Circuitry for generating a distortion-free sector display in a cathode ray tube for displaying signals from an ultrasonic transducer moving back and forth in an arcuate path. Sine and cosine beam sweep signals are developed using signals respectively representing the angular position .theta. of the transducer on its angular path (representing the sine) and 1-.theta..sup.2 /2(representing the cosine). A transducer position signal is stored on a relatively large capacitor, and a capacitor of smaller capacitance is used to generate a ramp signal in producing the sine and cosine beam sweep signals.