According to various embodiments, a mobile device continuously andor automatically scans a user environment for tags containing non-human-readable data. In one embodiment, the present invention describes a method for measuring blood glucose in a subject. The mirror delivers optical power in at least a radial and axial direction and propagates light in a multipass optical path of a predefined path length. By adopting the proposed solution it is possible to efficiently use adaptive antennas in a system carrying e.