  High-precision magnetic field measurement is an ubiquitous issue in physics
and a critical task in metrology. Generally, magnetic field has DC and AC
components and it is hard to extract both DC and AC components simultaneously.
The conventional Ramsey interferometry can easily measure DC magnetic fields,
while it becomes invalid for AC magnetic fields since the accumulated phases
may average to zero. Here, we propose a scheme for simultaneous measurement of
DC and AC magnetic fields by combining Ramsey interferometry and rapid periodic
pulses. In our scheme, the interrogation stage is divided into two signal
accumulation processes linked by a unitary operation. In the first process,
only DC component contributes to the accumulated phase. In the second process,
by applying multiple rapid periodic $\pi$ pulses, only the AC component gives
rise to the accumulated phase. By selecting suitable input state and the
unitary operations in interrogation and readout stages, and the DC and AC
components can be extracted by population measurements. In particular, if the
input state is a GHZ state and two interaction-based operations are applied
during the interferometry, the measurement precisions of DC and AC magnetic
fields can approach the Heisenberg limit simultaneously. Our scheme provides a
feasible way to achieve Heisenberg-limited simultaneous measurement of DC and
AC fields.
