Conventional radars commonly use a linear frequency-modulated (LFM) waveform as the transmitted signal. The LFM radar is simple system, but its impulse-response function produces −13.25 dB sidelobe, which in turn can make detection of weak targets difficult by drowning out adjacent target information with sidelobe strong target. To overcome this challenge, paper presents modeling and optimizati...

Design, simulation and optimal selection of cosine-linear frequency modulation waveform (CNLFM) based on correlated ambiguity function (AF) method for the purpose of Synthetic Aperture Radar (SAR) is done in this article. The selected optimum CNLFM waveform in contribution with other waveforms are applied directly into a SAR image formation algorithm (IFA) and their quality effects performance ...

The stochastic resonance (SR) in a bistable system driven by nonlinear frequency modulation (NLFM) signal and strong noise is studied. Combined with empirical mode decomposition (EMD) piecewise idea, an adaptive re-scaled SR method based on the optimal intrinsic function (IMF), proposed to enhance weak NLFM signal. At first, considering advantages of EMD for dealing non-stationary signals, segm...

background and aim: it has been several decades since the technology of frequency lowering (fl) has been proposed. however, primary research has revealed no benefits regarding the use of this technique. currently, new methods for fl and improvement of perception of speech and fricative sounds have led to the application of these methods by numerous companies to produce hearing aids. in this stu...

In order to improve the reliability of detecting debonding defects at interface thermal barrier coatings (TBC), a non-linear frequency modulated (NLFM) infrared wave detection method is proposed. A NLFM system built, and zirconia TBC specimens are prepared tested. The effects defect diameter, excitation power, initial termination on effect analyzed. Three algorithms such as principal component ...

Recent research in Phase-Sensitive Optical Time Doman Reflectometry (ϕ-OTDR) has been focused, among others, on performing spatially resolved measurements with various methods including the use of frequency modulated probes. However, conventional schemes either rely phase-coded sequences, involve inflexible generation probe modulation or mostly employ simple linear (LFM) pulses which suffer fro...

Photonics-assisted microwave instantaneous frequency measurement (IFM) is considered as a promising technique for detecting an unknown radio-frequency (RF) signal, which has advantages of broad range and fast processing speed. Up to date, there no photonics-assisted IFM system that can essentially measure RF signal time-frequency information with power fluctuating seriously. Moreover, the accur...

In active sonar systems, proper selection of the transmitted waveform is critical for target detection and parameter estimation. Each signal has its own diverse characteristics. Linear FM suffers from relatively high autocorrelation (ACF) side-lobes. The ACF sidelobes could be reduced by shaping the signal; other methods include Gaussian NLFM, Rayleigh NLFM and the combination of both these pul...