Signal digitizer for bar code readers

A level detector for digitizing a continuous time varying input signal comprising:

• a positive peak detector coupled to the input signal;
• a negative peak detector coupled to the input signal;
• divider means coupled to the positive and negative peak detectors for producing a threshold voltage representative of a voltage between the outputs of the positive and negative peak detectors;
• means for comparing the threshold voltage to the input signal and for producing one binary value when the input signal is more positive than the threshold voltage and a different binary value when the input signal is more negative than the threshold voltage;
• and
• separator means coupled to the outputs of the peak detectors for maintaining a minimum potential between the peak detectors regardless of the amplitude of the input signal.

A data converter for digitizing a continuous time varying input signal comprising:

• positive detector means for storing the value of the input signal, the positive detector means independently updating the stored value only when the input signal has a positive slope;
• negative detector means for storing the value of the input signal, the negative detector means independently updating the stored value only when the input signal has a negative slope;
• clamping means coupled to the positive detector means and the negative detector means for maintaining a specified maximum potential between the positive and negative detector means, the clamping means dependently updating the stored value of the negative detector when the input signal has a positive slope and the clamping means dependently updating the stored value of the positive detector when the input signal has a negative slope;
• divider means coupled to the positive and negative detector means for providing a threshold voltage;
• and
• comparator means coupled to the input signal and the threshold voltage for providing a binary signal, the value of the binary signal being dependent upon the relative potentials of the input signal and the threshold voltage.

An analog-to-digital converter for converting an analog signal to a discrete signal, the converter comprising:

• a positive peak detector coupled to the input signal for storing the most recent highest peak value of the input signal;
• a negative peak detector coupled to the input signal for storing the most recent lowest peak value of the input signal;
• clamping means for limiting the maximum potential between the positive peak detector and the negative peak detector to a first selected level;
• separator means for limiting the minimum potential between the positive peak detector and the negative peak detector to a second selected level;
• divider means coupled to the positive and negative peak detectors for producing a threshold voltage have a potential between the voltage potentials of the positive peak detector and the negative peak detector;
• and
• means for comparing the threshold voltage to the input signal and for producing one binary value when the input signal is more positive than the threshold voltage and a different binary value when the input signal is more negative than the threshold voltage.

A one-bit analog-to-digital converter comprising:

• a first precision diode having an anode and a cathode, the anode being connected to the input signal;
• a second precision diode having an anode and a cathode, the cathode being connected to the input signal;
• a first storage capacitor coupled to the cathode of the first precision diode;
• a second storage capacitor coupled to the anode of the second precision diode;
• a resistive voltage divider connected between the cathode of the first precision diode and the anode of the second precision diode, the voltage divider having an output representative of a voltage potential between the voltage potentials at the outputs of the precision diodes;
• a pull-down resistor connected between the anode of the second precision diode and ground;
• a pull-up resistor connected between the cathode of the first precision diode and a positive power supply;
• a clamping diode having an anode connected to the cathode of the first precision diode and a cathode connected to the anode of the second precision diode;
• and
• a comparator having one input connected to the output of the voltage divider and the other input connected to the input signal, the output of the comparator providing a binary signal representative of the potential of the input signal relative to the threshold voltage.