The ornamental design disclosed in this application is for a waveform generator. The waveform generator has a substantially rectangular front face with a substantially rectangular display disposed in a portion thereof, side surfaces having curved top edges, a top surface having curves surfaces adjacent to the curved top edges of the side surfaces that transition to a substantially flat surface extending from the front face to the rear, and control knobs, buttons and electrical connectors arranged on the front face adjacent to the rectangular display.
FIG. 1 is a perspective view of a waveform generator;
FIG. 2 is a front elevation view of the waveform generator;
FIG. 3 is a left side elevation view of the waveform generator;
FIG. 4 is a right side elevation view of the waveform generator;
FIG. 5 is a top plan view of the waveform generator;
FIG. 6 is a bottom plan view of the waveform generator; and,
FIG. 7 is a rear elevation view of the waveform generator.