coverage. This dynamic reconfiguration allows the system to optimize for different performance requirements based on operational mode.
Solution Approach 2:
The patent applies different operational characteristics to different VCOs based on local requirements. The first VCO serves as the primary oscillator, while the second VCO's behavior is locally optimized: connected in parallel when phase noise is the critical factor (MIMO mode), or operated independently with active PLL when frequency coverage is the critical factor (carrier aggregation mode).
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 results in a 3 dB reduction in phase noise performance and a 6 dB gain in oscillating signal magnitude, improving overall frequency synthesizer performance in MIMO modes while maintaining normal mode integrity.
Implementation Method 1
Each VCO may include a tank circuit and a negative transconductance (-Gm) circuit
Implementation Method 2
a second voltage-controlled oscillator (VCO) and a phase-locked loop (PLL) associated with the second VCO
Data Source
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AI summary
Certain aspects of the present disclosure provide methods and apparatus for using multiple voltage-controlled oscillators (VCOs) to increase frequency synthesizer performance, such as in stringent multiple-input, multiple-output (MIMO) modes. One example apparatus capable of generating oscillating signals generally includes a first VCO, a second VCO, and connection circuitry configured to connect the second VCO in parallel with the first VCO if a phase-locked loop (PLL) associated with the second VCO is idle.