Apparatus and method for detecting and discriminating various signal types in the presence of impulse distortions

An apparatus for detecting an amplitude modulated signal in the presence of impulse distortions, the amplitude modulated signal transmitted and received via a channel, the amplitude modulated signal having a first frequency component, the amplitude modulated signal having an amplitude modulated signal average power level, the apparatus comprising:

• a first band pass filter, the first band pass filter having a first center frequency corresponding to the first frequency component to filter the amplitude modulated signal to form a first band pass filtered signal, the first band pass filtered signal having a first band pass filtered signal average power level and further having distortions corresponding to an occurrence of impulse distortions in the amplitude modulated signal;
• a limiter coupled to the first band pass filter to limit the distortions of the first band pass filtered signal to a limit threshold to form a limited signal;
• a rectifier coupled to the limiter rectify the limited signal to form a rectified, limited signal;
• a second band pass filter coupled to the rectifier, the second band pass filter having a second center frequency corresponding to a second frequency component to filter the rectified, limited signal to form a filtered limited signal, the filtered limited signal having a filtered limited signal average power level;
• a first comparator to detect the presence of the first frequency component by comparing the amplitude modulated signal average power level to the first band pass filtered signal average power level;
• and
• a second comparator to detect the presence of the second frequency component by comparing the filtered limited signal average power level to the first band pass filtered signal average power level.

A data communication device for data transmission and reception, the data communication device having an initial training period for detecting an answer back tone signal and for detecting an sampled answer back tone signal, both the answer back tone signal and the amplitude modulated answer back tone signal transmitted via a channel, the answer back tone signal having a first frequency component containing phase reversals, the amplitude modulated answer back tone signal having the first frequency component containing phase reversals and having a second frequency component, the answer back tone signal having an answer back tone signal average power level, and the amplitude modulated answer back tone signal having an amplitude modulated answer back tone signal average power level, the data communication device comprising:

• a data access arrangement coupleable to a channel to receive a signal;
• an analog-digital converter coupled to the data access arrangement to sample the signal, to form a sampled signal;
• and
• a processor coupled to the analog-digital converter to receive the sampled signal, the processor responsive to band pass filter the amplitude modulated signal at a first center frequency corresponding to the first frequency component, to form a band pass filtered signal, the band pass filtered signal having a band pass filtered signal average power level and further having impulse distortions corresponding to an occurrence of phase reversals in the signal;
• the processor further responsive to limit the impulse distortions of the band pass filtered signal to a limit threshold, to form a limited signal;
• the processor further responsive to rectify and band pass filter the limited signal at a second center frequency corresponding to the second frequency component, to determine a limited signal average power level;
• the processor further responsive to compare the answer back tone signal average power level to the band pass filtered signal average power level to determine the presence of the first frequency component;
• and the processor further responsive to compare the limited signal average power level to the band pass filtered signal average power level to determine the presence of the second frequency component.

An apparatus for dynamically limiting impulse distortions in an amplitude modulated signal, the apparatus comprising:

• a rectifier to rectify the amplitude modulated signal to form a rectified signal;
• a low pass filter coupled to the rectifier to filter the rectified signal to form a rectified, low pass filtered signal, the rectified, low pass filtered signal having a low frequency average magnitude level;
• a threshold selector coupled to the low pass filter, the threshold selector responsive to the low frequency average magnitude level to form a threshold limit signal;
• and
• a limiter for receiving the amplitude modulated signal, the limiter further coupled to the threshold selector to receive the threshold limit signal, the limiter dynamically limiting the impulse distortions of the amplitude modulating signal to a magnitude determined by the threshold limit signal, to form a limited signal.