Tunable Multi-Phase DDS for Plasma RF Synchronization
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Solution Overview
Problem
Conventional plasma control systems require extensive startup periods due to the need for recalibration of multiple RF power generation units to achieve synchronization and optimal combined RF output, as they lack the ability to independently adjust frequency and phase without recalibrating all units, making frequency and phase shifting impractical.
Innovation Solution
A direct digital synthesizer (DDS) system with an accumulator generating frequency signals and multiple adders applying phase offset signals to achieve tunable frequency and phase shifts, allowing for independent adjustment of each RF power generation unit and reducing the need for system-wide recalibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a digital logic loop (DLL) is utilized to synchronize frequency and phase of power generator units, then synchronization accuracy is improved, but startup time is extended due to required calibration of each unit
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing frequency and phase offset values in lookup tables during system design or initialization. During operation, the DDS system directly retrieves these pre-computed values based on desired output parameters, eliminating the need for time-consuming real-time calibration of each power generator unit through DLL. This allows immediate frequency and phase adjustment without extending startup time.
Solution Approach 2:
The patent implements beforehand cushioning by incorporating compensation mechanisms that pre-account for frequency and phase variations across different operating conditions. The system stores corrected offset values in advance for various frequency and phase combinations, cushioning against the need for real-time recalibration and thereby preventing startup time extension while maintaining synchronization accuracy.
2Adaptability or versatility
If frequency and phase shifting is performed using conventional multiple DDS systems, then frequency and phase control is achieved, but system-wide recalibration is required making adjustments impractical
Solution Approach 1:
The patent applies segmentation by dividing the frequency and phase control functions into independent channels, each with its own DDS unit and lookup table. This allows individual adjustment of each power generator unit's frequency and phase offsets without affecting or requiring recalibration of other units. The segmented architecture enables independent control while maintaining overall system synchronization.
Solution Approach 2:
The patent introduces an intermediary lookup table mechanism that mediates between the desired frequency/phase commands and the actual power generator outputs. Instead of directly adjusting generator parameters which would require system-wide recalibration, the system uses the lookup table as an intermediary to translate commands into pre-computed offset values, enabling practical independent adjustments.
3Power
If multiple RF power generation units are combined to achieve sufficient power levels, then output power capability is improved, but system complexity increases requiring extended synchronization procedures
Solution Approach 1:
The patent applies merging by combining multiple DDS control functions into a unified system with shared lookup tables and common frequency synthesis architecture. While maintaining independent control of multiple power generation units, the merged DDS system eliminates the need for separate calibration procedures for each unit, reducing synchronization complexity despite the increased number of power amplifiers.
Solution Approach 2:
The patent implements universality by designing a multi-functional DDS control system that simultaneously manages frequency synthesis, phase control, and amplitude modulation for multiple power generation units. This universal control architecture handles all synchronization tasks through a single system that can adapt to different operating conditions, reducing overall system complexity compared to dedicated control circuits for each unit.
Data Source
AI summary
A plasma control system including a direct digital synthesizer (DDS) for generating more than one individual RF power signal, where the individual RF power signals are combined to define a combined RF power signal. The DDS includes an accumulator which receives a phase increment signal that defines a frequency of a frequency signal generated by the accumulator. The frequency signal is split and input to a plurality of adders. Each adder receives a phase offset signal that defines a phase shift of the frequency signal input to that particular adder. The phase increment signal and phase offset may be stored to reduce the startup portion of the plasma control system.