  We describe a method to stabilize the amplitude of the interrogating
microwave field in compact atomic clocks working in a Ramsey approach. In this
technique, we take advantage of the pulsed regime to use the atoms themselves
as microwave amplitude discriminators. Specifically, in addition to the
dependence on the microwave detuning, the atomic signal after the Ramsey
interrogation acquires a dependence on the microwave pulse area (amplitude
times duration) that can be exploited to implement an active stabilization of
the microwave field amplitude, in a similar way in which the Ramsey clock
signal is used to lock the local oscillator frequency to the atomic reference.
This stabilization results in a reduced sensitivity of the clock frequency to
microwave amplitude fluctuations that are transferred to the atoms through the
cavity-pulling effect. The proposed technique is then effective to improve the
clock stability and drift on medium and long term. We demonstrate the method
for a vapor-cell clock working with a hot sample of atoms but it can be
extended to cold-atom compact clocks.
