An ion transport apparatus for a mass- or ion-mobility-spectrometer comprises: (a) a plurality of strip electrodes in a series on a flat substrate; (b) an ion outlet aperture in the substrate disposed adjacent to a first one of the plurality of strip electrodes; (c) a cage electrode at least partially enclosing the plurality of strip electrodes and the ion outlet aperture; (d) a radio frequency (RF) voltage generator operable to supply an RF phase difference between each pair of adjacent electrodes; and (e) at least one DC voltage source operable to supply first and second DC voltages to the cage electrode and an extraction electrode and to supply respective DC bias voltages to each of the plurality of electrodes, wherein electrode strip widths of a series of the plurality of electrodes progressively increase away from the first one of the plurality of electrodes.