A Versatile Phase Measurement Method for Transmission-Line Networks (Correspondence)

Current phase-measurement methods for transmission-line circuits fall into two general categories. The first is the comparison method, where the path under measurement is compared with another calibrated, variable one. The phase shift through the variable path is adjusted to equal that of the unknown path, and this condition is shown by a null detector. Null indication by both phase and amplitude adjustment is usually required; however, null indication by phase adjustment alone can be effected. The second category of phase measurements includes those measurements which provide voltage or meter output indication of phase angle. This category includes direct high frequency phase-dectector circuits of limited frequency phase-dectector circuits of limited frequency range or frequency-conversion methods where analog or digital circuits measure phase at a converted lower frequency.