| 摘要 |
<p>A waveform shaper includes a level shifter (112) for controlling a DC offset voltage of an input digital signal, a comparator (103) for comparing a digital signal output from the level shifter with a predetermined reference voltage to shape a waveform of the input digital signal and output a shaped digital signal, an intermediate voltage detector (113) for detecting and outputting an intermediate voltage of a digital signal output from the level shifter, and a first controller (116, 117) for receiving the intermediate voltage and the predetermined reference voltage to output a control signal for changing the DC offset voltage to the level shifter. A signal analyzer includes, in addition to the above waveform shaper, a variable delay circuit (106) for delaying a phase of an input clock signal, a discriminator (104) for receiving an output from the comparator and an output from the variable delay circuit to determine a code of the output signal from the comparator at a timing determined by a delayed clock signal, an error measuring unit (121) for comparing a determination signal from the discriminator with a reference signal corresponding to the input digital signal to output an error signal, and a second controller (126) for receiving an output from the error measuring unit, detecting an intermediate delay amount of delay amounts corresponding to adjacent error signals having maximum values, and sending the intermediate delay amount to the variable delay circuit. <IMAGE></p> |
