  The periodic injection $n$ of electrons in a quantum conductor using periodic
voltage pulses applied on a contact is studied in the energy and time-domain
using shot noise computation in order to make comparison with experiments. We
particularly consider the case of periodic Lorentzian voltage pulses. When
carrying integer charge, they are known to provide electronic states with a
minimal number of excitations, while other type of pulses are all accompanied
by an extra neutral cloud of electron and hole excitations. This paper focuses
on the low frequency shot noise which arises when the pulse excitations are
partitioned by a single scatterer in the framework of the Photo Assisted Shot
Noise (PASN) theory. As a unique tool to count the number of excitations
carried per pulse, shot noise reveals that pulses of arbitrary shape and
arbitrary charge show a marked minimum when the charge is integer. Shot noise
spectroscopy is also considered to perform energy-domain characterization of
the charge pulses. In particular it reveals the striking asymmetrical spectrum
of Lorentzian pulses. Finally, time-domain information is obtained from Hong Ou
Mandel like noise correlations when two trains of pulses generated on opposite
contacts collide on the scatterer. As a function of the time delay between
pulse trains, the noise is shown to measure the electron wavepacket
autocorrelation function for integer Lorentzian thanks to electron
antibunching. In order to make contact with recent experiments all the
calculations are made at zero and finite temperature.
