An interferometer for radio astronomy with a single-lobed radiation pattern

The 150-foot slotted waveguide antenna for operation on a wavelength of 10 centimeters at the National Research Council, Ottawa, Canada, is now in operation as one element of an interferometer. The other element is itself a simple interferometer with element separation equal to that of the long array and is placed to the west on the common E-W axis. A rotary phase shifter in the arm between the array and simple interferometer is used, after Ryle, with a phase-sensitive detector. The resultant pattern consists of the product of three terms: 1) The single-lobe pattern of the long array; 2) the interference pattern of the simple interferometer, and 3) the interference pattern between the simple interferometer and array. This configuration gives a twofold increase in E-W resolving power over a uniformly collecting aperture of equal dimension. The presence of two interference patterns suggests the name, "compound interferometer," and the new antenna produces a fan-shaped beam2' E-W × 2-S. The instrument has been used to obtain daily drift curves of the sun.