An embodiment of the invention provides a transmissive passive repeater having two or more antenna arrays, each array comprised of a plurality of antenna elements. Each antenna array has an associated region. An aperture is defined by the antenna arrays with which energy at respective antenna arrays passes between each of the regions. Another embodiment of the invention provides a reflective passive repeater having an aperture. Energy received at the aperture is reflected back from the aperture. The aperture is configured to provide a conformal mapping between two regions as determined by complex coupling by individual antenna elements.