  Atom gravimeters are equivalent to non-multi-level corner-cube gravimeters in
translating the gravity signal into the measurement result. This enables
description of atom gravimeters as LTI systems. The system's impulse responses
by acceleration, velocity, and displacement are found to have the shape of
triangle, meander, and the Dirac comb resp. The effects of inhomogeneous
gravity field are studied for constant and linear vertical gradients and
self-attraction of the instrument. For the constant gradient the effective
measurement height is below the top of the trajectory at 1/6 and 7/24 of its
length for the fountain and the release types of the instruments resp. The
analysis is expanded to the gravimeters implementing the Bloch oscillations at
the apex of the trajectory. In filtering the vibrations these instruments are
equivalent to the first-order low-pass filters, while other atom gravimeters
are equivalent to the second-order low-pass filters.
