Stacked LO Synthesizer With Dynamic Divider for Low Phase Noise
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Microwave backhaul systems face challenges in accommodating increased capacity due to high phase noise, which hinders the evolution towards higher modulation schemes and multiple-input, multiple-output systems.
Innovation Solution
A stacked synthesizer for wide local oscillator generation using a dynamic divider, incorporating a phase locked loop with a plurality of SiGe voltage controlled oscillators and a dynamic divider that widens the tuning range while maintaining low phase noise, enabling local oscillator sharing and flexible frequency generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional synthesizer is used for local oscillator generation, then the system is simpler, but high phase noise is generated which hinders capacity increase
Solution Approach 1:
The synthesizer is divided into multiple independent VCOs (VCO1, VCO2, VCO3) operating at different frequencies, each contributing to the final output through a combiner. This segmentation allows each VCO to operate within its optimal tuning range with low phase noise, while collectively providing a wide frequency range output that would be difficult to achieve with a single VCO.
Solution Approach 2:
Multiple VCO outputs are merged in a combiner to produce the final synthesized output signal. By combining signals from multiple low-phase-noise VCOs, the system achieves both low overall phase noise and wide frequency coverage, resolving the contradiction between simple structure and performance requirements.
2Adaptability or versatility
If a single VCO is used to cover wide frequency range, then the device is simpler, but phase noise increases
Solution Approach 1:
The wide frequency range is segmented into multiple sub-ranges, each covered by a dedicated VCO. VCO1 covers 5-6 GHz, VCO2 covers 6-7 GHz, and VCO3 covers 7-8 GHz. This segmentation allows each VCO to maintain low phase noise within its specific operating range while collectively providing wide frequency coverage.
Solution Approach 2:
Each VCO is optimized for its specific frequency range with local quality characteristics tailored to that band. This allows each oscillator to operate at its peak performance with minimal phase noise, while the combiner integrates these locally optimized signals into a wide-range low-phase-noise output.
3Reliability
If multiple VCOs are stacked to reduce phase noise, then phase noise performance improves, but device complexity increases
Solution Approach 1:
The control system uses a universal approach where a single control voltage, after being divided by variable dividers, simultaneously controls multiple VCOs. This multi-functional control architecture reduces the need for separate control circuits for each VCO, thereby reducing overall device complexity while maintaining the benefits of multiple VCOs for low phase noise.
Solution Approach 2:
The system changes the division ratio parameter of the variable dividers to dynamically adjust the frequency outputs of multiple VCOs. By modifying this single parameter, the system can coordinate multiple VCOs to provide continuous frequency coverage with low phase noise, simplifying the control architecture while achieving complex performance goals.
4Adaptability or versatility
If dynamic divider is added to widen tuning range, then frequency flexibility improves, but circuit complexity increases
Solution Approach 1:
The system employs dynamic dividers that can change their division ratio in real-time based on control signals. This dynamic capability allows the synthesizer to widen its effective tuning range and improve frequency flexibility without requiring additional VCOs, as the same VCO outputs can be frequency-multiplied or divided to reach target frequencies.
Solution Approach 2:
The dynamic divider acts as an intermediary between the VCO outputs and the final output, providing frequency multiplication or division as needed. This intermediary component enables frequency flexibility and widens the tuning range without directly increasing VCO count or complexity, as it processes existing VCO outputs to achieve the desired frequency range.
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 solution effectively reduces phase noise, enabling higher capacity and flexible frequency generation in microwave backhaul systems, supporting advanced modulation schemes and multiple-input, multiple-output architectures while maintaining low phase noise performance.
Implementation Method 1
The stacked synthesizer includes a phase locked loop and a dynamic divider
Implementation Method 2
The phase locked loop includes a plurality of voltage controlled oscillators
Implementation Method 3
The dynamic divider is configured to receive an output of the selected output of one of the plurality of voltage controlled oscillators on the output line and to generate a synthesizer output based on a multiplication of the selected output of one of the plurality of voltage controlled oscillators by a factor (1+1/M)
Data Source
AI summary
A stacked synthesizer for wide local oscillator (LO) generation using a dynamic divider. The phase locked loop can include a plurality of voltage controlled oscillators (VCOs), and a selector that can be configured to select an output of one of the plurality of VCOs. The selected output of one of the plurality of VCOs can be provided to an on-chip dynamic divider and to an off-chip dynamic divider for LO sharing. The dynamic dividers can be configured to generate synthesizer outputs based on a multiplication of the selected output of one of the plurality of VCOs by a factor (1+1/M), where M is a variable number.