Phase-Shifted Parallel FDSM for Idle Tone Dispersion
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Solution Overview
Problem
Delta-sigma modulation-based frequency measurement devices suffer from idle tone noise, which degrades measurement accuracy, and existing methods to suppress this noise are ineffective, especially when frequency modulation signals are involved.
Innovation Solution
An idle tone dispersion device that employs multiple frequency delta-sigma modulation units with a phase adjustment unit to relative adjust the phase between measured and reference signals, ensuring the idle tone phase is different across units, thereby suppressing quantization noise by adding their outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If multiple parallel FDSMs are used to suppress idle tone, then idle tone suppression is improved, but the baseband signal component and quantization noise overlap causing measurement accuracy degradation
Solution Approach 1:
The patent divides the single FDSM into multiple parallel FDSMs, each processing a different frequency band. By segmenting the frequency spectrum and assigning different baseband signals to different parallel FDSMs, the quantization noise from each FDSM falls into different frequency bands, preventing overlap with the baseband signal and enabling effective idle tone suppression while maintaining measurement accuracy.
Solution Approach 2:
The patent introduces a frequency dimension separation by assigning different center frequencies to each parallel FDSM. This dimensional separation in the frequency domain ensures that the quantization noise from each FDSM does not overlap with its corresponding baseband signal, resolving the contradiction between idle tone suppression and measurement accuracy.
2Object-affected harmful factors
If delay is applied to measured signal for idle tone suppression, then idle tone dispersion is improved, but circuit complexity increases
Solution Approach 1:
The patent segments the delay function across multiple parallel FDSMs, where each FDSM applies a different delay corresponding to its frequency band. This segmented approach achieves effective idle tone dispersion while distributing the circuit complexity across modular parallel units rather than requiring a single complex delay circuit.
Solution Approach 2:
The patent applies different delay characteristics to different frequency bands processed by each parallel FDSM. This local optimization of delay parameters for each frequency band achieves effective idle tone dispersion while allowing each FDSM to use simpler, frequency-specific delay circuits rather than a single complex universal delay circuit.
Data Source
AI summary
An idle tone dispersion device includes n FDSM (1) to FDSM (n), a phase adjustment unit which relatively adjusts a phase between a measured signal and a reference signal such that a phase of an idle tone is completely different, and generates and supplies n sets of output measured signals and output reference signals to each of the n FDSM (1) to FDSM (n), and an adder which adds output data of the n FDSM (1) to FDSM (n) and outputs a frequency delta-sigma modulation signal.