Sparse Spectrum Excitation for Fast Broadband Transfer Analysis
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Solution Overview
Problem
Existing methods for broadband high-speed measurement of complex transfer functions face challenges with energy distribution and crest factor optimization in excitation signals, leading to low signal-to-noise ratios and measurement uncertainties, particularly with multisine and MLS excitations.
Innovation Solution
A method and device that generate a binary sparse spectrum sequence (SSS) with concentrated energy on specific frequencies, maintaining a crest factor of unity, allowing for simultaneous broadband measurement of complex transfer functions by optimizing the magnitude spectrum and forming uncorrelated signals for multi-path test systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multisine excitation is used for high speed parallel measurements, then measurement speed is improved, but crest factor increases causing low RMS level and insufficient excitation energy
Solution Approach 1:
The patent applies local quality by concentrating excitation energy specifically at desired frequency points rather than distributing it uniformly. The binary sequence is designed to have spectral lines only at specific frequencies of interest, with zero or minimal energy at other frequencies. This localized energy concentration at critical frequency points enables high-speed measurements while maintaining sufficient excitation energy where needed.
2Power
If rectangular wave excitations are used to provide more excitation energy, then power is improved, but higher harmonics are generated causing measurement uncertainties
Solution Approach 1:
The patent converts the potentially harmful higher harmonics of rectangular wave excitations into a beneficial feature by carefully designing the binary sequence so that its higher harmonics fall exactly at the desired frequency points. The spectral lines of the binary sequence are positioned to match the frequencies of interest, transforming what would normally be unwanted harmonic content into useful excitation energy at the target frequencies.
3Adaptability or versatility
If pseudorandom rectangular waveforms with uniform energy distribution are used to cover wide frequency band, then frequency coverage is improved, but power spectral density decreases at individual frequencies
Solution Approach 1:
The patent applies local quality by creating a non-uniform energy distribution in the frequency domain. Instead of spreading energy uniformly across all frequencies, the binary sequence is designed to concentrate energy at specific frequency points of interest while having zero or minimal energy elsewhere. This selective concentration provides high power spectral density at the desired frequencies while still covering a wide frequency band through the strategic placement of spectral lines.
4Adaptability or versatility
If MLS excitation is used for broadband measurement, then bandwidth coverage is improved, but energy is wasted at frequencies outside the measurement bandwidth
Solution Approach 1:
The patent applies the extraction principle by removing the unwanted frequency components from the excitation signal. The binary sequence is designed to have spectral lines only at the desired frequency points within the measurement bandwidth, with zero energy at frequencies outside the bandwidth. This extracts and eliminates the energy waste that occurs with MLS excitation, where energy is distributed uniformly including at frequencies outside the measurement range.
Data Source
AI summary
A method and device for high speed broadband testing of systems and substances using a binary, spectrally sparse sequence (SSS) as a periodic excitation waveform. The sequences with controllable frequency and magnitude spectra content are designed by component manipulation method or by edge manipulation method. The excitation waveform is typically pre-calculated, and kept in waveform memory, from where it is shifted out into digital to physical quantity converter (DQC).The sparse spectrum of the SSS makes it easy to create plenty of uncorrelated frequency sets with adjacent, but sufficiently different frequencies to form multi-path test systems, where all the paths can be measured simultaneously.The response of the sample under test (SUT) is sampled and the complex transfer function is calculated directly or indirectly via Impulse Response by Discrete Fourier Transform technique and its derivatives. The sequence bit interval and sampling interval have a predetermined ratio.