Abstract: A shim-tuned transformer for matching the impedance of a generator and a load coupled to the generator via a transmission line. The transformer includes an outer conductor having an inner surface and an inner conductor positioned within the outer conductor. The transformer further includes at least one shim disposed on the inner surface of the outer conductor and encircling the inner conductor. The at least one shim is slideable along the inner surface of the outer conductor for matching the impedance of the generator and the impedance of the load.