Method and apparatus for continuously variable slope delta modulation coding of signals

An encoder comprising:

• a thresholder having an analog input and a digital output representing the relationship between a signal amplitude at said analog input and a predetermined threshold;
• an integrator having an output and one input connected to the output of the thresholder and a second input that receives a step size value, the output of the integrator corresponding to a product of said thresholder output and said step size value;
• an adder having one input that receives an analog input signal that is to be encoded and a second input connected to the output of said integrator, the output of said adder being coupled to said analog input of said thresholder;
• a step size controller responsive to an analog signal level related to said analog input signal for varying said step size value in response to variations in said analog signal level;
• a source producing noise;
• a noise amplitude controller responsive to an analog signal level related to said analog input signal for varying the amplitude of said noise in response to variations in said analog signal level to produce noise having a controlled amplitude sufficient to reduce the correlation with said analog input signal of an error between the output of said integrator and said analog input signal;
• and
• an adder for adding the noise having a controlled amplitude to said analog input signal.

A method of encoding an analog input signal, comprising:

• thresholding the analog level at an input node to produce a digital output representing the relationship between a signal amplitude at said input node and a predetermined threshold;
• integrating the output of the thresholder in accordance with a step size value to produce an integration output;
• adding the analog input signal with a currently available version of the integration output and applying the result to said input node;
• and
• controlling, by a step size controller, said step size value in response to variations in an analog signal level related to said analog input signal, said step size controller also determining said step size value, said step size controller also determining and outputting whether an amplitude of the analog signal level is above a predetermined detector threshold, storing a previous step size value, restoring said step size value to said previous step size value based on the output of said amplitude detector, storing a largest value of said step size that was determined by said step size controller, and restoring the step size to the largest determined step size when the amplitude of the analog signal level exceeds the detector threshold of the amplitude detector.

A method of encoding an analog input signal, comprising:

• thresholding the analog level at an input node to produce a digital output representing the relationship between a signal amplitude at said input node and a predetermined threshold;
• integrating the output of the thresholder in accordance with a step size value to produce an integration output;
• adding the analog input signal with a currently available version of the integration output and applying the result to said input node;
• controlling said step size value in response to variations in an analog signal level related to said analog input signal;
• providing noise;
• varying the amplitude of said noise in response to variations in said analog signal level to produce noise having a controlled amplitude sufficient to reduce the correlation with said analog input signal of an error between the output of said integrator and said analog input signal;
• and
• adding the noise having a controlled amplitude to said input node.