부산대학교 도서관

The present paper describes an instantaneous frequency (IF) estimation method. The instantaneous amplitude and phase can be obtained simultaneously by converting the real signal into a complex time signal using the Hilbert transform. In addition, the IF is obtained by differentiating the instantaneous phase with respect to time. However, the amplitude of the signal obtained by phase-shifting the input signal by 90-degrees is different from that of the input signal because a ripple is generated in the frequency characteristics of the finite order finite impulse response (FIR) Hilbert transformer (HT). As a result, errors are contained in the IF. In the present paper, we theoretically show that the IF obtained using the finite order HT contains harmonics. Moreover, we propose a method by which to remove harmonics using an FIR filter with the specified transmission zeros.