Engineering topics
Publications and source records attributed to Donahoe, T..
Telemetry unit has been developed for possible use in measuring scalp-tissue pH and heart rate of unborn infant. Unit radius data to receiver as much as 50 ft. away. Application exists during hours just prior to childbirth to give warning of problems that might require cesarean delivery.
Phase shift in test device is measured by summing output of mixer with ramp voltage and comparing time interval between zero crossings of summed signal and ramp reference frequency. Circuit can be used to test devices at other frequencies by changing only signal source, phase splitter, and mixer; divider and time-interval counter need not be driven by oscillator.
A new time domain phase comparator is described. The device uses a novel technique to allow time domain phase measurements to be made with period and time interval counters without the use of offset reference oscillators. The device uses a single reference oscillator and allows measurements with a phase resolution greater than the noise floor of the reference. Data is presented showing a phase resolution of 0.02ps at 5 MHz with a crystal reference. The device has application in measuring the phase stability of systems where approximate phase quadrature can be maintained.