The presence of crossproduct terms in multiplicative receiving systems, in particular 2-aerial synthetic-aperture receivers, is illustrated. Methods for suppression of these terms are discussed, as well as the residual level that may be acceptable. It is shown that crossproduct terms are adequately suppressed if there are many cycles of relative-phase variation between sources during the synthesis period, and, from the theory presented, the minimum synthesis time can be computed for any particular source behaviour.