Multiplying element and array patterns can eliminate spatial aliasing without a physical line source

Evidence

Replacing each of the point sources with a continuous line source is equivalent to convolving it with the point array. Therefore, the effect of replacing the point source with the continuous sources is to multiply their far-field patterns together. … This pattern multiplication is well known, and the effect is for our example is shown in Figure A6.8. One can see that the aliased main lobes have been eliminated. In fact, the response has become equivalent to a continuous line source of the same extent as the array. Clearly, using directional sources, such as constant-directivity horns, can also be used to achieve similar effects. It is this that results in the success of large arrays based on them, providing the horns have directivity control before spatial aliasing occurs. Once the directivity of the individual elements is considered, the need for curved arrays also becomes apparent, as the spatial filtering effect of the sources must also be factored in. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2911

Categorization

• DEFINE: Explains pattern multiplication, the key mechanism by which directional elements suppress aliased lobes in arrays.