DFT Tone Frequency Amplitude Phase Measurement
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Solution Overview
Problem
Existing frequency measurement technologies, such as DFT and FFT, have limited direct frequency measurement accuracy to 2π/N radians and do not effectively measure tone amplitude and phase without introducing bias or increasing process complexity.
Innovation Solution
A DFT/FFT-based apparatus that combines jackknife-localized multi-tone frequency measurement (JKLMTM) for precise frequency measurement and tone amplitude and phase measurement (TAPM) to achieve greater than 2π/N radians accuracy, using a signal conditioner, analog-to-digital converter, parser, Fourier Transformer, and processors to process input signals for refined amplitude and phase calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If DFT/FFT is used for frequency measurement, then measurement efficiency and noise reduction are improved, but direct frequency measurement accuracy is limited to 2π/N radians
Solution Approach 1:
The patent applies segmentation by dividing the frequency measurement process into two distinct stages: (1) an initial coarse frequency measurement using DFT/FFT to identify the approximate frequency location, and (2) a refined precise frequency measurement using a quadratic interpolation formula applied to the DFT/FFT spectrum. This segmentation allows the system to benefit from the efficiency of DFT/FFT while achieving sub-bin frequency resolution through the interpolation of adjacent spectral components.
Solution Approach 2:
The patent employs preliminary action by using DFT/FFT to perform an initial frequency estimation that provides the starting point for the subsequent refined measurement. The initial measurement identifies the frequency bin and its neighbors, which are then used in the quadratic interpolation formula to calculate the precise frequency. This preliminary step enables the refined measurement to be performed efficiently without requiring a complete redesign of the measurement process.
2Reliability
If prior art frequency measurement methods are used, then noise reduction properties are improved, but frequency measurement accuracy remains limited
Solution Approach 1:
The patent introduces an intermediary element - the quadratic interpolation formula - that acts as a mediator between the DFT/FFT frequency bins. Instead of directly using the discrete frequency bins from DFT/FFT, the interpolation formula processes the spectral components at the identified bin and its neighbors to calculate a refined frequency estimate. This intermediary step preserves the noise reduction properties of DFT/FFT while overcoming its inherent frequency resolution limitation.
3Adaptability or versatility
If tone amplitude and phase measurement is added to frequency measurement, then complete tone parameter measurement is achieved, but process complexity increases
Solution Approach 1:
The patent applies universality by designing a measurement apparatus that can perform multiple functions using a unified processing framework. The same DFT/FFT-based processing structure is used for frequency measurement, and the refined frequency estimate is then utilized for both amplitude and phase measurements. This multi-functional approach allows the system to measure all three tone parameters (frequency, amplitude, phase) without requiring separate independent measurement systems, thereby reducing overall complexity while expanding measurement capability.
Data Source
AI summary
An apparatus for efficient, precise and accurate measurement of the frequency, amplitude, and phase of a single input tone frequency and/or multiple separable input tone frequencies. Tone separability can be achieved by proper selection of the parameter N, the sample length of the DFT/FFT. Application of the invention includes but is not limited to test and measurement, tone interference removal, and communications systems, where precise and accurate measurement of tonal parameters is needed.