Ultrasonic circular phased arrays have long been employed in sonar, NDT, and AGV applications. More recently, these arrays have been used in medical imaging applications. The ability of these arrays to image a 360° field makes them ideal for intravascular imaging applications. However, intravascular applications often require the diameter of the array to be on the order of 1 mm. The small size of the array dictates that trade‐offs in its design, such as the number of elements versus resolution, be made. Field patterns produced by a circular phased array, required to evaluate such design trade‐offs, have not been extensively examined. In this paper, a new field calculation method, which requires less computational time than existing methods for a given accuracy, is presented. The curved surface of the array, radiating either continuous‐wave or pulsed signals, is subdivided into incremental areas which are small enough that the Fraunhofer approximation can be applied. The field pressure is computed by summing the contributions from all the incremental areas using the Rayleigh‐Sommerfeld diffraction integral. Theoretical results obtained with this method are compared to those obtained using other methods as well as experimental data. The effects of some design parameters such as the geometry of the array, pulse bandwidth, and amplitude weighting of the excitation signal will also be presented.