An adjustable constant impedance phase shifter is provided. In the adjustable constant impedance phase shifter a conductive circuit path is arranged between a conductive sheet and a parallel plane that is parallel to the conductive sheet; an edge of a dielectric plate and an edge of a conductive plate are adjoined such that the dielectric plate and the conductive plate form a slide member; and the slide member is movably arranged along a slide path between the circuit element and the conductive sheet so that any point of the conducting circuit path is consistently enclosed between the slide member and the parallel plane, and so that the relative permittivity of a medium adjacent to a point on the conductive circuit path is simultaneously changed as the slide member is moved.