This invention relates to analog to digital converters utilizing frequency variations of a signal to indicate analog quantities.
Old methods of converting from analog voltage to digital format are complex and speed or accuracy limited. Available devices normally compare the input voltage to a set of reference voltages and serially process the differences to develop the individual bits of the digital word that represents the signal voltage. This serial process takes time and limits the rate at which new words can be generated to follow changes in the signal voltage with time. However, the article "High Speed Electro-Optic Analog-to-Digital (A/D) Converter," SPIE Vol. 176, Guided Wave Optical Systems and Devices 11 (1979) pp 28-35 discloses a new device which employs optical components with voltage variable delay lines to parallel process the individual bits. This device can operate at very high speeds but is limited by optical power handling ability to four bit word accuracy.