Synchrosqueezing with short-time fourier transform method for trinary frequency shift keying encoded SSVEP

2020 ◽  
pp. 1-15
Author(s):  
Dechun Zhao ◽  
Xiaoxiang Li ◽  
Xiaorong Hou ◽  
Mingyang Feng ◽  
Renping Jiang
Keyword(s):  
Fourier Transform ◽  
Frequency Shift ◽  
Recognition Algorithm ◽  
Short Time Fourier Transform ◽  
Frequency Shift Keying ◽  
Transform Method ◽  
Coherent Demodulation ◽  
Reconstructed Signal ◽  
Shift Keying ◽  
Short Time

BACKGROUND: The frequencies that can evoke strong steady state visual evoked potentials (SSVEP) are limited, which leads to brain-computer interface (BCI) instruction limitation in the current SSVEP-BCI. To solve this problem, the visual stimulus signal modulated by trinary frequency shift keying was introduced. OBJECTIVE: The main purpose of this paper is to find a more reliable recognition algorithm for SSVEP-BCI based on trinary frequency shift keying modulated stimuli. METHODS: First, the signal modulated by trinary frequency shift keying is simulated by MATLAB. At different noise levels, the empirical mode decomposition, singular value decomposition, and synchrosqueezing with the short-time Fourier transform are used to extract the characteristic frequency and reconstruct the signal. Then, the coherent method is used to demodulate the reconstructed signal. Second, in the paradigm of BCI using trinary frequency shift keying modulated stimuli, the three methods mentioned above are used to reconstruct EEG signals, and canonical correlation analysis and coherent demodulation are used to recognize the BCI instructions. RESULTS: For simulated signals, it is found that synchrosqueezing with short-time Fourier transform has a better effect on extracting the characteristic frequencies. For the EEG signal, it is found that the method combining synchrosqueezing with short-time Fourier transform and coherent demodulation has a higher accuracy and information translate rate than other methods. CONCLUSION: The method combining synchrosqueezing with short-time Fourier transform and coherent demodulation proposed in this paper can be applied in the SSVEP system based on trinary frequency shift keying modulated stimuli.

scholarly journals Communicating radar using frequency-shift keying and fractional Fourier transform for automotive applications

2019 ◽  
Vol 2019 (19) ◽  
pp. 6016-6020 ◽  
Author(s):  
Pasquale Striano ◽  
Christos V. Ilioudis ◽  
Carmine Clemente ◽  
John J. Soraghan
Keyword(s):  
Fourier Transform ◽  
Frequency Shift ◽  
Fractional Fourier Transform ◽  
Automotive Applications ◽  
Frequency Shift Keying ◽  
Shift Keying

scholarly journals METHOD OF AUTOMATIC DETERMINATION OF THE CARRIER FREQUENCY OF SHORT-TIME FREQUENCY-SHIFT KEYING SIGNALS

2019 ◽  
pp. 146-154
Author(s):  
O. A. Nahorniuk
Keyword(s):  
Frequency Shift ◽  
Frequency Spectrum ◽  
Carrier Frequency ◽  
Frequency Difference ◽  
Signal Spectrum ◽  
Frequency Shift Keying ◽  
Time Frequency ◽  
Shift Keying ◽  
Short Time

Method for determination of the carrier frequency of short-time frequency-shift keying signals based on searching for dominant harmonics whose frequency difference is close to the subcarrier spacing frequency is proposed in the article. In telecommunication systems with burst transmissions, the symbol distribution law of the modulating sequence is not always uniform, which under a limited signal duration leads to an increase in the errors in determining the frequency-shift keying parameters. The increase in errors is due to distortion of the amplitude-frequency spectrum of the signal and a decrease in the probability of the correct identification of the subcarrier oscillations harmonics. To improve the accuracy of determining the carrier frequency proposed method uses a priori information about the value of the spacing frequency of the subcarrier oscillations and the multiplicity of frequency-shift keying. The developed approach consists in obtaining the amplitude-frequency spectrum of the signal, calculating the search threshold of dominant harmonics, determining their frequencies which correspond to subcarrier oscillations, and calculating the carrier frequency as their arithmetic mean value. To calculate the signal spectrum was used the modified Welch periodogram method with has a low dispersion of spectral estimates. The harmonic search threshold is determined automatically based on the statistical characteristics of the amplitude-frequency spectrum. Among harmonics with amplitudes greater than the threshold value, those are determined that the frequency difference between which is closest to the subcarrier spacing frequency. The simulations performed in the MATLAB software environment showed that the error in determining the carrier frequency was halved compared to the classical approach under signal-to-noise ratio from -15 dB, and the developed method was efficient if the symbol appearance probability were from 0,5 to 0,8.

Ability of short-time Fourier transform method to detect transient changes in vagal effects on hearts: a pharmacological blocking study

2006 ◽  
Vol 290 (6) ◽  
pp. H2582-H2589 ◽  
Author(s):  
Kaisu Martinmäki ◽  
Heikki Rusko ◽  
Sami Saalasti ◽  
Joni Kettunen
Keyword(s):  
Fourier Transform ◽  
Time Course ◽  
Atropine Sulfate ◽  
Short Time Fourier Transform ◽  
Standing Posture ◽  
Transform Method ◽  
Before And After ◽  
Standing Up ◽  
Stationary Signals ◽  
Short Time

Conventional spectral analyses of heart rate variability (HRV) have been limited to stationary signals and have not allowed the obtainment of information during transient autonomic cardiac responses. In the present study, we evaluated the ability of the short-time Fourier transform (STFT) method to detect transient changes in vagal effects on the heart. We derived high-frequency power (HFP, 0.20–0.40 Hz) as a function of time during active orthostatic task (AOT) from the sitting to standing posture before and after selective vagal (atropine sulfate 0.04 mg/kg) and sympathetic (metoprolol 0.20 mg/kg) blockades. The HFP minimum point during the first 30 s after standing up was calculated and compared with sitting and standing values. Reactivity scores describing the fast and slow HFP responses to AOT were calculated by subtracting the minimum and standing values from the sitting value, respectively. The present results, obtained without controlled respiration, showed that in the drug-free condition, HFP decreased immediately after standing up ( P < 0.001) and then gradually increased toward the level characteristic for the standing posture ( P < 0.001), remaining lower than in the sitting baseline posture ( P < 0.001). The magnitudes of the fast and slow HFP responses to AOT were abolished by the vagal blockade ( P < 0.001) and unaffected by the sympathetic blockade. These findings indicate that HFP derived by the STFT method provided a tool for monitoring the magnitude and time course of transient changes in vagal effects on the heart without the need to interfere with normal control by using blocking drugs.

Analysis on Weak Signals with Short-Time Fourier Transform Method

2014 ◽  
Vol 556-562 ◽  
pp. 5003-5005 ◽  
Author(s):  
Qi Da Yu ◽  
Ya Lin Li ◽  
Jin Wang
Keyword(s):  
Fourier Transform ◽  
Diagnostic Methods ◽  
Diagnostic Efficiency ◽  
Analysis Method ◽  
Short Time Fourier Transform ◽  
Weak Signals ◽  
Transform Method ◽  
Fourier Transform Method ◽  
One Dimensional ◽  
Short Time

To make easy for the operators on the work of analyzing the weak signals, at the same time, for the purpose to improve unskillful operators analyze ability and diagnostic efficiency, at last to get the goal of fast diagnostic. Methods: We recommend STFT theory, then analyzed algorithm to design the programs by the way of LabVIEW2011, at last we realized to change one-dimensional weak signals into the form of intensity maps, which owns obvious recognition feature. Results: We have successfully used programs to realize the analysis on intensity maps, and also simplified judgmental process on illness. This method improves efficiency. Conclusion: Using the method described above can achieve the goal for improving the analysis method, it may work well as we thought before.

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