Retrodirective array using the heterodyne technique

A retrodirective array using a single microwave mixer to accomplish conjugate phase shift in each element is described. Reradiated patterns were measured for a four-element array to substantiate the predicted performance. This array has an advantage over the Van Atta array in that the elements are not restricted to being located on a plane surface. It is more efficient than the previously used method of employing two mixers to provide conjugate phase shift because of the reduction in converison loss and LO (local oscillator) power.