Time domain analysis and its practical application to the measurement of phase noise and jitter

The precise determination of phase is necessary for a very large set of measurements. Traditionally, phase measurements have been made using analog phase detectors which suffer from limited accuracy and dynamic range. This paper describes how phase digitizing, which uses time domain techniques, removes these limitations. Phase digitizing is accomplished using a time interval analyzer, which measures the signal zero-crossing times. These zero-crossing times are processed to compute phase deviation, with the reference frequency specified as a numerical value or derived from the times themselves. Phase digitizing can be applied even in the presence of modulation, as the underlying clock can be reconstructed in software to fit the data. Measurements derived from this phase data such as phase noise, jitter analysis, Allan variance (AVAR), maximum time interval error (MTIE), and time deviation (TDEV) are applied to such applications as the characterization of oscillators, computer clocks, chirp radar, token ring networks, and tributaries in communication systems.