Abstract: In a drift tube partitioned into a plurality of cascaded drift tube segments each followed by an ion elimination region, a method of separating ions as a function of ion mobility includes repeatedly, and alternating between at least two different time durations, establishing electric drift fields in the drift tube segments and in some of the ion elimination regions while establishing electric repulsive fields in others of the ion elimination regions such that ions having a predefined mobility or range of mobilities are transmitted through the drift tube at one or more frequencies which include one or more overtones of a fundamental frequency at which ions having the predefined mobility or range of mobilities are transmitted through the drift tube with the electric drift fields and electric repulsive fields repeatedly established with uniform time durations.

Abstract: In a drift tube partitioned into a plurality of cascaded drift tube segments each followed by an ion elimination region, for any integer M greater than 1, a method of separating ions repeats the following multiple times to cause only ions entering the drift tube that have a predefined ion mobility or range to traverse the drift tube: for each integer N beginning with 1 and sequentially advancing to M, establishing for a time duration an Nth electric repulsive field in the Nth ion elimination region and in every following Mth ion elimination region and an Nth electric drift field in each remaining ion elimination region and in each drift tube segment while deactivating for the time duration all non-Nth electric drift fields and non-Nth electric repulsive fields in each of the ion elimination regions and drift tube segments.

Abstract: An ion mobility spectrometer instrument has a drift tube that is partitioned into a plurality of cascaded drift tube segments. A number of electric field activation sources may each be coupled to one or more of the plurality of drift tube segments. A control circuit is configured to control operation of the number of electric field activation sources in a manner that sequentially applies electric fields to the drift tube segments with a activation duration of at least one of the electric field activation sources different than that of the others to allow only ions having a predefined ion mobility or range of ion mobilities to travel through the drift tube. The drift tube segments may define a linear drift tube or a closed drift tube with a continuous ion travel path.