  We develop a field theoretical approach based on the temporary basis
description as a tool to investigate the transmission properties of a
time-driven quantum device. It employs a perturbative scheme for the
calculation of the transmission of a monochromatic beam of particles through
the time-dependent set-up. The main advantage of the proposed treatment is that
it permits the use of the particle picture for the calculation of the
scattering matrix and the transmission coefficient. Therefore the elementary
physical processes contributing to the transmission can be identified and
interpreted in a transparent way. We apply the method to the simple but
prototype problem of transmission through an one-dimensional oscillating delta
potential and we demonstrate how it enables a deep understanding of the
underlying physical processes.
