  We propose and demonstrate a novel method for generating
propagation-invariant spatially-stationary fields in a controllable manner. Our
method relies on producing incoherent mixtures of plane waves using planar
primary sources that are spatially completely uncorrelated. The strengths of
the individual plane waves in the mixture decide the exact functional form of
the generated coherence function. We use LEDs as the primary incoherent sources
and experimentally demonstrate the effectiveness of our method by generating
several spatially-stationary fields, including a new type, which we refer to as
the "region-wise spatially-stationary field." We also experimentally
demonstrate the propagation-invariance of these fields, which is an extremely
interesting and useful property of such fields. Our work should have important
implications for applications that exploit the spatial coherence properties
either in a transverse plane or in a propagation-invariant manner, such as
correlation holography, wide-field OCT, and imaging through turbulence.
