Impulse noise effect reduction

A receiver comprising:

• an input terminal for receiving input signals;
• means coupling an adaptive filter means to said input terminal, said adaptive filter means being normally adjustable as a function of the signals received at said input terminal;
• detector means for sensing the amplitude of the input signals received at said input terminal and comparing the amplitude to a threshold level for producing a control signal having first value when the amplitude of the input signal is below the threshold level and having a second value when the amplitude of the input signal exceeds the threshold level;
• means responsive to said control signal coupled to said adaptive filter means for preventing adjustment of said adaptive filter means when said control signal has said second value
• said means coupling an adaptive filter means to said input terminal includes an analog-to-digital (A/D) converter having an input coupled to said input terminal and having an output;
• and
• a delay means coupled between the output of said A/D converter and said adaptive filter means for delaying the application of the received signals to the adaptive filter means;
• and
• wherein the output of the A/D converter is coupled to the detector for enabling the detector means to sense the presence of any received signal exceeding the threshold level and inhibiting adjustment of the adaptive filter means prior to the propagation of the signal to the adaptive filter means.

A method for reducing the effect of a noise impulse on the adaptive filter of a receiver system comprising the steps of:

• producing a control signal whenever an input signal to the receiver system exceeds a threshold level;
• applying the control signal to the adaptive filter of the receiver system for inhibiting a change in the response of the adaptive filter during the presence of an input signal exceeding the threshold level;
• and
• responsive to the expected occurrence of an input signal exceeding the threshold level, producing a control signal to inhibit a change in the response of said adaptive filter for a predetermined time preceding the expected occurrence of said input signal exceeding the threshold level.

A transmitter receiver system comprising:

• an input terminal for receiving input signals;
• an adaptive filter means having an input for the application thereto of input signals derived from said input terminal and having an output, said adaptive filter means having coefficients which are normally updated as a function of the input signals and an error signal applied to a control terminal of the adaptive filter means;
• means coupling the input of said adaptive filter means to said input terminal;
• detector means for sensing the amplitude of the input signals received at said input terminal and comparing the amplitude to a threshold level for producing a control signal having a first value when the amplitude of the input signal is below the threshold level and having a second value when the amplitude of the input signal exceeds the threshold level;
• means responsive to said control signal coupled to the control terminal of said adaptive filter means for inhibiting adjustment of said adaptive filter means when said control signal has said second value;
• and
• means responsive to the expected occurrence of an input signal exceeding the threshold level for producing a control signal coupled to said control terminal of said adaptive filter means for inhibiting adjustment of said adaptive filter means for a first period of time preceding the expected occurrence of a signal exceeding the threshold level and a second period of time following the expected occurrence of the signal exceeding the threshold level.

A transmitter receiver system comprising:

• an input terminal for receiving input signals;
• an adaptive filter means having an input for the application thereto of input signals derived from said input terminal and having an output, said adaptive filter means having coefficients which are normally updated as a function of the input signals and an error signal applied to a control terminal of the adaptive filter means;
• means coupling the input of said adaptive filter means to said input terminal;
• detector means for sensing the amplitude of the input signals received at said input terminal and comparing the amplitude to a threshold level for producing a control signal having a first value when the amplitude of the input signal is below the threshold level and having a second value when the amplitude of the input signal exceeds the threshold level;
• means responsive to said control signal coupled to the control terminal of said adaptive filter means for inhibiting adjustment of said adaptive filter means when said control signal has said second value;
• said means coupling the input of said adaptive filter means to said input terminal includes an analog-to-digital (A/D) converter having an input coupled to said input terminal and having an output;
• and
• a delay means coupled between the output of said A/D converter and the onput of said adaptive filter means for delaying the application of the received signals to the adaptive filter means;
• and
• wherein the output of the A/D converter is coupled to the detector for enabling the detector means to sense the presence of any received signal exceeding the threshold level and inhibiting adjustment of the adaptive filter means prior to the propagation of the signal to the adaptive filter means.

A receiver comprising:

• an input terminal for receiving analog signals;
• an analog-to-digital (A/D) converter having an input coupled to said input terminal and having an output;
• an echo canceler coupled to the output of said A/D converter, said echo canceler including a first adaptive filter means adjustable as a function of the amplitude of the signal at the output of said A/D converter;
• an adaptive equalizer coupled to the output of said A/D converter for processing and propagating the signal produced at the output of said A/D converter, said adaptive equalizer, including a second adaptive filter means adjustable as a function of the amplitude of the signal at the output of said A/D converter;
• detector means coupled between the output of said A/D converter and said first and second adaptive filter means for sensing when amplitude of the signal at the output of the A/D converter exceeds a predetermined value for inhibiting the adjustment of the first and second adaptive filter means when the signal exceeds the predetermined value;
• and
• means responsive to the detector means for inhibiting the adjustment of the first and second adaptive filter means for a first time period before the signal exceeds the predetermined value, and continuing the inhibition of the adjustment of the first and second adaptive filter means for a second period of time after the signal drops below the predetermined threshold level.