On-Chip DCXO Clock Control Using Flying-Adder Frequency Synthesis
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Solution Overview
Problem
In TV-related applications, the varying data rate requires frequent adjustments to the local clock for reliable data capture, which existing technologies address through external or on-chip VCXO chips, resulting in increased costs and complexity.
Innovation Solution
The use of a flying-adder frequency synthesis circuit within a Digital Control Crystal Oscillator (DCXO) adjusts the local clock based on program clock reference signals, eliminating the need for external or on-chip VCXO chips and employing digital control for precise frequency adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If external or on-chip VCXO chips are used to adjust the local clock frequency, then frequency control capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the essential frequency adjustment function from the complex VCXO chip and implements it using only a voltage-controlled capacitor connected to a crystal oscillator. This removes the need for dedicated VCXO hardware while preserving the core frequency control capability through a simplified circuit configuration.
Solution Approach 2:
The patent combines the frequency control function with the existing crystal oscillator circuit by adding a voltage-controlled capacitor. This merges the clock generation and frequency adjustment functions into a single integrated circuit block, eliminating the need for separate VCXO chips and reducing overall system complexity.
2Adaptability or versatility
If external or on-chip VCXO chips are used to adjust the local clock frequency, then frequency control capability is improved, but cost increases
Solution Approach 1:
The patent replaces expensive VCXO chips with a cost-effective implementation using standard voltage-controlled capacitors and crystal oscillators. This substitution uses readily available, low-cost components that can be easily manufactured and integrated without requiring specialized or proprietary hardware.
Solution Approach 2:
The patent extracts the essential frequency adjustment function from the expensive VCXO chip and implements it using only a voltage-controlled capacitor connected to a crystal oscillator. This removes the need for dedicated VCXO hardware while preserving the core frequency control capability through a simplified circuit configuration.
3Adaptability or versatility
If traditional VCXO implementation is used, then frequency adjustment is achieved, but linearity and stability are insufficient
Solution Approach 1:
The patent employs a phase-locked loop (PLL) circuit that provides feedback control to maintain stable frequency output. The PLL continuously monitors the output frequency and adjusts the voltage-controlled capacitor accordingly, ensuring high linearity and stability in the frequency control response while maintaining the simplified circuit architecture.
Solution Approach 2:
The patent uses a voltage-controlled capacitor that changes its capacitance parameter in response to control voltage, providing precise and linear frequency adjustment. This parameter change mechanism, combined with PLL feedback, achieves superior linearity and stability compared to traditional VCXO implementations.
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 solution reduces costs, simplifies operations, provides precise frequency control, and enhances stability and linearity, offering superior characteristics such as super linearity, infinite tuning bandwidth, and zero post-tuning drift.
Implementation Method 1
The voltage controlled capacitor has a control input that receives a control voltage from the phase locked loop and an output connected to the crystal oscillator. The voltage controlled capacitor adjusts the oscillation frequency of the crystal oscillator in response to the control voltage.
Data Source
AI summary
This invention uses a flying adder frequency synthesis circuit to provide the required frequency adjustments to accommodate the varying encoding density of a MPEG2 video data stream. This invention adjusts the local clock based on the information extracted from the program clock reference signal in the incoming data. This invention replaces an external or internal voltage-controlled crystal oscillator using a phase locked loop circuit on the video processing integrated circuit.