Patent ID: 8391346

Claim:
A data signal quality evaluation apparatus comprising: a waveform data acquiring unit ( 21 ) that performs sampling on a data signal to be evaluated which has a desired bit rate and a desired amplitude to acquire waveform data of the data signal; a display unit ( 40 ); an operating unit ( 50 ); an eye pattern display unit ( 31 ) that displays an eye pattern of the data signal on the display unit on the basis of the waveform data acquired by the waveform data acquiring unit; a mask setting unit ( 32 ) that sets a mask which has a polygonal shape substantially similar to a shape of a region surrounded by the eye pattern of the data signal and has a size corresponding to the bit rate and amplitude of the data signal as a reference mask for evaluating quality of the data signal; a mask display unit ( 33 ) that displays the reference mask set by the mask setting unit at a desired position which overlaps the region surrounded by the eye pattern of the data signal; a quality evaluating unit ( 34 ) that determines a count value by counting a number of display points in the region of the reference mask among the display points of the waveform data forming the eye pattern, evaluates the quality of the data signal on the basis of the count value, and displays an evaluation result of the quality on the display unit; and a mask region limiting unit ( 35 ) that limits an effective range of the reference mask to a range determined by an arbitrary width and angle designated by an operation of the operating unit and displays the limited effective range on the display unit, wherein the quality evaluating unit performs quality evaluation on the limited effective range.