Abstract
The estimation of instantaneous frequency (IF) method is introduced to compensate for the group velocity of electromagnetic wave in dispersive medium. The location of the reflected signal can be obtained by using the time-frequency cross correlation (TFCC), following which it is used to extract the transmitted signal from the total signal acquired. The signal propagated in the dispersive medium is attenuated and distorted by the attenuation characteristics, which depend on the frequency of the medium. By using the IF curve calculated for the transmitted signal, the changed center frequency and time terms can be obtained. The obtained terms are used to compensate for the group velocity error induced by signal distortion and attenuation. Through experiments and simulation, the accuracy of the proposed method is 2% higher than that of the conventional method when the signal propagates over a long distance.
Highlights
It is important to accurately measure the group velocity of electromagnetic wave in a dispersive medium to detect defects and measure distances
Reflectometry methods can be categorized into time domain reflectometry (TDR), frequency domain reflectometry (FDR), and time-frequency domain reflectometry (TFDR) [2,3,4,5,6,7] depending on the incident signal type
We propose a method for compensating the group velocity of poly-chromatic wave in a dispersive medium based on instantaneous frequency (IF) estimation
Summary
It is important to accurately measure the group velocity of electromagnetic wave in a dispersive medium to detect defects and measure distances. TDR and FDR use a step pulse and sinusoidal pulse defined in the time domain and frequency domain, respectively. They have been widely used in cable diagnostics owing to their ease of implementation. In TFDR, the impedance discontinuity distance is measured by obtaining the time delay of the reflected signal generated from the impedance discontinuity point for a given group velocity. Since the frequency components included in the chirp signal have different velocities, compensation is performed without taking into account dispersion, which causes an measurement error. We propose a method for compensating the group velocity of poly-chromatic wave in a dispersive medium based on instantaneous frequency (IF) estimation. The group velocity compensation is carried out through the derived terms
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