| 摘要 |
PURPOSE:To make a phase adjustment with high precision, by detecting the phase relation of a data signal and a sampling clock on the 0 deg.-phase and 90 deg.-phase axes of the sampling clock and displaying it on an oscilloscope in the form of vectors. CONSTITUTION:A pulse (a) has the same frequency with a sampling clock (SC). The output of a 1/2 frequency dividing circuit 11 is inverted at falls of the pulse (a). Its pulse width is the same with a clock run-in signal. Therefore, pulses (b) are assumed to be the data signal and the SC is phase-adjusted. The output (d) of a phase shifting circuit 13 is 90 deg. out-of-phase with the pulses (a). A phase comparator 14 detects the phase difference between the signal (c) and pulses (a) and a phase detector 15 detects the phase difference between the signals (c) and (d); the both outputs DC voltages. When the X axis and Y axis on a CRT17 are deflected by the outputs of the phase comparators 14 and 15 to display the phase relation of the pulses (d) to the pulses (b) in the form of vectors. This phase adjusting device employs such circuit constitution that +AV when the outputs of the comparators 14 and 15 have the same frequency and are in phase with each other, -AV when opposite in phase, or OV when 90 deg. out of phase is obtained. So that a bright point is as shown in a figure (e), a phase adjusting circuit is adjusted, making an adjustment to an optimum phase. |
