Mitigation of Band Edge Effects in Fourier Transform Based Time Domain Gating

Time domain gating is a well-known signal processing technique by first converting frequency domain data to time domain via inverse Fourier Transform. Time domain gating is thereafter applied as a filter to include or exclude certain time periods. One of the side effects of time domain gating is band edge effects where data near band edges is unreliable. Several mitigation techniques have been reported and implemented in commercial vector network analyzers, i.e., pre-gate windowing and post-gate renormalization. Even after applying these mitigation techniques, edge errors can still be significant. In this paper, we summarize these common mitigation methods, and utilize a different approach, referred to as Spectrum Extension Edgeless Gating (SEEG) method. In SEEG, frequency domain data is first extended beyond the edges smoothly, and time domain gating is applied over the extended data. In a wide range of antenna measurement applications, SEEG method is shown to be superior for reducing uncertainties from gating edge effects.