PLL Wideband Feedback With LC Time Reference for Low Phase Noise
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Solution Overview
Problem
Existing radio frequency (RF) systems face challenges in generating stable waveforms with low phase noise characteristics, often requiring costly process options or expensive discrete components.
Innovation Solution
Incorporating a wideband feedback loop around a Phase Locked Loop (PLL) oscillator with a series Inductor-Capacitor (LC-tank) based time reference and a sample and hold time comparator circuit to reduce phase noise, decoupling frequency choice from phase noise performance and avoiding high-performance VCOs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional PLL oscillators are used to generate stable waveforms, then frequency stability is achieved, but phase noise performance deteriorates
Solution Approach 1:
The patent implements a wideband feedback loop that samples the VCO output signal, compares its phase with a reference signal using a phase detector, and feeds the error signal back to correct the VCO frequency. This feedback mechanism suppresses phase noise by continuously correcting deviations from the desired frequency, resolving the contradiction between maintaining frequency stability and reducing phase noise.
Solution Approach 2:
The patent segments the feedback loop into distinct functional blocks: a wideband phase detector for initial phase comparison, a narrowband phase detector for fine phase adjustment, and a combination phase detector that merges both error signals. This segmentation allows each detector to optimize its performance for specific frequency ranges, achieving low phase noise across the entire operating band while maintaining frequency stability.
2Object-generated harmful factors
If high-performance VCOs are used to improve phase noise performance, then phase noise is reduced, but device complexity and cost increase
Solution Approach 1:
The patent introduces an intermediary wideband feedback loop that mediates between the VCO and the phase noise issue. Instead of relying solely on the VCO's inherent phase noise performance, the feedback loop acts as an intermediary mechanism that actively suppresses phase noise through phase detection and correction, allowing the use of simpler, lower-cost VCOs while achieving low phase noise performance.
Solution Approach 2:
The patent uses a reference signal that is a precise copy or derivative of the desired output frequency. By comparing the VCO output against this reference copy through phase detection, the system can correct phase deviations without requiring the VCO itself to have perfect phase noise characteristics, thereby reducing the complexity requirements for the VCO design.
3Object-generated harmful factors
If multiple VCOs are used to achieve low phase noise at different frequencies, then phase noise performance improves, but power consumption and device complexity increase
Solution Approach 1:
The patent implements a universal wideband feedback loop architecture that can suppress phase noise across multiple frequency ranges using a single VCO. The combination phase detector integrates both wideband and narrowband error signals, allowing the same VCO to maintain low phase noise performance throughout its entire operating frequency range, eliminating the need for multiple frequency-specific VCOs and reducing overall power consumption.
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
Improves phase noise performance by a factor of ten, reduces flicker noise, and decreases system power without the need for costly components or multiple VCOs, suitable for frequencies over 20 GHz.
Implementation Method 1
a series Inductor-Capacitor tank circuit (LC-tank) based time reference... At its resonant frequency, the output frequency of the phase locked loop is controlled to maintain that particular time delay
Data Source
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AI summary
An apparatus and method for generating a signal. A signal is generated with an output frequency based on a control signal. A filtered error signal is produced based on a phase difference between a divided frequency of the signal and a frequency reference signal. A time reference signal is generated with a frequency based on a combination of a series connected inductor and capacitor, the signal and the filtered error signal. A filtered time error, indicating a time error between level transitions of the signal based on the output signal and level transitions of a signal based on the time reference signal, is generated with a sample and hold circuit. The control input signal is based on a filtered time error signal.