Apparatus and methodology for digital telemetry of biomedical signals

An improvement in a biomedical apparatus for monitoring biopotentials derived from a patient comprising:

• instrumentation means for detecting said biopotentials from said patient and for processing an analog signal at said patient corresponding thereto;
• analog-to-digital conversion means for converting said analog signals corresponding to said biopotential signals to digital format at the situs of said patient;
• and
• transmitter means for telemetering digital signals corresponding to said digitized biopotential signals generated by said analog-to-digital conversion means, said transmitter means being a tunable frequency modulated radio transmitter,
• wherein said tunable frequency modulated radio transmitter includes a phase-lock-loop circuit comprising:
• a phase detector having an input for receiving an input frequency, and an output;
• a loop filter having an input coupled to the output of said phase detector, and an output;
• a voltage controlled oscillator for generating an output frequency in response to a control input coupled to an output from said loop filter;
• a divider for feeding back said output frequency to said phase detector divided by a selected integer;
• a microcontroller coupled to a lock detect signal from said phase detector, said lock detect signal signifying whether or not said phase-lock-loop circuit has achieved lockup and if not, whether the desired frequency is greater or less than that at which said voltage controlled oscillator is positioned;
• a digital-to-analog converter coupled to said microcontroller and controlled thereby, said digital-to-analog controller having an output coupled in turn to said voltage controlled oscillator to preposition said voltage controlled oscillator at a frequency as determined by input to said digital-to-analog converter from said microcontroller.

An improvement in a biomedical apparatus for monitoring biopotentials derived from a patient comprising:

• instrumentation means for detecting said biopotentials from said patient and for processing an analog signal at said patient corresponding thereto;
• analog-to-digital conversion means for converting said analog signals corresponding to said biopotential signals to digital format at the situs of said patient;
• and
• transmitter means for telemetering digital signals corresponding to said digitized biopotential signals generated by said analog-to-digital conversion means,
• wherein said instrumentation means comprises:
• a biopotential amplifier, said biopotential amplifier receiving said biopotential signals from said patient and for generating an output signal, and having an input,
• said improvement further comprising:
• a microcontroller having an input coupled to said output signal;
• and
• a digital-to-analog converter having an input coupled to said microcontroller, an output of said digital-to-analog converter being fed back to said amplifier as a correction signal, said microcontroller for determining a DC value of said output signal and for generating a correction signal coupled to said input of said digital-to-analog converter so that said DC value is removed from said output signal by signal compensation into said input of said amplifier.