Compact, U-shaped microwave resonators have been designed and implemented with RF MEMS switches to obtain frequency tunable narrow-band devices. The U-shape has been used to develop a resonator optimizing its size. In addition, RF MEMS ohmic switches have been introduced to implement the frequency tunability in a small range and to provide a high signal rejection ratio in the ON-OFF states. Device configurations working at frequencies between 20 GHz ca. and 26 GHz ca. have been studied.