High resolution quantizer

A system for digitally quantizing, at high resolution, relatively small vations of an analog input signal. Initially, a reference level signal having a preselected value close to the average magnitude of the analog signal being quantized is compared with the analog input signal. The difference between these two signals is amplified and then analog to digital converted. By an iterative process, the reference level is adjusted as necessary to closely track the gross magnitude level of the analog input signal. Analog to digital conversion is applied only to the small difference signal, thereby allowing quantization to occur with high resolution. The system automatically keeps track of gross signal excursions so that the magnitude of the quantized signals is also available to the user.

What is claimed and desired to be secured by Letters Patent of the United States is:

1. An analog to digital conversion system for quantizing in digital form changes that occur in an analog input signal comprising:

means for establishing in both analog and digital form a reference level signal related to the magnitude of said analog input signal;

a differential amplifier having a gain greater than one for comparing said analog input signal with said reference level signal, whereby an amplified difference signal proportional to and greater than the difference between said analog input signal and said reference level signal is produced;

an analog to digital converter coupled to the output of said differential amplifier whereby a digital deviation signal equivalent to said amplified difference signal is generated;

a digital comparator coupled to the output of said analog to digital converter and to an external source for providing a threshold level signal, for generating a reference update instruction whenever the magnitude of said digital deviation signal exceeds said threshold level;

means coupled to said digital comparator and to said analog to digital converter for generating a modified reference level signal in digital form in response to said reference update instruction; and

a digital to analog converter coupled to said modified reference level signal generator for converting said digital form modified reference level signal into analog form wherein said analog form modified reference level signal is coupled to said differential amplifier.

2. A method for quantizing in digital form changes that occur in an analog input signal comprising the steps of:

establishing in both analog and digital form a reference level signal related to the magnitude of said analog input signal;

comparing said analog input signal with said reference level signal, whereby an amplified difference signal proportional to and greater than the difference between said analog input signal and said reference signal is produced;

converting said difference signal into digital form to produce a digital deviation signal;

comparing said digital deviation signal with an externally generated threshold level;

generating a reference update instruction whenever the magnitude of said digital deviation signal exceeds said threshold level signal;

generating a modified reference level signal in digital form in response to said reference update instruction; and

converting said digital form modified reference level signal into analog form.