Phase-Optimized Noise Generator for Low-Crest-Factor Spectra
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Solution Overview
Problem
Conventional digital noise generators produce noise signals with high crest factors, leading to intermodulation and broadening of the noise spectrum, which cannot generate noise spectra with gaps and meet the stringent requirements of minimizing interfering components outside the desired frequency spectrum, particularly in applications like suppressing mobile communications frequencies in aircraft.
Innovation Solution
A noise generator that modulates I and Q signal components using a vector modulator, employing a specific phase positioning formula for sinusoidal signals to create a noise signal with a low crest factor, allowing for the generation of noise spectra with gaps and optimized edge steepness, thereby reducing intermodulation products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional digital noise generators use equidistant signal lines to fill the noise spectrum, then the noise spectrum can be generated, but the crest factor becomes high leading to intermodulation and spectrum broadening
Solution Approach 1:
The patent applies parameter changes by optimizing the phase relationships of individual sinusoidal signal lines according to a specific mathematical formula. This phase optimization transforms the conventional equidistant signal lines into a configured set of signals with controlled phase positions, thereby reducing the crest factor from high levels to below 6 dB while maintaining the noise spectrum generation capability. The parameter change specifically targets the phase angles of each signal component to achieve low crest factor and minimize intermodulation products.
Solution Approach 2:
The patent implements dynamics by introducing adjustable parameters (TSTART, TSTOP, C) into the phase calculation formula. These parameters allow dynamic configuration of the noise spectrum characteristics, enabling the system to adaptively optimize the phase relationships based on specific application requirements. The dynamic adjustment capability permits flexible control over the noise spectrum shape, gap positioning, and crest factor without requiring hardware changes.
2Productivity
If noise generators generate continuous noise spectrum without gaps, then the noise signal can be produced, but interfering components outside the desired spectrum cannot be suppressed
Solution Approach 1:
The patent uses parameter changes to create gaps in the noise spectrum by adjusting the phase optimization formula parameters. By modifying TSTART and TSTOP values, the system can selectively exclude certain frequency ranges from the noise spectrum, creating gaps where interfering components (such as mobile communication frequencies) do not appear. This parameter-based control enables precise spectral shaping to suppress harmful interfering components while maintaining noise signal generation in desired bands.
Solution Approach 2:
The patent applies segmentation by dividing the frequency spectrum into distinct regions: desired noise bands and gap regions. The phase optimization formula is configured to generate signals only in the desired bands while intentionally leaving gaps in specific frequency ranges. This segmentation approach separates the noise spectrum into functional zones, allowing interfering components to be excluded from the generated signal while maintaining continuous noise generation in the permitted bands.
3Manufacturing precision
If the noise spectrum has high edge steepness and low undulation, then spectral purity is improved, but the device complexity increases
Solution Approach 1:
The patent replaces complex analog filtering mechanisms with a digital signal generation approach. Instead of using physical filters to achieve high edge steepness and low undulation, the system generates the noise spectrum directly with the desired spectral characteristics through phase-optimized sinusoidal summation. This substitution of mechanical/analog filtering with digital signal processing achieves superior spectral purity while reducing overall device complexity, as the spectral shaping is accomplished through software-based phase calculation rather than hardware filtering.
Data Source
AI summary
A noise generator for generating band-limited noise from a plurality of sinusoidal signals at the same level and equidistant frequency position in the noise spectrum is provided. A noise signal has a low crest factor and for this purpose the phase position of each individual sinusoidal signal is determined.