Synthesis of a circular-aperture antenna with a specified intensity distribution along the near-field axis

The stationary-phase method is used to solve the synthesis problem for an optical-type antenna with an axisymmetric field distribution in the circular aperture. The solution is discussed in the context of two approaches: determination of the amplitude distribution A(p) of the wave in the aperture given its phase distribution phi(p), and determination of phi(p) given A(p). The former is more easily implemented from the mathematical standpoint, while the latter is preferable for practical antenna design. It is further shown that by use of a dielectric lens with appropriate shape of the refracting surface, it is possible to obtain constant amplitude and phase of the field distribution in the antenna aperture.