Abstract
We propose a simle scheme for detecting tone signals narrowly spaced in the frequency by employing a nonlinear device called Teager's energy tracker. When the input signal is a tone signal, the output of Teager's energy tracker is proportional to the energy and tone frequency of the input signal. When the envelope of the input tone is varying, this tracker can also track the energy of the envelope. By employing Teager's algorithm as a preprocessor, the detector for narrowly spaced tone signals can be implemented without the use of sharp notch filters. As an example, the proposed detector is applied to distinguishing ITU-T V.8 and V.25 tone signals. The detector perfodrmance is analyszed and is verified by computer simulation.
