Frequency Dispersion Compensation Through Variable Window Utilization in Time-Reversal Techniques for Electromagnetic Waves

In microwave imaging applications, propagating signals undergo additional attenuation in dispersive and lossy media compared to the nondispersive and lossless media. In this communication, we introduce a threshold approach and short-time Fourier transform (STFT)-based inverse filters to compensate for such additional attenuation in time-reversal (TR)-based imaging algorithms. The method introduced here is utilized to reduce the unwanted noise amplification in the received signals during the compensation stage. Additionally, optimum settings for window type and length in the STFT method are obtained through a scanning operation in the propagation medium. Different window types and lengths are studied to achieve the best focusing resolution in TR applications. While utilizing a large number of windows with short spatial lengths provides an improved TR focusing performance, it also increases the overall cost and complexity of the imaging system. The threshold method introduced here achieves improved TR focusing performance without increasing the cost by utilizing a lower number of inverse filters.