Cyclostationary Crosstalk Cancelation in High-Speed Transmission Lines

The theoretical and experimental evaluation of the cyclostationary random data transferring process corrupted by the individually and jointly cyclostationary crosstalk interference is presented. The interference and the message signals were measured by the real time digital oscilloscope. Autocorrelation functions were evaluated by synchronous cyclic averaging procedure. The analyzed periodic two-dimensional impulse response of the time-varying filter allows to obtain the output random process with the same cyclic frequency at the output of the filter by separation of orthogonal stationary waveforms constituting the input cyclostationary random process (CSRP). The filtering of the measured random process was implemented by the cyclic Wiener filter. The evaluation of the two-dimensional autocorrelation function and eye diagrams at the output of the cyclic Wiener filter showed significant reduction of the independent interference components in the estimated message signal.

Investigation of energy stealth of radar stations with band antennas from the radio monitoring complex

Using spectral representation of non-harmonic processes and partial characteristics of antennas, energy equations of transmissionreception of broadband signals in the radio channel with scattering on the object and the direct radio channel between the radar and the radio monitoring (RM) complex have been obtained. Energy of received signals is determined by value of product of spectral density of radiation power and partial moment of transmission-reception averaged in the range of cyclic frequencies. The signal-to-noise ratio at the receiver input reaches the highest value when the partial moment of transmission-reception of signals in the radio channel changes according to a linear law. At fixed average radar power, energy of information signals at incoherent accumulation can be increased due to selection of antennas with partial directive gain amplifying wave processes in areas of their spectra concentration. The range of the radar is proportional to the linear dimensions and significantly depends on the shape of the object. The rules of antenna characteristics selection are justified to ensure radar stealth from RM systems while maintaining the required range of target detection and recognition. When using an antenna with a partial directive gain constant in the range of working cyclic frequencies in the radar, and in the RM complex of an antenna system with a frequency-independent effective area, the partial moment of transmission-reception of signals in the forward radio channel is constant. Its value is determined by the product of partial directive gain at the central frequency of the range. Forms of pulses supplied to input of transmitting antenna and radiated into space coincide, and shape of signal at output of receiving antenna has the form of their derivative. Due to application of frequency-independent antennas in radar and RM complex, energy of probing signals increases compared to levels typical for antenna systems with partial directivity indices varying in proportion to current value of cyclic frequency in the first or second degree. This pattern is due to the significant effective area of the receiving antenna in the lower part of the frequency range, which parries the low efficiency of radiation of low-frequency components of the radar signal spectrum. In radio channels with partial moments of transmission-reception of signals varying with frequency increase according to linear law, energy supplied to receiver input increases in comparison with levels achievable at quadratic and cubic dependencies of partial moments on cyclic frequency due to the same type dependencies of partial directive gain antenna of radar and effective area of antenna of RM complex. Stealth of probing radiation increases as dimensions of radar antennas increase due to increase of partial directive gain and decreases as dimensions of antenna systems of RM complexes increase due to increase of their effective areas. The duty cycle of pulses forming regular sequences, established due to the condition of accumulation of energy of reflected signals due to irradiation of the object, which is required to complete the functional tasks of the radar, decreases in proportion to the increase of the partial directive gain antenna at the central cyclic frequency. Energy of information signals increases in proportion to coefficients depending on relative half-width of their spectra, and decreases with increase of central cyclic frequency to the second degree. As pulse repetition frequency increases at maximum permissible average density of radiation power limited by radar stealth requirements, energy density of probing signals decreases proportionally. The average power of the radar at a fixed level of spectral density varies in proportion to the bandwidth occupied by the probing signals due to a reduction in the following period.

An Experimental Investigation on Dynamic Characteristics of Soft Soils Treated by Vibration-Drainage Method

This paper presents an experimental investigation on the dynamic characteristics of soft soils that are treated by vibration-drainage method (VDM). The representative dynamic axial strain at a given number of cycles was obtained. The VDM-treated soft soil exhibited different dynamic deformation characteristics that are not only affected by the cyclic frequency but also influenced by the vibration frequency during the treatment process. Soil specimens at different cyclic frequencies show a similar variation trend that the axial strain systematically grows with increasing number of cycles. The rate of axial strain for all specimens systematically linearly decreases with the increase of number of cycles in the log-log scale. Results showed that both axial strain and strain rate exhibit relatively lower values at a given number of cycles under the condition that the applied cyclic frequency is equal to vibration frequency. It is expected that the soil structure will be more stable if the applied cyclic frequency is close to the vibration frequency that is applied on VDM-treated soil. Therefore, the vibration frequency close to the possible dynamic loading frequency is recommended in the process of soft soil improvement via VDM in the related engineering applications.

Cyclostationary Impulsive Noise Mitigation in the Presence of Cyclic Frequency Offset for Narrowband Powerline Communication Systems

Cyclostationary impulsive noise (CSIN) is the dominant source of additive noise in narrowband powerline communication (NB-PLC) systems. Frequency-shift (FRESH) filters have been applied to NB-PLC systems based on orthogonal frequency division multiplexing (OFDM) to mitigate CSIN and enhance the OFDM signals by leveraging the difference in cyclic frequency associated with CSIN and OFDM data symbols. Note that under the effects of frequency fluctuation in the mains voltage, the cyclic frequency offset associated with CSIN can degrade the performance of FRESH-filter receivers. To alleviate such an impact on the FRESH-filter receivers, this paper presents a method for the estimation of the cyclic frequency offset by observing phase variations in the coefficients of the FRESH filter. Computer simulations based on IEEE 1901.2 specifications demonstrate the effectiveness of the proposed scheme in suppressing the cyclic frequency relative error by at least 15.45 dB. Following compensation for the cyclic frequency offset, the proposed scheme achieved a bit error rate of 10 − 4 with an E b / N 0 loss of only 0.7 dB, compared with the ideal case. Compared to the case without the cyclic frequency offset compensation, the proposed scheme achieved an E b / N 0 gain of 2.7 dB.

An Improved Cyclic Modulation Spectral Analysis Based on the CWT and Its Application on Broken Rotor Bar Fault Diagnosis for Induction Motors

Induction motors (IMs) are widely used in many manufacturing processes and industrial applications. The harsh work environment, long-time enduring, and overloads mean that it is subjected to broken rotor bar (BRB) faults. The vibration signal of IMs with BRB faults consists of the reliable modulation information used for fault diagnosis. Cyclostationary analysis has been found to be effective in identifying and extracting fault feature. The estimators of cyclic modulation spectrum (CMS) and fast spectral correlation (FSC) based on the short-time fourier transform (STFT) have higher cyclic frequency resolution, which has proven efficient in demodulating second order cyclostationary (CS2) signals. However, these two estimators have limitations of processing the maximum cyclic frequency αmax that is smaller than Fs/2 (Fs is the sampling frequency) according to Nyquist’s Theorem. In addition, they have lower carrier frequency resolution due to the fixed window size used in STFT. In order to resolve the initial shortcomings of the CMS and FSC methods, in this paper, we extended the analysis of CMS algorithm based on the continuous wavelet transform (CWT), which enlarged the maximum cyclic frequency range to Fs/2 and provides higher carrier frequency resolution because the CWT has the advantage of multi-resolution analysis. The reliability and applicability of the proposed method for fault components localization were validated by CS2 simulation signals. Compared to CMS and FSC methods, the proposed approach shows better performance by analyzing vibration signals between healthy motor and faulty motor with one BRB fault under 0%, 20%, 40%, and 80% load conditions.