Method and apparatus for variable phasing of periodic signals

摘要

A periodic output signal is generated at a variable phase relative to a periodic input signal by comparing the input signal with a third periodic signal that has a frequency which is less than the frequency of the input signal and that has a duty cycle which is equal to one-half of the ratio of the frequency of the third periodic signal to the frequency of the input signal. The phase difference is detected between the input signal and a frequency component of the third periodic signal which has the same frequency as the input signal. The output signal is generated at a frequency to maintain a predetermined phase relationship between the periodic input signal and the frequency component of the third periodic signal, and the phase of the output signal relative to the third periodic signal is varied. A predetermined phase relationship is maintained between the output signal and a second periodic input signal by comparing the output signal and the second input signal and generating a signal having a variable that is representative of the phase difference between them. The value of the variable is compared with a reference level representative of its value when the output signal and the second input signal are in the predetermined phase relationship, and the result of the comparison is used to control the phase of the output signal through a phase shifter to maintain the predetermined phase relationship.