  The measurement of micron-sized mechanical resonators by electrical
techniques is difficult, because of the combination of a high frequency and a
small mechanical displacement which together suppress the electromechanical
coupling. The only electromagnetic technique proven up to the range of several
hundred MHz requires the usage of heavy magnetic fields and cryogenic
conditions. Here we show how, without the need of either of them, to fully
electrically detect the vibrations of conductive nanomechanical resonators up
to the microwave regime. We use the electrically actuated vibrations to
modulate an LC tank circuit which blocks the stray capacitance, and detect the
created sideband voltage by a microwave analyzer. We show the novel technique
up to mechanical frequencies of 200 MHz. Finally, we estimate how one could
approach the quantum limit of mechanical systems.
