| 摘要 |
The detector comprises an input terminal (94) for receiving a signal sine f(t). A second terminal (96) couples the Hilbert transform of this signal to a phase-inverting switch (90) and also to a zero crossing detector (97). The detector is coupled to one input of an AND gate (104). A third terminal (106) provides a signal from a decoder (38) to a full wave rectifier (108). The rectified output is coupled to a differentiator (110) and to an adder (112). The output of the adder is applied to a one-shot multivibrator (114), the output of which is coupled to a second input of the AND gate. The output of the AND gate represents only those zero crossings in the output of the detector 97 which coincide closely with the zero crossings of the signal at the third terminal. The output of the AND gate is applied to a flipflop (118) which controls the phase inverting switch. |
